DEPARTMENT OF THE INTERIOR

FRANKLIN K. LANE, Secretary

UNITED STATES GEOLOGICAL SURVEY

. GEORGE OTIS SMITH, Director

Bulletin 610

MINERALOGIC NOTES

SERIES 3

BY

WALDEMAR T. SCHALLER

WASHINGTON

GOVERNMENT PRINTING OFFICE 

1916

CONTENTS.

Page.

Introduction................................................................ 9

Koechlinite (bismuth molybdate), a new mineral............................ 10

Origin of investigation................................................... 10

Nomenclature......................................................... 10

Locality............................................................... 11

Paragenesis........................................................... 11

Crystallography........'............................................... 14

General character of crystals....................................... 14

Calculation of elements............................................. 14

Forms and angles................................................. 15

Combinations..................................................... 19

 < Zonal relations and markings...................................... 19

Habits........................................................... 21

Twinning........................................................ 23

Measured crystals................................................. 26

Etch figures...................................................... 27o

Intergrowths........................................................ 31

Relation to other minerals.......................................... 31

Physical properties.................................................... 32

Optical properties...................................................... 32

Chemical properties.................................................... 33

Pyrognostics...................................................... 33

Quantitative composition.......................................... 33

Diagnostic properties................................................... 34

Inyoite and meyerhofferite, two new calcium borates......................... 35

Relation of meyerhofferite to inyoite................................... 35

Nomenclature......................................................... 36

Locality and paragenesis.......................'....................... 36

Inyoite............................................................... 37

Crystallography................................................... 37

General character of crystals................................... 37

Calculation of elements......................................... 37

Forms......................................................... 38

Physical properties................................................ 38

Optical properties.................................................. 38

Chemical properties...............................................: 39

Pyrognostics.................................................. 39

Quantitative composition...................................... 39

Alteration.................................................... 40

Diagnostic properties............................................... 40

Meyerhofferite............... . ......................................... 41

Crystallography................................................... 41

General character of crystals................................... 41

Calculation of elements......................................... 41

Forms and angles............................................. 45

3
4 . CONTENTS.

Inyoite and meyerhofferite, two new calcium borates Continued. 

Meyerhofferite Continued.

Crystallography Continued. Page.

Combinations................................................. 48

Zonal relations................................................. 50

Habits....................................................... 50

Measured crystals............................................. 52

Physical properties................................................ 53

Optical properties.................................................. 54

Chemical properties................................................ 54

Pyrognostics.................................................. 54

Quantitative composition...................................... 54

Synthesis....................................................... 55

Diagnostic properties. v............................................ 55

Lucinite, a new mineral: a dimorphous form of variscite ..................... 56

Origin of investigation................................................. 56

Nomenclature and locality............................................. 56

Paragenesis........................................................... 56

Crystallography....................................................... 57

General character of crystals....................................... .57

Calculation of elements............................................. 58

Forms and angles................................................. 59

Combinations..................................................... 61

Zonal relations..................................................... 61

Habits........................................................... 61

Measured crystals................................................. 62

Relation to other minerals......................................... 64

Physical properties.................................................... 66

Optical properties...................................................... 67

Chemical properties.................................................... 67

Diagnostic properties.................................................. 68

The crystallography of variscite............................................. 69

Previous description.......................... i........................ 69

General character of crystals........................................... 69

Calculation of elements................................................. 69

Forms and angles.......:............................................. 71

Combinations......................................................... 73

Zonal relations......................................................... 73

Habits...... ; ........................................................ 73

Twinning.............................................................. 77

Relation to variscite crystals from Arkansas............................. 78

Schneebergite............................................................. 81

Origin of investigation................................................. 81

Historical sketch....................................................... 82

Bibliography......................................................... 85

Paragenesis........................................................... 86

Crystallography....................................................... 90

Physical properties.................................................... 91

Optical properties...................................................... 91

Chemical properties.................................................... 91

Pyrognostics...................................................... 91

Homogeneity of sample analyzed................................... 91

Analytical methods used........................................... 92

Quantitative composition. .......................................... 93
CONTENTS.

Romeite........................... ..........................' .:............ 95

Origin of investigation................................................. 95

Historical sketch....................................................... 95

Bibliography......................................................... 96

Paragenesis........................................................... 96

Crystallography....................................................... 97

Physical properties.................................:.................. 98

Optical properties...................................................... 98

Chemical properties.................................................... 99

Pyrognostics...................................................... 99

Quantitative composition.......................................... 99

The natural antimonites and antimonates..........\......................... 104

Velardenite, a new member of the melilite group............................ 106

The melilite group........................................................ 109

Historical sketch..................................................... 1. 109

Review of old theories............................................. 109

Characteristics of the melilite group. ................................. 110

New theory............................................................ Ill

Primary compounds................................................ Ill

Natural anhydrous calcium-aluminum silicates.................. Ill

Sarcolite...................................................... 113

Soda sarcolite.................................................. 115

JLkennanite.................................................. 116

Velardenite................................................... 117

Summary of properties of primary compounds................... 117

Isomorphous mixtures of two or more of the primary compounds...... 118

Composition of the mixtures........................................ 126

The composition of cebollite............................................... 129

The crystallography of thaumasite.......................................... 131

The chemical composition of tremolite...................................... 133

New occurrences of some rare minerals..................................... 137

Gigantic crystals of spodumene ............................................ 138

The probable identity of mariposite and alurgite............................ 139

The amblygonite group of minerals fremontite (=natramblygonite)......... 141

The crystallography of fremontite.........................................' 143

The chemical composition of nephelite ..................................... 145

Large crystals of bloedite.................................................. . 148

Alunite from Marysvale, Utah.............................................. 150

The composition and relations of custerite................................... 152

Occurrence and association. 1.......................................... 152

Physical and optical properties........................................ 152

Chemical properties.................................................. 153

Pyrognostics. ...................................................... 153

Quantitative composition......................................... 153

Interpretation of analysis ......................................... 154

Relation to other minerals......................................... 155

The composition of hodgkinsonite.......................................... 159

Occurrence and associations........................................... 159 .

Crystallography....................................................... 159

Chemical properties.................................................. 159

Pyrognostics...................................................... 159

Quantitative composition.......................................... 160

Crystals of pisanite from Ducktown, Tenn .................................. 161

The refractive indices of strengite................................. ........ 162

The calculation of a mineral formula.... .1.................................. 163
ILLUSTRATIONS.

Page. 

PLATE I. A, Crystals of inyoite on massive mineral; B, Group of crystals of

inyoite....................................................... 36

II. Alteration of inyoite to meyerhofferite: A, B, C, Reticulated structure of altered inyoite; D, Stellate groups of crystals of meyerhofferite on the surface of crystals of inyoite..................... 37

III. Ore specimens with schneebergite from Schneeberg, Austrian Tyrol. 88

IV. A, Romeite from Italy; B, Schneebergite from Austrian Tyrol...... 89

V. Gigantic crystals of spodumene, Etta mine, Black Hills, S. Dak.: A,

Largest crystal mined up to 1904; B, Molds of two immense crystals. 138 

FIGURE 1. A group of three crystals of koechlinite in parallel position........ 12

2. Sketch of unknown mineral A associated with koechlinite....... 12

3. Sketch of unknown mineral B associated with koechlinite........ 12

4. Sketch of unknown mineral C associated with koechlinite........ 13

5. Sketch of complex twin of unknown mineral G................... 13

6. Common appearance of crystals of koechlinite.................... 14

7. Distorted crystal of koechlinito................................. 14

8. Gnomonic projection of koechlinite forms......................... 20

9. Acute-angled markings on koechlinite........................... 20

10. Regular markings on koechlinite................................ 20

11. Square tabular habit of koechlinite.............................. 21

12. Stout tabular crystal of koechlinite.............................. 21

13. Intermediate habit of koechlinite............................... 21

14. Crystal of koechlinite elongated parallel to the vertical axis....... 22

15. Small.prismatic crystals of koechlinite included in a larger square

one......................................................... 22

16. Common extent of elongation parallel to edge a p of crystal of 

 ^ koechlinite................................................. 22

17. Extreme case of distorted elongation parallel to edge a p noted 

< on crystal of koechlinite..........................;.......... 22

18. Contact twin of koechlinite, composition face unit brachydome... 23

19. Contact twin of koechlinite, composition face macropinacoid...... 24

20. Cleavage piece of koechlinite............ 1........................ 24

21. A theoretical fourling of koechlinite............................. 25.

22. Crystal 3, koechlinite.......................................... 25

23. Clinographic projection of a penetration twin of koechlinite...... 25

24. Orthographic projection on the macropinacoid of a penetration twin

of koechlinite............................................... 25

25. Crystal 5, koechlinite.................\ ........................ 26

26. Crystal 2, koechlinite.......................................... 26

27. Crystal 4, koechlinite.......................................... 26

28. Crystal 7, koechlinite.......................................... 26

29. Crystal 6, koechlinite.......................................... 27

30. First stage of etch figures produced on a symmetrically etched

crystal of koechlinite........................................ 27

6
ILLUSTRATIONS. 7

Page.

FIGURE 31. First stage of etch figures produced on a twinned crystal of koechlinite....................................................... 28

32. Second stage of etch figures produced on koechlinite after the

. triangular figures............................................ 28

33. Third stage of etch figures produced on a twinned crystal of koechlinite. ...................................................... 29

34. Last stage of etch figures produced on koechlinite................ 29

35. Appearance of a corner of an etched and dissolving crystal of

koechlinite ......°........................................... 29

36. Intergrowth of unknown mineral C with koechlinite .............. 30

37. Intergrowth of unknown mineral C with koechlinite.............. 30

38. Diagram illustrating crystal forms of inyoite shown in Plate I, A. 36

39. Diagram illustrating crystal forms of inyoite shown in Plate I, B. 36

40. Inyoite crystal................................................ 38

41. Gnomonic projection of meyerhofferite forms. ..................... 50

42. Tabular prismatic crystal (No. 1) of meyerhofferite............... 51

43. Crystal 21, meyerhofferite....................................... 51

44. Crystal 2, meyerhofferite........................................ 51

45. Orthographic projection of crystal 17, meyerhofferite............ 51

46. Crystal 10, meyerhofferite....................................... 52

47. Crystal 3, meyerhofferite........................................ 52

48. Crystal 8, meyerhofferite....................................... 52

49. Orthographic projection of crystal 12, meyerhofferite............... 53

50. Crystal 16, meyerhofferite........... A......................... 53

51. Crystal 20, meyerhofferite...................................... 53

52. Octahedral crystals of lucinite perched on a larger tabular crystal

of variscite.................................................. 57

53. Tabular crystal of variscite resting on a bed of smaller crystals of

lucinite.................................................... 57

54. Gnomonic projection of lucinite forms........................... 62

55. Octahedral crystal of lucinite................................... 63

56. First modification of simple octahedral crystal of lucinite ........ 63

57. Second modification of simple octahedral lucinite on crystal 3.... 63

58. Both modifications occurring on lucinite crystal 6 ............... 63

59. Crystal of lucinite with large development of s .................. 63

60. A distorted crystal of lucinite,.................................. 63

61. Crystal 4, lucinite.............................................. 64

62. Gnomonic projection of variscite forms......................... 74

63. Very thin, elongated plates of variscite.......................... 75

64. A thicker crystal of variscite, with a richer combination.......... 75

65. A much stouter, tabular crystal of variscite...................... 75

' 66. Short prismatic habit of crystal of variscite ..................... 75

67. Stout prismatic, nearly equidimensional crystal of variscite....... 75

68. Long prismatic crystal of variscite.............................. 75

69. Short prismatic crystal of variscite with new dome............... 75

70. Clinographic projection of a stout rectangular crystal of variscite.. 76

71. Orthographic projection of a stout rectangular crystal of variscite.. 76

72. Crystal of variscite elongated parallel to the a axis ............... 76

73. Short prismatic crystal of variscite............................... 76

74. Stout rectangular crystal of variscite ............................. 76

75. Twin crystal of variscite ....................................... 77

-76. Crystal of variscite from Arkansas ............................... 78
8 ILLUSTBATIONS.

Page. 

FIGURE 77. Crystal of variscite from Arkansas showing sheaf-like structure ... 80

78. Sketch of specimen of schneebergite with concentric bands....... 86

79. A lens-shaped cavity in sphalerite filled in by alternating layers of

breunnerite and galena........................................ 86

80. Concentric structure of bands of minerals on specimen of schneebergite. ..................................................... 87

81. Granular calcite filling cavity in schneebergite specimen......... 87

82. Diagram of specimen shown in Plate III, A ..................... 88

83. Diagram of specimen shown in Plate Ilf, B ..................... 88

84. Diagram of specimen shown in Plate III, C ..................... 88

85. Diagram of specimen shown in Plate IV, A ..................... 89

86. Diagram of specimen shown in Plate IV, S...................... 89

87. Crystal of schneebergite......................................... 90

88. Optical structure of crystal of romeite........................... 98

 89. Triangular representation of the chemical composition of minerals

of the melilite group......................................... 127

90. Diagram showing hypothetical relation of refractive indices to

composition of mixtures of akermanite and sarcolite............ 128

91. Short prismatic crystal of thaumasite.............................. 131

92. Long prismatic crystal of thaumasite............................ 131

93. Compound crystal of thaumasite................................ 132

94. Terminated crystal of thaumasite................................ 132

95. Crystal of fremontite ........................................... 143

96. Crystalof bloedite............................................. 148

97. Crystal 1, pisanite.............................................. 161

98. Crystal 2, pisanite............................................. 161

99. Crystal 3, pisanite............................................. 161
MINERALOGIC NOTES, SERIES 3,

By WALDEMAR T. SCHALLEK.

INTRODUCTION.

The results of the smaller, independent pieces of mineralogic 

research work carried out by the writer in the chemical laboratory 

of the United States Geological Survey from July 1, 1911, to December 31, 1913, are here assembled. Earlier reports of a similar 

nature have been published as "Mineralogical notes" (1903-4), in 

Bulletin 262, 1904; " Mineralogical notes, series 1" (1905-1909), as 

Bulletin 490, 1911; and "Mineralogical notes, series 2" (1910-11), 

as Bulletin 509, 1912. In addition to these papers a report on the 

crystallography of ferberite from Colorado was revised for publication in Bulletin 583, and a report on the gem tourmaline field of 

southern California has been submitted for publication as Professional Paper 92.

The writer spent the-summer of 1912 in Europe and obtained a 

considerable amount of valuable material, especially from the collection in the Vienna Hof-Museum, and the results of study of two 

minerals thus obtained koechlinite, a new species, and schneebergite, analyzed completely for the first time are here presented. 

The papers on custerite and on hodgkinsonite were first published 

in conjunction with other investigators, and their contributions 

have been briefly summarized in the present notes.

The papers preceding the one on the crystallography of fremontite, 

except the one entitled "The composition of cebollite," have not 

been previously published.

9
KOECHLINITE (BISMUTH MOLYBDATE), A NEW MINERAL. 

ORIGIN OF INVESTIGATION.

Some years ago the writer l described a crystallized bismuth 

mineral from Nevada which occurred in hexagonal rhombohedral 

crystals and was optically uniaxial. Analysis of this mineral showed 

the presence of considerable water, and in accordance with the 

results obtained on bismuth qcher from California 2 the mineral from 

Nevada was considered to have the composition expressed by the 

formula Bi203 .3H20. The crystals from Nevada are very different 

from those assigned to the anhydrous oxide of bismuth, Bi203 , as 

given in Dana's Mineralogy.3 It seems doubtful, therefore, whether 

the anhydrous oxide exists in nature as such, and a sharp outlook 

has been kept for natural occurrences of crystallized Bi2 03 .

While the writer was at Vienna in 1912 he made an inquiry as to 

the presence of such specimens in the collections, and the custodian 

of the mineral collection of the Hof-Museum, Dr. Rudolf Koechlin, 

called particular attention to a specimen showing small greenish 

rectangular crystals which had been supposed to be torbernite but 

which Dr. Koechlin had found to give a strong bismuth reaction. 

On request, and on the approval of Dr. F. Berwerth, director of the 

mineralogic and petrographic division of the Hof-Museum, part of the 

specimen was given to the writer for study, and it is a great pleasure for him to express his thanks for the kindness and liberality of 

Drs. Berwerth and Koechlin in furnishing this valuable material.

The investigation showed that the mineral contained essentially only 

the oxides of bismuth and molybdenum, and the analyses yielded 

results from which the simple formula Bi2 03 .MoO3' was deduced.

The acquisition of the specimen by the Vienna Museum is thus 

described by Dr. Koechlin. The specimen was bought in 1884 

from a Mr. Kulda who carried on a small trade in natural-history 

objects. The specimen of koechlinite, No. D. 3478 in the Vienna 

catalogue, was labeled torbernite. As Dr. Koechlin ,had found 

considerable bismuth in the mineral, however, it had been relabeled 

bismuth ocher. According to him the mineral somewhat resembles 

uranospinite. The only observed phase of the mineral consists of 

sharp, minute tabular crystals which are described in detail below, 

under the heading "Crystallography."

1 Schaller, W. T., Bismite from Nevada: U. S. Geol. Survey Bull. 490, p. 33,1911. Compare also Ransome, F. L., The geology and ore deposits of Goldfleld, Nev.: U. S. Geol. Survey Prof. Paper 66, p. 121,1909,

2 Schaller, W. T., Bismuth ochers from San Diego County, Cal.: Am. Chem. Soc. Jour., vol. 33, p. 162. 

1911. 

»Dana, E. S., System of mineralogy, 6th ed., p. 200,1892.

10
KOECHLINITE (BISMUTH MOLYBDATE), A NEW MINEBAL. 11 

NOMENCLATURE.

The services of Dr. Rudolf Koechlin, both as investigator and as 

custodian of the mineral collection in Vienna, are too well known 

to call for any extended remarks, and in proposing the name koechlinite for the new bismuth molybdate herein described the writer 

takes a double pleasure, for not only the scientific attainments of 

Dr. Koechlin are thereby recognized, but in addition his charming 

personality and great willingness to help others, which were so 

manifest during the writer's stay in Vienna.

The formula of koechlinite is a simple one, but no other minerals 

were noted with which it could be closely related, and for the present 

it must be placed with other molybdates, although from analogy 

one might expect to find minerals similar in type but differing chemically, as, for example, the unknown compound Fe203 .S03 .

LOCALITY.

The locality as given originally by Mr. Kulda is the Daniel mine, 

Schneeberg, Saxony, Germany, and the already long list of secondary 

bismuth minerals found at this classic locality is now further extended.

PARAGENESIS.

The character of the matrix and its geologic relations are not 

known, but the specimens appear typically like parts of a mineralized 

quartz vein, rich in'cavities lined with well-developed quartz crystals, 

upon which rest the crystals of koechlinite.

The associated minerals are massive white quartz and quartz in 

colorless crystals, forming the main part of the specimen; abundant 

native bismuth, in cleavable masses, in part strongly iridescent; 

abundant smaltite, in cubic crystals ({100}, {111}) about 1 millimeter thick (wrongly described as chloanthite by Mr. Kulda); a red 

mineral (realgar ?) occurring sparsely as minute seams in the massive 

quartz; a few needle-like prisms of a gray metallic mineral (bismuthinite?, stibnite?) in the cavities with koechlinite; and three 

unidentified minerals found directly associated with the koechlinite.

The contents of some of the cavities were removed, and the 

larger crystals were picked out for measurement and analytical purposes. The remaining fine material was then embedded in cooked 

balsam dissolved in chloroform, which was then allowed to harden by 

gradual evaporation of the chloroform. The material in these microscopic slides was therefore not subjected to any heat. Many perfect crystals of koechlinite were found in this fine material, and their 

habit and optical properties could be well studied under the microscope. A group of three such crystals in parallel position is shown 

in figure 1. The very high index of refraction of the mineral gives 

all the crystals a thick black border, due to total reflection. The
12 MINERALOGIC NOTES SERIES 3.

striations on the tabular crystals are vertical and the bounding faces 

of the crystals are those of the unit pyramid. The angle of the edges

(lll)-(Tll): (iTl)-(ni) 

is 90° 08', thus giving 

°the rectangular shape to 

the crystals.

FIGURE 1. FIGURE 2. 

FIGURE 1. A group of three crystals of koechlinite in parallel position. The heavy black border is

caused by total reflection due to the very high refractive index of the mineral. 

FIGURE 2. Sketch of unknown mineral A associated with koechlinite.

The associated minerals became concentrated in the material forming the slides by the removal of the larger koechlinite crystals, and 

the description of these associated minerals is based entirely on the 

microscopic observations made on the slides.

The metallic associaets have already been given. Besides quartz, 

three nonmetallic minerals, none of which could be identified, were 

observed with the koechlinite. It does not necessarily follow, however, that any of them are new. For 

convenience o'f description these three 

associated minerals are called unknown 

A, B, and C, respectively.

Unknown mineral A was observed in 

about half a dozen pieces. Nearly all 

of them have an irregular outline which 

in small part is bounded by cleavage 

directions. A single fragment showed 

one apparently straight outline, bisecting 

the cleavage lines. The cleavage is very 

prominent and permeates the entire 

mineral, breaking up the fragment into 

numerous rhombs with an acute angle of 

about 52°. Figure 2 is a diagrammatic 

sketch of two such fragments. The 

color of the transparent and isotropic mineral is a light to dark brown. 

No interference figure could be obtained from any of the fragments.

FIGURE 3. Sketch of unknown mineral 

B associated with koechlinite.
KOECHLUSITTE (BISMUTH MOLYBDATE), A NEW MINEEAL. 13

FIGURE 4. Sketch of unknown mineral C associated with koechHnite.

Unknown mineral B is abundant as small mica-like scales, which 

for the most part are devoid of any regular outline, although here 

and there are scales that have a more or less regular boundary. 

The most perfect of these have a hexagonal shape and extinguish parallel to one pair of sides. One of the larger fragments observed 

is sketched in figure 3. The two 

straight sides at the top are inclined to each other at an angle of 

about 57°, and each was inclined 

about 62° to the extinction. The 

mineral is colorless and transparent 

and has a moderate to low double 

refraction. The parallel markings shown are parallel to the two 

straight sides. The axial angle is 

small and negative.

Unknown mineral C was observed about a dozen times, either 

as well-formed isolated crystals or 

intergrown with koechlinite. The crystals have the same shape and 

orientation as those of koechlinite and consist of the macropinacoid 

{100} large, bounded by faces of the unit pyramid {111}. The crystals 

of unknown mineral C are at once distinguished from koechlinite by

their lack of color and much 

lower double refraction. The 

very high index of refraction 

and the comparative thickness 

gives these crystals a very broact 

border of black, due to total reflection, as shown in figures 4 

and 5. They have a more constant habit than koechlinite, 

nearly all of them being about 

twice as long as wide. The vertical striations are not prominent, and one crystal showed 

vertical lines of minute inclusions, as shown in figure 4, which 

well illustrates the shape and appearance of the crystals. The crystals of unknown mineral C are twinned similarly to those of koechlinite. 

One crystal, between crossed nicols, showed a complex twinning (as 

illustrated in fig. 5) very similar in kind to that exhibited by koechlinite and shown in figure 20 (p. 24).

The crystals of unknown mineral C have a low birefringence, the interference colors being generally of the first order, even on the thicker 

crystals, whereas the thinnest cleavage plates of koechlinite seldom

FIGUKE 5. Sketch of complex twin of unknown mineral C associated with koechlinite.
14 MINEKALOGIC NOTES SEEIES 3.

show colors below the third order. The axial plane of unknown mineral C is parallel to c{001}, as in koechlinite, and the axial angle is 

very large, 2E being greater than the field of the microscope.

Koechlinite is clearly a secondary mineral formed in the cavities of 

the quartz rock by the reaction of different solutions, one containing 

bismuth and the other molybdenum. Some of the cavities lined 

with quartz crystals are free from any other mineral.

CRYSTALLOGRAPHY.

GENERAL CHARACTER OF CRYSTALS.

All the koechlinite occurs in distinct crystals. Eight of these were 

measured on the goniometer, but in addition a large number were

examined under the microscope, for with 

the knowledge obtained from the goniometer measurements the combinations 

of the crystals seen under the microscope 

could be easily deciphered. The crystals 

measured average about 0.5 millimeter in 

greatest length. The crystals on the 

specimens range in size from minute ones 

to those having a length of about 1 millimeter. The width of the crystals is either 

equal to or about half the length, and the 

third dimension is very small, as the crysFIGURE 6. Common appearance of crys- . -, 11 ,1 i.ri i i . tais of koechlinite, simulating rectangu- tals are all very thin and tabular in habit.

iar plates. Forms: a{ ioo}, p{ in >. The combinations observed on many 

of the crystals are simple, and in fact most of the crystals show 

only two or three forms. The general appearance of the crystals is 

shown in figure 6, and as the angle 

between the opposite pyramids is 

nearly 90°, the crystals appear as 

rectangular plates with diagonal 

striations. A marked feature of 

these crystals which heightens the 

impression that they are rectangular 

plates is a tendency for distortion 

in that the crystal is elongated parallel to one of the intersection directions of a{100} with p{ll\}, thus 

producing the^ effect shown in figure 7. 

Apparently the crystals should be 

so oriented that the edges a{100}: 

2>{111} are vertical and horizontal, but the direction of the striations 

on a{100} shows the true position, which is verified by the angle 

measurements. The crystals are both simple and twinned.

FIGUKE 7. Distorted crystal of koechlinite, elongated parallel to one of the intersected directions of a{ 100} with p{ 111}.
KOECHLINTTE (BISMUTH MOLYBDATE), A' NEW MINERAL. 15

CALCULATION OF ELEMENTS.

The crystals of koechlinite are orthorhombic, and the measurements of the unit pyramid are utilized for the calculation of the 

elements. The prism zone being vertically striated, the crystals 

were readily adjusted in polar position, and measured on the twocircle goniometer. The value for v0 was found by averaging the 

readings on a{100} and the theoretic readings on &{010} obtained by 

averaging the corresponding pairs of v readings of the unit pyramids 

{111}. The signals reflected from the large faces of a{100} were 

sharp and bright, whereas those from the very narrow pyramid faces 

were mostly faint and not very distinct. The measurements on five 

crystals show fairly good agreement, though future measurements of 

larger and better crystals would doubtless yield more accurate 

results. The values obtained are as follows:

Measurements of unit pyramid.

Crystal 1.

4>

o /

4542 

45 27 

45 26 

45 38

P

o /:!

55 02 

54 55 

55 08 

55 21

Crystal 2.

0

o /

45 40 

45 42 

45 27 

45 50

p

0 /

55 07 

55 10 

55 01 

55 08

Crystal 5.

<f>

o /

45 26 

45 47 

45 49 

45 36

p

o /

55 00 

55 05 

55 09 

55 05

Crystal 7.

0

o /

45 20 

45 51

45 58 

45 48

P

o /

55 59 

55 04 

55 10 

54 33

Crystal 8.

0

0 /

46 10 

45 48 

47 34 

45 03

P

o /

54 58 

.54 59 

54 59 

55 20

From the average of these measurements the values p0 = 1.0258, 

#0 = 1.0026, and the axial ratio a : I : c = 0.9774 : 1 : 1.0026 are 

obtained. The axial ratio of koechlinite is very close to the 1:1:1 

ratio of the isometric system, but in its tabular habit and perfect 

cleavage parallel to a {100}, the mineral differs greatly from one of 

isometric character.

FORMS AND ANGLES.

A total of 13 forms was determined on the crystals of koechlinite. 

These are as follows:

Pinacoids: 6{010}, a{100}.

Prisms: Z{130}, n{230}, j{450}, m{110}, fc{430}, £-{210}.

Pyramids: p{lll}, r{322}, s{533}, tt{131}, z{362}.
16 MINERALOGIC NOTES SERIES 3.

The average of the measured angles as compared with the calculated values is shown in the following list:

Measured and calculated angles of Jcoechlinite.

No.

1

2

3

4

5

6

7

8

9

10

11

12

13

Letter.

6

a

I

n

3

m

h

k

P

r

s

u

X

Symbol.

Goldschmidt.

Ooo

ooO

oo3

oo*

«4

oo

*°°

2oo

1

11

fl

13

|3

Miller.

010

100

130

230

450

110

430

210

111

322

533

131

362

Measured.

0

0 /

0 29

90 00

17 46

34 55

39 20

44 09

53 10

65 07

45 39

55 56

58 55

18 22

27 13

P

0 /

90 00

90 00

90 00

90 00

90 00

90 00

90 00

90 00

55 07

60 54

62 55

72 09

73 21

Calculated.

.*

0 /

0 00

90 00

18 50

35 32

39 18

45 39

53 45

63 57

45 39

56 55

59 37

18 50

27 06

P

0 /

90 00

90 00

90 00

90 00

90 00

90 00

90 00

90 00

55 07

61 26

63 14

72 32

73 31

a {100}. The macropinacoid, parallel to which there is a good 

cleavage, is the dominant form of koechlinite, and all the crystals 

are tabular parallel to this form. The faces are vertically striated. 

Nearest the prism faces the striations become prominent enough to 

round the face and to give a blurred distended reflection, but the 

larger part of the face gives a bright and clear reflection. The 

macropinaooid and the unit pyramid are the only two forms which 

were observed on all the crystals examined.

& {010}. The brachypinacoid was observed on four crystals, .as 

small and narrow faces. The reflections were very poor and the <£ 

measurements gave -O007', + 00 22', + 2 006',-a0 27', instead of 0°00'. 

On crystal 8 the face was uneven and vertically striated.

Z {130}. The single face of this form is a short line face giving a 

very poor reflection.

n {230}. The prism n is the third most prominent form, and 

although it was observed on only five of the eight measured crystals, 

it was determined to be present on many of the crystals studied 

microscopically. In fact, it is the dominant prism form of the 

mineral, many crystals showing only the three forms a, p, n. (Compare figs. 12, 13, and 14, on. pp. 21, 22.) The measurements of this 

form are as follows:
KOECHLINITE (BISMUTH MOIA'BDATE), A NEW MINERAL. 17

Measurements of (j> angle ofn{230}.

Crystal No.

 V

1....................... 1. ...................... 1. ......................

2.......................

5.......................

5.......................

6.......................

6.......................

6.......................

7.......................

7....................:..

Size.

Minute.........

.....do.........

.....do.........

line face. 

Line face ......

.....do.........

.....do.........

.....do.........

.....do.........

.....do.........

Broad line face.

Reflection.

Glimmer o....

.....do.......

.....do.......

Poor. ........

Glimmer «....

.....do.......

.....do.......

.....do.......

Poor.........

Glimmer o....

Poor.........

Measured.

0 /

34 18

34 50

33 03

36 22

36 04

36 09

37 42

33 03

35 00

33 13

34 26

Calculated.

0 /

35 32

35 32

35 32

35 32

35 32

35 32

35 32

35 32

35 32

35 32

35 32

a Measured by position of brightest illumination, which was generally only a glimmer.

j {450}. The two observed faces of j are mere line faces giving an 

exceedingly faint reflection. The measured <£ angles (39°22' and 

39° 18') agree well with each other and with the calculated angle

(39°18/).

m {110}. The unit prism was seen only once as a line face giving 

a poor reflection.

Ji {430}. The four faces of Ji, observed on as many crystals, are 

all line faces giving poor reflections. The measured <J> angles are 

51°41', 52°33', 53°41', 54°46' (calculated 53°45').

fc {210}. The single face of Tc is a line face yielding only a glimmer 

of light.

p {111}. The unit pyramid is the dominant terminal form, and is 

present on all crystals examined. It is as a rule long and narrow, 

rarely becoming broader, whereby the whole crystal becomes thicker. 

It is striated in the zone (100): (111): (Til): (TOO).

r{322}. This pyramid occurs as a very narrow line face between a 

and p. The reflections were considerably distended on account of 

the minute width of the faces, and they could not be measured with 

great accuracy. The form was definitely determined on only one 

crystal (No. 2) but is probably present on some of the other crystals. 

The measured angles are as follows:

</>meas. = 56°33' <£calc. = 56°55'. pmeas. = 61°10' pcalc. = 61°26'.

s{533}. The faces of s, like those of r, are the merest line faces, and 

then* measurements are likewise not very accurate. The form was 

identified positively on four crystals but may be present on several 

more. The two forms r{322} and s{533} were not both determined 

on the same crystal. The measurements for s are given in the following table:

97888° Bull. 610 16 2
18 MINERALOGIC NOTES SERIES 3. 

Measurements of s{533}.

Crystal No.

5.....................................

5........:............................

5.....................................

5.....................................

7.....................................

8.....................................

Measured.

 *

0

59 

58 

58 

59 

58 

58

09 

52 

48 

23

57 

22

P

o

63 

62 

62 

62 

62 

62

32 

50 

50 

50 

37 

50

Calculated.

*

o

59 

59 

59 

59 

59 

59

37 

37 

37 

37 

37 

37

P

o

63 

63 

63 

63 

63 

63

14 

14 

14 

14 

14 

14

The following interfacial a'ngles were measured on crystal 3. Only 

a {100} gave good reflections.

Interfacial angles measured on crystal 3 ofkoechlinite.

<!' 

a'

a7>-

Angle.

p (100) : (111) ............................................

/-^(lOO) : (111) ...........................................

p"- (100): (III). .........................................

s=(100) : (533) ............................................

S-mi):(533)... ..........................................

.

Measured.

o /

54 27

54 10

54 00

54 05

40 08

13 52

Calculated.

o /

54 05

54 05

54 05

54 05

39 38

14 27

11 28

and x{362}. These two pyramids were measured only once, 

both forms showing a well-developed face on crystal 7 (fig. 28, p. 26). 

It is believed that additional occurrences of these forms were seen on 

other crystals under the microscope, but they could not be positively 

identified. On crystal 7 the face of ^(131), although striated somewhat in the zone u a, gave a fan- reflection. The face of z(362) is a 

line face between u and a and gave a poor reflection. The measured 

and calculated angles (given on p. 16) agree well. 

From their occurrence the thirteen forms may be grouped as follows:

Common forms: a{100}, p{lll}, n{230}.

Less common forms: 6{010}, A{430}, ;'{450}, s{533}.

Rare forms: m{110}, Z{130}, £{210}, r{322}, «{131}, z{362}.
KOECHLINITE (BISMUTH MOLYBDATE), A NEW MINERAL. 19 

COMBINATIONS.

The combinations observed on the eight crystals measured are 

shown in the following table:

Combinations of koechlinite crystals.

Form.

o{100}..........

fe{010}. .........

Z{130}. .........

n{230}..........

^{450}. ..........

m{110}..........

AJ430}..........

£{210}..........

p{lll}..........

r{322}... .......

«{533}..........

M{131}..........

z{362}..........

Crystal No.

1

a 

b

n

h

P

2

a

n

P

r

3

a

P

s

4

a 

b

P

5

a

n

fc

P

s

6

a

I

n

h

P

7

a 

b

n 

j

h

P

s

8

a 

b

j

h

P

s

Percentage of occurrence.

100 

50 

13 

63 

25 

13 

50 

13 

100 

13 

50 

13 

13

Illustrated in 

figures 

6, 7, 11-14, 21, 23-29. 

11, 28.

11-14, 21, 23-29.

6, 7, 11-14, 21, 23-29. 

26. 

25, 28.

28. 

28.

The common combinations observed on many crystals not measured are a p, a n p, a & n p, with occasional modifications due to 

rarer forms such as probably li and s.

ZONAL RELATIONS AND MARKINGS.

«

All the 13 forms of koechlinite lie in three zones, the prism zone, 

with & I n j m Ji Ic a; the pyramid zone ra p with m s r p; and the 

pyramid zone a x u, as shown in figure 8. The three zones above 

named are all striated, and the intensity of the striation varies 

directly as the number of forms in that zone.

In addition to the regular striations there are markings of two 

other kinds on some of the crystals of koechlinite which deserve 

brief mention. Both kinds were observed under the microscope on 

the a {100} faces.

The surfaces of a few of the crystals are crowded with a mass of 

acute-angled markings, nearly equal in angle and nearly parallel. 

The acute points all face in one direction, as shown in the freehand sketch reproduced hi figure 9. The symmetry of such markings indicates hemimorphism.

The markings of the second kind consist of straight lines, forming 

regular closed figures, one side of which is parallel to the vertical 

axis and the other side parallel to the intersection edge a p (shown 

in fig. 10). The vast majority of the linos parallel to the intersection edge a p are in one direction. In the drawing shown in
20 MINEKALOGIC NOTES SERIES 3.

FIGURE 8. Gnomonic projection of koechlinite forms.

FIGURE 9. FIGURE 10. 

FIGURE 9. Acute-angled markings on o{100}, koechlinite.

FIGURE 10. Regular markings on a{\00}, koechlinite. Note excessive development of lines parallel to 

intersection a(100)-p(lll) over those parallel to intersection of a(100)-p'(lll).
KOECHLINITE (BISMUTH MOLYBDATE), A NEW MINERAL. 21

figure 10 only two of these lines are parallel to the edge (lOO)-(Hl), 

whereas, as drawn, there are 31 lines parallel to the edge (100)- 

(111). The string of bubbles shown in the lower part of the figure 

are also approximately parallel to the edge (lOO)-(lll). Such a 

preference to one of two supposedly equal directions naturally

FIGURE ll. FIGURE 12.

FIGURE 11. Square tabular habit of koechlinite (crystal 1). Forms: a{100}, b{010>, w{230}, p{lU}. 

FIGURE 12. Stout tabular crystal of koechlinite. Forms: o{100>, m{230>, p{lll}.

suggests hemimorphic development. The markings shown in figure 

9 suggest hemimorphism in the direction of ftie vertical axis, whereas 

those shown in figure 10 suggest hemimorphism in the direction of 

the edge a p, which is inclined 45° to the vertical axis. The peculiarly distorted crystals (shown in fig. 7) in which the crystals are 

elongated parallel to one of the intersection 

edges of a and p also suggest the possibility 

of a hemimorphic development. Opposed to 

such an idea, however, are the holohedral distribution of the faces as determined on many 

crystals and the lack of conclusive evidence 

from the etch figures.

HABITS.

All the crystals of koechlinite are tabular 

in habit, but the thin tablets vary in shape 

from square ones to elongated ones, as already 

shown in figures 6 and 7.

The square tablets are very abundant and 

either consist of only the two forms a{100} and p{lll} (see fig. 6, 

p. 14) or else-have two of their edges modified by forms of the prism 

zone, as for example the first crystal measured, shown in figure 11. 

A few crystals are not so thin as this one, and these slightly stouter 

crystals are also somewhat elongated parallel to the vertical axis. 

Such crystals were observed only under the microscope, but their

FIGURE 13. Intermediate habit 

of koechlinite.
22 MINERALOGIC NOTES SERIES 3.

combination could be determined to be a n p, with possibly other 

forms present as line faces that would not modify the habit of the 

crystals. The approximate relative thickness and size of three

such crystals, chosen to show the

variation in habit,

are reproduced in

figures 12, 13,

and 14. 

Included in

larger square

crystals are a few

small prismatic

crystals which are

an extreme exFIQURE 14. ample of elonga- 

£S?"5!l* tionpmdlel to the 

gated parallel vertical axis, as

to the vertical i n FIGURE 15. Small prismatic crystals of koechlinite 

axfe Shown U1 IlgUre included in a larger square one.

15. Such crystals

were not observed by themselves, but as inclusions in larger ones 

they are not rare. They have a characteristic platy structure that 

was not seen on the individual -short prismatic crystals (fig. 14). 

Figure 15 shows a sketch of a number of such minute prismatic crys-

\

\

\

\

\

N/

FIGURE 16. FIGURE 17.

FIGURE 16. Common extent of elongation parallel to edge o(100) -p(lll) of crystal of koechlinite. 

FIGURE 17. Extreme case of distorted elongation parallel to edge a p noted on crystal of koechlinite.

tals included in a larger square one. Some of these included prismatic crystals may be in twin position, either to each other or to 

their larger host, but not all of them are thus regularly oriented.

Some of the tabular crystals are grouped together in parallel position 

and the individual crystals show neither exactly the same habit nor the 

same combination, although in general they are very similar. One 

such group, as it appeared under the microscope, is reproduced in 

figure 1 (p. 11). In this group the central crystal is decidedly elon-
KOECHLINITE (BISMUTH MOLYBDATE), A NEW MINERAL. 23

gated parallel to the vertical axis, whereas the one on the right is 

nearly square.

' In addition to the vertical extension of the prismatic crystals (figs. 

13 and 14), the elongation parallel to one set of intersection edges of 

the unit pyramid p with the macropinacoid a is prominently developed. An example of such elongation has already been shown in 

figure 7 (p. 14), but the most abundant of such distortions occur 

where the elongation is about twice the width of the crystal, as shown 

in figure 16.

It is to be noted that contact twins of square habit will yield a crystal of similar shape to that shown in figure 16, but the difference in 

direction of the striations on a {100} at once differentiates these twin 

crystals (compare fig. 18) .from the simple ones. The extreme observed distortion in a single crystal along the edge a p is shown in 

figure 17. The elongation of this crystal is 11 times its width.

TWINNING.

Twinning is common for koechlinite, and both contact and penetration twins occur. The twinning plane is the unit brachydome 

{Oil } , a form not observed on any of the crystals. By such twinning 

the faces of the macropinacoid a remain in the same 

plane, and as the angle 

(010) : (Oil) is 44° 56', the 

angle between the twinned"1 

and untwinhed adjacent 

faces of (Oil) is only 0° 08', 

being thus so small as to be 

hardly detectable under 

the microscope. Consequently the different parts 

of a twin crystal extinguish 

so nearly the same that no 

difference can be seen under 

the microscope. In fact, in 

thin cleavage pieces a twin x/

Crvstal can not be told from FlQUKE 18.-Contact twin of koechlinite. Composition face 

. , , , . , . is{011>. Compare figure 16.

a simple one. On the thicker

crystals a slight difference in shade of color, due to the pleochroism, 

can be noticed for the parts of a twin crystal. If the natural f aces of 

a {100} are present, the striations on it at once furnish a satisfactory 

means of deciphering the twinning structure.

In the contact twins the composition face is either {011} or {100}. 

If the twinning plane is the composition face, then the twinned crystal resembles in shape a simple crystal elongated parallel to the edge 

a p (as shown in fig. 16), but the difference in striations on a{100}
24 MINERALOGIC NOTES SERIES 3.

suffices to differentiate them. Twins in which the composition face 

is a{ 100} are rare. These two varieties of contact twins are shown in 

figures 18 and 19.

By a repeated or synthetic twinning with {011} as composition 

face, a complex crystal may be built up. Figure 20 represents a 

cleavage piece of such a twinned koechlinite observed under the 

microscope. In the absence of the guiding striations on a{100} it 

is impossible to determine whether this is a repeated twin with 

{Oil} as composition face or a simple crystal with cleavage or parting 

lines parallel to ^{111} As no such cleavage or parting lines have 

been found on the mineral, however, it is more reasonable to refer the 

observed structure to repeated twinning.

A symmetrically twinned fourling, with {011} as composition face, 

would yield a regular figure, in which tfye parts would only lack a few

minutes of forming a theoretically 

closed solid, such as is shown in 

figure 21. This sketch explains the 

structure of the penetration twins 

described in the following para-

\

Y

\/

FIGURE 19. FIGURE 20.

FlQUBE 19. Contact twin of koechllnite. Composition face is o{ 100 >.

FIQUBE 20. Cleavage piece of koechlinite, probably a polysynthetic twin with {011} as composition face.

graphs. An example of a twin, with {011} as composition face, is 

afforded by crystal 6, drawn in clinographic projection (fig. 29, p. 27).

Crystal 3 is an example of a crystal in which the two parts of a 

twin do not have the same combination. It is shown as it appeared 

under the microscope in figure 22.

The larger individual, elongated parallel to the edge a p, has the 

combination a p, whereas the smaller individual shows a prominent 

prism zone development. (Compare fig. 1, p. 11.)

The penetration twins are probably abundant, but unless the 

striated macropinacoid is present their detection is very difficult. 

Such a crystal, observed under the microscope, is shown in clinographic projection in figure 23.

A somewhat similar condition is presented by the imperfect 

crystal shown in figure 24 in orthographic projection on a {100}. 

The central part of the crystal (I) is in normal position, and III may
' KOECHLTNITE (BISMUTH MOLYBDATE), A NEW MINERAL. 25

be considered as belonging to the untwinned central part (I). Part 

II, in twin position to I, lies between it and III. Part III may nevertheless be just as well considered as twinned to II, even though this 

brings it into parallel position with I. The crystal is thus similar to

the one just described and 

illustrated in figure 23. By 

referring back to the theoretical twin shown in figure 21, it

FIGURE 21. FIGURE 22.

FIGURE 21. A theoretical fourling of koechlinite. Orthographic projection on o{100}. Forms: a{100},

n{230},p{m}. 

FIGURE 22. Crystal 3, koechlinite. Contact twin with {011} as composition face. The smaller individual

has a different combination of forms from the larger one.

is seen that this can be interpreted in two ways. First I and III 

(fig. 21) may be considered as the same untwinned unit, to which II 

and IV (as one unit) are twinned. A preferable explanation, howFiGURE 23. FIGURE 24.

FIGURE 23. Clinographic projection of a penetration twin of koechlinite. The clear field (II) is free from 

strlations, and its orientation is not known. The lower quadrant (III) is twinned on the upper one 

(I), and the remaining one (IV) may be considered as twinned on III, although it is in parallel position 

with the untwinned I. The continuity of the striations of I and IV would seem to indicate, however/ 

that IV is not twinned but belongs inherently to I. Forms: a{100}, w{230}, p{lll}.

FIGURE 24. Orthographic projection on <i{100} of a penetration twin of koechlinite. Part II is twinned 

on I, and apparently III is twinned on II, yet III and I are to parallel position. Compare figure 23. 

Forms: o{ 100}, n{230}, p{ 111}.

ever, is that the drawing represents a fourling, in which I is twinned 

on IV, II on I, and III on II. A similar explanation is believed to 

hold for the crystals shown in figures 23 and 24.
MINEBALOGJC NOTES SEEIES 3. 

MEASURED CRYSTALS.

Crystal 1, representing one of the square habit, with a {100}, 

n{230}, &{010}, and #{111}, is shown in figure 11 (p. 21). The 

form ^.{430} is not shown in the drawing.

FlGUKE.25. FIGURE 26.

FIGURE 25. Crystal 5, koechlinite. Forms: <z{100>, n{230}, p{Hl>, s{533}. 

FIGURE 26. Crystal 2, koechlinite. Forms: <z{100}, n{230>, p{lll>, r<322}.

Crystal 5 (fig. 25) represents one of similar habit, showing the 

line faces of s{533}. The rare prism £{210}, not shown in the 

figure, was observed only.on this crystal.

FIGURE 27. FIGURE 28.

FIGURE 27. Crystal 4, koechlinite. Forms: o{ 100 }, p{ 111}, rz{230}.

FIGURE 28. Crystal 7, koechlinite. Forms: <z{100}, 6{010}, m{230>, p{lll}, s{533}, w{131>, z{362}.

Crystal 2 (fig. 26) is one of the distorted habit, elongated parallel 

to the edge a p. The pyramid r{322} is present with p{lll}.

Crystal 4 (fig. 27) is interesting as showing a twinned portion of 

the crystal with a face of n{230} in the position of a macrodome.
KOECHLINITE (BISMUTH MOLYBDATE), A NEW MINERAL. 27

The angle a{100}: n{230} (54° 280 is close to the angle a{100}- 

(203) (56° 10').

Crystal 7 (fig. 28) is the only one on which the two pyramids 

u{l31] and x{362} were definitely determined. In addition to the 

forms shown in the drawing, 

the two prisms ?'{450} and 

7i{430} were observed on this 

crystal.

Crystal 6 is shown in orthographic projection on a{100} 

in figure 29. The crystal is a 

well-developed contact twin with 

an irregular- composition face, part 

of which appears to be &{010}

in the upper part of the drawing,

but which, is more Hkely rather n<JUKE 29._Crystal 6> ^ orthographic

irregular. In addition to the Projection on o{100} of twin crystal. Forms:o{100>,

forms shown in figure 29, faces n< 230 >' p{m>-

of Z{130}, m{110}, and {430} were determined on this crystal.

ETCH FIGURES.

The symmetry of the markings observed on some of the crystals, 

coupled with the prominent distortion along one set of intersection

edges of a, and p, strongly suggested a deviation from holohedral symmetry, and the concealing twinning might give 

the distribution of the faces an 

apparently higher grade of symmetry than the mineral in reality possessed. Recourse was 

therefore had to the effect of 

etching by dilute hydrochloric 

acid, and very interesting results were obtained, although 

the evidence is of an apparently conflicting nature and is 

thought not to justify decisive 

conclusions.

Minute pits or etch figures are produced on the a{100} faces of 

koechlinite in a few minutes when a crystal is immersed in cold dilute 

hydrochloric acid (about 1:5). If the acid is drained off and weaker

FIGURE 30. First stage of etch figures produced on a 

symmetrically etched crystal of koechlinite.
28 MINEBALOGIO NOTES SERIES 3.

acid substituted the progress of the etching can be retarded and regulated. The effects produced can be readily studied by covering the 

crystal (on a glass slide) with a cover glass which, by its own weight,

removes all but a film of 

solution from the a faces. 

The cover glass is then removed and fresh acid 

added to the crystal whenever it is desired to have 

the process of solution 

continue.

The process of solution 

of the crystal, in hydrochloric acid, as observed, 

was not continuous, nor 

were the conditions constant, as the concentration 

^ of the acid, for example, 

FIGURE si. First stage of etch figures produced on a was changed a number of

; winned crystal of koechlinite. times It is not believed,

however, that these interruptions are the cause of the apparent inconsistent facts observed.

The first etch figures produced are triangular and rectangular in 

shape. The triangular ones are symmetrical to a horizontal plane 

but not to a vertical plane. Moreover, some face to the right and 

others to the left. The rectangular figures may be conceived 

as a combination of right and 

left triangular ones. The distribution of these three kinds of 

figures does not necessarily

bear any relation to the

crystal itself. Each kind has

been observed scattered over

part of the entire crystal. An

exceptionally symmetrically

etched crystal is sketched in

figure 30. As can readily be

seen, the right-facing triangles

are all on one side and the

left-facing triangles are all on

the other side. The rectangular figures, which may be built up of

right and left triangles, occur only in the center.

A twin crystal shows similar etch figures, oriented in position with

the twin part of the entire crystal, as shown in figure 31.

FIGTOE 32. Second stage of etch figures'produced on 

koechlinite after the triangular figures.
KOECHLINITE (BISMUTH MOLYBDATE), A NEW MINEBAL. 29

It is to be specially noted that these triangular etchings parallel 

with one another have an apparent hemimorphic symmetry in the 

direction of the & axis.

A little later etch figures are developed which, .while hemimorphic 

in character, show this hemimorphism not in the direction of the & 

axis, like the triangular figures just described, but in 

the direction of the vertical 

or c axis. These etchfigures 

are sketched in figure 32.

At a still, later period the 

triangular etch figures have 

all developed into rectangular ones and the vertically 

hemimorphic figures into 

hexagonal ones. They are 

shown in figure 33 as they 

were observed on a twin 

crystal. In a number of instances the gradual change 

in shape and symmetry from 

an original hemimorphic 

etch figure to the final rectangular or hexagonal one was continuously observed under the 

microscope, and the changes, as noted, are given in figure 34.

The final effect observed was most remarkable. The remnant of the crystal 

was bounded by sharply rectangular 

lines and its interior was full of similarly

FIGURE 33. Third stage of etch figures produced on a 

twinned crystal of koechlinite. All the figures now have 

holohedral symmetry.

FIGURE 34. FIGURE 35. 

FIGURE 34. Last stage of etch figures produced on koechlinite. Change in shape and symmetry from

figures with an original hemimorphic symmetry (inner outlines) to the final holohedral figures (outer

outlines). 

FIGURE 35. Appearance of a corner of an etched and dissolving crystal of koechlinito.

sharply bounded rectangular holes, and the process of solution of the 

crystal continued in this way until the entire crystal was dissolved. 

The appearance of a corner of the crystal at a given moment is shown 

in figure 35. 
30 MINERALOGIC NOTES SERIES 3.

The final etch figures developed on koechlinite by dilute hydrochloric acid are strictly holohedral in their symmetry, whereas those 

first produced are strongly heinimorphic. Is the symmetry of the 

figures first produced to be regarded as having no bearing on the 

symmetry of the mineral itself, or are the later holohedral etchings to 

be considered as twinned hemimorphic figures, thus ascribing to the 

mineral an intricate polysynthetic twinning? (See p. 21.)

The following observed facts seem to lend support to the idea of 

hemimorphic symmetry for koechlinite: The hemimorphic character 

of the markings observed on a {100}, the common distortion in unFlGURE 36. FIGURE 37.

FIGURE 36. Intergrowth of unknown mineral C with koechlinite. The areas occupied by koechlinite

are marked K. 

FIGURE 37. Intergrowth of unknown mineral C with koechlinite (K).

twinned crystals along one pair of edges a p; the unequal size of the 

different faces of a form on the same crystal; and the hemimorphic 

symmetry of the artificially produced etch figures, as shown in figures 

30, 31, and 32.

Opposed to the idea of hemimorphic symmetry of the crystals are 

the facts that the final etch figures are strictly holohedral in their 

symmetry and that the distribution of faces on the crystals favors 

holohedral symmetry, although it must be said that the measured 

crystals were not developed perfectly enough nor were the terminal 

faces sufficiently large to warrant a definite conclusion.
KOECHLINITE (BISMUTH MOLYBDATE), A NEW MINERAL. 31 

INTERGROWTHS.

Intergrowths of koechlinite' with the colorless mineral described on 

page 13 as unknown mineral C were observed several times. The two 

minerals are, so far as the observations go, in parallel untwinned 

position, the striations being parallel. The contact line is straight 

in some intergrowths and very irregular in others. In the typical 

example of an intergrowth shown in figure 36 the main mass of the 

crystal consists of the colorless unknown mineral C and there are 

three smaller portions of koechlinite.

In the best developed example of this intergrowth, reproduced in 

figure 37, the main mass of the crystal consists .of unknown mineral C 

twinned, and each twin portion contains intergrown koechlinite.

RELATION TO OTHER MINERALS.

There are no known minerals with which koechlinite shows a close 

analogy in type of chemical formula. The mineral jeremejevite has 

the formula A1203 .B203 , which, in type, conforms to the formula of 

koechlinite, but jeremejevite is hexagonal, although the so-called 

eichwaldite, intergrown with jeremejevite, has been interpreted as 

orthorhombic, with axes which, if doubled, are not far from those of 

koechlinite:

Eichwaldite, £o:6:«c=1.1046:l:1.0868. 

Koechlinite, a:fc:c=0.9774:l:1.0026.

A number of hydrous minerals are analogous to koechlinite in 

composition except for the water, but crystallographically they seem 

to show no close relation to koechlinite. These hydrous minerals are 

listed below.

Koechlinite.........Bi203 .Mo03 .....................Orthorhombic.

Montanite..........Bi203 .Te03 .2H20.

Ferritungstite....... Fe203 . W03 . 6H20............... Hexagonal.

Utahite............. Fe203 .S03 .4H20?............... Hexagonal.

Planoferrite ........Fe203 .S03 .15H20...............Orthorhombic.

Aluminite........... A1203 .S03 .9H20.

Attention may be called to a furnace product which in composition is similar in type to koechlinite but of which unfortunately few 

crystallographic data seem to be available. This is a crystalline 

compound described by Pearce l and having, according to his analysis, the composition expressed by the formula As203 .S03 . The crystallographic data are too meager to warrant any conclusion as to 

the relation of the compound to koechlinite. Pearce describes it 

as follows:

The usual condition of the material was small spear-shaped crystals of a pearly 

luster. * * * These crystals were in many cases more than 1 inch in size and

1 Pearce, Richard, On a remarkable crystalline compound of arsenious and sulphuric acids: Colorado 

Sci. Soc. Proc., vol. 3, p. 255,1888-1890.
32 MINERALOGIC NOTES SERIES 3.

beautifully modified. The form'will, in all probability, be found to be monoclinic. 

They are semitransparent to transparent; color, white; cleavage, perfect; luster, 

somewhat pearly and adamantine.

PHYSICAL PROPERTIES.

The cleavage of koechlinite is perfect parallel to the macropinacoid 

a{100}. A second imperfect cleavage seems to exist after some 

other form in the prism zone. The crystals are very brittle, breaking readily under the slighest pressure. The extreme thinness of 

most of the crystals naturally increases their tendency to break. 

The hardness and density are not known.

OPTICAL PROPERTIES.

The body color of the crystals is greenish yellow and corresponds 

to "oil-yellow" on Plate V of Ridgway's "Color standards.."1 

When heated but not fused the greenish-yellow crystals become 

brown, but on cooling they revert to their original color. The 

fused mineral becomes dark brown and on cooling suddenly changes 

to a very pale yellow which becomes white when cold. The luster 

is vitreous, slightly adamantine. The streak is pale greenish yellow. 

The crystals are transparent, the transmitted color being greenish 

yellow, like the body color.

A bisectrix emerges normal to the macropinacoid, and the trace 

of the axial plane is normal to the striations and therefore parallel 

to c{001}. The axial angle seen on a {100} is very large and the 

obtuse bisectrix probably emerges normal to a{100}. On this 

assumption the orientation of the mineral is as follows:

a axis = Z

& axis = X

c axis = Y

If the a axis is the direction of the obtuse bisectrix, then the mineral 

is negative.

The refractive indices are very high. Mr. Esper S. Larsen kindly 

determined the index by the embedding method 2 and found /3Li = 2.55 

with an estimated birefringence of about 0.1.

The crystals have a very slight pleochroism, observable only on 

the thicker ones. As observed on a{100}, the mineral is not pleochroic, except that on the thicker crystals the color is slightly deeper 

normal to the striations than parallel to the striations.

1 Ridgway, Robert, Color standards and color nomenclature, Washington, 1912.

2 Merwin, H. E., and Larsen, E. S., Mixtures of amorphous sulphur and selenium as immersion media 

for the determination of high refractive indices with the microscope: Am. Jour. Sci., 4th ser., vol. 34, p. 42, 

1912.
KOECHLINITE (BISMUTH MOLYBDATE), A NEW MINERAL. 33 

CHEMICAL PROPERTIES. 

PYBOGNOSTICS.

The mineral fuses readily in a closed tube without giving off water 

or any sublimate. The color changes are described on page 32. 

The crystals dissolve readily in HC1 but not so readily in HNO3 . 

The deep-blue color of a lower oxide of molybdenum is readily obtained by heating the mineral with concentrated H2S04 and evaporating nearly to dryness in a white porcelain crucible. The bismuth 

iodide sublimate on charcoal is strong and characteristic.

QUANTITATIVE COMPOSITION.

The material analyzed was nearly free from inclusions except for 

admixed quartz. The three unknown minerals already described 

were present in only minute amounts in the samples analyzed, as

the crystals of koechlinite were separately picked out of the material 

removed from the cavities. The mineral was at first taken to be 

Bi203, and as the first analysis totaled only 78.2 per cent, it was 

thought that a mistake had been made in the determination of 

bismuth. On a second sample a determination of bismuth gave 

the same result. As each analysis totaled less than 100 per cent, it 

was evident that an unrecognized constituent was present. Nearly 

all the remaining material was sacrificed in the determination of 

this unknown constituent, which was finally identified as molybdenum. 

Another specimen of the mineral had then to be utilized to obtain 

material for a quantitative determination of the molybdenum. 

The absence of the common bases and of any sulphate, phosphate, 

carbonate, borate, or tungstate radicle was qualitatively determined. The results obtained are shown below.

Analyses of koechlinite.

Weight of sample. ................... .grain . .

Bi203 . ....................................

Mo03 . .....................................

1

0. 0925

73.0

Not det.

.2

5.0

78.2

2

0. 1003

51.6

Not det.

34.1

85.7

3

0. 0424

71.9

21.2

5.4

98.5

97888° Bull. 610 16 3 33
34 MINERALOGIC NOTES SERIES 3.

The results are restated below with the admixed quartz deducted, 

being thus reduced to a comparative basis.

Analyses and ratio of koechlinite with quartz deducted.

BiO

Mo203 .-. ....

2

1

76.8

.2

77.0

2

78.3

78.3

3

76.1

22.4

98.5

Average.

77.1

22.4

. .2

99.7

Ratio.

0.166 or 1.00

.155 or .93

Calculated.

76.36

23. 64

100.00

The ratio obtained leads to the formula Bi203 .Mo03 , which can be 

interpreted as bismuthyl molybdate (BiO

DIAGNOSTIC PROPERTIES.

The rectangular crystals with diagonal striations, and particularly 

the elongated distorted crystals, are very characteristic of koechlinite. The absence of water and a qualitative determination of 

bismuth and molybdenum on such crystals would positively identify 

koechlinite.
3^ 

35]

 n 0O mc O j> i" -1 O

i O

0) O

n >

U) c 

	X

ro <C n

r <

m O -f ^

DEVONIAN CARBONIFEROUS
INYOITE AND MEYERHOFFERITE, TWO NEW CALCIUM

BORATES.

RELATION OF MEYERHOFFERITE TO INYOITE.

Two specimens of large crystals having a rhombic shape were collected by Hoyt S. Gale, of the United States Geological Survey, in 

the Death Valley region of California. The fact that tlie mineral was 

a borate was determined, but its specific relation could not be fixed. 

As a preliminary examination failed to identify the specimens with 

any known mineral, they were delivered to the writer, who would 

here express his gratitude to Mr. Gale for his kindness in allowing the 

free use and description of the material.

The large crystals, whose rhombic shape could not be correlated 

with that of any known borate mineral, are opaque and covered with 

small shining, transparent colorless prismatic crystals. A broken surface of the rhombic crystals shows a peculiar reticulated structure 

formed by a white silky fibrous material. The inner structure of the 

latge crystals, as revealed on the broken surfaces, indicated that a 

change had taken place and that the .material now forming the crystals was different from that of which they were originally composed. 

The chemical investigation has confirmed this inference. When one 

of the large crystals was broken up a nucleus of fresh, unaltered 

glassy material was found in its center. By alteration this glassy 

material has changed into the silky fibrous material that now forms 

the bulk of the specimens.

The investigation has shown that both parts of the specimen are 

mineralogically new and that two distinct mineral species are present. 

The glassy material, of which the large rhombic crystals were originally formed, is here named inyoite. It is a hydrous calcium borate 

having the formula 2Ca0.3B203 .13H20. Inyoite alters to a similar 

hydrous calcium borat-e with only seven molecules of water, which is 

here called meyerhofferite. The silky fibrous masses and the shining 

transparent prisms are but two different forms of meyerhofferite. 

Inyoite is therefore the parent mineral which has altered to an aggregate of fibrous and prismatic crystals of secondary meyerhofferite.

The two specimens are shown in Plate I and the forms of the 

secondary meyerhofferite are shown in Plate II.

NOMENCLATURE.

The name inyoite is derived from the locality where the specimens 

were found Inyo County, Cal. The second of the new borates is 

named meyerhofferite after Wilhelm Meyerhoffer, who with J. H.

35
36 MINERALOGIC NOTES SERIES 3.

van't Hoff worked for many years on the composition of the saline 

minerals and so about 1906 came to study the calcium borates. His 

death occurred soon after he began his investigation of these borates and it seems that one of 

the very last of the salts studied by him was the compound 

2Ca0.3B203 -7H20. Now that 

this compound has been found in 

nature as a mineral, it is appropriately named after him.

LOCALITY AND PARAGENESIS.

The exact locality from which 

the specimens were obtained is a 

prospect tunnel in the Mount 

Blanco district, on Furnace 

FIGURE 38. Diagram illustrating crystal forms of inyo- Creek, near Death Valley, Inyo

ite shown in Plate I, A. Tho large crystal on the nminfv pa l Thpfnllnwincr notp«? right was broken up, and glassy unaltered inyoite ^ounlJ»^al- L nel° UOWUlg notes

was obtained from its center. Nearly the entire On the OCCUTreilCe of the minerals

specimen has altered to meyerhofferite. haye been supplied by ^ Gale>

The tunnel was referred to by Mr. Corkill, in charge of developments on 

the property, as the "jewelry shop," because of the display of beautifully crystalline colemanite throughout the greater part of its length. 

The tunnel had penetrated 

what Mr. Gale considered to 

be vein material in a rather 

unusual crystalline form. 

The glassy colemanite lay 

as if crystallized in large 

geodes formed of broad horizontally disposed cavities 

lined with coarsely drusy 

botryoidal bunches, the surfaces of which were completely covered with transparent crystals, with sharp 

edges and corners. In the 

light of the candles used to 

examine the tunnel the reflections from the myriads 

of minute sparkling crystal faces made a very brilliant display.

The two new minerals, inyoite and meyerhofferite, were directly 

associated with this colemanite, the particular specimens collected 

having been pried off in the geode-like cavities.

FIGUBE 39. Diagram illustrating crystal forms of inyoite 

shown in Plate I, B.
U. S. GEOLOGICAL SURVEY BULLETIN 610 PLATE I

A. CRYSTALS OF INYOITE ON MASSIVE MINERAL, NATURAL SIZE.

11. GROUP OF CRYSTALS OF INYOITE, ENLARGED 2 DIAMETERS.
U. S. GEOLOGICAL, SURVEY BULLETIN 610 PLATE I

ALTERATION OF INYOITE TO MEYERHOFFERITE.

A. B, C. Reticulated structure of altered Inyoite. Enlarged 2} diameters. D. Stellate 

groups of crystals of meyerhofferite on the surface of cyrstalsof inyoite. Enlarged about 7 

diameters. . ...
INYOITE AND MEYERHOFFEB^TE, TWO NEW CALCIUM EQUATES. 37

The new minerals are probably of similar origin to the colemanite, 

which is apparently an open-space vein filling, the deposit being in 

fissures cutting shales and sandstones composed largely of tuffaceous 

material, variously referred to in California and Nevada under the 

terms Rosamond series, Esmeralda series, and Siebert "lake beds." 

The veins are closely associated with interbedded volcanic flows, 

which consist of vesicular and locally amygdaloidal basalt, also with 

dikes of similar composition.

The colemanite from these deposits has not yet been mined commercially, and all the properties are still in the prospect stage. The 

Mount Blanco deposit has, however, often been referred to as the 

largest in the United States. Besides colemanite, it contains a very 

considerable quantity of pandermite. It is said that ulexite found 

in the surface soils of the hills below the colemanite vein was originally scraped and worked for borax along with the ulexite deposits in

the valley.

INYOITE.

CRYSTALLOGRAPHY. 

GENERAL CHARACTER OF CRYSTALS.

The large crystals of inyoite, as shown in Plate I, are so grown 

together that only a few angles could be measured on each crystal. 

Moreover, the alteration to meyerhorTerite, particularly the development of stellate groups of prismatic crystals on the surfaces of the 

original inyoite crystals, as shown in Plate II, D, makes it difficult to 

obtain good measurements. A further trouble was found in that the 

only pyramidal form observed on inyoite was narrow and became 

considerably uneven and rounded by the alteration. The discovery 

of better crystals of inyoite, especially if unaltered, would necessitate 

a revision of the crystallographic data here presented.

Six crystals which afforded the most suitable material for measurement were utilized. The crystals are all simple and had the same 

general rhombic habit, as shown in Plate I and figure 40 (p. 38).

CALCULATION OF ELEMENTS.

The crystals are monoclinic, and the elements were calculated from 

the average of the following measurements made with a simple contact goniometer:

Measurements of angles of inyoite.

Angle.

(001):(110).............

(110H110).. ...........

(110 :(111).............

(010):(001).............

1

68°, 67°, 68° 80°

35°

, 2

71°, 70°

79°

35°

3

38°

91°

4

80°

5

80°

37°

6

72°'

Average.

69° 20'

79° 45'

36° 15'
38 MINERALOGIC NOTES SERIES 3.

From the three fundamental angles given, namely, (001) : (110) = 

69° 20', (110) : (1TO) =79° 45', and (110) : (111) =36° 15', the axial 

elements were calculated and found to be as follows:

. a : & : c = 0.9408 : 1 : 0.6665; 0 = 62° 37V

FORMS.

The total number of forms observed is four, as follows:

Pinacoids: c{001}, 6{010}. 

Prism: m{110}. 

Pyramid: p{ 111}.

The basal pinacoid c{001} is the dominant form and the crystals 

are tabular parallel to this form. (Compare fig. 40.) It is also a

direction of cleavage. The 

brachypinacoid is small 

and the least prominent 

form. It was observed on 

about half the crystals examined. The unit prism is 

medium in size and approximately one-third as large 

as the base. The unit pyramid varies in size, even on 

the same crystal, but is always much smaller than the 

prism.

The relative size of the 

different forms and the general tabular habit are shown in figure 40.

FIGURE 40. Inyoite crystal. Forms: c{001>, m{HO},

PHYSICAL PBOPERTIES.

The cleavage of inyoite is good parallel to the basal pinacoid 

c{001}. The lower crystal of the group shown in Plate I, A, shows 

this cleavage, and so do the fresh pieces of inyoite found in the interior 

of the large crystals. The fracture is irregular, and the mineral is 

brittle. The hardness is about 2. The density, determined by 

means of Thoulet solution, is 1.875.

OPTICAL PROPERTIES.

The fresh inyoite is glassy and colorless; the altered material 

(meyerhofferite) is white. The luster is vitreous, and the mineral is 

transparent, although the progressing alteration soon clouds the 

fresh mineral, making it opaque.

The optical orientation could not be determined, as the fresh 

pieces found in the interior of the large altered crystals showed no 

crystal boundaries. Cleavage pieces, parallel to the basal pinacoid,
INYOITE AND MEYERHOFFERITE, TWO NEW CALCIUM BORATES. 39

showed the emergence of an inclined bisectrix. The axial angle is 

large and negative. The angle 2E for sodium light was measured as 

118°. No change in this result could be observed for lithium or 

thallium light. Numerous markings on the base are nearly rectangular, having measured angles between 80° and 90°. These markings 

are apparently parallel to the unit prism and may represent the 

traces/ of an imperfect prismatic cleavage. On the assumption 

that the orientation of these markings on the basal cleavage is 

correct, the optical orientation of inyoite can be stated as follows: 

Axial plane parallel to 6 {010}; acute negative bisectrix obliquely 

emergent on c{001}.

The refractive indices were kindly measured by the immersion 

method by Mr. Esper S. Larsen, who obtained the following results:

a=1.495. 0=1.51. 7 = 1-520. (7-a) =0.025.

CHEMICAL PROPERTIES. 

PYROGNOSTICS.

Heated before the blowpipe, the mineral decrepitates and fuses 

with much intumescence, giving a greenish boron flame. When it is 

heated in a closed tube abundant water is readily given off. The 

mineral is easily soluble in acids.

QUANTITATIVE COMPOSITION.

The transparent glassy material was free from any inclusions of 

other minerals, and the sample analyzed was free from adhering 

meyerhofferite. The total available amount of unaltered inyoite 

was very small, and for the analysis only 0.1037 gram could be 

obtained. The boric acid was not determined, and qualitative 

tests showed the absence of silica, alumina, magnesia, alkalies, 

phosphate, sulphate, carbonate, etc. The analysis-and ratios deduced 

therefrom are as follows:

Analysis and ratios of inyoite.

CaO................... ......

BS08 .....................

H20 below 110°.. ............

H20 above 110°.. ............

Analysis.

20.5

IV7 91

26.1

16.2

100.0

Ratios.

0.366 or 2.02 or 2X1.01. .......

.531 or 2.93 or 3X .98........

1.450 or 8.01 or 8X1.00........

.900 or 4.97 or 5X .99........

Calculated.

20.2

37.8

25.9

16.1

100.0
40 MINERALOGIC NOTES SERIES 3.

The ratios conform closely to the numbers 2 :3 :8 : 5, giving the 

formula 2Ca0.3B2 03 .13H20. Of the water & goes off below 110°, 

so that in the conventional way the formula may be written 

2Ca0.3B203 .5H20 + 8H20.

ALTERATION.

The specimens shown in Plate I were very largely altered when 

collected and should perhaps be called " meyerhofferite pseudomorph 

after inyoite," rather than inyoite. The alteration to meyerhoff erite 

has changed the large rhombic crystals of the inyoite from a colorless 

transparent and glassy material to a compact aggregate of white, 

opaque, silky fibers. These fibers are arranged either in irregular 

masses, in radiating groups, or more commonly and characteristically 

in parallel oriented groups, which for the most part form a rectangular network, such as is shown in Plate II, A, B, and G. In this network are areas of parallel fibers which lie at an angle of about 45° to 

the rectangular ones, as is well shown in Plate II, A. Most of these 

fibers are silky white and opaque, although embedded in them are 

numerous transparent glassy prisms of the same material. The 

lower portion of the specimen shown in Plate I, A, is similarly composed of these compact fibers of meyerhoff erite.

It would be a most interesting study to trace the orientation of 

the individual meyerhofferite crystals, both with regard to the reticulated structure of the entire mass as well as to the original inyoite 

crystals, but such a study could not be undertaken for lack of time.

A second mode of occurrence of the meyerhofferite crystals is as 

stellate groups on the surface of the large crystals of altered inyoite. 

These radiating clusters appear both singly and in groups, and a 

particularly rich and well-developed cluster is shown enlarged in 

Plate II, D. These prismatic meyerhofferite crystals are transparent 

and glassy. It was at first thought that the opaque, white, silky, 

fibrous crystals were different from the transparent, colorless glassy 

prisms, but they have been proved to be identical.

Meyerhofferite contains less water than inyoite, and it might 

be expected that the crystals would show a further loss- of water on 

long exposure to the air, but no such loss has been observed. Under 

the conditions which existed at the place of formation of the specimens 

meyerhofferite seems to be the stable compound

DIAGNOSTIC PROPERTIES.

The rhombic shape of the large crystals, now altered to a fibrous 

aggregate of white and colorless prisms, and the low refractive 

index of the mineral (1.5) serve to distinguish inyoite from the other 

known borates.
INYOJTE AND MEYERHOFFERITE, TWO NEW CALCIUM EQUATES. 41

MEYERHOFFERITE.

CRYSTALLOGRAPHY.

GENERAL CHARACTER OF CRYSTALS.

The 21 crystals measured averaged about 2 to 3 millimeters in 

length and about 0.3 to 0.5 millimeter in thickness. Crystals 1 

millimeter thick and 1 centimeter long are not rare. All the crystals 

examined are prismatic in habit. No twins were detected.

CALCULATION OF ELEMENTS.

The triclinic crystals were measured by the two-circle goniometer, 

the prismatic habit rendering it very easy to adjust the crystals in 

polar position. The excellent clinopinacoidal cleavage was usually 

developed enough to give a good reflection, and its measurement, 

aided by the readings on the other faces of the prism zone, gave good 

results for %. The few forms whose measurements could be used 

for a calculation of the elements were as follows: a{100}, m{110}, 

M{ilQ}, £{101}, y{TO!}, 2?.{111}. The measurements of these six 

forms yielded nine angles, of which only five are necessary. The 

method of two-circle measurement allows the use of all the available 

angles, and all nine were therefore used, the final results being a 

better average of all the measurements than could be obtained 

by the arbitrary selection of only five angles.

Details of the method of calculation are given in the publications 

of Borgstrom. and Goldschmidt 1 and of Moses and Rogers.2

The angles of £{101}, y{Wl}, and jp{lll} were used for obtaining 

an average value for x'0 , and p'0 sin v, from which, as v is known 

( = $(100)), p'0 is readily calculated. An independent value of v is 

also obtained from the values of £{101} and p{lll}. Values for y'0 

are obtained from t{ 101}, ?/{T01} and p{ 111} and for <z'0 from p{111}.

Vr 

Independently from the terminal forms, v and *-r are calculated from

2 o_

the measurements of the prisms ra{ 110} and M{ 110}. By taking the 

value found for p'0 from the terminal faces, a second value for q'0 can

v' 

be found from the ratio of ^r, obtained from the prisms.

# o

The averages of the measured angles of the six forms used are as 

follows, and from these figures average values for the crystallographic 

elements are calculated.3

1 Borgstrom, L., and Goldschmidt, V., Krystallberechnung im triklinen System illustriert am Anorthit: 

Zeitschr. Kryst. Min., vol. 41, p. 63,1905.

2 Moses, A. J., and Rogers, A. F., Formulas and graphic methods for determining crystals in terms 

of coordinate angles.and Miller indexes: School of Mines Quart., vol. 24, p. 1,1902.

3 The writer wishes to express his gratitude to Prof. Victor Goldschmidt, of Heidelberg, who kindly 

verified the crystallographic calculations of meyerhofferite.
42 MINEKALOGIC NOTES SERIES 3. 

Averages of measured angles ofmeyerhojferite.

Form.

o{100}.. .........................................

Jf { 110 }..........................................

t{ 101 }..................:.........................

#{111}

Number of 

measurements.

26

19

13

9

8

9

*

o /

93 12

54 15

129 49

94 01

87 00

47 34

p

o /

90 00

90 00

90 00

38 35

50 22

46 54

The values obtained are as follows:

a/0=-0.2049 from t{10l} and y{101}. 

3/0= -0.2085 from y{lOl} and p{lll}. 

2^0=0.0036 from £{101} andj/{101}. 

2/0=1.0005 from t{101], y{101}, and p{Ul}. 

2'0=0.7769 from #{111}.

2)^

<j'/0=0.7761 from value of p'0 and ^-7 (prisms). 

, _ 2 o

££-=1.2940 from £{101}, y{101}, and p{lll}.

?o .

^=1.2870 from m{110} and .¥{110}.

9 o

v =93°12'froma{100}.

v =93° 14'from m{110} and M{llQ}.

The elements obtauied from the average of these values, with their 

proper weights, are shown in the following table. The figures given 

were not obtained by arbitrarily assuming certain values 'as correct, 

but by averaging all the available results obtained directly from the 

measurements. It will be found, therefore, that the angles calculated from these elements are not the same as those with which the 

determinations originally started but vary slightly therefrom.

Axial elements ofmeyerhofferitc.

Projection elements.

0/0= -0.2067

y'0= 0.0036

jt/0= 1.0005

5/0= 0. 7763

v= 93° 13X

A=" 1

Polar elements.

p0= 0. 9798

q0= 0. 7602

r = 1

\= 89° 48X

M= 101° 41X

v= 93° 13X

X0= -0.2024

yo= 0. 0036

Linear elements.

a0=l. 0222

6 0=1. 2902

c0=l

a=0. 7923

6=1. 0000

c=0. 7750

a=89° 32r

13=78° W

7=86° 52'

On a gnomonic projection carefully plotted directly from the measurements the elements could be read off .and showed a close agreement with the calculated results.
INYOITE AND MEYERHOFFERITE, TWO NEW CALCIUM BORATES. 43 

Comparison of calculated and graphic values.

r'

w' .............. ' ......

J/ ..........................................

a

Calculated.

-0. 2067

.0036

1. 0005

.7763 93° 13'

Measured on 

gnomonic 

. projection.

-0. 206

.005

1.01

.772 93° 307

The measurements from which these averages are obtained are as

follows:

Measurements ofa{100}, meyerhofferite.

Crystal 

No.

1 

1 

2 

2 

4 

6 

7 

7 

9 

9 

10 

10 

11 

12 

13 

13 

14 

14 

15

Reflection.

Good ......

Good ......

Good ......

Poor. ......

Excellent. . 

Fair ......

Fair. ......

Poor. .......

Fair

Good ......

Fair ......

Fair.

Fair

Good ......

Fair ......

Good ......

Fair ......

Poor. ......

Size of 

face.

Large 0 . 

Large a . 

Large. . . 

Large. . . 

Small a. 

Large. . . 

Large. . . 

Large. . . 

Large c. . 

Large. . . 

Large °. . 

Large c. . 

Large c. . 

Large 0.. 

Large. . . 

Large... 

Large... 

Medium 

Large. . .

</>

0 /

93 10 

93 18 

93 06 

93 11 

693 34 

93 15 

93 06 

93 07 

93 03 

92 48 

693 40 

93 17 

<*93 41 

^93 45 

93 14 

93 32 

93 17 

92 48 

o"93 36

Crystal

No.

15 

16 

16 

, 17 

17 

18 

18 

19 

20 

21 

21

Average 

Average 

reflec 

Average 

Average 

Calculal

Reflection.

Fair.. . . .

Fair .....

Poor. .....

Fair... . .

Excellent. 

Fair

Fair

Good .....

Good. ....

"Pnrvr

Poor. .....

of 26 measi 

of good an 

tions .......

) of fair refle 

) of poor refl 

ted

Size of 

face.

Large. .... 

Large 0 .. . . 

Large. .... 

Large 0 . ... 

Medium . . Medium 0 . 

Large. . ° . Medium . . 

Large. .... 

Line face. 

Line face.

irements ... 

i excellent

ections ....

*

0 / 

^93 45 

93 09 

93 17 

93 11 

93 11 

93 17 

93 10 

93 03 

93 12 

93 13 

93 09

93 12

93 16J 

93 09 

93 11 

93 13

a Cleavage (?) face.

6 High, but included because of good reflection.

c Striated face, 

d Excluded from a^

Measurements oft{101}, meyerhofferite.

Crystal 

No.

6 

9 

10 

11 

12 

15 

16 

19 

20

Avei 

Calc

Reflection.

Poor. ......

Poor. ......

Poor. ......

Poor.......

Fair........

Poor.......

Good......

Poor.......

T*nni*

f&&Q

Size of face.

Minute.... . 

Narrow .... 

Small.....

Medium.... 

Medium.... 

Large......

Medium....

ulated......... ...........

*

0 /

« 90 04 

93 56 

93 40 

93 41 

94 08 

94 12 

94 07 

94 03 

94 .22

94 01 

93 48

p

0 /

39 00 

38 26 

38 58 

38 49 

38 18 

38 18 

38 14 

38 39 

38 37

38 35 

38 27

<» Excluded from average.
44 MINERALOGIC NOTES SERIES 3. 

Measurements of y{101}, meyerho/erite.

Crvstal 

No.

2 

6 

9 

12 

15 

16 

18 

20

Avei 

Gale

Reflection.

Poor.......

Poor.......

Poor.......

Good......

Poor. ......

Poor... ....

Poor... ....

"a^e ^

Size of face.

Minute..... 

Medium.... 

. Medium.... 

Line face.. 

Minute..... 

Minute..... 

Line face..

ulated.......!... .........

4>

0 /

87 35 

89 56 

87 30 

87 21 

85 20 

85 53 

87 34 

.84 48

87 00 

87 10

p

o '/

50 23 

50 16 

50 22 

50 19 

50 35 

« 49 42 

50 31 

50 44

50 22 

50 21

a Excluded from average.

6 The <t> values vary so much that a general average was taken of all the angles.

Measurements ofm{110}, meyerhofferite.

Crystal No.

1 

2 

2 

5 

5 

' 6 

6 

9 

10 

10 

11 

11 

12 

12 

13 

13

Reflection.

Fair......

Good.... 

Poor. ....

Poor..... 

Good.... 

Fair...... 

Fair......

Good.... 

Poor..... 

Poor..... 

Fair......

Poor..... 

Fair......

Poor..... 

Fair...... 

Good....

Size of face.

Small.....

Large......

Line face. . 

Small.

Small.....

Medium.... 

Medium....

Small.....

Medium.... 

Narrow. .. . 

Narrow .... 

Medium.... 

Line face. . 

Medium.... 

Medium....

<t>

0 /

54 34 

54 30 

« 54 09 

54 30 

54 28 

a 55 12 

a 55 03 

53 50 

a 55 10 

«&54 59 

54 01 

&54 14 

54 06 

a 54 38 

&54 22 

53 54

Crystal No.

14 

14 

15 

16 

17 

18 

18 

19 

20

Averag 

Averag 

Averag 

Averag 

Calculs

Reflection.

Fair......

Good.... 

Good.... 

Good.... 

Fair...... 

Fair...... 

Fair...... 

Fair......

e of measur 

e of good re 

e of fair ref 

e of poor re 

i ted

Size of face.

Narrow. .. . 

Narrow. ... 

Medium.... 

Medium.... 

Medium.... 

Narrow .... 

Medium.... 

Medium.... 

Medium....

ements. .....

flections.....

flections.....

<t>

0 /

54 04 

54 05 

54 01 

54 10 

54 05 

54 18 

&54 28 

54 19 

54 42

54 15 

54 08 

54 19 

54 .16 

54 13

o Excluded from average. & Striated. 

Measurements of M{fiO], meyerhofferite.

Crystal No.

1 

2 

6 

9 

9 

10 

11 

12 

12 

13 15'

Reflection.

Good .... 

Good.... 

Fair..... 

Good .... 

Poor. .... 

Good .... 

Fair. .... 

Fair..... 

Fair..... 

Poor. .... 

Fair. ....

Size of face.

Small.....

Small «. ... 

Medium. . . . 

Medium a. . 

Medium &. . 

Medium a. . 

Narrow. ... 

Medium &.. 

Narrow. ... 

Narrow. .. . 

Narrow. .. .

<t>

° , f 

129 49 

129 55 

129 48 

129 33 

cl29 11 . 

129 57 

129 33 

cl29 12 

129 45 

130 57 

129 46

Crystal No.

16 

18 

18 

19 

20 

21

Averag 

Averag 

Averag 

Calculs

Reflection.

Fair. .... 

Fair..... 

Poor. .... 

Fair..... 

Poor. .... 

Poor. ....

e of 13 mea 

e of good rt 

e of fair ref 

i ted

Size of face.

Medium.... 

Medium.... 

Line face. . 

Large &..... 

Medium. . . . 

Narrow. ...

surements. . . 

flections. . . . 

lections. ....

*

0 /

129 53 

129 54 

c!29 20 

129 51 

129 49 

cl30 10

129 49 

129 49 

129 47 

129 48

Cleavage (?) face. & Striated face. Excluded from average.
1NYOITE AND MEYEEHOFFEEITE, TWO NEW CALCIUM BOBATES. 45

FORMS AND ANGLES.

A total of 27 forms was determined on the measured crystals of 

meyerhofferite. These may be grouped as follows:

Pinacoids: a{100}, 6{010}, c{001}.

Positive prisms: fc{370}, ^{120}, ^{350}, j{450}, m{110}, ?{210}, n{520}, s{310},

£{510}, r{810}.

Negative prisms: i;{350}, M{110}, w{430}, h{310}.

Positive domes: £{101}, d{12.0.11}, e {706},/{605}, ^{504}, i{705}, z{302}, z{12.0.1}. 

Negative dome: y{lOl}. 

Pyramid: p{lll}.

The average of the measured angles is shown in the table below.

Measured and calculated angles of meyerhojferite.

No.

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

Letter.

c

b

a

k

I

A

3

m

1

n

s

B

r

V

M

w

h

t

d

e

f

9

^

X

z

y

p

Number of

crystals.

- 6

20

20

2

1

2

1

16

1

3

2

1

2

3

16

3

5

13

1

1

2

2

1

1

1

10

15

Number of 

measurements.

6

33

37

2

1

3

1

29

1

4

2

1

2

4

23

3

6

13

1

1

2

2

1

1

1

10

15

Symbol.

001

010

100

370

120

350

450

110

210

520

310

510

810

350

110

430

310

101

12. 0. 11

706

605

504

705

302

12. 0. 1

101

111-

Measured.

<t>

0 /

-89 47

0 00

93 12

29 33

33 51

39 01

46 58

54 15

71 56

75 31

78 50

84 13

87 54

143 20

129 49

122 41

107 55

94 01

94 16

94 03

93 40

93 52

93 45

93 45

93 03

-87 00

47 34

P

o /

11 48

90 00

90 00

90 00

90 00

90 00'

90 00

90 00

90 00

90 00

90 00

90 00

90 00

90 (ft)

90 00

90 00

90 00

38 35

40 53

43 45

44 -35

45 56

49 50

52 12

84 21

50 22

46 54

Calculated.

<*>

0 /

-88 59

0 00

93 13

29 39

33 44

38 55

47 32

54 13

71 37

.75 43

78 32

84 20

87 39

143 30

129 48

122 26

107 30

93 48

93 44

93 42

93 40

93 39

93 36

93 34

93 15

-87 10

47 35

P

.0 t

11 41

90 00

90 00

90 00

90 00

90 00

90 00

90 00

90 00

90 00

90 00

90 00

90 00

90 00

90 00

90 00

90 00

38 27

41 30

43 50

44 50

46 14

50 03

52 18

85 09

50 21

47 01

c{001}. The basal pinacoid is represented in most of its occurrences as a broad line face between the positive and negative unit 

domes. On one crystal, No. 6, it is a large face lying between the 

line faces of the two domes. Its average size relative to the other 

terminal forms is shown in the orthographic projection of crystal 12
46 MINEKALOGIC NOTES SERIES 3.

shown in figure 49 (p. 53). The angles on which the form is based are 

shown below:

Measurements ofc{001}, meyerhofferite.

Crystal No.

6.........

7.........

8.........

9.........

12........

20........

Reflection.

Fair . 

Poor. . 

Poor.. 

Poor. . 

Poor. . 

Poor. .

Size of face.

Large......

Small.....

Line face . . 

Small.....

Line face. . 

Line face . .

Measured.

<t>

0 /

-89 56 

-88 37 

-86 00 

-89 36 

-85 52 

-89 41

p

0 /

11 51 

11 50 

12 00 

12 00 

11 37 

11 45

Calculated.

$

0 /

-88 59 

-88 59 

-88 59 

-88 59 

-88 59 

-88 59

P

o /

11 41 

11 41 

11 41 

11 41 

11 41 

11 41

6(010}. It is not always possible to determine whether a certain 

face of 6 is natural or due to the perfect cleavage which is parallel to 

this form. The natural faces are mostly line faces, very narrow as 

compared with the other faces in the prism zone. Rarely they 

become broader, though most of the occurrences of broad 6 faces 

are clearly due to cleavage.

a{100}. The macropinacoid is the dominant form of the mineral 

and is developed on many crystals as a broad face vertically striated. 

The relatively large size of the a face causes the crystal to become 

tabular parallel to it, as shown in figures 42, 46, 49, 50, and 51. On 

a few crystals it is equaled in size by some other form in the prism 

zone. On 8 of the 10 crystal drawings of meyerhofferite chosen 

to show the various habits and combinations a{100} is the largest 

form. The measurements of the faces of a{100} have already been 

given under the calculation of the elements. . m{110} and M{11Q}. The unit prisms are of medium size, varying from line faces to faces nearly as large as those of a{100}, but 

generally are about half as large or somewhat less. The faces are 

striated vertically, although not so strongly as those of a{100}. The 

average size of m{110} is somewhat larger than that of JfjlTO}.

The other prism forms, with the exception of ^.{350}, ?{450}, ?i{520} 

and i>{350}, are all line faces. Some of these prisms were observed 

but once and their measured angles are shown in the table just given. 

The values for those prisms which were measured more than once are 

given in the following table:
INYOITE AND MEYERHOFFERITE, TWO NEW CALCIUM BORATES. 47 

Measurements of rare prisms of meyerhofferite.,

Form.

.4(350)..

w(520)..

s (310)..

r(810)...

v (350) . .

w (430) . .

fc(3lO)..

Crystal 

No.

4

4

9

3

5

5

18

12*

21

18

90

4

14

14

21

1

7

19

12

12

13

14

17

18

J.VO-U-C-1^

tio'n.

Good....

"Pnrvt*

Poor. ....

Good....

Good....

Poor.....

Poor.....

Poor. ....

Poor.....

Poor.....

Good....

Poor.....

Fair ....

Poor.....

Poor. ....

Poor.....

Poor.....

Poor.....

Poor.....

Poor......

Poor.....

Poor.....

0

Size of face.

Small.. ...........

Small.. ...........

Small. ............

Small.............

Line face...........

Line face...........

Small.. ...........

Line face............

Measured

0 /

QQ m

38 11

39 50

76 00

75 20

75 16

75 54

78 41

79 00

87 57

87 50

143 20

143 30

143 29

143 01

122 35

122 45

122 43

107 13

108 16

107' 54

107 21

108 43

108 05

<*>

Calculated

0 /

38 55

38 55

38 55

75 43

75 43

75 43

75 43

78 32

78 32

87 39

87 3Q

143 30

143 30

143 30

143 30

122 26

122 26

122 26

107 30

107 30

107 30

107 30

107 30

107 30

. The positive unit maorodome is one of the three dominant 

terminal forms, the other two being y{IOl} and p{lll}. The faces 

of this form are generally large, though on a few crystals it occurs as a 

narrow face. The form is shown on a number of the crystal drawings 

(figs. 46, 47, 48, 49, 50, and 51). It has not been observed as the 

only terminal form, although crystal 13 is terminated by a single form, 

namely/{605}. which is very near Z{101}.

. The negative unit dome occurs nearly as frequently as 

but is smaller in size and in several crystals is present as a line 

face. The form is the only negative dome observed. It is shown in 

figures 48 and 49.

The remaining domes, seven in number, form a remarkable series 

in that five of them are very close to £{101} and, if each one occurred 

separately on a distinct crystal, would be considered as all belonging 

to a single form vicinal to the unit dome. The faces of these domes, 

however, are distinct and yield separate reflections and occur in such
48 MINEEALOGIC NOTES SERIES 3.

a way as not to allow their being grouped together as one form. 

The occurrence of the forms in the zone a(100), c(001), a(TOO) is 

shown below for the crystals containing domes other than the unit

domes.

Occurrence of forms in the zone a{100}: ^{100}, meyerhofferite.

Crystal 11.

100

101

504

100

Crystal 13.

loo

« 605

100

Crystal 19.

100

101

705

302

12. 0. 1

100

Crystal 20.

loo

101

001

101

12. 0. 11

706

605

504

100

« The only terminal form on this crystal.

The occurrence of the two series of domes shown on crystals 19 and 

20 is very unusual for these crystals. 

The two measurements for/{605} and #{504} are shown below.

Measurements off{605} and g{504], meyerhofferite.

Form.

/{605}

0(504}

Crystal 

No.

13 

20

11 

20

Reflection.

Poor... 

Poor...

Poor... 

Poor...

Size of 

face.

Large......

Line face...

Line face. . 

Line face. .

Measured.

<t>

0 /

93 16 

94 03

93 41 

94 03

p

o t

44 26 

44 43

45 37 

46 14

Calculated.

*

0 /

93 40 

93 40

93 39 

93 39

p

0 /

J 44 50 

44 50

46 14 

46 14

The remaining domes are all line faces giving poor reflections and 

the angles measured are shown in the table on page 45.

Crystal 20, with its wealth of domes/is shown in figure 51 (p. 53).

The common forms of meyerhofferite, or those observed on at least 

ten crystals, are b{QW}, a{100}, m{110.}, Jf{lTO}, *{101}, y{T01}, 

and p {1 11}. The less common forms, observed on three to nine 

crystals, are e{001},n{520},v{350}, w{430},7i,{3lO}. Theremaining 

forms, 15 in number, are all rare; 9 of them were observed only once.

COMBINATIONS.

The combinations observed on the 21 measured crystals of meyerhofferite are shown in the following table:
Combinations of forms on meyerhofferite crys

^§ Letter.

GO 

CO

o

1 Cc ..............................

pi b. ..............................

o> Jb. ...............................

SZ................................

1 ^1.. .......... ...................

S -i «j................................

I g. ...............................

^ n. ..............................

B................... .............

r ...............................

v ...............................

If. .............................

h.. .............................

t.......... ......................

d. ..............................

f....................... .........

a. ..............................

^

y. ..............................

p...............................

Symbol.

001

010

100

. 370

120

350

450

110

210

520

310

510

810

350

110

430

310

101

12.0.11

706

605.

504

705

302

12. 0. 1

101

111

1

b

IM

P

2

b

M

'

y

P

3

b

t

P

'4

b

A

5

b

*n

G^

b

M

t

y

7

b

M

t

y

p

8

b

-

M

t.

P

9

b

A

M

t

y

p

10

b

M

t

p
50 MINERALOGIC NOTES SERIES 3.

ZONAL RELATIONS.

The zonal relations are very well developed on the crystals of 

meyerhofferite, all the forms lying in three zones, and 96 per cent of 

the forms lying in two zones, namely, the prism zone with 16 forms 

and the macrodome zone with 11 forms, as shown in figure 41. The

\y

FIGUKE 41. Gnomonic projection of meyerhofferite forms. The form z{\2. 0. 1}, not shown, falls outside

of the projection.

unit pyramid ^{111} lies in such zones as c{001}, p{lll}, m{lH)}, 

and<{101},p{lll}, &{010}.

The prism zone is characteristically striated vertically, and the 

macropinacoid shows the striations most prominently.

HABITS.

The crystals of meyerhofferite are all prismatic, but a distinction 

may be made between the tabular prismatic crystals and those with 

equal horizontal thickness. The tabular habit is caused by the
INYOITE AND MEYEBHOFFEBITE, TWO NEW CALCIUM BORATES. 51

large development of the macropinacoid a {100}, as shown in figure 

42. The prisms m{110} and M{lTO} are both very narrow on such 

tabular crystals. As the crystals become thicker the a {100} faces 

decrease in size, with a consequent enlargement'of the prisms, as 

shown in figure 43. When one or both of the prisms equals the

M~

FIGUBE 42. FIGURE 43. FIGURE 44. 

FIGUBE 42. Tabular prismatic crystal (No. 1) of meyerhofferite. Forms: &{010>, m{110>, a{100>, M{\lQ},

FIGURE 43. Crystal 21, meyerhofferite. Intermediate in habit.

FIGURE 44. Crystal 2, meyerhofferite. Nearly equally thick in horizontal directions.

macropinacoid in size, the crystal becomes of nearly the same horizontal thickness in every direction, as 'shown in figure 44 and also 

in figure 50 (p. 53). A crystal (No. 17) which has a nearly square 

cross section is shown in orthographic projection in figure 45. Only 

the prism zone is developed on this crystal. The faces of &{010} do

not seem to be cleavage faces, 

and in the large development 

of the faces of the clinopinacoid 

& the crystal is unusual.

The terminations of meyerhofferite crystals consist either 

of a single large face or of three 

large faces, with perhaps one 

or two minute accompanying 

line faces. A termination 

showing a richer combination 

is very rare.

The single termination consists of theunitpyramid2?{ 111 } 

(crystal 1, fig. 42) and in one crystal of the dome /{ 605 }. In a crystal 

whose termination is composed of two forms they may be either tp (as 

in crystal 10, fig. 46, and crystal 3, fig. 47), t y (as in crystal 16, fig. 50, 

in which the rear dome y{101} is not shown), or p y (as in crystal 2, 

fig. 44, in which the rear dome y{101} is likewise not shown). The

FIGURE 45. Orthographic projection of crystal 17, 

meyerhofferite. Only the prism zone is shown on 

this crystal. Forms: &{010>, o{100>, m<110>, fc<370>,
52 MINERALOGIC NOTES SERIES 3.

presence of three large terminal faces (t y p) is shown in clinographic 

projection in figure 48 (crystal 8) and in orthographic projection in 

figure 49 (crystal 12). In crystals in which the three forms all show 

large faces the basal pinacoid c{001} is usually present as a line 

face. None of the terminal faces can be said to exert a decided influence on the habit of the crystals. The forms t y and p exert an 

equal influence, the faces of the other terminal faces being small.

MEASURED CRYSTALS.

The tabular to thicker crystals have already been illustrated in 

figures 42 to 45, which show the chief forms on crystals 1,21,2, and 17.

Crystal'2, figure 44, shows only y{Wl} in addition to the forms 

figured, whereas on the other crystals a number of other forms, 

especially line-face prisms, are present.

MFIGURE 40. FIGURE 47. FIGURE 48. 

FIGURE 46. Crystal 10, meyerhofferite. Forms: b{Q10},m{nO},u{iOO}M{UO},t{l01},p{ni}. 

^FIGURE 47. Crystal 3, meyerhofferite. Forms: &{010> cleavage, w{f>20}, o{100}, JjlOl}, $ 111}.

FIGURE48. Crystal8,meyerhofferite. Forms: 6{010>a.(100>, M{nQ},t{Wl},y{lQl},c{(K>l},p{in}: The 

large unlettered prism is so rounded and striated as to be undeterminable.

Crystal 10, figure 46, has only the two terminal forms shown in 

the drawing, which in fact represents the. complete combination of 

the crystal as determined.

Crystal 3, figure 47, similarly has only the two terminal forms t and 

p, which have developed in a steplike form. The clinopinacoid faces, 

which may possibly be due to cleavage, are unusually large. The 

large development of the single face of 7i{520} is noteworthy. The 

face is strongly striated.

Crystal 8, figure 48, shows a similar large striated face between 

a{100} and 5{010}, which, however, is so rounded and striated that 

it could not be determined. It may be a face of n{520}, like that on 

crystal 3 (fig. 47), or it may be the unit prism or a combination of 

several prisms. One side of the crystal is determined by a large 

cleavage face of &{010}. The termination shows £{101}, y{Wl},
1NTOITE AND MEYERHOFFERITE, TWO NEW CALCIUM BORATES. 53

and p{lll}, all large, with the basal pinacoid, c{001}, between the 

domes as a line face.

A terminal combination, similar to that on crystal 8, shown in 

figure 48, is present on crystal 12, and is shown in figure 49 in orthographic projection, in order to show better the relative size of the four 

forms.

In addition to the forms shown in figure 49, line faces of the rare 

prisms Z{120}, s{310}, and Ji{310} are present on the crystal.

Crystal 16, figure 50, shows a large face of £{101} and a minute 

one (not shown in the figure) of y{101} as the only terminal forms. 

In general appearance, crystal 13 (not shown) is very similar to crystal 

16 (fig. 50), except that the large terminal face is not £{101} but the 

rare dome/{605}.

A series of domes are well developed on crystals 20 

and 21, and crystal_20 is shown in figure 51. The 

forms c{001} and y{10l} are present as line faces, but

FIGURE 49. FIGURE 50. FIGURE 51. 

FIGURE 49. Orthographic projection of crystal 12, meyerhofferite. Forms: &{010},m{110}-,a{100},

FIGURE 50. Crystal 16, meyerhofferite. Forms: 6{010>, m{110>, a{100>, M{110}, t{101}. 

FIGURE 51. Crystal 20, meyerhofferite. The series of domes is notable. Forms: 6{010}, j{450}, m{110}, 

}, ?{504},/'{605>, e{706},

are not shown in the drawing. The presence of a single large face of 

j{ (450} is notable, and a line face of r{810} (not shown in the figure) 

was also determined.

Crystal 6, not shown, is unusual in having a large face of the basal 

pinacoid c{001}, while both domes t and y are minute line faces.

PHYSICAL PROPERTIES.

The cleavage of meyerhofferite is perfect parallel to the clinopinacoid, &{010}. Indications of other less perfect cleavages in the 

prism zone were encountered during the measurement of the crystals. 

Such indications were noted a number of times for a { 100 } and M { 1TO } . 

The perfect clinopinacoidal cleavage causes the crystals to break 

readily in thin prisms. The hardness of the mineral is about 2.

The density of meyerhofferite, determined on colorless, transparent 

crystals by means of heavy solution, is 2.120. The same value was 

obtained on the artificial mineral by Van't Hoff and Meyerhoffer. 1

> Van't Hofl, J. H., Untersuchungen xiber die Bildung der ozeanischen Salzablagerungen , I/T. Kiinstliche 

r>arStellung von Colemanit: Preuss. Akad, Wiss. Sitzber., 1900, p. 089.
54 MINERALOGIC NOTES SEEIES 3.

The white opaque prisms of meyerhofferite have apparently a slightly 

lower density, but the lower value is more apparent than real and is 

probably due to a small amount of air inclosed in the partly cleaved 

crystals.

OPTICAL PROPERTIES.

Meyerhofferite crystals that have not been affected by outside 

influences are colorless; others are white. The luster is vitreous and 

on the opaque white masses somewhat silky. The colorless crystals 

are transparent; the white ones translucent to opaque.

The extinction on &{010} is c/\X' = 33°; ona{100} it is c/\Z' = 25°. 

The plane of the optic axis is across the elongation (c) and the obtuse 

bisectrix (Z) makes a moderate angle with the normal to the face 

(100). The axial angle 2 V is nearly 90°, but the bars are perceptibly 

curved. The mineral is optically negative.

The refractive indices, as determined-by the immersion method by 

Mr. Esper S. Larsen, for sodium light, are as follows: a = 1.500, 

|8 = 1.535, 7 = 1.560. The birefringence (7 - a) is high, 0.060.

CHEMICAL PROPERTIES. 

PYROGNOSTICS.

Meyerhofferite when heated in a blowpipe flame fuses readily 

without decrepitation but with intumescence to an opaque white 

enamel, imparting a greenish color to the flame. Heated in a closed 

tube, it fuses, giving off abundant water. The mineral is readily 

soluble in acids.

QUANTITATIVE COMPOSITION.

Two analyses were made of meyerhofferite, one on 0.0607 gram of 

the colorless transparent crystals, and one on gram and half-gram 

portions of the abundant opaque white variety. The boric acid had 

to be determined by difference hi the colorless crystals. B.oth 

analyses yield the same result, as shown above.

Analyses and ratios of meyerhofferite.

Opaque, white, fibrous mass.

CaO................

B208 :..~... .......

H20 (below 110°)..

H2O (above 110°)..

1

25. 23 

46.40 

1.01

« 27. 75

2

25.66

a 28. 00

.........

3

........

& 27. 49

........

Average.

25.45 

46.40 

1.01

27.75

100. 61

Ratios.

2. 05 or 2 

2. 99 or 3

6. 96 or 7

..........

Colorless, 

transparent 

crystals.

25.6 

[45. 6] 

.3

28.5

100. 00

Calculated.

25.02 

46.85 

.00 

28.13

100. 00

a. Loss on ignition. f> Loss on ignition with ignited CaO.
INYOITE AND MEYEBHOFFEBITE, TWO NEW CALCIUM BOBATES. 55

The ratios yield the formula 2Ca0.3B203 .7H20, and the analysis 

of the colorless transparent crystals agrees well with that of the opaque, 

white, fibrous mass. Both analyses are also in close agreement with 

the calculated composition given in the last column.

The new minerals meyerhofferite and inyoite belong to the colemanite series of compounds. Of the compounds of 2CaO.3B2O3 with 

water the following are known:

2Ca0.3B203.5H20 (artificially prepared), colemanite. 

2Ca0.3B203 .7H20 (artificially prepared), meyerhofferite. 

2Ca0.3B203 .9H20 (artificially prepared). 

2Ca0.3B203 .llH20. 

2Ca0.3B203 .13H20, inyoite.

SYNTHESIS.

Meyerhofferite. was artificially prepared by Meyerhoffer and Van't 

Hoff * by the following method. The hexahydrate of calcium monoborate, CaO.B203 .6H20, was treated with boric acid solution at 100°, 

when the compound 2Ca0.3B203 .9H20 was formed in well-crystallized augite-like forms. By heating this enneahydrate with a 3 per 

cent boric acid solution at 100° the compound 2Ca0.3B203 .7H20 was 

formed in well-crystallized long rectangles.

DIAGNOSTIC PROPERTIES.

The prismatic, partly tabular crystals, perfect cleavage, and 

.inclined (triclinic) extinctions serve, with the chemical testa, to distinguish meyerhofferite from all other natural borates.

1 Meyerhofler, Wilhelm, and Van't Hoff, J. H., Krystallisirte Calcium-1)orate: Annalen der Chemie, 

vol. 351, p. 100,1907
LUCINITE, A NEW MINERAL: A DIMORPHOUS FORM OF

VARISCITE.

ORIGIN OF INVESTIGATION.

A short time after the description of crystallized variscite from 

Utah1 had heen finished, Messrs. Edison & Bird, of Lucin, Utah, 

kindly furnished, in response to a request from the writer, several 

specimens which showed minute octahedral crystals associated with 

the tabular crystals of variscite. Preliminary measurements showed 

a close resemblance, in angular values, to variscite, and in a short 

note 2 these octahedral crystals were referred to as variscite. Subsequent more extended measurements showed, however, that although 

the angular values were close, they could not be referred to those of 

variscite. The mature consideration of the problem has led to the conclusion that the octahedral crystals belong to a second modification of 

the same chemical compound as variscite, and the new mineral is 

named lucinite. The specimens that show crystals of lucinite are 

scarce, but it is not improbable that a search at the locality for more 

material would show that the new mineral occurs in some abundance. 

In the compact granular phase lucinite is not distinguishable from 

variscite. In fact, it is impossible from our present knowledge of 

these two minerals to say whether the compact material used in 

jewelry 3 is variscite or lucinite.

Mr. G. W. Fiss, of Philadelphia, kindly sent to the writer a quantity of variscite from Lucin, Utah, in which were found several specimens of lucinite that were a welcome addition to the meager quantity 

at hand. . . -

NOMENCLATURE AND LOCALITY.

The name lucinite is derived from the locality, the specimens 

having been found in the northern part of Utahlite Hill, 5 miles 

northeast of Lucin, Boxelder County, Utah.

PARAGENESIS.

Lucinite occurs in compact massive pieces that in thin section tire 

seen to be composed of small equidimensional areas which, while 

optically units, only here and there show distinct crystal outline.

iSchaller, W. T., Crystallized variscite from Utah: U. S. Geol. Survey Bull. 509, p. 48,1912. 

2 Schaller, W. T., The crystallography of variscite: Washington Acad. Sci. Jour., vol. 2, p. 143,1912. 

'Sterrett, D. B., Gems and precious stones: U. S. Geol. Survey Mineral Resources, 1910, pt. 2, pp. 894- 

896,1912.

56
LUCIN1TE, A NEW MINERAL : A DIMORPHOUS FORM OF VARISCITE. 57

Numerous cavities are present in this massive phase, and these cavities are lined with minute crystals of lucinite and variscite. Cavities 

can be seen containing only lucinite, others have only variscite, and 

in many others both minerals are present. The crystals of lucinite 

are found only in the cavities of the massive granular material, and 

on many specimens are directly associated with variscite crystals. 

In some of the material several crystals of lucinite were perched on 

a larger tabular crystal of variscite (fig. 52), and again a variscite 

crystal was seen to rest on a bed of smaller lucinite crystals (fig. 53). 

Such associations would indicate a more or less similar condition of 

formation of the two modifications. In many cavities lucinite forms 

the lining, and the variscite crystals are perched on this lining and 

seem, therefore, to be of later formation.

FIGURE 52. FIGURE 53.

FIGURE 52. Octahedral crystals of lucinite perched on a larger tabular crystal of variscite. 

FIGURE 53. Tabular crystal of variscite resting on a bed of smaller crystals of lucinite.

The paragenesis of lucinite is the same as that of variscite, and the 

description given for variscite applies as well for the lucinite. The 

only identified associated minerals are variscite and massive quartz.

CRYSTALLO GRAPHY.

GENERAL CHARACTER OF CRYSTALS.

The crystals of lucinite are minute, the largest having a diameter 

of about 1 millimeter and most of them being much smaller. The six 

measured crystals were all less than 1 millimeter thick, ranging in 

size from about 0.2 to 0.5 millimeter. No twins were observed, and 

the crystals all had the same general octahedral habit.
58 MINEEALOG1C NOTES SERIES 3.

CALCULATION OF ELEMENTS.

The minute crystals presented even and highly polished surfaces 

which.gave distinct reflections that could be accurately measured. 

The basal pinacoid was present on most of the crystals and served to 

adjust them in polar position on the two-circle goniometer. The 

different faces of the same form were then utilized for further adjustment, and by a process of averaging the crystals were finally placed 

in correct polar position.

After the symmetry of the crystals had been determined, the two 

crystals yielding the best reflections, Nos. 1 and 2, were remeasured 

after being accurately adjusted in polar position. The measurements 

of the pyramids then gave values from which the axial ratio was 

calculated. The average of p0 and g0; obtained directly from the 

angles $ and p, are p0 = 1.1225, q0 = 0.9788. From these values, the 

axial ratio a:b:c is calculated and found to be 0.8729:1:0.9788.

*y .

Values ofp0 and q0 , lucinite. *

Crystal 

No.

1........

1........

1.. ......

 1........

1. .......

1........

1. .......

1........

1. .......

1. .......

1. .......

Form.

i 

i 

i 

i 

P 

P 

P 

P 

s 

s 

s

112 

112 

112 

112 

111 

111 

111 

111 

121 

121 

121

Po

1. 1208 

1. 1186. 

' 1. 1307 

1. 1143 

1. 1124 

1. 1120 

1. 1270 

1. 1318 

1. 1373 

1. 1270 

1. 1147

?o

0. 9760 

.9799 

.9812 

. .9698 

.9716 

.9707 

. 9791 

.9821 

.9849 

.9806 

. . 9679

Crystal

No.

1.. ......

2........

2........

2........

2........

2........

2........

2........

2........

Average..

Form.

s 

i 

i 

.i 

i

P 

P 

P 

P

121 

112 

112 

112 

112 

111 

111 

111 

111

Po

1.1269 

1. 1233 

1. 1046 

1. 1429 

1. 1105 

1. 1343 

1. 1345 

1. 1180 

1. 1093

1.1225

9o

0. 9786 

.9662 

.9876 

.9935 

.9796 

' . 9878 

. . 9978 

.9765 

.9654

.9788

The interfacial angles in the zone c p were also measured on many 

of the crystals, and by expressing the measured angles in terms of the

angle c(001) : p(lll),1 the following values were obtained:

» 

Interfacial measured angles in zone c p expressed as the angle c(001): pdll), lucmite.

Crystal 1.

0 / 0 /

56 07 56 06 

56 05 56 08 

56 09 56 04 

56 11 56 00 

56 01 56 05 

55 55

Av. 56 03. 7

Crystal 2.

o /

56 03 

56 06 

56 11

56 06.7

Crystal 4.

0 /

56 10 

56 09 

56 10 

56 18 

56 15 

56 12

56 12.3

Crystal 5.

0 /

56 23 

56 06 

56 03 

56 19 

56 13

56 12.8

Crystal 6.

0 /

56 08 

56 02 

56 07 

56 08 

55 57

56 04.4

i For instance, the measured angle p(lll): p(lll)=67° 47' would be changed to 90°-J (67° 47')=56° 06J'
LUCINITE, A NEW MINERAL : A DIMORPHOUS FORM OF VARISCITE. 59

The average of 30 measurements on five crystals gives the value 

56° 07.3', whereas the angle (001): (111) calculated from the axial 

ratio a: 1: c = 0.8729: 1: 0.9788, as given above, is 56° 06.4', thus serving as a check on the correctness of the axial ratios as given . Further 

evidence of the same fact is afforded by the close agreement between 

measured and calculated angles, as given on the following page.

FORMS AND ANGLES.

Eight forms were established for lucinite. These are distributed 

as follows:

Pinacoids: c{001), «{100}.

Prism: d{120}.

Brachydome: e{012}.

Pyramids: r{113}, i{U2}, p{lll}, s{121}.

The averages of the measured angles as compared with the calculated values are shown in the following table :

Measured and calculated angles, lucinite.

[a=0.8729, c=0.9788, p0=1.1225.]

No.

1.... ..:.......

2..............

3..............

4..............

5..............

6..............

7..............

8..............

Letter.

c 

a 

d

e 

r

i

P

 s

Symbol.

001 

100 

120 

012 

113 

112 

111 

121

Number 

of crystals.

6 

2

2 

3 

1 

6 

6 

5

Number 

of faces 

measured.

. 9 

3 

3

7 

2 

26 

28 

14

Measured.

<*>

0 /

90 11 

30 14 

0 00 

48 42 

48 51 

48 55 

30 00

P

0 /

0 00 

90 00 

90 09 

26 13 

26 35 

36 39 

56 07 

66 07

Calculated.

*

0 /

90 00 

29 48 

0 00 

48 53 

48 53 

48 53 

29 48

P

0 /

0 00 

90 00 

90 00 

26 05 

26 33 

36 39 

56 06 

66 06

c{001}. The basal pinacoid is present on all the crystals measured 

but is not present on many of the lucinite crystals seen on the specimens. It is rectangular in shape and always small in comparison 

with the other forms.

a {100}. The macropinacoid was observed on only two crystals as 

minute faces. It is shown in the drawing of crystal 4 (fig. 61, p. 64).

<2{120}. The prism d is also a rare form, being likewise observed 

on only two crystals. It forms a line face, as shown in figure 61, and 

the measurements of the three faces gave the following <l> angles: 

31° 00', 29° 19', 30° 23'; calculated, 29° 48'.
60 MINERALOGIC NOTES SERIES 3.

e{012}. The brachydome e{012} was determined on half the measured crystals as minute faces giving poor reflections. It is shown in. 

figures 58 and 61. The measurements of the form are as follows:

Measurements of e{012}.

Crystal 

No.

2.......

9

4.......

4.......

6.......

6.......

Measured.

0

0 /

0 00 

0 10 

0 07 

0 00 

0 04 

0 04

p

0 /

26 28 

26 30 

26 07 

26 10 

26 05 

26 02

Calculated.

0

0 /

0 00 

0 00 

0 00 

0 00 

0 00 

0 00

p

0 /

26 05 

26 05 

26 05 

26 05 

26 05 

26 05

r{113}. The pyramid r was determined on crystal 4, on which 

it occurred with two faces, in the zone cp. The p measurements of 

two faces gave 26° 35', 26° 35', the remaining two faces surrounding 

the rectangular base not being measurable because of their minute 

size. The form is shown in figure 61 (pi 64).

 i{112}. This form is present on all the measured crystals as a 

narrow or broad line face surrounding the rectangular base. It is 

shown on many of the drawings illustrating the crystals of lucinite.

2?{111}. The unit pyramid p is the dominant form of lucinite and 

determines the ^ctahedral shape of the crystals. On many crystals 

it is evidently the only form, and, the axial ratio of the mineral being 

close to unity, crystals of lucinite showing only 2>{111} (fig. 55) 

closely resemble the octahedron of the isometric system (shown in 

fig. 87, p. 90, with which fig. 55 may be compared). Although the 

faces of p generally have a triangular shape, the large development 

of the faces of s{121} causes the p faces to become rhombic in shape, 

as shown in figures 59, 60, and 61.

s{121}. The pyramid s is the second largest form on the lucinite 

crystals and seems to be present on nearly all crystals which show 

any form in addition to ^{111}. The faces of s {121} range in size 

from minute ones to some nearly as large as those, oi p{lll}.

A number of other forms, of very simple indices three of them, 

in fact, belonging to the "unit forms" were observed and measured, but they were so minute that their measurements are several 

degrees from the calculated values. The forms are therefore not 

further described, but are given for comparison with possible future 

measurements. They are {010}, {110}, {101}, {102}.
LUCINITE, A NEW MINERAL: A DIMORPHOUS FORM OF VARISCITE. 61

COMBINATIONS.

The combinations observed on the six measured crystals are as

follows:

Combinations on measured crystals of lucinite.

Form.

c 

a

d 

e 

r

i

P 

s

001] 

100 

120 

012 

113 

112 

111 

121

1

c

i

P 

s

2

c

e

i

P 

s

(fig. 57).

c

i 

P

(fig. 61).

c 

a 

d 

e 

r 

i

. P 

s

5

c

i

P 

s

6

(fig. 58).

c

d

e^

i

P 

s

Besides the combinations given above, the following were commonly observed on crystals not measured but carefully examined 

with a hand lens: p/(fig. 55), p s (fig. 56), p c i (fig. 57). The combination p c i is very common.

ZONAL RELATIONS.

The chief zone of lucinite is c p, with four forms in it, namely, c, 

r, i, and p. The zone (100) : (012) contains a, i, and e, and the 

zone (010): (101) the forms s and p. The prism zone has only a 

and d. The paucity of known forms on lucinite renders it difficult 

to say what are the chief zones. The relative positions of the zones 

can be seen in figure 54 (p. 62).

HABITS.

The crystals of lucinite show only the octahedral habit, somewhat modified by the large development of forms other than the 

unit pyramid. If 2>{.lll} is the only form present, then the crystals 

resemble an octahedron very much, as shown in figure 55. On 

some crystals small faces of s{121} are present (fig. 56), and on still 

others small faces of c{001} and i{112} appear (fig. 57). Oh many 

crystals both modifications occur together, as shown in figures 58, 

59, and 60.

The large development of the faces of s{121}, although retaining 

the octahedral habit, causes the crystals to have a somewhat different appearance, as shown in figure 59. Many such crystals were 

seen on the specimens with a hand lens. Distorted crystals of this 

combination are very abundant, the faces of s{121} being large at 

one end and small at the opposite end. The faces of the basal 

pinacoid c{001} are likewise of different size on many crystals, one 

of which, as seen with a hand lens, is reproduced in figure 60 (p. 63).
62 MINERALOGIC NOTES SERIES 3.

Crystal 4, shown in figure 61, has all the observed forms of lucinite, 

and the combination, drawn in ideal symmetry as near like the actual 

crystal as possible, shows well the relative size and shape of the 

different forms of lucinite.

FIGUEE 54. Gnomonic projection of lucinite forms. 

MEASURED CRYSTALS.

Crystal 1, not shown in any of the drawings, resembles the crystals 

shown in figures 59 and 60 in the large development of s{121} and 

consequent rhombic shape of ^{111}. The right half of figure 60 

represents closely the habit and development of the forms on 

crystal 1.
LUC1NITE; A NEW MINERAL : A DIMORPHOUS FORM OF VARISCITE. 63

FIGURE 55. FIGURE 56.

FIGURE 57. FIGURE 58.

FIGURE 59. FIGURE 60.

FIGURE 55. Octahedral crystal o. lucinite. Form: p{lll>. Compare with figure 87 (p. 90). 

FIGURE 56. First modification of simple octahedral crystal of lucinite. Forms: p{lll} and s{121}. 

FIGURE 57. Second modification of simple octahedral lucinite on crystal 3. Forms: p{lll>, c{001}, and

FIGURE 58. Both modifications occurring on lucinito crystal 6. Forms: c{001}, c{012}, i{112}, p{lll},

FIGURE 59. Lucinite crystal with large development of *{ 121 }, with c{001}, »{ 112}, and p{ 111}. 

FIGURE 60. A distorted crystal of lucinite. Same combination as shown in figure 59.
64 MINERALOGIC NOTES SERIES 3.

Crystal 2 is like that shown in figure 58 except that the faces of 

s{121} are perhaps still smaller. Both crystals 1 and 2 are well 

developed and the plane and brilliant faces give good reflections, 

which were measured for the calculation of the axial ratios of the 

mineral.

Crystal 3, figure 57, shows the simple combination dp, which was 

also observed on many crystals that were not measured.

Crystal 4, figure 61, is remarkable for the many forms 

found on it; in fact, all the 

eight forms determined for lucinite were measured and identified on this crystal. Figure 

61 represents a symmetrical 

development of the forms 

given, with their relative size 

as they occur on the crystal.

Crystal 6, figure 58, shows 

a line face of the prism d{120} , 

not shown in the drawing. 

The faces of i{112} are somewhat broader than usual on 

this crystal. The three uncertain unit forms, given in the last, line on 

page 60, were measured on this crystal.

RELATION TO OTHER MINERALS.

Lucinite falls naturally into the same mineral group as dcorodite, 

as shown in the following table:

Scorodite group of minerals.

FIGURE 61. Crystal 4, lucinite, showing all the eight 

forms of the mineral. Forms: c{001>, a{100}, d<120}., 

e{ 012}, r{ 113 }, i{ 112), X HI}, s{ 121 >.

Name.

Strengite .............

Lucinite.............

Variscite.............

Vilateite &. ..........

Formula.

Fe203 .AsA4 .H20. ....................

Fe203 .P205 .4H20. . ....................

A1203 .P205.4H20. .....................

Fe203 .P205 .3p[2 0?. ..................

A1203 .P205 .4H20. . ..................,'.

« axis.

0. 8658

.8652

.8729 

.8772

.8944

.8479

c axis.

0. 9541

.9827

.9788 

. 1.0660

1. 0919

.8886

a This orientation of phosphosiderite is obtained by interchanging the a and c axes in the position given 

by Dana and then doubling the new a axis.

ft Vilateite is supposed to be similar to strengite in composition and is described as mpnoclinic, with 

0=89° 27', but the angular differences from orthorhombic symmetry are slight, and Lacroix (Mineralogie 

de la France.vol. 4, p. 477,1910) states that optically the mineral behaves somewhat like an orthorhombic 

substance. Half of the a axis, as given by Lacroix, has been taken in the above table.
LUCINITE, A NEW MINERAL: A DIMORPHOUS FORM OF VARISCITE. 65

The close agreement in the axial ratios for strengite and lucinite on 

the one hand and those for variscite and phosphosiderite on the other, 

suggests that perhaps phosphosiderite is a dimorphous form of 

strengite and not identical with it, as the writer has previously suggested.1 The formula would then, however, have to be like that of 

strengite and not Fe203 P205 3£H20, as given in the literature. The 

varying data given for the angles of scorodite also strongly suggests 

the possibility that dimorphous minerals have been grouped together 

under the common name scorodite.

The angular relations of lucinite and variscite have been carefully 

studied, and it has not been possible so to orient them as to make 

both minerals referable to one axial ratio.

If the & and c axes of lucinite are interchanged, the a axis being 

retained as such, then the symbols of the forms change as follows, the 

axial ratio of lucinite, as given, being expressed as a : & : c, whereas 

the new orientation, due to the interchange of the 6 and c axes, is 

expressed as a':bf : cf .

a :b : c a':' b': cf

100 100

010 001

001 010 .

110 101

101 . 110

Oil Oil

111 111

The new axial ratio, a':b':c', then becomes 0.8918 :1 :1.0217, 

which is closer to the ratio of variscite, namely, 0.8952 : 1 : 1.0957, 

than the ratio adopted for lucinite. The value of a' (lucinite) is 

nearly identical with a' (variscite), the <£ angles of {110} being 

48° 17' and 48° 10', respectively. It is to be noted, however, that 

the difference hi the c axes is considerable.

cf (lucinite)=1.0217, P {011}=45° 37' 

c (variscite)=1.0957, p{011}=47° 37'

The fact that the crystals of lucinite and of variscite are not 

identical in angular value can also be readily shown by the comparison of the angle between the unit pyramid 2?{111} an(i the three 

pinacoids. There are only three pinacoids and of course only one 

unit pyramid in the orthorhombic system, so that the angles a p, 

& p, c p would show at once any identical values between two orthorhombic minerals, no matter how they were oriented. As earlier 

given, the angle between one pinacoid and the unit pyramid was 

accurately measured on the lucinite crystals. In the orientation

i Schaller, W. T., Crystallized variscite from Utah: TJ. S. Geol. Survey Bull. 509, p. 61,1912.

97888° Bull. 610 16 5
66 MINERALOGIC NOTES SERIES 3.

adopted for that mineral this is the angle c{001} : p{111}. This angle 

has a measured value of 56° 07'. The three pyrainid-pinacoid angles 

of variscite are calculated to be {001}:{111} - 58° 36', {010}: {111} = 

55° 20', {100}: {111} =50° 29', with none of which does the lucinite 

angle of 56° 07' agree. The closest yalue is {010} :{111} = 55° 20', 

which, however, differs 47', or nearly 1°, from the lucinite angle.

The fact that the two modifications of a mineral occur together, 

as shown in figures 52 and 53 (p. 57), is by no means unusual. Compare, for instance, the occurrence of rutile, anatase, and brookite, 

described by Palache.1

PHYSICAL PROPERTIES.

Lucinite does not show any cleavage, and in that respect it resembles variscite. No indication of twinning was seen on the octahedral 

crystals of- lucinite, whereas twinning on the associated variscite is 

by no means rare. (The twinning of variscite is described on p. 77.) 

The hardness of lucinite is about 5.

The density of lucinite was not accurately determined. The 

crystals are so minute that it is difficult to obtain a crystal absolutely 

free from any adhering gangue. The density was therefore determined on fragments of the granular material, which on analysis was 

found to contain 26.29 per cent of quartz. The results obtained were 

not altogether satisfactory. They are as follows, 25 small fragments 

about 2 millimeters in diameter being suspended in Thoulet solution:

Density.

2.576

2.573

2.558

2. 548

Sank.

3

9

19

24

Floated.

22

16

6

1

The results indicate that the density of the specimens lies between 

2.57 and 2.56, with perhaps 2.566 as an average value. Correcting 

these values for the 26.29 per cent admixed quartz (density 2.66) 

gives the density of lucinite as between 2.52 and 2.53. It is therefore 

nearly identical with that of variscite, which was determined on 1.3 

grams of the tabular crystals by the pycnometer method to be 

2.536, or in round numbers 2.54. The assumption that the granular 

material is lucinite and not variscite is based on the fact that all the 

drusy crystals coating cavities are lucinite. No tabular variscite 

crystals were seen on this material.

' Palache, Charles, Anatas, BrwWt iffld Titanit von Somerville, Mass.: Rosenbusch Festschrift, p. 311, 

1906r
LUCINITE, A NEW MINEKAL: A DIMORPHOUS FORM OF VAMSOITE. 67

OPTICAL PROPERTIES.

Lucinite is green and on being heated undergoes the same color 

change to deep lavender as the associated variscite. The luster is 

vitreous; -the streak white or gray. The small fragments are transparent when bounded by parallel faces.

The optical orientation could not be determined.

The refractive indices are slightly higher than those of variscite. 

For instance, in crushed material all the indices are higher than 

1.555, whereas for variscite a = 1.546, 0 = 1.556, 7 = 1.578. The 

results of the examination have yielded minimum and maximum 

values for the indices and these may be tentatively given for the 

mineral as a = 1.56, 7 = 1.59. The birefringence, 7 a = 0.03, is 

high, about the same as that of variscite. On one section, an interference figure was observed with 2E large (at least about 100°). Its 

sign is negative, whereas variscite is positive.

The crystals are practically nonpleochroic, the color of the transmitted light being a pale green.

CHEMICAL PROPERTIES.

The pyrognostic properties of lucinite are the same as those of 

variscite.

A sample of the granular material whose cavities were lined with 

crystals of lucinite was analyzed and found to contain 26.29 per cent 

of silica, due to admixed quartz which was later identified in a thin 

section. The close similarity in crystal angles of luoinite and variscite made it imperative that the crystals of lucinite be analyzed. 

With great difficulty a sample was prepared which contained about 

10 per cent of tabular variscite crystals, 10 per cent of granular 

material (lucinite or variscite ?), and 80 per cent of octahedral crystals 

of lucinite. The entire sample analyzed weighed only 25 milligrams, 

but the results verified the fact that the composition of the octahedral lucinite crystals was the same as that of the tabular variscite 

crystals. The results obtained are shown below.

Analyses of ludnite.

AlaOa ..... ..'......

PA----.-.--..

E220-- ...........

SiOa ..............

Granular 

material.

25.82

31..56

16.80

26.29

100.47

Same with 

quartz deducted.0

34.97

42.75

22. 75

100. 47

Octahedral 

crystals. b

29

44

22

1

96

Variscite 

tabular 

crystals.

c 32. 96

44.73

22.68

100. 37

Calculated 

for AlaO,. 

Pa05 .4Hab.

32.31

44. 93

22.76

100. 00

o Other impurities may have been present in the sample, but no allowance is m^de for them. 

6 Probably had about the following composition: Octahedral crystals, 80 per cent; tabular variscite 

crystals, 10 per cent; granular material, 10 per cent, 

c The percentage of A12 03 is 32.40. The figure given includes V2O3, 0.32; Cr2 03 , 0.18; Fe203) 0.00.
68 MINERALOGIC NOTES SERIES 3.

The analyses agree well enough with the calculated values for the 

formula A1203 .P205 .4H2O to show that the chemical composition of 

lucinite and variscite are the same.

The amount of water given off by the granular mass qf lucinite 

(which can not be told from granular variscite in the absence of 

crystals) at 100° is about the same as that found for variscite. At 

least, the available data are not sufficient to show whether or not 

the water is combined in a different way in lucinite than in variscite. 

All the water in lucinite is given off below 180°.

Lucinite contains a small amount of vanadium. No test was 

made for chromium, though doubtless it also is present. In fact, 

the chemical properties of lucinite and variscite have not shown any 

difference so far as they have been determined.

DIAGNOSTIC PROPERTIES.

The octahedral shape of the lucinite crystals serves to differentiate 

the mineral from the other crystallized aluminum phosphates.
THE CRYSTALLOGRAPHY OF VARISCITE.

PREVIOUS DESCRIPTION.

The crystallography of variscite was described by the writer 1 in 

1912 as determined on material from Lucin, Utah. A collection of 

specimens was later sent to the Survey by Messrs. Edison & Bird, of 

Lucin, and on these specimens were noted numerous crystals of variscite which showed several different habits from that given in the 

original description. Knowledge of the crystallography of variscite 

has been considerably extended by the study of the new material, 

on which the following description is based.

The variscite crystals either form coarsely granular masses which 

are only loosely coherent or partly fill cavities in the granular material. Some of these cavities contain only variscite crystals; in others 

the variscite is intermingled with crystals of lucinite. (Compare description of occurrence of lucinite crystals, p. 57.)

GENERAL CHARACTER OF CRYSTALS.

Eighteen crystals were detached and measured on the two-circle 

goniometer. The crystals averaged about 1 millimeter in length 

and were much smaller in their other dimensions. They are both 

simple and twinned crystals. The general habit is tabular, with several modifications, as described beyond.

CALCULATION OF ELEMENTS.

The measured crystals of variscite yielded additional angular values 

which are close to those earlier obtained. The fundamental angles 

from which the axial ratio was calculated in the published description 

of the variscite crystals are shown below, with the present measurements given immediately beneath them.

Former measurement: (010): (110)=48° 10'.6, (010): (012)=61° IT. 

Present measurement: (010): (110)=48° 12/.6, (010): (012)=61° 25'.5.

A new value for variscite was therefore calculated by combining 

the former and the present measurements. The new axial ratio varies 

but slightly from the published ratio but is somewhat more accurate. 

From the 22 good measurements of m{110} here given an average 

value of 48° 12'.6 is calculated for the <f> angle. This is almost identical with the value earlier calculated as the average of 26 measurements, namely, 48° 10'.6. The average of these two values gives 

48° 11'.5, from which the a axis is calculated as 0.8944. From the

i Schaller, W. T., Crystallized variscite from Utah: U. S. Geol. Survey Bull. 509, p. 57,1912.

69
70 MINERALOGIC NOTES SERIES 3.

17 good measurements of e{012} is obtained an average of 28° 34'.5, 

which is slightly different from the previous value of 28° 43'. An 

average value of 1.0919 is obtained for c, as follows:

Average of 17 measurements, P (012)=28° 34'.5, c=l. 0893 

Average of 12 measurements, p (012)=28° 43', c=l. 0957

Average of 29 measurements, c=l. 0919

The new value for the axial ratio of variscite, as calculated, is

therefore

a: l:c = 0.8944: 1:1.0919. p0 = 1.2208.

The former value was a: I: c = 0.8952:1:1.0957. 

The measured angles of m{110} and e{0l2} } from which the axial 

ratio was calculated, are given in the following table. For comparison the measurements of those faces which gave poor reflections are 

. also included, but they were excluded from the average value of the 

good reflections.

Measurements ofm{110} ande{012} variscite.

Crystal No.

1....................

1....................

2....................

3....................

Q

5....................

6....................

6....................

7....................

8....................

9....................

11....................

12....................

19

19

13....................

13....................

13....................

13....................

15....................

15....................

16....................

16....................

16....................

16....................

17....................

18....................

is.....:..............

18....................

' »(]

Good 

reflection.

0 /

48 28

48 22

48 23

48 06

48 08

48 05

48 09

47 4Q

48 14

48 15

48 04

48 13

48 27

48 09

48 32

48 04

48 16

47 51.

47 51

48 26

48 21

48 24

48 12.6

10}

Poor 

reflection.

0 /

' 48 06

47 27

47 47

48 19

48 19

47 36

47 56

e(0

Good 

reflection.

o /

28 37

28 26

28 39

28 34

 28 36

28 34

28 39

28 29

28 43

28 31

28 36

28 35

28 31

28 32

28 36

28 33

28 35

28 34. 5

12}

Poor 

reflection.

0 /

28 31

28 49

28 58

28 33

28 31

28 40
THE CRYSTALLOGRAPHY OF VARTSCITE. 71

FORMS AND ANGLES.

In the writer's first work on variscite only four lorms were determined, namely, &{010}, a{100}, m{110}, and e{012}. The study of 

additional crystals has extended this list to 14 forms, 9 new ones 

having been found on the 18 measured crystals and the presence of 

the base c{001} on crystals from Arkansas having been verified. 

The forms now established for variscite are as follows:

Pinacoids: cfOQl}, 6{010}, a{100}..

Prisms: Z{130}, j{250}, d{l20}, fc{340}, m{110}, g{210},/{520}.

Domes: e{012}, 0{032}, £{102}.

Pyramid:

The average of the measured angles, as compared with the calculated values, is shown in the table below:

Measured and calculated angles for variscite.

[New forms are marked with a star.]

No.

1. .........

2..........

3..........

4..........

5.......... 

6. .........

7..........

8..........

9.......... 

10..........

11. .........

12..........

13..........

14. .........

Letter.

CO....

&.....

a.. ...

*Z......

*j...... 

*d.....

*/».....

*<?..... 

*/...-.-

*ff- 

*t

*pb .

Symbol

001 

010 

100 

130 

250 

120 

340 

110 

210 

520 

012 

032 

102 

111

Number of 

crystals.

is

5 

4 

3 

3 

2 

18 

1 

2 

18 

6 

1 

3

Number of 

measurements.

22 

5 

6 

4 

3 

2 

45 

2 

4 

30 

12 

1 

1

Measured.

0

0 /

6 66

90 00 

20 30 

24 08 

29 20 

40 10 

48 13 

65 51 

70 10 

0 00 

0 00 

90 07

P

0 /

90 00 

90 00 

90 00 

90 00 

90 00 

90 00 

90 00 

90 00 

90 00 

28 35. 

58 22 

31 54

Calculated.

0

0 /

0 00 

90 00 

20 26 

24 06 

29 12 

39" 59 

48 12 

65 54 

70 19 

0 00 

0 00 

90 00 

48 12

P

0 /

0 00 

90 00 

90 00 

90 00 

90 00 

90 00 

90 00 

90 00 

90 00 

90 00 

28 38 

58 36 

31 24 

58 36

« The form c^OOl} not found on the crystals from Utah, is discussed on p. 79. 

b The faces otp{\\\\ were not measured by their coordinate angles. See p. 73.

c{001}. For description of the basal pinacoid, see p. 79. The form 

is not present on the crystals from Utah.

&{010}. The brachypinacoid& is the dominant form of variscite and 

is by far the largest form observed on all of the crystals. It is vertically striated, although on some crystals the striations are so faint as 

to be hardly discernible. The striations are strongly developed on the 

twin crystals.

a {100}. The macropinacoid a, a rare form, was seen on only five 

crystals, on all of which a single line face represented the form. The 

4> angle, theoretically 90° 00', was measured as 89° 41', 90° 05', 90° 08', 

89°, 90° 08'.
72 MINERALOGIC NOTES SEEIES 3.

m{110}. The unit prism is the second largest form on variscite. A 

faint vertical striation was noted on a few faces, whereas generally 

the faces of m are smooth and give good reflections. The measurements of the form have been already given.

The occurrences and measurements of the new prisms I, j, d, h, #, 

and / are given in the following table:

Occurrences and measurements of new prisms on variscite. 

[Bold-faced figures show calculated values. Reflections poor. All line faces.]

Form and crystal No.

Z{230}. ....!.................

1...........................

2.....1......:..............

3...........................

3...........................

3...........................

15..........................

j{250}.......................

1...... .....................

1........ ...................

12..........................

13..........................

d{120}............ ..........

1............ ...............

2...........................

16....................;.....

4>

0 /

20 26

19 08

21 24

21 12

19 38

20 34

21 05

24 06

24 06

24 08

25 23

22 55

29 12

29 37

28 35

29 49

Form and crystal No.

h{^40}. .....................

1...........................

2........................:..

<?{210}......................

2...........................

2...........................

/{520}. ........... ...........

13..........................

13..........................

13..........................

16..........................

*

0 /

39 59

40 29

39 52

65 54

65 50

65 51

70 19

69 42

69 26

71 13

70 17

v e{012}. The brachydome e is the third largest form on variscite 

and, with m and b, forms the combination of most of the crystals of 

the mineral. The measurements of e have already been given.

The new brachydome #{032} is very characteristic of the nearly 

square crystals, whose combination is &, m, e, g. On some crystals 

the faces of g are smaller than those of e; on other crystals they are 

much larger. The occurrences and measurements are shown below.

Occurrences and measurements of g{032), variscite.

Crystal 

No.

4.......

4.......

6.......

6.......

7.......

7.......

8.......

9.......

Reflection.

Poor.......

Poor.......

Fair. .......

Fair........

Poor.......

Fair........

Poor.......

Fair........

Size of face.

Small.. ...

Medium . . .

Medium. . .

Line face . .

Small.

Small.-. ...

p calculated 58° 36'.

0 /

57 42

57 41

58 18

58 28

57 40

58 23

58 10

58 17
THE CRYSTALLOGRAPHY OF VARISCITE. 73

The new dome £{102} was observed only once, on crystal 1, as a 

medium-sized face giving a good reflection. It lay in the zone of 

and between c{001} and a{100}.

The unit pyramid ^{111} was observed on three crystals as 

minute faces truncating the corners of the rectangular face of & {010}. 

It was measured on only one crystal, on which the angle &{010}: 

^{111} was found to be 55° 34' (calculated 55° 20'). The unit 

pyramid was also observed under the microscope on several additional crystals which were obtained by crushing the coarsely granular

mineral.

COMBINATIONS.

The combinations observed on the 18 measured crystals from 

Utah are shown in the table below.

Combinations on variscite crystals from Utah.

Letter.

b 

a

I

t,

h

m

}

e

t,

P

1 

I

OQ

010 

100

130

BfiO

1?0

340

110 

?10

520

012 

03?

10?

Ill

1

b

I

j

d

h

m

e

2'

b

I

d

h

m

q

e

3

6 

a

I

m

e

4

b

m

e

5

b

m

e

P

6

b

m

e

j

7

b

m

e

P

8

b '

m

e

P

9

b

m

e

10

b

m

e

11

 6 

a

m

e

12

b

j

m

e

13

b

j

m

f

e

14

b

m

e

15

b 

a

I

m

e

1C

b

d

m

f

e

t

17

b

m

e

18

b

m

e

ZONAL RELATIONS.

The zonal relations of variscite can be seen on the accompanying 

gnomonic projection (fig. 62, p. 74), which is to be compared with the 

projection of lucinite forms shown in figure 54 (p. 62). The prism zone 

is by far the richest, as it contains 9 out of a total of 14 forms. The 

other three zones are: c e g 1), c t a, c p m.

HABITS.

All the crystals examined are more or less tabular in habit, but 

several modifications were noted, as described below.

Very thin, elongated plates, tabular parallel to 6(010}.

Short prismatic crystals.

Stout prismatic, nearly equidimensional crystals.

Long prismatic crystals.

Stout rectangular plates.

Very thin, elongated plates, tabular parallel to &{010}, are abundant 

on some of the specimens. A simple combination, 6 m e, is shown in
74 MINERALOGIC NOTES SEEIES 3.

figure 63, whereas a somewhat thicker crystal with a richer combination is shown in figure 64. A much stouter tabular crystal, intermediate between the very thin plates and the short prismatic crystals, 

is shown in figure 65.

Other crystals are much stouter than the one shown in figure 65, 

and these crystals are also much shorter, so that their habit may be

FIGURE 62. Gnomonic projection of variscite.

described as short prismatic. The combination observed on crystals 

of this habit is always & m e. The variation in habit of the short prismatic crystals to the stout prismatic, nearly equidimensional crystals 

is shown in figures 66 and 67.

The stout prismatic, nearly equidimensional crystals (fig. 67) are 

rather rare, but such habits as are illustrated in figures 63 to 66 are 

much more common.
THE CBYSTALLOGBAPHY OF VAR1SCITE. 75

On a few specimens were noticed long prismatic crystals, similar in 

combination to those shown in figures 66 and 67, except that they

md

FIGURE 63. FIGURE 64. FIGURE 65. FIGURE 66.

FIGURE 63. Very thin, elongated plates of variscite, tabulated parallel to 6{010>. Forms: &{010}, m{110},

<K012}. 

FIGURE 64. A thicker crystal of variscite with a richer combination. Forms: &{010}, Z{130}, <i{120}.

m{110>, q{2W}, e{012}.

FIGURE 65. A much stouter, tabular crystal of variscite. Forms: 6{010}, m{110}, e{012}. 

FIGURE 60. Short prismatic habit of crystal of variscite. Forms: 6{010>, m{110>, c{012}.

are elongated parallel to the vertical axis. Such a long prismatic 

crystal is shown in figure 68.

A very few crystals of a short to stout prismatic habit showed 

large development of the new brachydome </{032}, as shown in figure

FlGUEE 67. FIGURE 68.

\

FIGURE 69.

FIGURE 67. Stout prismatic, nearly equidimensional crystal of variscite.

FIGURE 68. Long prismatic crystal of variscite.

FIGURE 69. Short prismatic crystal of variscite with new dome. Forms: fr{010}, m{110}, e{012}, ^{023}.

69, and serve as a connecting link between the prismatic tabular 

crystals (figs. 63 to 66) and the stout rectangular plates (figs. 70 

to 72).
76 MINEEALOGIC NOTES SERIES 3.

TTV TTV

FIGURE 71. 

FIGURE 70. Clinographic projection of a stout rectangular crystal of variscite, with 6{010> drawn in

front. Forms: &{010>, m{110>, c{012>, ?{023V.

FIGURE 71. Orthographic projection on 6{010} of a stout rectangular crystal of variscite. Same forms as 

in figure 70.

e

FIGURE 72. Crystal of variscite elongated parallel to the a axis. Drawn with &{010} in front. Forms:

6{010}, m{110>, e{012>, 0{023>.

\

FIGURE 73. FIGURE 74.

FIGURE 73. Short prismatic crystal of variscite, with faces of p{lll}.

FIGURE 74. Stout rectangular crystal of variscite (No. 5), drawn with 6{010> in front. Forms: &{010}, 

o{100>, m{110>, c{ 012}, (7^023},
THE CRYSTALLOGRAPHY OF VARISCITE. 77

The stout rectangular plates, nearly as wide as high, are abundant 

on a few specimens, but do not occur directly with the prismatic 

forms. The combination of these stout rectangular plates is essentially & ra e g; rarely a line face of a{ 100} or a minute face of p{ 111} 

is also present. A clinographic projection of such a stout rectangular 

crystal, drawn with the brachypihacoid &{010} in front, is shown in 

figure 70. A similar crystal, in orthographic projection on l{ 010}, is 

shown in figure 71, in which the relative sizes of the four forms 

&, m, g, and e can be well seen.

An extreme case, in which the crystal is elongated parallel to the 

a axis, is shown in figure 72. Only one such crystal was noted. Figure 73 represents a crystal observed under the microscope. It has 

a short prismatic habit and is noteworthy for the large developFIGURE 75. Twin crystal of variscite. Twinning plane and composition face t{102}. Forms:

}, Z{120>, e{012>.

mentof faces of the unit pyramid p {111} which are unequally developed in their size, for the rear upper faces are very small.

A stout rectangular crystal with well-developed small faces of 

is shown in figure 74, with &{010} drawn in front.

TWINNING.

Twinning is by no means rare for the crystals of variscite, and several such twins have been measured. The prism-zone is generally well 

developed on these twins, and several prisms, notably Z{120}, are to 

be found on them in addition to m{110}.

The twinning plane is 2 {102}, and all the twins seen are contact 

twins with the twinning plane as the composition face. Such twins 

have been observed previously under the microscope, but on the 

present material they occur in measurable crystals. A contact twin 

of variscite is shown in figure 75, with the twinning plane {102} 

vertical.
78 MINEKALOGIC NOTES SERIES 3.

REIATION TO VARISCITE CRYSTALS FROM ARKANSAS.

The crystals of variscite from Arkansas were described in 1878 by 

Chester, 1 whose crystal drawing is here reproduced as figure 76. 

Chester describes these crystals as follows:

The crystals are rarely distinct but are usually found in complicated groups, sometimes forming clusters of a sheaf form. Very rarely single prismatic crystals are 

found, sufficiently distinct to admit of measurement. Figure 1 [fig. 76] gives the 

most common form, belonging to the orthorhombic system, and showing faces of 

I[m{110}], il [a{100}]f flf [6(010}], and 0 [c{001}]. In this crystal 7:7=114° 6'. In 

general but one termination is seen, but crystals showing both ends are sometimes 

found lying on the quartz matrix, the bases being similar to each other. The face 

il [a{100}] is very small and therefore easily overlooked, and t£ [6{010}] is about the 

same size as 7, so that these crystals may readily be mistaken for hexagonal prisms.

Crystals showing a simple termination like that 

in figure 1 [fig. 76] are seldom seen. More frequently the basal plane is * * * more complicated. These planes are often covered with a 

thin opaque white coating, probably of quartz.

Although Chester does not mention 

any striations on his prismatic crystals, 

yet the "sheaf forms" composed of 

"prismatic crystals" would indicate a 

vertical striation in the prism zone.

FIGUKE 76.-Crystal of variscite from Ar- From the angle (110) : (110) = 114° 06',

(After A. H.Chester.) The in- as given by Chester, the angle of a pinaterpretation of the forms, after Chester, is -i . ,1 , ,-i-ro^r./ » o=<ooi>,i={iioUMioo>,ii={oio>. cold to the unit prism is 57° 03'. An

Probably a more correct interpretation attempt to Correlate this angle with an 

is to make 1= {210}. , r , TT , . . ° , . .

angle on the Utah variscite or lucimte

has not led to any conclusive correlation, as shown in the table 

below.

Comparison of angles of variscite.

Arkansas variscite measured by Chester.

0 /

<010):(110)={jg 57

Utah variscite.

0 /

(010) : (130) =20 26 

(010) : (250)=24 06 

(010) : (120)=29 12 

(010) : (340) =39 59 

(010) : (110) =48 12 

(010) : (210)=65 54 

(010) : (520)=70 19

Utah lucinite.

0 /

(010) : (120) =29 48

(010) : (110) =48 53 

(010) : (210) =66 25

The only form of Utah variscite which approaches in angular 

value the measurement of Chester (32° 57') is d{l2Q}, whose $ 

angle, 29° 12', is 3° 45' less. Chester makes the statement that the

1 Chester, A. H., Note on the crystallization of variscite: Am. Jour. Sci., 3d sen, vol. 15, p. 207,1S78.
THE CRYSTALLOGRAPHY OF VARISCITE. 79

faces of 5(010} and m{110} are of about the same size, and it seems 

not impossible that the angle Chester measured is not, as he gives it, 

prism to prism, m :m, but brachypinacoid to prism, & :m, or (010) : 

(110). If this is true, his measurement, 114° 06' or 65° 54', is 

identical with the angle (010) : (210) = 65° 54' of the Utah variscite. 

It seems probable, therefore, that Chester's unit prism is in reality 

the prism (210), for with this change the Arkansas variscite becomes 

identical in angular value with the Utah variscite.

The question still remains whether the basal pinacoid, 0 of Chester, 

is hi reality a distinct form or only a coalescence of numerous nonparallel faces of some other form or forms.

The collection of the late Albert F. Holden, which is now in the 

Mineralogical Museum of Harvard University, contains several 

specimens of the Arkansas variscite which on visual inspection 

seemed to possess measurable crystals. Through the kind permission 

of Mr. Holden several of the crystals were detached and measured. 

It was soon found, however, that nearly all the crystals consisted of 

barrel-like or sheaf-like groupings of numerous crystals, hardly any 

two of which were in parallel position. Finally a crystal was found 

that allowed approximate measurement, with the following result. 

The crystal was not a single unit, but was built up of several in nearly 

parallel position. The faces being defined by their size, the measurements may be given as follows: What is here described as a face, 

however, consists of numerous faces in approximate parallel position, 

the reflections of which varied several degrees from one another. .The 

measured angle represents the center of these masses of reflections.

Measurement of prism zone of variscite from Arkansas.

Angle.

To next medium face. ............................

To next large face. ................ ; ..............

To next small face ..............................

To next small face. .............................

Back to first. ...................................

o

. .... 57

..... 29

..... 33

..... 58

..... 61

..... 29

..... 93

Interpretation.

Form.

120 

010 

120 

100 

120 

010 

(120) 

100

Calculated 

angle.

o /

60 48 

29 12 

29 12 

60 48 

60 48 

29 12

90 00

If the interpretation above set forth is correct, then the prism forms 

on the crystal measured are &{010}, a{100}, and d{l20}, whereas, 

according to the interpretation here given of Chester's measurements,
80 MINEEALOGIC NOTES SERIES 3.

the combination in the prism zone on his crystal was 6{010}, a{100}, 

g{210}. The coincidence of the first measured angle (57°) with 

Chester's measurement (57° 03') is more apparent than real, for the 

different values of the same angle as measured on 

the crystal here described are 57°, 61°, 57°, 62°, 61°, 

average 59° 50'.

Although the base was convexly rounded, the 

series of reflections ceased at a p angle of 17° on 

one side and 14° on the other that is, the outermost reflecting face on one side of the base was 

inclined about 17° to the main axis of the composite crystal, and the outermost reflecting surface 

on the other side of the base was inclined about 

14° from the main axis. The crystal can readily 

be seen to have a sheaf form, as shown in figure 

77, and as the known forms nearest to the base are 

inclined thereto at considerably more than 17° 

(001) : (102) =31° 24'; (001) : (012) =28° 38' it is 

concluded that the terminal face is in reality the 

basal pinacoid. The form c{001} must therefore 

be.included in the form system of variscite. 

The approximate appearance of one of these sheaf-like crystals, 

with the interpretation of the forms as deduced from the measurements, is shown in figure 77.

FIGURE 77. Crystal of 

variscite from Arkansas, showing sheaf-like 

structure'. The forms 

present are probably: 

c<001>, b{QW>, a{WO}, 

<Z{120>.
SCHNEEBERGITE.

ORIGIN OF INVESTIGATION.

Schneebergite, which was incompletely described in 1880 by its 

discoverer, was considered to be closely related to atopite until 

Eakle and Muthmann 1 in 1895 put it in the garnet group. Koechlin 

in 1901 showed that such a conclusion was not correct, and the 

true status of schneebergite has remained in uncertainty ever since.

When the writer was in Vienna in 1912 Dr. Koechlin brought out 

the specimens of schneebergite and readily agreed to furnish the 

material for a reexamination of the mineral. With his customary 

liberality he sent his entire collection of specimens to Washington, 

where they were studied as time afforded. Hearty thanks are due 

to Dr. Koechlin for his willingness to sacrifice his valuable material 

in order to have the properties of schneebergite determined.

The results obtained may be briefly summarized as follows: 

Schneebergite is an isometric mineral crystallizing in octahedra 

which show anomalous double refraction. Chemically it is an 

iron-calcium-antimony compound, of the empirical formula CaSb03 . 

The antimony exists in two states of oxidation, and the formula, 

written 2CaO.Sb204 , is interpreted as 2CaO.Sb203 + 2CaO.Sb205 . 

Although related to romeite and atopite, it is very distinct from 

them and forms a well-characterized, definite mineral species. In 

order to correlate schneebergite with the other known calcium 

antimonates, it became necessary to investigate also romeite and 

atopite, and the results obtained are stated in the following paper. 

For comparative purposes it may be stated here that in romeite 

the anthnony does not exist in two states of oxidation as given by 

Damour but only in the higher state. The formula for romeite is 

5CaO.3Sb205 . The formula for atopite, based only on Nordenskiold's 

analysis, is 2CaO.Sb2 05 . The Brazilian so-called atopite is romeite. 

Possibly the Swedish ^atopite is the same as romeite.

Although some of the writers who have described schneebergite 

confused that mineral with garnet and gave therefore not a description 

of schneebergite but of garnet, the results obtained by them are 

of interest and value and have been abstracted at some length, 

especially the descriptions of the paragenesis. The following historical sketch is thereby somewhat extended, but the facts already 

published are best given in one section and can then be conveniently 

referred to as a whole.

1 See page 85 for bibliography. 

97888° Bull. 610 16 6 81
82 M1NERALOGIC NOTES SEK1ES 3.

HISTORICAL SKETCH.

Schneebergite was first described by Brezina in 1880. It was 

found at the Pockleithner-Halde, Schneeberg, Tyrol, Austria, in 

transparent honey-yellow octahedra, which had a vitreous to adamantine luster. The average of nine measurements of the octahedral angle was 70° 31.9' (calculated 70° 31.7'), the limits being 

70° 26.5' and 70° 36.6'. The small octahedra, ranging in size from 

0.5 to 1 millimeter, occurred isolated in anhydrite, gypsum, or 

chalcopyrite. The mineral also formed layers in the chalcopyrite. 

Other associated minerals were magnetite, sphalerite, and pyrrhotite. 

Many of the octahedra of schneebergite had microscopic inclusions 

of magnetite or of negative crystals, and the mineral was then 

birefringent; otherwise it was isotropic. The crystals were brittle 

with a conchoidal fracture and showed traces of a cleavage after 

{110}. The hardness is 6.5. The density was determined on 0.17 

gram as 4.1 (average of 3.9, 4.1, 4.3). When heated before the blowpipe, the crystals turned slightly brown but did not fuse. Longcontinued fusion with sodium carbonate finally dissolved them. 

Qualitative tests showed the presence of much antimony and lime, 

a small amount of- iron, and traces of copper, bismuth, zinc, magnesia, and sulphuric acid.

The material studied by Elterlein, who was the second writer on 

schneebergite, was similar to that used by Brezina, except that calcite and breunnerite took the place of anhydrite and the schneebergite occurred not as individual crystals, but only as a crystalline 

aggregate, in part in reniform masses. Most of Elterlein's schneebergite was garnet. The paragenesis of the ores of Schneeberg are 

given in detail by Elterlein, and the following paragraphs contain 

notes taken from his description.

The chief ore at Schneeberg is a massive, mostly deep-black sphalerite, which occurs either in pure masses or in intimate mixture with 

one or more of the other materials, particularly with breunnerite and 

quartz, but also with tremolite (called Strahlstein in German), galena, garnet, etc. Galena is the second most abundant ore mineral, 

followed by pyrite, chalcopyrite, magnetite, pyrrhotite, boulangerite, 

tetrahedrite, and others. The chief nonmetallic minerals are quartz, 

breunnerite, and calcite. The general succession of minerals in the 

ore veins of Schneeberg is given as (1) quartz, (2) sulphides, (3) carbonates. In more detail, the order of succession is given as quartz, 

sphalerite (rarely pyrite or breunnerite), breunnerite (rarely galena), 

galena.

In addition to the above-named minerals, the following have been 

found in the Schneeberg veins: Silver, greenockite, arsenopyrite, 

argentite, ilmenite, brown iron ore, fluorite, dolomite, goslarite, malachite, gypsum, schneebergite, apatite, almandite, biotite, muscovite, 

and chlorite.
SCHFEEBEBGITE. 83

Out of the 39 mineral successions given by Elterlein, schneebergite 

is given in only one, No. 20, which is (1) breunnerite, (2) schneebergite, granular [doubtless garnet and not schneebergite]. He also 

claims to have traced under the microscope the alteration of calcite 

and breunnerite into schneebergite and in fact considers the breunnerite as the mother mineral of schneebergite [doubtless garnet]. He 

also remarks that garnet correspondingly disappears as the breunnerite increases in amount. Elterlein describes the garnet as red 

and showing either {110} or {110} with {211}, and his garnet is a 

different variety from what he called schneebergite. As will be 

pointed out later, what Elterlein called schneebergite was in fact 

garnet. The view is supported by the fact that the analysis of Eakle 

and Muthmann was made on material from a series of specimens 

collected by Elterlein.

Many of the ore veins, as figured by Elterlein, consist of parallel 

even layers of pure quartz, sphalerite, galena, or pyrite, or of mixtures 

of these with other minerals. Other occurrences show a concentric 

filling of open spaces (fig. 79, p. 86) with the same minerals, and 

many of the specimens of schneebergite at the writer's disposal show 

a concentric arrangement of the mineral layers. (Compare figs. 78 

and 80.)

The material analyzed by Eakle and Muthmann is described by 

them as follows:

Most of the mineral appears as crystalline aggregates upon the ore, which latter 

consists of a mixture of magnetite, zinc blende, and chalcopyrite; the gangue mineral 

is massive quartz. The aggregate's are partly kidney shaped and consist of rounded 

crystal grains, with scarcely recognizable form. The color varies from honey-yellow 

to bright wine-yellow; the surface is often brown from a slight decomposition, the 

color being due to a thin coating of iron hydroxide. The perfectly fresh, undecomposed crystals are isotropic and occasionally show weak and abnormal double refraction, especially when they contain inclusions of fine particles of the ore.

On other ore specimens the mineral appears as thin coatings or as a deposit; occasionally well-defined crystals can be observed, all of which show the single form of 

the octahedron. The crystals are generally accompanied by calcite and breunnerite, 

from which the mineral has evidently originated, as has been shown by v. Elterlein; 

commonly the schneebergite surrounds the calcite, if it has not entirely replaced it. 

The paragenesis can be followed still better in sections under the microscope. It 

can be seen that the calcium-iron carbonate changes at first to a light-yellow doublerefracting mineral of indefinite composition, which by further change becomes granular and isotropic and finally passes into the pure schneebergite.

The description of what Elterlein calls schneebergite is so similar 

to that of the material analyzed by Eakle and Muthmann (and found 

to be garnet) that there can be no question that what 'Elterlein called 

schneebergite was in reality a garnet. Eakle and Muthmann found 

the density of their material t'o be 3.838. In a blast flame it fused 

to a dark-brown liquid, whereas Brezina describes schneebergite as
84 MINERALOGIC NOTES SEEIES 3.

infusible. t The analysis of Eakle and Muthmann showed their material to be a pure lime-iron garnet.

Analysis of garnet (supposed to be schneebergite). 

[Eakle and Muthmann, analysts.]

,

Si02 ......................................

Fe203 - ....................................

CaO......................................

Found.

1 -

32.33

32.58

2

35.45 

32.11

Calculated 

for 3CaO. 

Fe203 . 

3Si02 .

35.43 

31.50 

33.07

The facts which indicate that Elterlein and also Eakle and 

Muthmann confused garnet with schneebergite are briefly summarized as follows:

1. Elterlein's succession No. 20 (1) breunnerite, (2) schneebergite, which should read (1) breunnerite, (2) garnet was observed 

by the writer on many specimens (figs. 83 and 84).

2. The alteration of breunnerite to schneebergite as described by 

Elterlein and by Eakle and Muthmann could not be found by the 

writer, whereas the derivation of garnet from breunnerifce is common.

3. The reciprocal abundance of red dodecahedral garnet and 

breunnerite, as noted by Elterlein, suggests the derivation of garnet 

from the carbonate mineral and makes the view plausible that the 

yellow octahedral garnet (the so-called schneebergite) may also 

have been derived from breunnerite.

4. Elterlein's garnets showed only {110} and {211}. Therefore 

he did not recognize the presence of octahedral garnet and took 

such a rare form of garnet to be schneebergite.

5. The specimens in Munich, which furnished the material on 

which Eakle and Muthmann made their analysis, were originally 

collected by Elterlein and doubtless formed in part the basis of his 

own description.

As a result of the analysis given by Eakle and Muthmann, schneebergite was considered as a garnet and was included as such in the 

textbooks of mineralogy. In 1902 Koechlin reviewed the history 

of schneebergite and, after pointing out some inconsistencies between 

the results obtained by Eakle and Muthmann and those given by 

Brezina, gave the results of his own interrupted investigation of 

the mineral. Koechlin quotes a letter from Fr. Loffler, who said 

that schneebergite occurred in anhydrite only in the first specimens 

found. Moreover, anhydrite and gypsum have been found only 

rarely. Most of the specimens were obtained from the dump, and
SCHNEEBERGITE. 85

those most likely to contain schrieebergite consist df drusy sphalerite, 

which contains also pyrite, chalcopyrite, ankerite (the breunnerite 

of. Elterlein), or calcite. The druse was coated with secondary 

calcite which, when removed with acid, showed the schneebergite 

crystals. Koechlin found schneebergite on about a quarter of the 

specimens supplied by Loffler; the others show only the garnet of 

Eakle and Muthmann.

A distinct succession was observed by Koechlin as follows: The 

lower part of the specimens consists of pure sphalerite. Next 

follows a layer consisting chiefly of breunnerite and calcite, but 

containing also quartz, tremolite, sphalerite, chalcopyrite, and 

magnetite. In this layer occurs also the garnet. Above this is 

a layer in which magnetite and chalcopyrite predominate, but the 

carbonates are hardly visible. Toward the upper portion of this 

layer the sulphides are drusy, and on this drusy layer and embedded 

therein is the true schneebergite. The layer of secondary calcite 

which originally coated the schneebergite had been completely 

removed by acid when the specimens were received by Koechlin. 

The schneebergite was therefore the next to the last mineral to 

form in the " Hohlraumausf tillungen mit concentrischkrustenformiger Textur," which are abundant in the veins at Schneeberg. 

The schneebergite was never seen in the lower layers or bands.

Koechlin made a partial analysis of schneebergite, with the following result: CaO, 20.14 per cent, 19.91 per cent; Fe203, 8.48 per cent; 

MgO, 0.18 per cent; traces of bismuth, alumina, potassium, sodium, 

arsenic, tin, and lead. Silica, copper, zinc, and sulphuric acid were 

absent. Moreover, antimony, though not quantitatively determined, 

was found to be present in large amount.

A determination of the refractive index of schneebergite gave 

EQawatsch the result n = 2.10, thereby confirmmg the work of Koechlin and disposing of the erroneous conclusion that schneebergite was 

only a lime-iron garnet.

BIBLIOGRAPHY.

The .following is a list of the publications cited discussing schneebergite:

BREZINA, A., Ueber ein neues Mineral, den Schneebergit: K. k. geol. Reichsanstalt

Wien Verb., 1880, p. 313. 

ELTERLEIN, A. VON, Beitrage zur Kenntniss der Erzlagerstatte des Schneebdrgs bei

Mayrnin Siidtirol: K. k. geol. Keichsanstalt Wien Jahrb., vol. 41, p. 289, 1891. 

EAKLE, A. S., and MUTHMANN, W., Ueber den sogenannten Schneebergit: Zeitschr.

Kryst. Min., vol. 24, p. 581, 1895; Am. Jour. Sci., 3d ser., vol. 50, p. 244, 1895. 

KOECHLIN. R., Zur Schneebergitfrage: Min. pet. Mitt., vol. 21, p. 15, 1902. 

HLAWATSCH, C., Der Brechungsei.ponent des Schneebergits: Min. pet. Mitt., vol.

21, p. 21, 1902.
86 MINEBALOGIC NOTES SERIES 3.

FIGURE 78. Sketch of specimen of schneebergite with 

concentric bands. Compare figure 79. S, Schneebergite; C, chalcopyrite; M, magnetite; Ca, calcite; 

B, breunnerite; T, tetrahedrite; Sp, sphalerite.

PARAGENESIS.

The following descriptions of the paragenesis of schneebergite are 

based entirely on the specimens obtained from Dr. Koechlin. No 

data are available to indicate the relation of the specimens to the

vein or rock of the region. The 

descriptions apply therefore only 

to the specimens themselves.

A very marked feature of 

nearly all the specimens is a 

distinct banding. The bands 

are nearly parallel on some 

specimens and decidedly concentric on°others. The parallel 

bands, in fact, may be only apparently parallel and may be 

part of an elongated concentric 

structure. One specimen in 

particular had an ellipsoidal arrangement of the bands, as is shown 

diagrammatically in figure 78. Elterlein describes the occurrence of 

"concentrischkrustenformige Textur" in the "Hohlraumausfullun-. 

gen," and the structure of the specimen, as shown in figure 78, shows 

this same concentric arrangement of 

the cavity filling. According to Elterlein 

many of these lens-shaped bodies are 

built up of alternating layers of breunnerite and of galena. Figure 79 is a 

copy of Elterlein's sketch illustrating 

this relation. It is believed that the 

specimens of schneebergite represent 

similar "filling in" of cavities, although 

the concentric structure is not well 

shown on most of the specimens. It is 

to be remarked, however, that many 

small specimens from a filled-in cavity 

of the shape shown in figure 79 could 

be obtained that would show only 

parallel bands in which the concentric 

structure would be lost.

Two other specimens also show well 

the concentric arrangement of the bands and are sketched in figures 80 

and 81. A part of the original calcite covering the schneebergite still 

remains on the specimen shown in figure 80. The presence of two 

small bodies of garnet (shown in solid black in fig. 80), one of them 

completely embedded in the schneebergite, is anomalous, but there is

FIGURE 79. A lens-shaped cavity in sphalerite (a) filled in by alternating layers 

of breunnerite (6) and galena (c). Onefourth natural, size. (After Elterlein.) 

Compare with figure 78.
SCHNEEBERCflTE. 87

FIGURE 80. Concentric structure of bands 

of minerals on specimen of schneebergite. C, Chalcopyrite; M, magnetite; 

S, schneebergite; 0, garnet; Ca, calcite. 

Solid black, garnet embedded in schneebergite.

no reason why a secondary mineral like this garnet should not 

migrate and finally be deposited wherever conditions were favorable. The specimen illustrated in figure 80 is the only one ever 

seen by Dr. Koechlin that shows the 

direct association of garnet with schneebergite.

Figure 81 represents a portion of a 

specimen so broken as to show the granular calcite, which has been removed on 

most of the specimens.

Four specimens show the associations 

of schneebergite very well and are therefore briefly described. They are illustrated in Plate III, A, B, 0, and Plate 

IV, B. Figures 82, 83, 84, and 86 give 

the necessary explanation.

Plate III, A, shows a small specimen 

which has four distinct bands a lower band containing a mix- 

,,-=- ., ture of quartz and sphalerite, then mag- 

,;' \ netite with inclosed nodular masses of 

garnet, a thin layer of white calcite, 

and on top an aggregate of chalcopyrite 

and magnetite. On the upper surface 

of this aggregate isolated crystals of 

schneebergite are to be found. No chalcopyrite is present in the bands below 

the chalcopyrite and magnetite mixture but galena in small specks is scattered through all the bands except the 

lower one.

The specimen illustrated in Plate III, 

B, is very rich in schneebergite, and the 

material used for the chemical analysis 

was in part obtained from the left-hand 

corner of the upper layer of this specimen. The lower portion of the specimen is an aggregate of chalcopyrite 

and garnet in which are two large remnants of breunnerite (mixed with chalcopyrite). Above this is an aggregate 

of chalcopyrite and magnetite which 

is somewhat porous in its upper part, and it is here that an abundant schneebergite is found, intimately mixed with the chalcopyrite 

and magnetite.

FIGURE St. Granular calcite (Ca) filling 

cavity in banded arrangement of 

s?hneebergite (S) and associated minerals. C, Chalcopyrite; M, magnetite; 

G, garnet.
88 MINERALOGIC NOTES SEEIES 3.

Plate III, 0, shows the following succession of minerals: The lower 

portion, a little less than half of the specimen, is quartz, above

which is an irregular band of breunnerite. 

Isolated masses of quartz occur in the 

breunnerite, and breunnerite is also found 

as inclusions in the quartz. An incomplete small band of magnetite lies partly 

between the breunnerite and quartz and 

partly in the breunnerite. Above this 

is a black layer of calcite and magnetite,

FIGURE 82. Diagram of specimen shown which is followed by a layer of white

in Plate in, A. SP, Sphalerite; Q, caicite . The bands of breunnerite, calquartz; G,garnet; M, magnetite; Ca,cal- .. . n 

cite; C, chalcopyrite; S, schneebergite. Cite, and magnetite, With included Small

quartz masses, do not show sharp boundaries, but grade into 

one another. Several 

nodular masses of garnet are inclosed in this 

series of bands. Chalcopyrite is also scattered irregularly 

through these bands. 

Above these bands, but 

not sharply separated 

from the white calcite,

is a layer of chalcopyrite FIGURE 83. Diagram of specimen shown in Plate III, B.

1 ,., , . net; C, chalcopyrite: B. breunnerite; M, magnetite; S. and magnetite contain- - -

G, Garschneebergite

Ca+M

ing schneebergite 

in its upper portion.

In the specimen 

pictured in Plate 

IV, 5, massive 

black sphalerite 

forms the lower 

third. Above it 

lies a broad band 

composed essentially of a mixture 

of sphalerite, ga1 e n a, magnetite, 

and breunnerite. 

Some tremolite is 

also present. An 

irregular narrow band of magnetite overlies this broad band and is in 

turn followed by one of quartz or quartz and breunnerite. A band

FIGUBE 84. Diagram of specimen shown in Plate III, C. Q, Quartz; B, 

breunnerite; M, magnetite; G, garnet; Ca, calcite; C, chalcopyrite; S, 

schneebergite; solid blank, galena.
U, S. GEOLOGICAL SURVEY BULLETIN 610 PLATE Ml

ORE SPECIMENS WITH SCHNEEBERGITE FROM SCHNEEBERG, AUSTRIAN TYROL. 

For explanation see figures 82 to 84. All natural size. - - - .
U. S. GEOLOGICAL SURVEY BULLETIN 610 PLATE IV

A. ROMEITE FROM ITALY. 

For explanation see figure 85. Natural size. Described on page 96,

1$. SCHNEEBERGITE FROM AUSTRIAN TYROL. 

For explanation see figure 86. Natural size.
SCHNEEBERGITE. 89

of calcite and magnetite comes next, and over it is a mixture of chalcopyrite and magnetite containing schneebergite in its upper portion. 

No garnets were seen on this specimen, but they may well be present, 

especially in the band of quartz and breunnerite. No chalcopyrite 

occurs below the upper layer, but galena is scattered throughout the 

specimen.

The succession of minerals on the schneebergite specimens as 

described and illustrated in 

Plates III and IV and figures 

82, 83, 84, and 86 may be 

summarized as follows:

FIGURE 86.

FIGURE 85. Diagram of specimen shown in Plate.IV, A. Described on page 96. Br, Braunite; R,

romeite; A+P, albite and piedmontite. 

FIGURE 86. Diagram of specimen shown in Plate IV, B. Sp, Sphalerite; Oa, galena; M, magnetite,

B, breunnerite; Tr, tremolite; Q, quartz; Ca, calcite; S, schneebergite.

Succession of minerals on specimens of schneebergite.

10.. 

9...

8...

7... 

6...

5... 

4...

9

?,

i.:.

PL III, A.

1

Calcite 0 .... .....

[Schneebergite. .... 

| Chalcopyrite....;. 

[Magnetite........

f Chalcopyrite...... 

\Magnetite........

'WTTni'p pnlfifp

("Quartz. .........

\Sphalerite. ......

Sphalerite .......

PL III, B.

Calcitea... ......

[Schneebergite..... 

< Chalcopyrite......

f Chalcopyrite. . ....

[Garnet. .........

< Chalcopyrite. ..... 

I Breunnerite......

iQuartz ..........

(?)..............

(?)..............

(?)..............

PL III, C.

Calcitea .........

[Schneebergite..... 

| Chalcopyrite...... 

[Magnetite........

( Chalcopyrite.. ... .

White calcite..... 

Black calcite and 

magnetite.

PL IV, B.

Calcite. 0 

[Schneebergite. 

| Chalcopyrite. 

[Magnetite. 

JGhalcopyrite. 

\Magnetite. 

White calcite. 

Black calcite and 

magnetite.

Garnet?

f Quartz. 

\Breunnerite. 

M'agnetite. 

Sphalerite. 

Galena. 

' Magnetite. 

Breunnerite. 

Sphalerite.

Now removed.
90 MINEEALOdlC NOTES SERIES 3.

This succession shows a marked uniformity. The first mineral 

of the specimens was either quartz or sphalerite. After this came 

bands composed of more than one mineral, such as sphalerite, quartz, 

magnetite, and breunnerite. Garnet occurs on all the specimens, 

either with or directly above the breunnerite, but always directly 

associated with it. The garnet is the only mineral which occurs 

not as distinct bands but as nodular masses, and it is found only in 

the breunnerite bands, from which it is probably derived, as stated 

both by Elterlein and by Eakle and Muthmann. All these writers, 

however, considered the garnet to be true schneebergite. Above 

the garnet comes a mixture of black calcite and magnetite, over 

which is a small band of purer white calcite. This white calcite 

grades into the mixture of chalcopyrite and magnetite which is the 

matrix of the schnesbergite.

That the succession of minerals is not the reverse of that given is 

proved by their mode of occurrence as concentric fillings, in which, as 

shown in figure 78, the schneebergite is the nucleus. The mode of 

occurrence, as described by Elterlein, shows that .they could not 

be concretions, growing from the center outward.

The association of schneebergite is characteristic. It lies on and 

embedded in the mixture of chalcopyrite and magnetite, which is 

surrounded by bands of minerals in a well-defined succession. Tne 

garnet, mistaken for schneebergite, has a different place in the order 

of succession.

There is also a gradual change in the state of oxidation .of those 

elements existing in more than one form. The mineral first formed 

sphalerite has all its iron in the ferrous condition. The breunnerite 

likewise contains only ferrous iron. The next iron minerals to form,

garnet and magnetite, have both ferrous 

and ferric iron, and in harmony with this 

partial oxidation to a higher valency, the 

mineral last formed, schneebergite, has its 

antimony in two states of oxidation.

CRYSTALLOGRAPHY.

The crystals of schneebergite show only 

the octahedron o { 111} and have the appearance shown in figure 87. The measureFIGURE 87. crystal of schneeber- ments of Brezina, as given on page 82, show 

gite,o-<m>. a yery cjoge agreement with the octahedral

angle of the isometric system.

Nearly all the faces of the crystals measured were uneven and gave 

several indistinct reflections. The best measurement gave o : o' = 

109° 24' (calculated, 109° 28'). By placing a crystal in polar 

position on the two-circle goniometer, it was seen that the reflections
SCHNEEBERGITE. 91

from the four octahedral faces fell in a vertical line which had the 

correct p position for the isometric octahedron. Schneebergite is 

therefore, without question, isometric in its geometric symmetry.

PHYSICAL PROPERTIES.

Breziua gives a doubtful cleavage after {110}. No such cleavage 

could be detected by the writer, but a distinct cleavage parallel to the 

octahedron o{lll} was found. The cleavage is by no means as 

good as that of romeite from Brazil (the so-called atopite).

The density was given by Brezina as 4.1 (determined on 0.17 gram). 

The material used by him was without question not pure, and the 

amount of material used very small. A new determination of the 

density was made with a pycnometer on 2.0676 grams of pure material 

and found to be 5.41.

OPTICAL PROPERTIES.

The color of a mass, of pure crystals is "honey-yellow" according to 

Ridgway's Color standards,1 and the color of the powdered crystals 

is "baryte-yellow." The luster is adamantine. When examined 

optically, the crystals seem to be free from inclusions, and the suggestion arises that the magnetite inclusions observed by Brezina occurred 

not in the schneebergite but in the garnet, where such inclusions were 

also found by Eakle and Muthmann.

Schneebergite, being isometric, should be isotropic, but many of 

the crystals show anomalous low double refraction. The compound 

is probably dimorphous, the high temperature form being isometric.

The refractive index was determined by the embedding method by 

Mr. E. S. Larsen and found to be 2.09.

CHEMICAL PROPERTIES.

PYBOGNOSTICS.

Schneebergite would be classed as infusible, but in fine splinters the 

edges are with difficulty fused and rounded. In closed and open 

tubes no reactions occur. The mineral is insoluble in acids, but it is 

decomposed without difficulty in a sodium carbonate fusion. It 

becomes readily reduced when heated in hydrogen.

HOMOGENEITY OF SAMPLE ANALYZED.

The microscopic examination did not reveal any inclusions of foreign matter in the crystals of schneebergite. Pieces of the specimens were crushed so as to separate the individual minerals, and by 

a long-continued process of hand picking, by the use of the electromagnet and of heavy solutions, and by treatment with acids, a pure

sample was finally obtained. The acids used were hydrochloric, aqua

 *

1 Ridgway, Robert, op. cit.,p. 32. ' ,
92 MINERALOGIC NOTES SEEIES 3.

regia, and hydrofluoric. The concentration, of the acids used was 

not great nor was their use long continued at any one time. It was 

found that schneebergite was slightly attacked by aqua regia, but 

as all the products of attack went into solution no differential separation of the constituents took place and moreover the total amount 

of material dissolved was very slight. The crushed material was 

finally subjected to another careful examination under a magnifying 

glass, and the few impurities which remained were picked out by 

hand.

The purification of the material, although not worked on continuously, extended over several months. A final sample of 2.0676 grams 

was obtained, in which no impurities could be detected by a microscopic examination.

ANALYTICAL METHODS USED.

The density of the sample was first determined with a pycnometer. 

The mineral was then air dried for several weeks and finally was 

ground in a mechanical grinder for several hours, as it was thought 

necessary to have the mineral in a state of very fine subdivision in 

order to obtain decomposition. The results of the analyses have 

indicated that for schneebergite and also for romeite (including the 

the Brazilian "atopite") a very fine powder is not necessary and 

that .the difficulty of decomposition of these minerals has been 

exaggerated.

Part of the sample was fused in a platinum crucible with sodium 

carbonate, and in the resulting acid solution antimony was thrown 

out by hydrogen sulphide. In the filtrate iron and calcium were 

determined as usual. A special search was made for the elements 

reported by earlier investigators, and the following elements could 

not be detected in the sample: Copper, lead, bismuth, tin, arsenic, 

aluminum, zinc, magnesium, and potassium. These elements, as 

found by earlier analysts, doubtless owed their presence to admixed 

minerals. Another portion of the sample was reduced in hydrogen 

and the water formed was collected and weighed. The 0.5-gram 

samples were placed in a nickel boat, inserted in a hard-glass tube 

properly arranged, and a current of dried carbon dioxide was passed 

through the apparatus for an hour. The glass tube with its boat 

containing the finely powdered schneebergite was then dried by 

being gently heated, the current of carbon dioxide being continued. 

After cooling, hydrogen was passed through the apparatus for half 

an hour, after which, the weighed calcium chloride tube being 

attached, the mineral was gently heated until decomposition began. 

Toward the end of the operation the boat and its contents were heated 

to a dull red. The hydrogen used was generated by the action of 

sulphuric acid on zinc. The gas, first washed, was then passed
SCHNEEBERGITE. 93

through an alkali solution of pyrogallic acid, then through sulphuric 

acid, and then through a tower of calcium chloride. Both gases 

passed through a different final series of three calcium chloride tubes 

placed just before the ignition tube containing the mineral. The 

percentage of water occurring as such in the mineral powder was 

determined by loss on ignition, as it did not belong to the mineral, 

but was introduced or absorbed by the very fine powder during the 

grinding of the sample. Individual unground crystals did not yield 

any water when ignited, as special tests on this point were made.

QUANTITATIVE COMPOSITION.

The results of the analysis are stated below. The antimony is 

reported as the metal (calculated from the weighed Sb2S3 ), and the 

oxygen combined with the antimony (calculated from the weighed 

H20) is given as such.

Analysis and ratios of schneebergite.

Sb., ........................................

0..................... .......................

FeO... .......................................

CaO. ........................................

Na20......... ...............................

H20&.......................................

Analysis.

57. 40

15.19

8.51

17.42

.10

.30

1.67

100. 59

Ratio.

0.478

. 948

.1181

.322 0.441

. OOlJ

1. 02 or 1

2. 03 or 2

. 94 or 1

« A small residue of undissolved larger grains from the sodium carbonate fusion, 

b Determined by loss on ignition. The water was absorbed by the finely ground powder, as special tests 

showed that the unground crystals yielded no water on ignition.

The amount of oxygen as actually determined by collecting the 

water given off on decomposing the mineral in hydrogen is 17.83 per 

cent. The amount of oxygen combined with the iron, or 1.90 per 

cent, is to be deducted from the 17.83 per cent, leaving 15.93 per cent 

of oxygen combined with the antimony. At the time this determination was made it was not known that the powdered substance 

had absorbed water during grinding. The tube containing the powdered schneebergite was heated before the quantitative determination was made, but it is not known whether the heat was sufficient to 

drive off all the absorbed water in the schneebergite powder. On 

the assumption that all the water was driven off, the figure above 

given for oxygen combined with antimony, namely, 15.93 per cent, 

is correct. If, however, none of the absorbed water was driven off, 

then the percentage of oxygen obtained is to be lowered by the amount 

of oxygen in the absorbed water, namely, 1.48 per cent, giving for
94 MUSTEEALOGIC NOTES SERIES 3.

oxygen combined with antimony 14.45 per cent. As it is not known 

which condition is the true one, and as it is believed that an intermediate condition is probably more correct that is, that some of the 

water was driven off and some retained an average of the two 

figures, or 15.19 per cent, is taken as the true value.

The ratios of the analysis show that the oxidation of the antimony 

must be that expressed by the oxide Sb204 . That such a result is 

obtained by either one of the three interpretations just given for the 

percentage of oxygen in the mineral is shown by the following calculation. With the determination of antimony (57.40 per cent Sb) 

as a basis, the required percentage of oxygen for the three possible 

states of oxidation of the antimony has been calculated. As can 

readily be seen, the determinations of oxygen agree only with the 

value calculated from the Sb2 04 state of oxidation.

Comparison of oxygen percentages in schneebergile.

SbaO,..:........................ ...............

Sb204 . .........................................

Sb205 ----- -------------------------------------

Per cent of oxygen.

Calculated.

11.48 

15.31 

19.14

Found.

< 

[15.93 maximum. 

< 15. 19 average. 

(l4.45 minimum.

The ratios yield the formula Sb02 (R"0) or R"Sb03 , in which 

K" is one-fourth Fe" and three-fourths Ca. The formula may 

then be written more exactly Fe"Ca3Sb4012 . The analyses of romeite, 

however, have shown that in these minerals the bases Ca, Fe", 

Mn", and Na^ must be considered as isomorphously replacing one 

another, and the formula for schneebergite is therefore written in its 

simplest form as CaSb03 . The antimony exists in two states of oxidation and the formula 4Ca0.2Sb204 ( = 4CaSb03 ) is interpreted as 

2CaO.Sb203 + 2CaO.Sb205 .

Schneebergite, empirically CaSb03 , is most simply regarded as a 

mixed salt, namely a calcium pyro-antimbnite, 2CaO.Sb203 , with a 

calcium pyro-antimonate, 2CaO.Sb2 05 . To regard the trivalent 

antimony as a base, to be added on to the calcium, throws too heavy 

a burden on the pentavalent antimony, which must then serve as 

acid for an overwhelming base.
. ROMEITE. 

ORIGIN OF INVESTIGATION.

In order to compare the composition of schneebergite with that of 

rorneite and atopite, it was necessary to undertake a reexamination, 

with analysis, of these two later minerals. Through correspondence 

a collection of romeite specimens was obtained from Capt. Albert 

Pelloux, of Genoa, which furnished the material for this description. 

The writer's thanks are due to Capt. Pelloux for his liberality in 

furnishing these rare and valuable specimens.

Atopite from the original locality at Langban, Sweden, described 

by Nordenskigld, was not available, but as Hussak had stated that 

the results of his study of the later-described Brazilian material 

agreed with the description and composition of the original Swedish 

atopite, specimens of the Brazilian atopite were purchased from 

Groebel & Wendler, of Geneva, Switzerland, and form the basis of 

the writer's work on the mineral. Unexpectedly, the analysis of the 

Brazilian atopite showed that mineral to have the same composition 

as the Italian romeite, and a critical review of Hussak's data showed 

that his statement that the Brazilian mineral agrees completely with 

the original atopite is incorrect.

HISTORICAL SKETCH.

Romeite was described by Damour l in 1841, and as the result of 

a later analysis, published in 1853, the composition of the mineral 

has been given in all textbooks as CaSb204 . Moreover, as a result of 

Dufre*noy's contribution to Damour's first article, the mineral has 

always been considered as tetragonal, with angles very close to the 

isometric octahedron. The tetragonal character of the mineral was 

considered verified by Bertrand's observation of strong double refraction and uniaxial interference figure. Bertrand 'considered the 

tetragonal octahedron as built up of a group of eight 90° rhombohedra 

grouped around a point.

The measurements of Dufre"noy, published in 1841 and made by 

means of the sun's reflection, are not confirmed by the recent work 

of Pelloux, whose measurements agree closely with those required for 

isometric symmetry. Pelloux measured (111): (110) as 35°13' (for 

isometric system this angle is 35° 16'); and (311): (131) as 50° 20' 

(for isometric system this angle is 50° 28£')- He remarks, moreover,

1 See p. 90 for bibliography.

95
96 MINEBALOGIC NOTES SEEIES 3.

that the octahedron is too uneven to yield good measurements, a 

statement also made by Dufr6noy and confirmed by the writer. 

Pelloux has determined the forms d{lW}, m{311}, and 7i{211}, in 

addition to the octahedron o{lll}.

Nordenskiold, in 1877, described a new mineral from Langban, 

Sweden, which he named atopite, and showed wherein, if Damour's 

results were correct, atopite differed considerably in chemical composition from the older known mineral.

The paper by Hussak, describing the Brazilian so-called atopite, 

is the last published contribution dealing with the chemical composition of the mineral. Hussak claimed that his analysis agreed with 

that of the Swedish atopite and fully verified the formula 2CaO.Sb205 , 

but, as is shown later in this paper, his analysis leads not to the atopite 

formula just given but to the formula of romeite, 5Ca0.3Sb205 . The 

Brazilian so-called atopite is in fact identical with the romeite from 

Italy.

BIBLIOGRAPHY.

DAMOUR, A., Sur la romelne, nouvelle espece mine'rale, de Saint-Marcel en Pie'mont

Annales des mines, 3d ser., vol. 20, p. 247, 1841. 

DAMOUR, A., Nouvelles recherches sur la composition de la romelne, espece min^rale:

Annales des mines, 5th ser., vol. 3, p. 179, 1853. 

NORDENSKIOLD, A. E., Mineralogiskameddelanden: 4, Nya mineralier franLangban;

7. Atopit: Geol. Foren. Stockholm Forh., vol. 3, p. 376, 1877. 

BERTRAND, E., Sur les cristaux pseudo-cubique: Soc. min. France Bull., vol. 4, p.

237, 1881. 

HUSSAK, E., Ueber Atopit aus den Manganerz-gruben von Mignel Burnier, Minas

Geraes, Brazilien: Centralbl. Mineralogie, 1905, p. 240. 

PELLOUX, A., Nuove forme della romeina di S. Marcel in Valle d'Aosta: Mus. civ.

storia nat. Geneva Ann., 3d ser., vol. 6, p. 22, 1913. 

SCHRODER, R., Atopite: Goldschmidt's Atlas der Kristallformen, vol. 1, Text, p.

121, 1913.

PARAGENESIS.

A simple inspection of the specimens received from Capt. Pelloux 

showed that the Italian romeite occurs in minute veins traversing 

the associated minerals or more abundantly lying along the boundary 

of masses of two different minerals. A characteristic association 

seems to be that figured in Plate IV, A (p. 89), where minute veins 

of romeite lie between the braunite and the aggregate of albite and 

piedmontite. The mineral is also found as nests and veins in the 

associated braunite, albite, piedmontite, etc. The nests seem to be 

local enlargements of the veins rather than distinct isolated bodies 

at least, the specimens at the writer's disposal all show the romeite in 

distinct veins. The occurrence of romeite as the main constituent 

of a vein seems therefore to be somewhat different from that of 

schneebergite, which is not known to occur as veins but only as the 

filling of ellipsoidal cavities.
BOMEITE. 97

The romeite from Brazil (the so-called atopite) occurs in cavities 

and also as isolated crystals scattered through the secondary manganese oxides of the Miguel Burnier manganese district. The specimens obtained from Groebel & Wendler show the romeite as isolated 

crystals or groups of crystals embedded in the compact manganese 

oxide, which is associated with quartz on some of the specimens. 

The occurrence of the well-formed isolated crystals of romeite in the 

massive compact manganese ore recalls the occurrence of wellformed pyrite crystals in compact schists and shales and suggests a 

similar origin.

CBYSTALLO GRAPHY.

The crystals of the Italian romeite at the writer's disposal are not 

suitable for accurate measurement. The octahedron is the only form 

identified, but its surfaces are all uneven and give a group of reflections on the goniometer. It could be shown, however, on the twocircle goniometer that the angles of the octahedron of romeite are 

very close to those of the isometric octahedron.

The crystals of romeite from Brazil, on the other hand, show even 

and brilliant faces which yielded perfect reflections. Although 

Hussak does not give any measured angles, he states that the mineral 

is isometric and holohedral and shows predominantly the octahedron 

o{lll}, with <2{110}, a{100}, and more rarely m{311}. Pelloux gives 

o d m with ^{211} for the Italian romeite.

On the Brazilian romeite the p angle of the octahedron was measured as follows:

Measurements of the p angle of the octahedron o {111} on romeite from Brazil. 

[Calculated p=54°44'.]

1

o

54

54

54

54,

41

43

47

44

o

54

54

54

54

44

44

45

45

2

o

54

54

54

54

42

44

4446'

The angle o to o' was also measured directly as 109° 27' (calculated 

109° 28'). The isometric .symmetry of the romeite from Brazil is 

therefore established, and the isometric form of the mineral from 

Italy, as indicated by Pelloux's measurements, is confirmed.

The form -y{133}, found by Schroder on the Brazilian romeite, was 

also observed once as a line face by the writer.

Measured $, 45° 00'; calculated <j>, 45° 00'. Measured p, 76° 11'; 

calculated p, 76° 44'.

97888° Bull. 610 16 7
98 MINERALOGIC NOTES SERIES 3.

PHYSICAL PROPERTIES.

An imperfect octahedral cleavage was noted on the crystals from 

Italy, whereas the Brazilian romeite showed a good octahedral 

cleavage.

The density was determined by Damour for small crystalline grains 

as 4.714 and 4.711 and for very fine powder as 4.675. The value 

given in textbooks, namely, 4.713, is the average of the first two of 

Damour's determinations. In his analysis, made presumably on 

material similar to that used for his determinations of density, 

Damour gives 2.86 per cent of soluble silica and foreign siliceous material (quartz, albite?). If an arbitrary density of 2.7 is assigned to 

the 2.86 per cent of foreign matter in his sample of romeite, and the 

density '(4'.713) is corrected, a new value of 4.77 (Damour) is obtained 

for the pure romeite. The even higher value 5.074 was obtained by 

the writer by determining the density of 2.6768 grams of pure 

romeite from Italy with the pycnometer. The density of the Brazil-, 

ian romeite (given by Hussak as 5.1) was determined by the writer 

on 6.7372 grams to be 5.044.

OPTICAL PROPERTIES.

The color of uncrushed romeite from Italy, freed from the interfering effect of the strongly colored associated minerals, is a "russet"

according to Bidgway's " Color 

standards." The color of powdered 

romeite is a "seashell-pink." The 

color of the Brazilian romeite is 

"old gold," and the color of its powder is "very light buff." The luster 

is vitreous to greasy and not as 

adamantine as that of schneebergite. 

Optically the mineral is doubly 

refracting, although the material 

examined shows low double refraction and not high double refraction, 

as found by'Bertrand and by Pelloux.. The interference colors are seldom above a yellow of the 

first order. The structure of the Brazilian romeite as revealed 

between crossed nicols is shown in figure 88. The mineral, like 

schneebergite, is probably dimorphous, the high-temperature form 

being isometric.

The refractive index was determined by Mr. E. S. Larsen as 1.87 

on romeite from Italy and 1.83 on romeite from Brazil. The Brazilian 

romeite varied somewhat in its index of refraction and birefringence.

FIGURE 88. Optical structure of crystal of 

romeite.
ROMEITE. 99

CHEMICAL PROPERTIES.

PYROGNOSTICS.

When heated before the blowpipe, romeite is infusible. In the 

closed and open tubes no reactions take place. The mineral is 

insoluble in acids, although readily decomposed by fusion with 

sodium carbonate.

QUANTITATIVE COMPOSITION.

Pure samples were obtained by the same procedure as was used for 

schneebergite. The methods of analysis were also the same. The 

results of the quantitative analysis of romeite from Italy are as 

follows:

Analysis and ratios of rom'eite from Italy.

Sb... .................................

0............... .......................

FeO

MnO............................. ......

CaO. ..................................

Na20. .................................

H20............. .......................

Analysis.

56.15

18. 57

1.12

6.27

15.81

.81

1 3Q

100. 12

0.467

1.161

. 0161

.0881

.282[

.013J

Ratios.

^ qq r,r ft vi 00

14. 88 or 15X0. 99

.399 5. 12 or 5X1.02

The ratios yie]d the formula 5R"O.Sb6015 , in which R" is composed chiefly of Ca but contains also smaller amounts of Fe", Mn", 

and Na2 . The formula may be written, considering all of the R" as Ca, 

as 5Ca0.3Sb2 05 or Ca5Sb6020 .

Romeite can not be directly interpreted as a salt of any of the six 

acids given on page 104, if all the antimony is considered as an acid. 

The mineral can be regarded as a salt of a partly dehydrated pyroantimonic acid, 3Sb2 05 .6H20-H2 0 = 3Sb2 05 .5H2 0 or H10Sb6020 . 

Another interpretation would be to consider it a salt of a mixed acid, 

two parts of pyro-antimonic acid with one of meta-antimonic acid, 

2(Sb2 05 .2H2Oj+(Sb2O5 .H2 0) = H8Sb4 014 + H2Sb2 06 . It is preferred 

to regard romeite as a pyro-antimonate.

The interpretation of the percentage of oxygen in the mineral, as 

determined by reduction in hydrogen, is affected in a similar way to 

that of schneebergite (p. 93), on account of the small amount of water 

absorbed by the fine powder during grinding. The results are 

treated in the same way as was done for schneebergite, and the 

figures obtained are as follows:
100 MISTERALOGIC NOTES SERIES 3.

Comparison of oxygen percentages'of romeite from Italy.

Sb203 .. ........................................

SbO

Per cent of oxygen.

Calculated.

11.21 

14. 95.

18.69

Found.

(

17.95 minimum. 

18.57 average. 

19.18 maximum.

The above results show that the amount of oxygen combined with 

the antimony is such that the state of oxidation of the metal is that 

expressed by the formula Sb2 05 .

The analysis of romeite from Brazil gave the following results:

Analysis and ratios of romeite from Brazil.

Sb. .................................

o.... ................................

FeO................................

MnO......... ........................

CaO... ..............................

NaaO...... ..........................

HaO................................

Analysis.

56. 02

18.70

1.29

2.62

14.81

5.08

1.12

99.64

Ratios.

0.466 5. 95 or 6X0.99

1.169 14. 93 or 15 XI. 00

. 0181

flQ7

 264 1 0' 401 5. 12 or 5X1.02

.082

The ratios yield the same formula as was obtained from the analysis 

of the Italian romeite, namely, Ca5Sb6 020 . The ratio of Na20 to 

CaO + FeO + MnO is 1 :3.89, or nearly 1 :4, so that the formula 

could be written NaCa4Sb6 020 . To judge from the analyses, however, 

it seems necessary to regard the Na2O, FeO, and MnO as replacing 

the CaO and to group them together under CaO

Interpretation of the percentage of oxygen found yields the following results for the Brazilian romeite:

Comparison of oxygen percentages of romeite from Brazil.

Per cent of oxygen.

Sb2 03 ... .......................................

SbaO4 ...... .................................... 

SbA '.......................................

Calculated.

11.18

14. 92

18.64

Found.

.-

1

18. 20 minimum. 

18. 70

19. 19 maximum.
ROMEITE. 101

The results show that, in complete conformity with the analysis of 

the Italian romeite, the antimony in the Brazilian mineral is in its 

highest state of oxidation, namely, Sb205 .

Hussak stated that the formula of atopite (from Sweden), namely, 

2(Ca, Mn, Na2 ).Sb207 or 2R"O.Sb2O5 , also accorded with his analysis 

of the Brazilian mineral. That such assumed accordance does not 

exist can be readily shown.

The analysis of the Swedish atopite, as given by Nordenskiold, is as

follows:

Analysis and ratios of atopite from Sweden.

[A. E. Nordenskiold, analyst.]

Sb20B ............................................

FeO............................................

MnO... ..........................................

CaO.. ............................................

K*0. ...........................................

Na.,0.. ................... I.... ...................

Analysis.

72. 61

9 7Q

1.53

17.85

.86

4.40

100. 04

0.227

03Q1

.022

31 Q

. .009

.071,

Ratios.

1.00

0.460 2.03

The ratios yield the simple formula 2 R/'O.Sb205 , in which E = Fe", 

Mn", Ca, K2 , and Na2 . Another analysis would definitely determine 

whether this simple formula is correct or whether, as a possibility, 

the Swedish atopite is not the same as romeite. There seems to be 

no reason, however, for questioning Nordenskiold's analysis, but his 

figures are very similar to those obtained for romeite.

The analysis of the mineral from Brazil, by Hussak, gave the following results:

Analysis and ratios of romeite (wrongly called atopite} from Brazil. 

[E. Hussak, analyst.]

Sb2o6 -- ....................................

FeO

MnO.......................................

CaO.......................................

Na20. .....................................

K20. .....................................

Analysis.

76.20

Trace.

5.70

12.68

5.70

Trace.

100. 28

Ratios.

0.238

.0801

.226 [0.398

.092J

2. 99 or 3

5. 01 or 5

The ratios yield the formula 5R/'O.3Sb205 , which is identical with 

that obtained from the writer's analysis of romeite from Brazil and 

from Italy. If the ratio of Sb205 is made 1.00, then the ratio for
102 MINEKALOGIC NOTES SERIES 3.

B/'O becomes 1.67 and not 2, as would be required if Hussak's 

analysis led to the same result as Nordenskiold's analysis. The 

mineral from Brazil is therefore not atopite but romeite, as proved by 

the independent analyses made by Hussak and by the writer. The 

three analyses of romeite given above are shown together in the 

following table, to which is also added Damour's last analysis:

Analyses of romeite.

Sba06 .. ........................

FeO..........................

MnO.................... .......

CaO..........................

Na20....... ...................

K20.........................

H,0....... ...................

SKX, etc.....................

Italy.

Damour.

a 77. 61 

1.70 

1.21 

16.29

2.86

99.67

Schaller.

74. 72 

1.12 

6.27 

15.81 

.81

1.39

100. 12

Brazil.

Hussak.

76.20 

Trace. 

5.70 

12.68 

5.70 

Trace.

100. 28

Schaller.

74.72 

1.29 

2.62 

14.81 

5.08

1.12

99.64

a This represents the percentage of what Damour considered Sba

The last three analyses all 

5Ca0.3Sb,(X The results of

yield the same formula, namely, 

Damour's analysis must .be considered inaccurate so far as the determinations of the antimony and 

of the oxygen combined with it are concerned. NThe analyses show, 

moreover, the variability in the replacement of CaO by the other 

bases and the improbability that one of these bases (soda, for example) 

should be considered by itself.

The last analysis of romeite made by Damour (in his two earlier 

analyses he did not determine the state of oxidation of the antimony) 

is reproduced below with the ratios derived therefrom.

Analysis and ratios of romeite from Italy. 

[A. Damour, analyst.]

Sb ....................................

0............................. .........

FeO

MnO...................................

CaO...................................

SiOo, etc................................

Analysis.

62.18

15. 43

1.70

1.21

16.29

2.86

99.67

0.517

.964

.024]

.017

.291

Ratios.

3. 13 or 3'X1. 04

5. 84 or 6X0. 97

0. 332 2. 01 or 2X1 01
EOMEITE. 103

The ratios obtained give the formula Ca2Sb308 or" 4Ca0.3Sb204, 

which, as stated by Dana/ agrees closer with the analysis than the 

simpler formula CaSb204 usually given in textbooks.

Nordenskiold failed to get decisive results on atopite by reducing 

the mineral at a low temperature in hydrogen and determining the 

state of oxidation of the antimony by the loss in weight of the mineral, 

as was done by Damour, and ascribes his failure to three conditions 

the volatility of some of the antimony, even at a low temperature; 

the incompleteness of the reduction even after long-continued heating 

in hydrogen; and the fact that a part of the unreduced mineral 

seemed to be soluble, after the treatment in hydrogen, in hydrochloric acid, whereas the untreated material is not soluble in acids.

Whatever may be the reason to which the difficulty is assigned, 

Damour's results were not verified by the writer's analysis, and as 

his figures yield the rather improbable formula 4Ca0.3Sb204 , it 

must be concluded that his figures do not accurately represent the 

composition of the Italian romeite.

1 Dana, E. S., System of mineralogy, 6th ed., p. 862,1892.
THE NATURAL ANTIMONITES AND ANTIMONATES.

The acids of antimony are six in number, as follows:

Acids of antimony.

Name of acid.

Ortho-antimonous. .............

Name of salt.

Pyro-antimonite ........

Meta-antimonite. .......

Ortho-antimonate. ......

Formula.

Sb203 .3H20-H6Sb20(i .

Sb203 .2H20=H4Sb205 .

Sb2Os.H20 =H2Sb2 04 .

Sb205 .3H20=H6Sb208 .

Sb205 .2H20=H4Sb207 .

Sb205 .H20 =H2Sb206 .

Hypo-antimonic acid, H2Sb205 , is supposedly derived from antimony 

tetroxide, Sb204 , but this tetroxide may be just as well considered 

a salt, namely, antimonous ortho-antimonate, Sb/" (Sb"'"O4) 2 .

The natural antimonites and antimonates are grouped according 

to the acid in the following tabulation. In addition to the antimonites and antimonates, shown in heavy type, the list includes 

some examples of corresponding arsenates, phosphates, vanadates, 

columbates, tantalates, nitrates, and titanates.

Ortho-antimonites, salts of ortho-antimonous acid, H6Sb206 :

No minerals known. 

Pyro-antimonites, salts of pyro-antimonous acid, H4Sb2 05 :

No minerals known. Schneebergite may be a salt of a mixed acid corresponding

to H4Sb205+H4Sb207 . 

Meta-antimonites, salts of meta-antimonous acid, H2Sb204 :

Nadorite............. (FbCl)'aSb204 .

Schneebergite may be a salt of a mixed acid corresponding to H2Sb204+H6Sb208. 

Ortho-antimonates, salts of ortho-antimonic acid, H6Sb208 :

Monimolite.......... (Pb,Fe,Ca)"3Sb208 :............ Isometric.

Berzeliite............. (Ca,Mg,Mn)//3As208 ............ Isometric.

Pseudoberzeliite......(Ca,Mg,Mn)//3As208 ............Orthorhombic (?).

Caryinite.............(Pb,Mn,Ca,Mg)//3As208 ........Monoclinic (?).

Fergusonite........... Y^CbaOs-...................Tetragonal.

Pucherite.............Bi^^Os-...................Orthorhombic.

Triphylite............ (LiFe''/'^*^................ Orthorhombic.

Wagnerite............ (MgF)/2Mg2P208 ................Monoclinic.

Amblygonite.......... (AlF)"2Li2P208 ...............Triclinic.

Cervantite.......... . Sb^Sl/""^ ................ Orthorhombic.

Stibiconite......... .Sb^SV^A^HjjO.......... .Amorphous.

. Flajolotite......... .. .Fe"'2Sb'""208-zH20...........Amorphous.

Schneebergite may be a salt of a mixed acid corresponding to H6Sb208+H2Sb204 . 

104
THE NATURAL ANTIMONITBS AND ANT1MONATES. 105

Pyro-antimonates, salts of pyro-antimonic acid, H4Sb207 :

Atopite.............. .Ca2Sb207 .......................Isometric.

Microlite l . ...........Ca2Ta207 .....................Isometric.

Tripuhyite........... Fe"2Sb2 07 ...................... Biaxial.

Bindheimite...... . ...Pb2Sb207 .a;H20?.....:......... .Amorphous.

Romeitc.............. Ca5Sb6020 -..'.................. Isometric.

Schneebergite may be a salt of a mixed acid corresponding to H4Sb207 4-H4Sb2O6 . 

Meta-antimonates, salts of meta-antimonic acid, H2Sb206 :

Stibianlte 2 ......... .H2Sb206(?).

T . .. |3(CaSb206)...................\T Lewisite........... -T ................. >ometnc.

Mauzeliite..........| __ .... ((CaSb206 )...... J p * «' , , . K(Oa^)2 liO3 ) (.',

PerovsHte............ CaTi03 ........................ Isometric.

Pyrochlore............ (CaTi03 .n(CaCb206) (?).........Isometric.

_ _ . I (Fe"Sb206)...................I,,*,, ., , ,. Derbyllte............|^Fe//T?06J (?)0rthorhombic.

Columbite............Fe//Cb2 06 .....................Orthorhombic.

Niter.................K2N206 ....................... Orthorhombic.

Lewisite (with which mauzeliite is identical) seems to be predominantly CaSb206 

with a small amount of perovskite isomorphously mixed with it.

Derbylite seems to represent an orthorhombic modification of (Fe"Ti03), already 

known in a tetragonal form (in iserite), a trigonal form (ilmenite), and possibly 

in an isometric form (in pyrochlore, dysanalyte, or knopite?). 

Mixed antimony acids:

0 . ... . 23................... T

Schneebergite..... . A on .-. 0, >. }Isometnc.

^

Romeite may be a salt of a mixed acid corresponding to 2(H2Sb206)+H0Sb2 08 . 

Schneebergite may be a salt of a mixed acid corresponding to H2Sb200 -f-H6Sb206. 

Relations not clear:

Ochrolite. .......... . PbeCl4Sba07 . ................... Orthorhombic.

The relations of ochrolite and ecdemite (Pb6Cl4As207) are not clear. 

Manganostibiite ....9MnO.Sb205?................... Orthorhombic (?).

The other antimonates of Igelstrom are too indefinite for consideration.

1 Apparently essentially CasTajO?. Sodium, fluorine, and other elements seem to be present in some - 

varieties of microlite.

2 According to the formula givtn stibianite would not be an antimonate but the antimonic acid itself. 

The composition of stibianite can not be considered as conclusively determined*
VELARDENITE, A NEW MEMBER OF THE MELILITE

GROUP.

The compound 2CaO.Al2O3 .Si02 has been found to play an important part as one of the.members of an isomorphous series of minerals whose mixtures are well known under the names of melilite and 

gehlenite. The relations of the members of the melilite group are 

given in the following paper. A review of the literature on the composition of melilite and gehlenite has shown that the "gehlenite" 

from the Velardena mining district, in Mexico, described by Wright 1 

in 1908, is in fact the compound 2CaO.Al2 03 .Si02 , mixed with about 

20 per cent of akermanite. This compound also occurs in quantity 

in several melilites and gehlenites. It therefore deserves to be recognized as a mineral species, which is appropriately named velardenite, 

after the locality.

Velardenite was artificially prepared by Weyberg 2 in 1904 by 

fusing kaolin with a small amount of calcium bromide. The material, 

after the soluble portion of the melt had been dissolved, consisted of 

minute square prisms, which gave parallel extinction and in cross 

section were uniaxial, negative. The prisms were therefore a combination of a tetragonal prism with the basal pinacoid. Two analyses 

of material, not entirely pure, were made by Weyberg and, together 

with the calculated percentages of the formula 2CaO.Al2 03 .Si02 , are 

reproduced in the table below.

Analyses of artificial velardenite. 

[Z. Weyberg, analyst.]

8iOz ... ...................................

Al O

CaO......................................

1

25.79

36.66

37.42

99.87

2

. 22. 56

37. 06

40.30

99.92

Calculated.

21.99

37.23

40.78

100. 00

Some years later the same compound was artificially prepared by 

Shepherd and Rankin,3 who also give the chief properties of the 

material. (The optical determinations were made by F. E. Wright.)

* Wright, F. E., On three contact minerals from Velardefia, Durango, Mexico [gehlenite, spurite, and 

hfllebrandite]: Am. Jour. Sci., 4th ser., vol. 26. p. 545,1908.

2 Weyberg, Z., Ueber einige basische haloidhaltige Calciumalumosilicate: Centralbl. Mineralogie, 1904, 

pp. 729-734.

3 Shepherd, E. S., and Rankin, G. A., Preliminary report on the ternary system CaO-Al20rSi02; a study 

of the constitution of Portland cement clinker: Jour. Ind. and Eng. Chemistry, vol. 3, p. 211,1911.

106
VELABDENITE, A NEW MEMBEE OF THE MELILITE GROUP. 107

The following table shows a comparison between the properties of 

velardenite from Mexico, as given by Wright, and the properties of 

artificial pure velardenite:

Properties of velardenite.

Symmetry. ...........

Sign.. ...............

Velardenite from Mexico (80 per cent 

pure velardenite, 20 per cent pure 

akermanite).

3.039................................

Negative. ...........................

1.666................................

1.661................................

0. 0055. ..............................

Artificial pure 

velardenite.

Tetragonal.

{001} distinct.

3. 038.

Negative.

1. 667.

1. 658.

0. 009.

« Well marked in thin section.

The other properties of velardenite, as given by Wright, are as 

follows: Color, dark gray or gray-black from minute inclusions of 

magnetite arid other particles, rarely amber-yellow; luster, resinous 

to greasy; translucent to transparent in thin flakes; fracture, uneven 

and irregular, conchoidal to splintery; hardness about 5.5; gelatinizes 

readily with acid and fuses with difficulty.

The interpretation of Alien's analysis, as quoted by Wright, is 

shown in the table below. The analysis has been recalculated by 

combining Ti02 with Si02 , Fe2 03 with A1203 , FeO + MnO with MgO, 

and K20 + Na20 with CaO, neglecting the water (1.85 per cent), 

and reducing the analysis to 100 per cent. The formula of akermanite 

is 4Mg0.8Ca0.9Si02 . (See p. 116.)

Comparison of velardenite analyses.

Si02 .................. .........

A1203 ..........................

CaO........... ................

MgO...........................

Ti02 ..................... ......

Fea08 ............. .............

FeO

MnO.........................

Na-0............. .............

K26..........................

H20.. ..........................

Original 

analysis by 

E. T. Alien.

26.33

27.82

39.55

2.44

.03

1.43

.50

.01

.21

.10

1.85

100. 27

Analysis 

recalculated.

26.98

29. 53 .

40.70

2.79

100. 00

Calculated 

composition, 79 .8 per 

cent velardenite, 20.2 

per cent 

akermanite.

27.03

29.68

40.46

2.83

100. 00

Difference.

+0.05

I IK

- .24

+ .04
108 MINEBALOGIC NOTES SERIES 3.

The interpretation of the analysis of the mineral from Velardefia 

shows a close agreement between the analytical figures and the figure 

calculated, for the assumed mineral composition.

Of the seventeen analyses of members of the melilite series green in 

the following paper, six show no velardenite and the remaining 

eleven show that it is present, in isomorphous mixture, to the following percentages: 6.5, 9.5, 9.8, 11.3, 15.0, 15.8, 43.5, 44.7, 55.6, 

63.8,79.3.

As three of the analyses show the compound 2CaO.Al203 .Si02 to 

be present in natural minerals in excess of 50 per cent, it is justifiable to consider it a definite mineral species, velardenite, with the 

properties given.
THE MELILITE GROUP. 

HISTORICAL SKETCH.

REVIEW OF OLD THEORIES.

The composition of the melilite group has never been satisfactorily 

explained. The earlier writers assigned definite formulas to melilite 

and to gehlenite, although these are, as Dana l says, "uncertain, since 

the analyses fail to agree." The analyses of gehlenite, as listed by 

Dana, agree better with a single definite formula than those grouped 

under melilite.

Vogt 2 suggested that the natural melilites were mixtures of 

gehlenite (3CaO.Al203 .2Si02 ) and an artificial product of the general 

formula 4R//0.3Si02 , to which the name akermanite 3 was given. 

Calcium was the predominant base of this compound, and the formula 

of akermanite has been written 4Ca0.3Si02 , with appreciable amounts 

of MgO and other bases replacing, in part, the CaO. The failure of 

Vogt's theory to find general acceptance is due to the facts that (1) 

he assumed gehlenite, 3CaO.Al203 .2Si02 , as one of the end members, 

whereas gehlenite is not a distinct and definite species but is itself a 

variable mixture of definite end members; and (2) he assumed the 

formula 4Ca0.3Si02 for akermanite, whereas the correct formula is 

4Mg0.8Ca0.9Si02 .

Bodlaender 4 found that the analyses of natural melilites did not 

agree with Vogt's theory and suggested that the optically negative 

melilites were mixtures of R"Si03 with R"R'"2 04 , whereas the 

optically positive melilites represented mixtures of R"Si03 with R"3R'"206 .

Zambonini 5 has adopted Bodlaender's theory, although in an 

earlier paper ° he had considered three possible explanations of the 

composition of the melilite group. If gehlenite (3CaO.Al2 03 .2Si02 ) is 

considered as one end member, then, according to Zambonini, the 

other end member is CaSi03 and melilites are mixtures of the two 

types of compounds R'^R^^SijO^ and R"Si03 . On the other

» Dana, E. S., System of mineralogy, 6th ed., p. 475,1892.

2 Vogt, J. H. L., Mineralbildung in Schmelzmassen, p. 96,1892.

«Akermanite was named after R. Akerman and, as originally given by Vogt, is spelled with only one n. 

The spelling akermannite, sometimes seen, is erroneous. The & is pronounced like long o.

< Bodlaender, G., Die Zusammensetzung des Meliliths: Neues Jahrb., 1892, Bd. 1, p. 53; 1893, Bd. 1, 

p. 15.

6 Zambonini, F., Mineralogia Vesuviana, p. 254,1910.

' Zambonini, F., tiber eine krystallizierto Schlacke der Seigerhiitte bei Hettstcdt, nebst Bemerkungen 

iiber die chemische Zusammensetzung des Melilith: Zeitschr. Kryst. Min., vol. 41, p. 226,1906.

109
110 MINEBALOGIC NOTES SERIES 3.

hand, he states that melilites may be treated as having the general 

composition R"R'"2Si208 .7iR"2Si04 . Zanibonini also states- that 

Bodlaender's theory, according to which melilites are composed of 

R"Si03 and R"A1204 , agrees well with the facts.

Busz and Riisberg,1 in a recent paper, gave analyses of two samples. 

of artificial melilite crystals, and, having found that Vogt's theory 

does not fit their analyses, they suggested that melilite is a mixture 

of either (1) gehlenite and R7 '3Si207 , or (2) the three components 

3RO".R'"203 .2Si02 (gehlenite), Ca2Si04 , and CaSi03 .

Clarke 2 has recently suggested that gehlenites are mixtures of 

2CaO.Al203.Si03 and 9CaO.Al203 ,6Si02 .

Several other theories have been proposed, but, as admitted by 

their originators, they are not entirely satisfactory for explaining all 

the observed facts and need not be repeated here.

It seems to the writer that, with the exception of Vogt's, all the 

proposed theories are mainly attempts to express the composition of a 

given melilite by the summation of a number of compounds whose 

only reason for existence is that they are rational and theoretically 

possible chemical compounds. They show no relationship either 

among themselves or to the melilites in form or in properties. What 

resemblance is there between melilite and CaSiO3 or Ca2SiO4, or for 

that matter why should the metasilicate and orthosilicate of lime be 

grouped together in isomorphous mixture when the properties of their 

known forms are so different ?

If it is admitted that melilite represents an isomorphous mixture 

of a certain number of end products, then the problem is solved when 

these end members are identified. But these end members must 

satisfy the requirements of isomorphism; they must be related 

chemically, they must have a similar crystal form, they must form 

mixtures with the same crystal forms as the end members themselves, 

and all natural occurrences of melilite must be capable of being 

expressed quantitatively as mixtures of these end members.

All the proposed theories fail to meet these requirements, although 

Vogt's theory comes nearest to the truth. . The essence of his theory 

is correct, but the foundations are not correct the composition of 

his end members was not correctly expressed.

CHARACTERISTICS OF THE MELILITE GROUP.

The melilite group is well defined and includes the minerals known 

under the names melilite, gehlenite, and fuggerite. They are tetragonal, and when in distinct crystals form short, square prisms and

1 Busz, K., and Rusberg, F. W., Mineralogisch-chemische Untersuchungen am Olivin- und Melilithkristallen in Hochofenschlacken: Centralbl. Mineralogie, 1913, p. 625.

2 Clarke, F. W., The constitution of the natural silicates: U. S. Geol. Survey Bull. 588, pp. 31-34,1914.
THE MELILITE GROUP. Ill

tabular forms (especially the artificial products). The cleavage is 

parallel to the base and the prism. The hardness is from 5 to 6, the 

density 2.9 to 3.1, the refractive index between 1.60 and 1.67, and 

the double refraction low. Some crystals are positive and others 

negative. Chemically the minerals are silicates of lime and alumina 

with smaller and varying amounts of magnesia, alkalies (especially 

soda), iron, etc. They readily gelatinize with acids.

The properties of the minerals of the melilite group, as outlined 

above, are characteristic and also fairly uniform. It follows, therefore, that the properties of the end members are probably similar 

among themselves and similar to those given above for the members 

of the group. In fact, the properties of the mixtures, as given above 

for the melilites (and gehlenites), are so nearly constant that the 

properties of the end members may be almost determined from the 

properties of their mixtures. One of the end members must have a 

density of about 2.9, another of about 3.1; the refractive .index of 

one must be about 1.60, of another 1.67; one must be negative, 

another positive. . The properties of the end members as proposed 

herein are consistent with the properties of their mixtures (melilites, 

gehlenites).

NEW THEORY. 

PRIMARY COMPOUNDS. 

NATURAL ANHYDROUS CALCIUM-ALUMINUM SILICATES.

A review of the literature shows that the anhydrous calciumalumiimm silicates occurring in nature are few in number. They are 

given below, with their crystal symmetry.

Anhydrous calcium-aluminum silicates occurring in nature.

Name.

Anorthite. ................

O-pVllpTTl tp

Formula.

CaO.Al203 .2Si02 . . ............

2CaO.3Al203 .9Si02 ............

3CaO.Al203 .3Si02 . ............

3CaO.Al203 .3Si02 . ............

2CaO.Al203 .Si02 ..............

(?)............................

(?)............................

Crystal symmetry.

.Triclinic.

Tetragonal.

Tetragonal.

Tetragonal.

Tetragonal.

Sphenoclase, considered a doubtful species with the formula 

6CaO.Al2O3 .6Si02 , has been shown by V. M. Goldschmidt* to be a 

rock composed chiefly of pyroxene and grossularite.

1 Goldschmidt, V. M., Ueber den sogenannten Sphenoklas: Centralbl. Mineralogie, 1911, pp. 35-36.
112 MINERALOGIC NOTES SERIES 3.

Meionite, supposed to be 4Ca0.3Al203 .6Si02 , has been shown by 

Borgstrom l to have the composition CaC03 .3CaAl2Si208 .

To the above list of minerals is added akermanite, a. tetragonal 

silicate of lime and magnesia, which has the crystal form of melilite, 

and whose physical and optical properties are also very similar to 

those of melilite.

Sarcolite and velardenite are the only tetragonal minerals listed 

above whose composition is definitely known. A few trials soon 

showed that all the suitably described members of the melilite and 

gehlenite group can be satisfactorily explained as isomorphous mixtures of the primary compounds, sarcolite (3CaO.Al203 .3Si02), 

a theoretical soda-sarcolite (3Na2O.Al203 .3Si02), velardenite 

(2CaO.Al203 .Si02), and akermanite (4Mg0.8Ca0.9Si02). Sarcolite 

and akermanite occur in nature in a pure state as distinct mineral 

species, and velardenite forms 80 per cent of a mineral occurring at 

Velardena, Mexico, akermanite forming the remaining 20 per cent. 

The physical and optical properties of these minerals are known .and 

well defined and the important ones are grouped together on page 117.

The chemical composition of these tetragonal primary compounds, 

if expressed by empirical formulas, does not show a close relationship, but their formulas may be written in such a way as to suggest 

that a possibility of relationship exists, as shown by the formulas 

given below. No contention is made that these formulas structurally express the composition of the individual minerals; they are 

given only to show that a possible chemical relation exists between 

the minerals above named, which, in isomorphous mixture, comprise the minerals of the melilite group. Inasmuch as no aluminum 

is present in akermanite, it is necessary to consider that the aluminum in sarcolite and velardenite plays the part of a base and not an 

acid. In the formulas given below the univalent group (A102Ca),

or Al-Q )>Ca, is the only base in velardenite. Two forms for sarcoXX

lite are given to show better the relationship of sarcolite to velardenite 

and to akermanite, respectively. The sarcolite 1 formula is more 

closely related to that of velardenite than the sarcolite 2 formula, 

but in turn the formula of sarcolite 2 is more closely related to that 

of akermanite than the formula of sarcolite 1.

» Borgstrom, L. H., Zeitschr. Kryst. Min., vol. 54, p. 238,1914.
THE MELILITE GROUP. 113

X) (A102Ca) /

Si 0 (A102Ca) SiI \0 (A102Ca) I \0 (A102Ca) 

0 0

Si = 0 Lo i

I /O (A102Ca) | /Q (A10)

Si 0 (A103Ca) Si 0\

\) (A102Ca) \)/Ca

Velardefiite. Sarcolite 1.

Ox Os

Si O/ a Si (

I0 >Ca 0 

XX

Si 0

0 \a I ^

\/ Si '0

0'

Sarcolite 2. Akermanite. R//=(Ca, Mg) in the ratio

of 1:2.

SARCOLITE.

Sarcolite (3CaQ.Al2 03 .3Si02 ) is a rare mineral found in the ejected 

masses of Monte Somma, Vesuvius. The properties of the mineral 

are defined as follows by Zambonini.1 Tetragonal, hemihedral, 

c = 0.8861; density 2.92 (2.936 Breithaupt, 2.932 Rammelsberg); uniaxial, positive, for sodium light w = 1.6035, e= 1.6147, e-co = 0.0112.

Three analyses of sarcolite are available and are given below. Of 

these, the one by Scacchi seems to be of less value than the other two. 

A small amount of soda is given in all three analyses. It doubtless 

replaces lime (CaO) but has been considered in this paper as belonging to a theoretical soda sarcolite, 3Na2O.Al3 02 .3Si02 . It would 

make no difference for comparative purposes whether the soda were 

reduced to its equivalence of lime or whether, as is done in this paper, 

it were kept by itself as belonging to a distinct compound.

1 Zambonini, F., Mineralogia Vesuviana, p. 247,1910. Zambonini states that the optical properties given 

by Pauly (Centralbl. Mineralogie, 1906, p. 266) for sarcolite were in reality determined on some other mineral. Pauly gives <o= 1.6404, e= 1.6566, for sodium light

97888° Bull. 610 16 -8
114 MINERALOGIC NOTES SERIES 3.

The agreement of the analyses of sarcolite with the values calculated from its formula is shown below.

Comparison of analyses ofsarcolite with calculated composition.

Si02 . ........................

A1203 - .......................

CaO... ........................

Na20........................

K20..........................

MgO.........................

Scacchi.a

42.11

24.50

32.43

2.93

' 101.97

Rammelsberg. &

40.51

21.54

32.36

3.30

1.20

98.91

Pauly. c

39.34

21.63

33.70

4.43

.36

99.46

Calculated 

for3CaO. 

Al203 .3Si02 .

40.08

22.65

37.27

100. 00

o Scacchi. A., Quadri Crystallographia, p. 66, Naples, 1842.

& Rammelsberg, C., Ueber die chemiscne Zusamensetzung einiger seltenen Mineralien des Vesuvs: Poggendorfi's Annalen, vol. 109, p. 570,1860. 

c Pauly, A., Zur mikroskopischen Charakterisierung des Sarkolith: Centralbl. Mineralogie, 1906, p. 266.

The sarcolite from Vesuvius analyzed by Scacchi is composed of 

an isomorphous mixture of 7.2 per cent of soda sarcolite and 92.8 

per cent of sarcolite. Calculated composition of this mixture is 

shown below.

Comparison of analysis ofsarcolite by Scacchiwith calculated composition of isomorphous

mixture.

~

Si02 . ........................

A1203 .............. ...........

CaO...........................

Na20........... ...............

Original 

analysis.

42.11

24.50

32.43

2.93

101. 97

Analysis 

reduced.

41.29

24.03

31.80

2.88

100. 00

Calculated.

39.96

22.58

34. 58

' 2.88

100. 00

Difference.

 i 33

-1.45

+2.78

.00

The differences are considerable and indicate that the analysis is 

not very exact or, more probably, that the sample analyzed was not 

pure and homogeneous.

The sarcolite from Vesuvius analyzed by Rammelsberg is composed of an isomorphous mixture of 10.5 per cent of soda sarcolite 

and 89.5 per cent of sarcolite. The analysis agrees fairly well with 

the calculated composition, as shown below.
THE MELILITE GROUP. 115

Comparison of analysis of sarcolite by Rammelsberg with calculated composition of isomorphous mixture.

SiOa ...........................

Al O

CaO...........................

Na20..........................

K20..........................

Original

analysis.

40.51

21.54

32.36

3.30

1.20

98.91

Analysis 

reduced.

41.12

21.87

' 32. 85

4.16

100. 00

Calculated.

39.92

22.56

33.36

4.16

100. 00

Difference.

 1 20

+ fiQ

+ CT

.00

The sarcolite from Vesuvius analyzed by Pauly is composed of an 

isomorphous mixture of 2.6 per cent of akermanite, 11.2 per cent of 

soda sarcolite, and 86.2 per cent of sarcolite. The agreement of the 

analysis with the calculated composition is good. A small admixture 

of akermanite is introduced to account for the small amount of 

magnesia in the analysis.

Comparison of analysis ofsarcolite by Pauly with calculated composition of isomorphous

mixture.

8i02 ............ ...............

A1203 ..........................

CaO................:..........

N&,Q*. ......................

MgO......... ..................

Original 

analysis.

39.34

 21. 63

33. 70

4.43

.36

99.46

Analysis 

reduced.

39.56

21.75

33.88

4.45

.36

100. 00

Calculated.

40.09

21.96

33.14

4.45

.36

100. 00

Difference.

+0.53

4- 91

- .74

no

.00

a Trace of K2 0. 

SODA SARCOLITE.

As stated under sarcolite, a soda sarcolite (3Na2O.Al203 .3Si02 ), corresponding in formula to sarcolite, has been assumed to be present in 

the sarcolites analyzed and also in nearly all the natural occurrences 

of the melilites and gehlenites. Its amount is never large, the maximum being 12.2 per cent in a melilite from Vesuvius analyzed by 

Damour.. Most of the analyses show amounts less than 10 per cent. 

The reference of the soda to a compound of the sarcolite type is 

justified because sarcolite is the only naturally occurring end member 

of the melilite group containing soda. If no independent soda compound were assumed, an arbitrary assignment of the soda to either 

CaO or MgO would have to be made. The properties of soda sarcolite 

are not known, but its molecular weight (469) is so close to that of 

sarcolite (451) that their properties are doubtless very similar
116 MINEEALOGIC NOTES SERIES 3.

AKERMANITE.

Akermanite (4Mg0.8Ca0.9Si02 ), as a mineral, was identified by 

Zambonini x at Vesuvius. Its properties, as given by him, are as 

follows: Tetragonal, cleavages, 001 and 110; density, 3.12 (3.05 

Freda); uniaxial, positive; for sodium light, co = 1.6332, e= 1.639, 

e-co = 0.006.

The two analyses reproduced in the subjoined table fully substantiate the formula 4Mg0.8Ca0.9Si02 . As shown below, the samples 

analyzed contained small amounts of the isomorphic mineral sarcolite, and if this is allowed for, the agreement with the formula is still 

closer.

Comparison of analyses of akermanite with calculated composition.

SiOa ......................................

A1203 ............................ .........

CaO......................................

MgO......................................

FeO. ......................................

Analyses.0

Freda.

46.70 

1.09 

39.62 

13.38

100. 79

Zambonini.

46.55 

.96 

39.30 

13.30 

.12

100. 23

Calculated 

for 4MgO. 

8CaO. 

9Si02 .

47.08

38. 93 

13.99

100. 00

o Zambonini, F., Mineralogia Ves'uviana, p. 255,1910.

The akermanite from Vesuvius analyzed by Freda is composed of 

an isomorphous mixture of 95.4 per cent of akermanite and 4.6 per 

cent of sarcolite. The analysis agrees closely with the calculated 

composition.

Comparison of analysis of akermanite by Freda with calculated composition of isomorphous mixture.

Si03 .. .......................

AI n

CaO...........................

MgO.........................

Original 

analysis.

46.70

1 OQ

39.62

13. 38

100. 79

Analysis 

reduced.

46.47

Qfi

39. 23

13.34

100. 00

Calculated.

46.76

1.04

38.86

13. 34

100. 00

Difference.

+0.29

+ .08

- .37

.00

1 Zambonini, F., Mineralogia Vesuviana, p. 255,1910.
THE MELILITE GROUP. 117

The akermanite from Vesuvius analyzed by Zambonini is composed of an isomorphous mixture of 94.9 per cent of akermanite and 

5.1 per cent of sarcolite. This analysis also shows only slight differences from the calculated composition.

Comparison of analysis of akermanite by Zambonini with calculated composition of

isomorphous mixture.

$]Q2 .. .......................

AI n

GaO........... ................

MgO.........................

PeO.................... '......

Original 

analysis.

46.55

.96

39.30

13.30

.12

100. 23

Analysis 

reduced.

46.33

1.08

39.31

13.28

100. 00

Calculated.

46.72

1.16

38.84

13.28

100. 00

Difference.

+0.39

+ .08

- .47

.00

The suggestion of Shepherd, Rankin, and Wright 1 that the correct 

formula for pure akermanite is 3CaO.2Si02 is not in agreement with 

the facts. . '

VELARDENITE.

%

The properties of velardenite (2CaO.Al2O3 .Si02 ), the third mineral species and primary compound which occurs in isomorphous 

mixture in the members of the melilite group, have already been 

described on page 107.

SUMMARY OF PROPERTIES OF PRIMARY COMPOUNDS.

For comparison and convenience, the properties of the primary 

compounds used in the following discussion of the isomorphous mixtures of two or more of the primary compounds are summarized in 

the following table:

Summary of properties of tetragonal primary compounds.

Optical sign. ................................

T^i rpfnn CPPTIPP

Sarcolite.

2.92

Positive.

1. 6035

1. 6147

.0112

Akermanite.

3.12

1. 6332

1.639

.006

Velardenite.

3.04

1.667

1.658

flftQ

1 Shepherd, E. S., and Rankin, G. A., Preliminary report on the ternary system CaO AlaOa Si02! a 

study of the constitution of Portland cement clinker, with optical study by F. E. Wright: Jour. Ind. and 

Eng. Chemistry, vol. 3, p. 224,1911.
118 MIETEKALOGIC NOTES SERIES 3.

ISOMORPHOUS MIXTURES OF TWO OK- MORE OF THE PRIMARY

COMPOUNDS.

In the following pages all the reliable analyses of minerals of the 

melilite group (including gehlenite) have been tested to see whether 

their composition can be expressed as mixtures of the four primary 

compounds just given. It may be said, in advance, that with 

the exception of the iron-rich melilites from Capo di Bove and the 

one from Colorado, all the samples analyzed agree very well with 

the interpretation here given.

The literature previous to 1892 has not been searched, as the 

analyses given by Dana 1 have (with some exceptions) been taken. 

To these are added the analyses that have been published since 

1892. Of the melilite analyses given by Dana only those by Damour could be utilized. Von Kobell's analysis,, published in 1832, 

was omitted, as the original paper was not available and no proof 

could be had as to the purity of the sample analyzed. The last 

melilite analysis given by Dana was made by Schulze on a small 

amount of material, which was, moreover, contaminated with 

olivine, whence the high percentage of MgO + FeO.

It has also been necessary to disregard several of the gehlenite 

analyses. Dana's Nos. 4 and 5, published by Ktihn 2 in ]?846, have 

to be omitted, as reference to the original article showed that Kuhn 

treated his material with very dilute acid to remove calcium carbonate and furthermore did not determine the state of oxidation 

of the iron. The figures for iron represent arbitrary assumptions. 

The two analyses by Janovsky 3 (Dana's Nos. 6 and 7) were both 

made on impure material, and No. 7 especially (not No. 6, as given 

by Dana) contained considerable mixed vesuvianite. No. 6 is 

stated to have contained vesuvianite but was considered much 

purer than No. 7.

It was decided to omit all analyses of artificial melilites, as these 

were for the most part accidentally formed and did not represent 

pure products. It would be difficult to determine the purity of 

some of the artificial melilites whose analyses have been published, 

and any assumptions as to the composition of the impurity would 

be so uncertain that the results derived from a consideration of 

analyses of artificial melilite would be of no value.

The comparison of the analyses of the natural minerals with the 

calculated composition has been simplified by combining several 

bases and then recalculating the original analyses to 100.00 per 

cent. Water and other foreign matter have been simply omitted.

1 Dana, E. S., System of mineralogy, 6th ed., pp. 475,476,1892.

2 Kuhn, 0. B., Mineralanalysen; 4, Gehlenit: Annalen d. Chemie und Pharmacie (Wohler und Liebig), 

Bd. 59, p. 371,1846.

8 Zepharovich, V., Mineralogische Mittheilungen: 2, Gehlenit von Oravicza: Akad. Wiss. Wien Sitzungsber., Bd. 69, Abth. 1, p. 26,1874.
THE MELILITE GEOUP. 119

Ferric iron, as Fe2 03 , has been recalculated to alumina (A12 03). 

Ferric iron exists in large amount in the melilite from Capo di Bove, 

near Rome. In fact, the analyses of the brown melilite, the variety 

richest in Fe203 , show a higher actual percentage of Fe2 03 than of 

A12 03, but considered molecularly the iron does not exceed the 

A1203 . In the analyses showing the greatest amount of iron the 

ratio of Fe2O3 to A1203 is almost exactly 1:1. Another primary 

component, namely, an iron-calcium silicate, should possibly have 

been introduced, but the number of components would then have 

become five and the expression of the interpretation would have 

been complicated considerably. The Fe2 03 has therefore been 

recalculated and combined with the A1203 .

As Fe303 has not been determined to exist in notable quantity 

in any of the pure end members, it would furthermore be impossible 

to decide to which of the three end-member minerals it should be 

assigned. The compound 3CaO.Al2 03 .3Si02 (sarcolite) is polymorphous, for the formula represents that of grossularite as well as 

that of sarcolite. Now an iron-calcium garnet, 3CaO.Fe2 03 .3Si02 , 

andradite, is a common mineral, and the ferric iron in meHlites would 

naturally then be ascribed to the presence of a ferric iron sarcolite, 

3CaO.Fe2 03 .3Si02 . A recent paper by Scrivenor 1 describes an 

iron-calcium garnet which was "quickly and completely decomposed 

when reduced to powder and heated with hydrochloric acid, silica 

being liberated." The garnet was isotropic and showed very clearly 

the form of the rhombic dodecahedron. Crystals of sarcolite resemble 

those of the isometric system, and, as sarcolite is tetragonal, basal 

cleavage pieces would be isotropic. Could a ferric iron sarcolite 

(3CaO.Fe2 03 .3Si02 ) have been present?

The remaining bases which in the recalculated analyses are to be 

added to other bases are few in number. K20 naturally goes with 

Na20, and FeO and MnO have been added to MgO, CaO therefore 

standing by itself and not receiving any increment in the form of 

replacing bases. It is doubtful if much difference in the ratios 

would have been found if the FeO + MnO had been added to CaO. 

In silicates, however, it seems as if CaO on the one hand and 

FeO + MnO + MgO on the other hand exist as separate groups which 

do not replace each other.

The recalculated and reduced analyses may represent the original 

analyses inaccurately in that the combination of bases may not be 

correct; in that the omission of the water as such may be wrong, for 

the water may, in part at least, belong to an associated hydrous 

mineral; and in that the reduction to 100.00 per cent distributes an error 

in the determination of a single constituent over the whole analysis.

i Scrivenor, J. B., A calcium-iron garnet from China: Mineralog. Mag., vol. 17, p. 51,1913.
120 MINERALOGIC NOTES SERIES 3.

The fact, however, that the following comparisons show a very close 

agreement indicates that perhaps these inaccuracies are not great.

The gehlenite from Velardena 1 analyzed by Alien (quoted by 

Wright) is composed of an isomorphous mixture of 20 per cent of 

akermanite, 0.7 per cent of soda sarcolite, and 79.3 per cent of 

velardenite.

Comparison of gehlenite analysis by Alien with calculated composition*1 of isomorphous

mixture.

SiOa .. .........................

A1208 - - - ---------------

CaO...........................

Na20..........................

MgO................... ........

Ti02 ... ........................

FeA - -- - -

K20..........................

FeO..........................

MnO.........................

H.,0..........................

Original

analysis.

26.33

27. 82

39.55

.21

2.44

.03

1.43

.10

.50

.01

1.85

100. 27

Analysis 

reduced.

26.99

29.43

40.50

.29

2.79

100. 00

Calculated.

27.10

29.65

40.17

.29

2.79

100.00

Difference.

+0.11

+ .22

- .33

.00

.00

« The reduced analysis and the calculated composition differ slightly from the values given on p. 107 

simply because there the soda was combined with the lime, whereas here it is treated separately.

The gehlenite from Monzoni analyzed by Rammelsberg 2 is composed 

of an isomorphous mixture of 36.2 per cent of akermanite and 63.8 

per cent of velardenite.

Comparison of gehlenite analysis by Rammelsberg with calculated composition of isomorphous mixture.

Si02 ..... ...................... Ai2o3 .. ........................

CaO...........................

MgO...........................

Fe203 ......... .................

FeO

MnO.........................

O »/

Original 

analysis.

29.78

22.02

37.90

3.88

3.22

1.63

.19

1.38

100. 00

Analysis 

reduced.

> 

30.81

24.91

39.21

5.07

100. 00

Calculated.

31.04

23.73

40.16

5.07

100. 00

Difference.

+0.23

-1.18

+ .95

.00

1 This is the mineral called velardenite. See p. 106.

2 Dana, E. S., System of mineralogy, 6th ed., p. 476,1892.
THE MELILITE GKOUP. 121

The gehlenite from Monzoni, .analyzed by Lemberg, 1 is composed 

of an isomorphous mixture of 28.7 per cent of akermanite, 15.7 per 

cent of sarcolite, and 55.6 per cent of velardenite.

Comparison of gehlenite analysis by Lemberg with calculated composition of isomorphous

mixture.

SiOa ............ ...............

Al O

CaO.............. .............

MgO...........................

Fe203 ............ ..............

Original 

analysis.

30.01

21.33

36.74

3.77

3.56

4.72

100. 13

Analysis 

reduced.

31.88

25.08

39.03

4.01

100. 00

Calculated.

32.00

24.24

39.75

4.01

100. 00

Difference.

+0.12

- .84

 4- 79

.00

The gehlenite from Monzoni analyzed by Damour 1 is composed of 

an isomorphous mixture of 16.4 per cent of akermanite, 0.8 per cent 

of soda sarcolite, 38.1 per cent of sarcolite, and 44.7 per cent of 

velardenite.

Comparison of analysis of gehlenite by Damour with calculated composition of isomorphous

mixture.

Si02 ............. ..............

A1203 ..........................

CaO..........................

Na20............... ...........

MgO...........................

Fe2 03 -- ------- --- --- ----- - 

H20..........................

Original 

analysis.

31.60

19. 80

38.11

.33

2.20

5.97

1.53

99.54

Analysis 

reduced.

32.97

24.64

39.76

.34

2. 29

100. 00

Calculated.

33.09

25.42

38.86

.34

2.29

100. 00

Difference.

+0. 12'

+ .78

- .90

.00

.00

The melilite from Colorado analyzed by Schaller 2 is composed of 

an isomorphous mixture of 41.3 per cent of akermanite, 8.7 per cent 

of soda sarcolite, and 50 per cent of sarcolite.

1 Dana, E. S., op. cit., p. 476.

* Larsen, E. S., and Hunter, J. F., Melilite and other minerals from Gunnison County, Colo.: Washington 

Acad. Sci. Jour., vol. 4, p. 473,1914.
122 MINERALOGIC NOTES SERIES 3.

Comparison of analysis ofmelilite by Schalkr with calculated composition of isomorphous

mixture.

SiO,.. ........................

A1203 -. .......................

CaO..........................

Na,0........... ..............

MgO.... ..'....................

Ti02 ..........................

Fe208 ............... ..........

FeO... .........................

MnO................... .......

P O

c§::::::::::::::::::::::::::

H20...........................

K20..... .......................

Original 

analysis.

42.07

10.30

35.41

3.24

4.15

20

.50

2.18

.16

.82

.90

.47

Trace.

100. 40

Analysis 

reduced.

44.56

11.25

34.98

3.43

5.78

100. 00

. Calculated.

42.85

13.22

34.72

3.43

5.78

100. 00

Difference.

+1.71

-1.97

+ .26

.00

.00

The melilite from Vesuvius analyzed by Damour x is composed of 

an isomorphous mixture of 42.5 per cent of akermanite, 12.2 per cent 

of soda sarcolite, 34 per cent of sarcolite, and 11.3 per cent of velardenite.

Comparison of analysis ofmelilite by Damour with calculated composition of isomorphous

mixture.

Si02 ......... .................

Al O

CaO............................

Na.,0......... :...............

MgO..........................

Fe203 --------------.--- -------

K20.................. .........

Original

analysis.

. 40.69

10.88

31.81

' 4.43

5.75

4.43

.36

98.35

Analysis 

reduced.

42. 11

14.19

32.92

4.83

5. .95

100. 00

Calculated.

40.77

14.57

33.88

4.83

5.95

100. 00

Difference.

-1.34

+ .38

+ .96

.00

.00

The melilite from Capo di Bove analyzed by Bodlaender is composed of an isomorphous mixture of 42.5 per cent of akermanite, 9.8 

per cent of soda sarcolite, 41.2 per cent of sarcolite, and 6.5 per cent 

of velardenite.

i Dana, E. S., op. cit.j p. 476.
THE MELILITE GROUP. 123

Comparison of analysis of melilite by Bodlaender with calculated composition of isomorphous mixture.

Si02 . .........................

AL03 . ........................

Cab .........................

NazO.........................

MgO.... ......................

Fe2 03 .........................

KaO........ ...................

H20........... ................

Original 

analysis.

41.09

10.93

34.78

3.40

5.87

3.40

.68

.24

100. 39

Analysis 

reduced.

41.63

13.28

35.24

3.90

5.95

100. 00

Calculated.

41.67

13.89

34.59

3.90

5.95

100. 00

Difference.

+0.04

+ .61

- .65

.00

.00

The yellow melilite from Capo di Bove analyzed by Damour 1 is 

composed of an isomorphous mixture of- 49 per cent of akermanite, 

7.8 per cent of soda sarcolite, 33.7 per cent of sarcolite, and 9.5 per 

cent of velardenite.

Comparison of analysis of yellow melilite by Damour with calculated composition of isomorphous mixture.

Si02 ............ ..............

A1J)3 ............ .............

CaO..........................

Na,0... .......................

Mgt).. ........................

Fea08 .........................

KaO...........................

Original 

analysis.

39.27

6.42

32.47

1.95

6.44

10.17

1.46

98.18

Analysis 

reduced.

41.77

13.75

34.54

3.09

6.85

100. 00

Calculated.

41.67

12.86

35.53

 3.09

6.85

100. 00

Difference.

-0.10

- .89

+ .99

.00

.00

The yellow melilite from Capo di Bove analyzed by Zambonini 2 

is composed of an isomorphous mixture of 49.5 per cent of akermanite, 8.3 per cent of soda sarcolite, 32.4 per cent of sarcolite, and 9.8 

per cent of velardenite.

1 Dana, E. S., op. cit, p. 476.

2 Zambonini, F., Ucber eine krystallisierte Schlacke der Seigerhutte bei Hettstedt, nebst Bemerkiingen 

iiber die chemische Zusammensetzung des Melilith: Zeitschr. Kryst. Min., vol. 41, p. 266,1906.
124 MINEEALOGIC NOTES SERIES 3.

Comparison of analysis of yellow melilite by Zambonini with calculated composition of

isomorphous mixture.

Si02 ...........................

ALO............... ............

Cab...........................

NaaO......... .......... .......

M>O

Fe203 ..........................

FeO..........................

KaO..........................

H20..........................

Ti02,MnO......................

Original 

analysis.

40.14

6.47

32.98

2.18

6.33

9.95

.53

1.49

.27

Trace.

100. 34

Analysis 

reduced.

41.93

13.40

34.45

3.30

6.92

100. 00

Calculated.

41.63

12.80

35.35

3.30

6. 92

100. 00

Difference.

-0.30

- .60

+ .90

.00

.00

The brown melilite from Capo di Bove analyzed by Damour 1 is 

composed of an isomorphous mixture of 50.3 per cent of akermanite, 

8.2 per cent of soda sarcolite, 26.5 per cent of sarcolite, and 15 

per cent of velardenite.

Comparison of analysis of broiun melilite. by Damour with calculated composition of

isomorphous mixture.

/

SiOa ............ ...............

AI n

CaO...........................

Na20..........................

M"0

Fe~0a~-. ...................... K26.8.........................

Original 

analysis.

38. 34

8.61

32.05

2.12

6.71

10.02

1.51

99.36

Analysis 

reduced:

40.26

15.77

33.65

' 3.28

7.04

100. 00

Calculated.

40.73

13. 37

35.58

3.28

7.04

100. 00

Difference.

+0.47

-2.40

+1.93

.00

.00

The brown melilite from Capo di Bove analyzed by Zambonini 2 

is composed of an isomorphous mixture of 47.9 per cent of akermanite, 8.3 per cent of soda sarcolite, 28 per cent of sarcolite, and 15.8 

per cent of velardenite.

1 Dana, E. S., op. cit., p. 476.

2 Zambonini, F.^ op. cit., p. 266.
THE MELILITE GEOUP. 125

Comparison of analysis of brown melilite by* Zambonini with calculated composition of

isomorplious mixture.

SiOa ................... ........

Ala03 .... .......................

CaO.......... .................

NaaO............... ...........

M>0

Fea08 ..........................

K20..........................

H20..........................

Ti02,MnO... ..................

Original 

analysis.

39.20

7.56

32.18

2.21

6.41

11.34

1.45

.21

Trace.

100. 56

Analysis 

reduced.

40.93

1 15. 47

33. 60

3.31

6.69

TOO. 00

Calculated.

40.42

14.05

35.53

3.31

6.69

100. 00

Difference.

-0.51

-1. 42

+1.93

.00

.00

The main difference between the calculated composition and the 

reduced analyses shown in the last two tables is that in the calculated composition A12 03 is too low and CaO too high. The two 

analyses of brown melilite from Capo di Bove both show a large 

amount of Fe203 and no FeO. It seems possible that a part of the 

iron in these melilites may exist as FeO but had become oxidized, 

possibly by fine grinding, so that the determination of Fe203 as 

given in the analysis is too high. A readjustment on such a basis 

would give results agreeing much closer with the calculated composition than the actual analysis does.

The fuggerite from Monzoni analyzed by E. Mayr 1 is composed 

of an isomorphous mixture of 35.3 per cent of akermanite, 5.2 per 

cent of soda sarcolite, 16 per cent of sarcolite, and 43.5 per cent 

of velardenite.

Comparison of analysis offuggerite with calculated composition of isomorplious mixture.

SiQ,.. .........................

AlaO».... ......................

CaO...........................

Na 20......... .................

MgO.... .......... .............

Fea08 .. ........................

KaO,MnO.....................

Original 

analysis.

34. 04

17.97

37.65

2.04

4.89

3.49

.12

Trarp

100. 20

Analysis 

reduced.

34. 45

20.45

38.10

2.06

4.94

100. 00

Calculated.

34.59

20.93

37. 48

2.06

4.94

100. 00

Difference.

+0. 14

+ ;48

- .62

.00

.00

i Weinschenk. E.. Fuggerit. ein neues Mineral aus dem Fassathal: Zeitschr. Kryst. Min., vol. 27, p. 577, 

1896. '
126 MINERALOGIC NOTES SERIES 3.

COMPOSITION OF THE MIXTURES.

In order to show more clearly the relations of the minerals whose 

composition has been discussed on the previous pages, the 17 mineral 

analyses have been plotted on a triangular plan with the three 

minerals akermanite, sarcolite, and velardenite as the three apices 

(fig. 89). The percentages of sarcolite and soda sarcolite have been 

added together, a procedure justified by the nearly equal molecular 

weight of the two compounds. (Compare p. 115.)

The mineral compositions as plotted on figure 89 are summarized 

below, \vith the same numbering as used in the diagram.

Summary of mineral composition of members of the melilite group, graphically shownin

figure 89.

No.

1

2

q

4

5

«

7

8

9

10

11

12

13

14

15 

Ifi

17

Mineral.

.....do............ 

..... do.... ........

.....do............

defiite).

t-roViloTn tf*

.....do............

.....do............

.....do............

.....do............

Brown melilite....

.....do............ 

Melilite...........

Fu£?G?ente

Locality.

.....do........ 

.....do........

.....do........

.....do........

Velardena,

Mexico.

.....do........

.....do........

.....do........

Capo di Bove.

Italy. 

.....do........

.....do........

.....do........

.....do........ 

Colorado.

Author.

Rammelsberg . .

Freda. .........

Wright.. .......

Damour........

.....do.........

Bodlaender. . ..

Damour. .......

Zambonini. . . .

Zambonini ....

Hunter.

\\7pl Tl Qf* n ATI t

Akermanite.

0

0 

2.6

QK A

Q4 Q

20.0

36.2

28.7

16.4

49 *»

49 ^

49.0

49.5

en q

47.9 

41.3

qc q

Sarcolite.

100

100 

Q7 4

4.6

5.1

.7

.0

IK 7

OQ Q

4fi 9

51.0

41.5

40.7

q4 7

36.3

. 58.7

91 9

Velardenite.

0

0 

0

0

0

7Q 3

63.8

CLK 0

44.7

11.3

6.5

9.5

9.8

15.0

15.8 

0

4Q K.

The "gehlenites" have a varying composition, as is clearly shown 

in figure 89, and do not all correspond to the simple formula 

3CaO.Al203 .2Si02 , as has. been advocated. Together with those of 

velardenite and fuggerite, however, their symbols he in the velardenite portion of the triangle, and, like velardenite, all the " gehlenites" are optically negative. They represent isomorphous mixtures 

of the three minerals, in which the negative velardenite occurs in 

greater amount than either of the other two. The properties of 

fuggerite as given by Weinschenk are not accurately in accord with 

those of the other gehlenites, and the fact that the symbol of a double 

salt with properties differing from those of velardenite, akermanite, 

or sarcolite falls in this part of the diagram may explain the unusual 

properties shown by fuggerite.
THE MELILITE GKOUP. 127

Now, if, as has been suggested by the chemical composition, melilite 

is essentially an isomorphous mixture of akermanite and sarcolite (all 

the melilites contain over 80 per cent of akermanite and sarcolite), 

both of which are optically positive, then the melilites should likewise 

be positive. In fact melilites are mostly negative, though occasionally 

a positive one is seen. Melilites which are almost isotropic have 

also been described.

The plotted analyses of melilite are confined to a small portion of 

the triangular field (fig. 89), although out of seven analyses only three 

localities are included. The melilite from Colorado is apparently the

Velardenite

Akermanite Sarcolite

FIGURE 89. Triangular representation of the chemical composition of minerals of the melilite group, 

including akermanite (A), sarcolite (5), velardenite (0 6), melilite (M), gehlenite (G" to GO), and 

fuggeriteCF).

simplest in composition, for it is composed of only two end members, 

sarcolite and akermanite. It is to be noted, however, that the agreement of the analysis with the calculated composition, as given on 

page. 122, is not very close. Over 84 per cent of the other melilites 

consist of sarcolite and akermanite. Now, both these two minerals 

are optically positive, whereas melilite is generally negative, although 

positive varieties are known.

Two explanations suggest themselves to explain the apparent discrepancy. One is that an isomorphous mixture of two optically 

positive substances is not necessarily of the same sign throughout, for
128 MINEKALOGIC NOTES SERIES 3.

the sign depends on the relative values of the refractive indices. For 

positive minerals, e is greater than w, but for negative minerals it is 

less. If the refractive indices of all isomorphous mixtures of sarcolite 

and akermanite are linear functions of their composition, then negative melilite can not be such a simple isomorphous mixture. On the 

other hand, if the indices are not linear functions of the composition, 

then negative melilites may be isomorphous mixtures of two positive 

minerals, the refractive indices changing with the composition, as 

shown in figure 90. If some such relation held good, then most melilites would be negative, a smaller number would be positive, and a

Isotropic Isotropic

1 y

-Positive > < - ---- -- Negative - --------- --- -- > < .-pCSitjve~--->

i.60p« ; 

Akermanite Melilite from 

Colorado

Sarcolite

FIGUEE 90. Diagram showing hypothetical relation of refractive indices to composition of mixtures of

&kermanite and sarcolite.

very small number would be isotropic. With relations as shown in 

figure 90, there are two mixtures (about 14 per cent and 79 per cent of 

akermanite) which are isotropic.

A second explanation, however, deserves careful consideration, 

although at present its possibility can only be suggested. It is 

dependent on the existence of a double compound of akermanite 

and sarcolite which would be optically negative, and the melilites 

would consist essentially of this double compound with smaller 

amounts of akermanite, sarcolite, and velardenite in solid solution.

The concentration of the symbols representing the melilite analyses 

in a small portion of the field (fig. 89) is in a way somewhat suggestive of the existence of a double compound.
THE COMPOSITION OF CEBOLLITE.

Cebollite, an alteration product of melilite, was found near Cebolla 

Creek, Gunnison County, Colo., and as described by Larsen 1 forms 

compact masses of a fibrous character. The mineral is probably 

orthorhombic, biaxial, positive, a = 1.595 ± 0.003, 18 = 1.60, 7 = 1.628 ± 

0.005. It resembles the zeolites in its properties and composition. 

Hardness = 5, specific gravity = 2.96.

The mineral gelatinizes with acids and gives off water when heated 

in a closed tube. An analysis of a sample containing as little as 

possible of the associated insoluble diopside and garnet gave the 

following results:

Analysis and ratios of cebollite.

Insoluble a . ....................... 

Soluble in HC1: 

SiO........ .................

A1203 ------ ----....-- ........

Fe2 03 ........................

CaO.. .......................

FeO................. .........

MgO.........................

Na20.. ......................

HaO+.. ......................

H20.................. .......

Ti02) K20..... ................

Analysis.

18.05 

27.06

11.49

2.81

29.27

.17

3.84

2.10

5.13

.00

Trace.

99.92

Insoluble deducted.

33.02

14.02

3.43

35.72

.21

4.69

2.57

6.26

99.92

0.550

.1371 - 02ij-158

.6381

.003 ?qq .117f- 799

.04lJ

.348

Ratios.

3.26 or 3X1-09

0.94 or 1X0.94

4.74 or 5X0.95

2.06 or 2X1.03

a Diopside and garnet.

The formula derived from the analysis is 3SiO2 .Al2O3 .5R/'O.2H20, 

in which R" is chiefly Ca with smaller amounts of Mg and Na2 . 

The ratio of Na20 : MgO + FeO : CaO is 1 : 3 : 16. Considering all 

the R"0 as CaO, the formula, Si3Al2Ca5H4016, may be written in 

two ways (Si04 ) 3 .Ca5 .[Al(OH) 2] 2 or (Si04 ) 3 .(CaOH) 4 .Ca.Al2 .

The powdered mineral, treated with water, does not show an 

alkaline reaction with phenolphthalein, and if for certain minerals such a reaction indicates the presence of the CaOH group, as 

is suggested on page 154, the second of the formulas above given

'.Larsen, E. S., and Schaller, W. T., Cebollite, a new mineral; Washington Acad. Sci. Jour., vol.4, 

p. 480,1914.

97888° Bull. 610 16 9 129
130 MINERALOGIC NOTES SERIES 3.

becomes untenable, and the formula of cebollite is consequently 

(Si04 ) 3 .Ca5 .[Al(OH)2] 2 , which can be written structurally as follows:

/A1COH),

/Si04 / 

Ca< X)a

>Si04 =Ca 

Ca/ ^Ca

4 \U(OH) 2

The cebollite seems to belong to the zeolite group, although the 

presence of several per cent of magnesium is unusual.
THE CRYSTALLOGRAPHY OF THAUMASITE.

Several specimens of thaumasite from the well-known locality at 

West Paterson, N. J., showed well-developed crystals which reached 

a maximum length of about 5 millimeters. The crystals are hexagonal and consist of the prism m{10TO} and the base c{0001}. They 

show gradations from a short prismatic habit x(fig. 91) to a long 

prismatic habit (fig. 92). Although well-formed single crystals are

FIGURE 91. FIOUKE 92.

FIGURE 91. Short prismatic crystal of thaumasite. 

FIGURE 92. Long prismatic crystal of thaumasite.

not rare, many of them are composed of one or more large units, 

to which several smaller crystals are attached. These smaller 

crystals are either in parallel position or deviate slightly from strict 

parallelism, as is shown in figure 93, which represents such a group 

as it appeared under the microscope. The crystals are striated 

vertically.

A single terminated crystal was found and measured. It is shown 

in ideal development in figure 94. The forms present are m, c, and 

p{10T.l}. The p angles of the pyramid faces, of which only four 

could be measured, are 53°30', 51°30', 50°15', and 50°45 / ; average 

51°30', from which the c axis is calculated to be 1.09.

131
132 MINERALOGIC NOTES SEEIES 3.

The prism faces, although striated and built up of several faces, 

not all of which were in parallel position, were bright and. gave good 

reflections. Their interfacial angle seldom measured more than a 

degree different from 60°. The base is always dull and gave no reflection. The pyramid faces were likewise dull and could be measured 

only by means of maximum illumination.

The same crystal which showed the faces of p also had a minute 

face whose p angle was 31°40 / . On a different crystal a face was

FIGURE 93. FIGURE 94.

FIGURE 93. Compound crystal of thaumasite, with attached smaller crystals, as seen under the

microscope. 

FIGURE 94. Terminated crystal of thaumasite. Forms: w{10lO}, c{0001>, rtwll}.

measured whose p angle was 31°41 / and on a third crystal two faces 

gave p angles of 31°45 / and 31°53'. The 0 angles varied so much 

for these different faces that the position of the form could not be 

determined, although the faces measured may not belong to a definite 

form, yet it would seem remarkable to find faces on three different 

crystals which would give the same p angle.

Qualitative tests on a small sample of the selected crystals showed 

that they were thaumasite.
THE CHEMICAL COMPOSITION OF TREMOLITE.

In a recent paper Alien and Clement 1 have suggested that the 

water in tremolite is "not chemically combined, although the mineral 

in the powdered state is not completely dehydrated under 900°. It 

is to be regarded as dissolved water, and tremolite as a solid solution. 

* * * Diopside and tremolite seem to give off their water continuously, but not indefinitely, with rising temperatures, though it is 

quite possible the curves represent cases of false equilibria."

According to then1 view, then, the mineral tremolite, as found in 

nature, represents a chemical compound 4- water. The water present 

would not be a necessary inherent part of the mineral, and the true 

composition of the mineral would be shown by the analysis with the 

water excluded. This conclusion the authors reached as a result of 

finding that "the water in all the specimens is lost gradually as the 

temperature rises, without any sudden change of properties or loss of 

homogeneity. It can not, therefore, be chemically combined, even 

though it is given off so very slowly at a temperature of 900°."

It seems probable, however, that a different explanation may be 

offered from that which contends that the water in tremolite is dissolved and not a true part of the mineral. A similar conclusion 

was reached by Coblentz 2 as a result of experiments based on the 

absorption spectrum of water in minerals. He said: "From the 

present data it is evident that the water in tremolite is not present in 

the same condition as in other substances containing water in solid 

solution or dissolved water. * * * From the present data it appears that in tremolite the water is constitutional, with possible OH 

groups, the small band at 2.95 ju being complex, as in the other hydroxides just cited [brucite, diaspore, bauxite, gothite]. This is, of 

course, contrary to the vapor-pressure experiments; but it is the 

most satisfactory conclusion to be drawn from the present experiments. "

The zeolites have often been cited as examples of minerals in which 

the water is not chemically combined, but Beutell and Blaschke 3 

have recently contended that the water in stilbite is chemically combined, and they further question whether it has been proved that for 

any hydrosilicate the water is dissolved or absorbed.

1 Alien, E. T., and Clement, J. K., The r61e of water in tremolite and certain other minerals: Am. Jour. 

Sci., 4th ser., vol. 26, p. 101,1908.

2 Coblentz, W. W., Therdle of water in minerals: Franklin Inst. Jour., vol. 172, p. 334,1911.

3 Beutell, A., and Blaschke, K., Das Wasser im Dnsmin 1st chemisch gebunden: Centralbl. Mineralogle, 

1915, pp. 4-11; 1st die Existenz krystallisierter Hydrosilicate mit gelostem Oder absorbiertem Wasser 

erwiesen? : Idem, pp. 195-200.

133
134 MINERALOGIC NOTES SERIES 3.

Together with their experimental data, Alien and Clement give five 

analyses of tremolite which have not heretofore been accorded the 

attention they deserve, for not only were the samples carefully selected and purified, but the analytical work was done by a skilled 

analyst of the highest grade. The five analyses of tremolite are

reproduced below.

Analyses of tremolite. 

[E. T. Alien, analyst.]

Si02 ........................

Ti02 ........... .............

Al O

Fe2 03 .......................

FeO............... ........

MnO..... ............ .......

MgO........................

CaO........................

N&tO. .....................

K,p. ......................

TLJ). ......................

F... ............. ..........

0-F9 ... ...................

5 1

Ham 

Island, 

Alaska.

58.59

.10

24.78

13.95

.12

.10

2.31

TSfnTiP

99.95 

.00

99.95

2

Ossining,

N. Y.

57.35

.07

1.21

.11

.23

.01

23.87

14.02

.42

.19

2.21

.11

99.80 

.05

99.75

3

Gouverneur, 

N. Y.

56.92

.10

1.65

.36

23.81

12.51

1.22

.60

9 ftl

1.03

100. 21 

.43

99.78

4

Russell,

N. Y.

56.36

.06

1.88

.61

1.01

.04

22.97

12. 82

.94

.74

1.72

1.23

100. 38 

.53

99.85

5

Edwards. 

N. Y.

58.24

.04

.60

.43

None.

1.28

25.16

10.85

.82

.19

2.50

.24

100. 35 

.10

100. 25

Assuming that fluorine and hydroxyl replace each other and 

adding together the percentages of water (H2 0, equivalent to 20H) 

and one-half the percentages of fluorine (since F is equivalent to 

OH, F2 becomes equivalent to 20H or H2O), we obtain the following 

percentages of water plus fluorine for the five tremolite analyses: 2.31, 

2.27,2.53, 2.34, 2.62. These figures surely denote a constant quantity 

for a mineral which is a member of a large isomorphous group.

The ratios were calculated from the analyses just given. Titanium 

as Ti02 is combined with silica (Si02 ), Fe2 03 with A12 03 , MnO with 

FeO, K2O with Na2 0, and F2 witH H2 0.

Ratios of tremolite analyses.

SiO.........................

MgO........................

CaO..:.....................

H2 0.......................

Ala08 ........ ...............

FeO.......................

Na20.. .....................

1

0.971

.615

.249

.128

.001

.003

2

0.952

.592

.250

.126

.013

.003

.009

3

0.945

.591

.223

.139

.018

.026

4

0.936

.570

.229

.128

.022

.014

.023

5

0.967

.624

.193

.145

.009

.018

,015
THE CHEMICAL COMPOSITION OF TREMOLITE. 135

If all these bases are combined on an assumption of equal valence 

that is, RO=MgO+CaO + H20 + FeO + JA1203 the following results 

are obtained:

Comparison of ratios of total bases to silica in tremolite.

HO........................

SiOa .. ......................

ROSi02 ------------------------ 

R0-H20..................

R0-H20

Si02 -------------------

1

0.995

.971

1.02

.867

en

2

0.984

;952

1.03

.858

Qft

3

0. 985

.945

1.04

.846

on

4

0.971

.936

1.04

049

QO

5

0 QQ8

.967

1 ft3

pco

88

This table shows conclusively that if all the MgO, CaO, A12 03 , 

Fe203 , FeO, MnO, Na20, K2 0, H20, and F2 are considered as forming 

the base of the chemical compound of which Si02 (+ Ti02 ) is the acid, 

then the ratio of base to acid is 1 : 1, as it should be in tremolite. 

That the ratio of the bases is very slightly above 1 is doubtless due 

to the fact that the summation of the bases includes a maximum 

number of ten constituents. The chance of foreign material (dust, 

impurities in reagents, etc.) being added during the analysis is very 

much greater for these ten bases than for the single acid (Si02 ).

From the above table it can also be seen that if water (plus fluorine) 

is excluded from consideration, then the ratio of the bases to the

acid, o-/~v 2 - falls short of unity.

The same results can be shown by arbitrarily changing the ratio of 

silica (Si02 ) to 8.00 and recalculating the bases accordingly, as shown

below:

Recalculated ratios of tremolite analyses.

. 0

SiOy......... ...............

MgO........................

CaO........................

MO «. .....................

HoO b.. ....................

1

8.00

5.07

2.05

.02

1.07

2

8.00

4.97

2.10

.13

1.06

3

8.00

5.00

1.89

.27

1.18

4

8.00

4.87

1.96

.38

1.09

5

8.00

5.16

1.60

.30

1.20

a Includes FeO, MnO, Na 2O, K2 0, $(AhO8), $(Fe203 .) 6 Includes fluorine as (Fj).

Obviously the ratios of MgO + CaO + MO do not suffice to satisfy 

the eight parts of silica, and without the water the composition of 

the mineral is incomplete, unless so complex and improbable a formula 

as 7RO.8Si02 or 9R0.10Si02 is assumed for tremolite.
136 MINERALOGIC NOTES SERIES 3.

The constituents of MO can be so distributed between MgO and 

CaO, which they obviously replace, as to make the ratios of Si02 : 

MgO : CaO: H20 come very close to 8 : 5 : 2 :1 and it is suggested that 

the formula for tremolite is 8Si02 .5Mg0.2CaO.H20 and not 3MgO. 

Ca0.4Si02 , as given in the textbooks.

From the chemical side, it seems at least doubtful whether the conclusion of Alien and Clement is correct, and the writer suggests, in 

accordance with the conclusions of other authors (earlier cited), that 

the water in tremolite may be different'from "dissolved water."
NEW OCCUKEENCES OF SOME RARE MINERALS.

It seems advisable to put on record the identifications of some rare 

minerals which have been sent to the Geological Survey within the 

last few years.

A specimen of massive guanajuatite was sent by Mr. John E. Erickson from Salmon, Idaho. No mention of any other locality than the 

original one at Guanajuato, Mexico, could be found in the literature, 

so that the Idaho occurrence would make the second locality for this 

rare bismuth selenide.

Well-crystallized jarosite, in hexagonal scales reaching a diameter 

of 1 millimeter, was found in the Shattuck-Arizona copper mine at 

Bisbee, Ariz, and were sent in by Mr. Philip D. Wilson, of Bisbee. 

The brilliant crystals lie on massive iron oxide (hematite) and show 

only the base c{0001} and the rhombohedron r{10ll}. The angle 

c : r was measured as 53° 19', but the measurements were poor and 

not very reliable. Most of the crystals are uniaxial, negative; 

several of them show, in basal section, a division into six biaxial 

sectors (compare fig. 88) with the axial plane parallel to the edge cr. 

The measured angle 53° 19', between that of jarosite (55° 16') and 

natrojarosite 1 (51° 53'), suggested that the mineral from Bisbee 

might lie chemically between jarosite and natrojarosite, but qualitative tests showed that although a little soda was present potash 

was the predominant alkali.

Some rock specimens, sent in by Mr. George W. Davies, of Topaz, 

Cal., are thickly coated with brilliant yellow to orange greenockite.

1 Compare table given, by Hillebrand, W. F.,and Penfield, S. L., Some additions to the alnnite-jarosite 

group of minerals: U. S. Geol. Survey Bull. 202, p. 40,1905.

137
GIGANTIC CRYSTALS OF SPODUMENE.

The occurrence of gigantic crystals of spodumene in the Black Hills 

of South Dakota has been known for some time and has been several 

times referred to in the literature. Blake, 1 as early as 1885, wrote: 

"One crystal which extends horizontally parallel with a drift is 36 

feet in length in a straight line, and is from 1 to 3 feet in thickness. 

* * * Crystals from 5 to 20 feet long are numerous and incline in 

all directions." Hess 2 mentions a crystal that measured "42 feet in 

length, with a cross section of approximately 3 by 6 feet. Part was 

decayed and useless, but about 37 tons of spodumene was mined 

from it."

Ziegler 3 describes, in part, the immense size of the spodumene 

crystals as follows:

The crystals are often of enormous size. In the Etta mine, where they are best 

exposed both in the open cut and in the tunnel, they frequently attain a diameter of 

3 to 4 feet and a length of 30. The largest "log" so far found was 42 feet long and of 5 

feet 4 inches maximum diameter. This one log alone would yield 90 tons of spodumene.

Two photographs of such gigantic crystals are shown in Plate V. 

The upper picture, taken by Mr. S. C. Smith at the Etta mine, near 

Keystone, in 1904, shows the largest "log," as these crystals are 

called, which had been uncovered up to that time of which Mr. Smith 

had any record. The length of the exposed portion, calculated from 

the photograph, is 47 feet. In Plate V, B, two molds of such large 

crystals are shown. The length of each of these molds, measured by 

the writer in 1904, was 40 feet, and the thickness varied from 2£ to 3 

feet. In another part of the mine was seen a spodumene log whose 

exposed length was 25 feet and whose diameter was from 3 to 3 J feet.

These spodumene logs rarely contain any other mineral included as 

impurity. On a few crystals small amounts of quartz were seen, and 

more rarely minute amounts of cassiterite or struverite occur embedded in the spodumene or form small veins therein. The spodumene cleaves readily and as mined is broken up into blocks about a 

foot in diameter, A layer of some alteration product, several inches 

thick, coats many of the crystals. It has been estimated that 25 tons of 

waste rock have to be removed in the extraction of 1 ton of spodumene.

1 Blake, W. P., Spodumene crystals of gigantic size: Am. Jour. Sci., 3d ser., vol. 29, p. 71,1880.

2 Hess, F. L., Lithium: U. S. Geol. Survey Mineral Resources, 1909, Part II, pp. 649-653,1911. 

8 Ziegler, V., The mineral resources of the Harney Peak pegmatites II; Min. and Sci. Press, vol. 108, 

p. 654, Apr. 18,1914.

138
U. S. GEOLOGICAL SURVEY BULLETIN 610 PLATE V

A. LARGEST CRYSTAL MINED UP TO 1904. 

Photograph furnished by S. C. Smith.

Jl. MOLDS OF TWO IMMENSE CRYSTALS.

GIGANTIC CRYSTALS OF SPODUMENE, ETTA MINE, BLACK HILLS, S. DAK.
THE PROBABLE IDENTITY OF MARIPOSITE AND

ALURGITE.

A comparison of the two analyses of niariposite made by Hillebrand l with. Penfield 's analysis 2 of alurgite shows that the two 

minerals are probably identical, as can be seen by the following table:

Comparison of analyses of mariposite and alurgite.

SiOo. ......................................

Ti(X......... ..............................

A1263 .............. ........................

Fea08 ... ...................................

GrJO.... ....................................

Feb........................................

MnO. ................ ......................

MgO......... ...... ........................

CaO.......................................

Na20.. ....................................

K20.................. ......................

H20..... ..................................

Alurgite 

(Penfield).

53.22

21.19 

1.22

.87

.is

6.02

.34 

11.20 

5.75

99.99

Mariposite (Hillebrand).

White.

56.79 

a. 18 

a 25. 11 

&.63 

None. 

&.92

3.29 

.07 

c.17 

8.92 

4.72

<* 100. 80

Green.

55.35 

.18 

25.62 

.63 

.18 

.92

3.25 

.07 

c.12 

9.29 

4.52

100. 13

a The AlaOs+Ti02 is given by Hillebrand as 25.29 per cent.

b The total iron oxides are given by Hillebrand as 1.59. The ferrous and ferric oxides were not separately determined. As the total sum of FeO+FesOs in the green mariposite is 1.55 per cent, or nearly the 

same as in the white mariposite, the values for FeO and FeaOg in the white are taken from those given for 

the green.

c Includes Li2 0.

* The summation in Hillebrand's publication is 100.84.

A better comparison can be made by omitting the Ti02 , adding molecularly the Fe2 03 , Cr203 , and Mn20s to the A12 03 , the FeO, MnO, 

and CaO to the MgO, and the Na2 0 to the K2 0, and then reducing 

the analyses to 100 per cent.

Recalculated analyses of mariposite and alurgite.

8iOa ... ....................................

A1203 ., ....................................

MgO.......................................

KaO............... .........................

E.*0.....>........... .......................

Alurgite.

53.58

99 fiQ

6.16

11.78

5 7Q

100.00

White 

mariposite.

56.76

9*i 4Q

3.85

9.18

4 79

100. 00

Green 

mariposite.

55.74

Of! QO

3 84

Q M

4.56

100. 00

1 Hillebrand, W. F., Mineralogical notes: U. S. Geol. Survey Bull. 167, p. 74,1900.

2 Penfleld, S. L., On some minerals from the manganese mines of St. Marcel, in Piedmont, Italy: Am. 

Jour. Sci., 3d ser., vol. 46, p. 288,1893.

139
140 MINEEALOGIC NOTES SEEIES 3.

The ratios calculated from these analyses, with Si02 taken arbitrarily as 12.00, are as follows:

Ratios of analyses of alurgite and mariposite.

SiOo....... ................................

A1 O

MgO.......... .............................

K20................. .......................

H,0........... .............................

Alurgite.

12.00

2.99

2.08

1.69

4.38

White 

mariposite.

12.00

3.18

1.21

1.24

3. 34

Green 

mariposite.

12.00

3.34

1.23

1.31

3.29

In alurgite the ratios become simple if the water (H2 0) and potash 

(KjO) are taken together, for then the ratios yield the formula 

12Si02 .3Al2 03 .2Mg0.6(H2 ,K2)0. The ratios of the green mariposite, 

which show greater divergence from the alurgite formula than the 

ratios of the white mariposite, indicate that the mariposite micas 

represent a solid solution of which one end member is represented 

by alurgite but of whose other end member no representative has 

as yet been found. The trend of the ratios would indicate some 

such formula as 12Si02 .4Al2 03 .K20.3H2 0 for the second end member.

The physical and optical properties of these minerals, so far as 

determined, show a close relation, as is indicated by the following 

comparison:

Comparison of properties of aluryite and mariposite.

Pleochroism. .........

Optical sign..... ......

Axial angle (2E)......

Mean index. ..........

Alurgite.

2.835-2.849......................

Not very marked. ................

Rather strong. ..................

Negative. . ......................

Biaxial and uniaxial (due to

twinning) 2E=0°-57°. 

1.594...................'........

Mariposite.

2.787, 2.817.

Not perceptible.

ors, like talc. 

Negative.

Uniaxial.

1.63.

The name alurgite was proposed (in 1865) three years before the 

name mariposite (in 1868). Moreover, the first analysis of alurgite 

was published (in 1893) a few years before those of mariposite 

(1895). The name alurgite therefore clearly has priority.
THE AMBLYGONITE GROUP OF MINERALS FREMONTITE 

(= NATRAMBLYGONITE).

It has long been recognized that both a fluophosphate and a 

hydroxyphosphate of aluminum and lithium have been placed 

together under the name of amblygonite. Descloizeaux separated 

the two species in his Manuel de mineralogie, but Dana, in the sixth 

edition of the System of mineralogy, grouped them together under the 

common name amblygonite, although he clearly stated the difference 

in their properties.

A consistent, systematic treatment of mineral species necessitates 

the separation of what is called amblygonite into two distinct species, 

and Penfield's analyses * sufficiently indicate the existence of both 

a fluo-compound and a hydroxy-compound with many intermediate 

mixtures.

A few years ago the writer 2 described a new mineral which was 

in fact the soda equivalent of amblygonite, and in order to emphasize 

this point the new mineral was named natramblygonite. This name, 

however, being half Greek'' and half Latin, is objectionable. (Compare the section " Nomenclature" in Dana's System of mineralogy, 

6th edition, page xliii, No. 11.) A further objection to the name is 

found in the fact that in German it becomes "Natronamblygonit," 

a word that also means a "sodic amblygonite," which is not the 

intended meaning of "natramblygonite." A still further objection 

to the name is voiced by Gonnard,3 who justly states that the mineral 

should have been called natromontebrasite, inasmuch as the water, 

considered as hydroxyl, is present in nearly twice the amount of the 

fluorine.

In view of these facts, it is considered best to withdraw the name 

natramblygonite and to substitute for it the name fremontite, after 

Fremont County, Colo., in which the mineral was found.

Fremontite, then, is a hydrophosphate of aluminum and sodium, 

with the formula Na(A10H)P04 . The only published analysis of 

fremontite shows a partial replacement of the sodium by lithium and 

of the hydroxyl by fluorine.

1 Dana, E. S., System of mineralogy, 6th ed., p. 782,1892.

2 Schallcr, W. T., Natramblygonite, a new mineral: Am. Jour. Sci., 4th scr., vol. 31. p. 'IS, 1911.

3 Gonnard, F., Soc. fra§. min6ralogie hull., vol. 36, p. 120,1913.

141
142 MINEKALOGIC NOTES SERIES 3.

The amblygonite group consists of the following definite species, 

which very rarely occur in a pure state but whose mixture has been 

found at numerous localities:

Amblygonite, Li(AlF)P04 or Li20.Al203.P20s.F2. 1 

Montebrasite, Li(A10H)P04 or Li2O.Al203.P206 .H2 0. 

Fremontite, Na(A10H)P04 or Na2O.Al203 .P205 .H2 0. 

Durangite,2 Na(AlF)As04 or

1 Minus 1 atom of oxygen.

2 The crystallographic relations of durangite with amblygonite are not yet clear.
THE CRYSTALLOGRAPHY OF FREMONTITE.

The original material of fremontite did not show any crystal form, 

and its crystallographic relation to amblygonite could only be inferred. The optical properties did not indicate any variance from 

the -symmetry of amblygonite.

With zealous interest Mr. J. D. Endicott, of Canon City, Colo., 

continued development of the pegmatite in which the fremontite was 

found and procured a number of large crystals of that mineral. The 

best ones seen are in the collection of the late Mr. A. F. Holden, of 

Cleveland, Ohio, now in Harvard University, 

and through the kindness of Mr. Holden the 

writer was permitted to study and describe 

the crystals.

The smallest crystal is completely developed and is described below. Two specimens of pegmatite contain larger crystals 

built up of several individuals in parallel position. Both of the larger crystals are similar 

in combination and habit to the smaller one 

and are therefore not further described.

The small crystal is thick tabular in habit 

and is shown in projection in figure 95. The 

dimensions of the crystal are 35 by 28 by 13 

millimeters. The faces are all dull and uneven, and the edges are considerably rounded. 

In appearance the crystal resembles kaolinized orthoclase, though its high density (3.05) 

compared with that of feldspar is noted at 

once. A closer inspection of the crystal form 

likewise shows a difference from that of feldspar. The color is grayish 

white; on the two larger crystals it is reddish in places. Two cleavages are readily identified; the one better developed is parallel to the 

base c{001}, and the other one is parallel to the orthopinacoid a\ 100}. 

Cleavage planes were not present, but their orientation could readily 

be definitely determined by the direction of their traces. These were 

well developed as parallel lines on the faces of h{101}, e{021} and 

2{120}.

The angular values of the crystal could be only approximately 

obtained with the contact goniometer. These measurements, by

143

FIGURE 95. Crystal of fremontite. 

Forms: c{001}, &{010}, o{100>,
144 MINERALOGIC NOTES SEEIES 3.

which the crystal was correctly oriented, are given in the following 

table. Various other orientations were temporarily chosen, but only 

with the one adopted were the measured angles of fremontite in 

accord with those of amblygonite. The angular constants of amblygonite are taken for those of fremontite, pending the measurement of 

better crystals which would yield more accurate values. These constants are a : 6 : c = 0.7334 : 1 : 0.7633; a=108°31, /3 = 97°48'; 7 =

106°27'.

Measured and calculated angles for fremontite.

c 

a 

h 

c 

z 

a 

c 

b 

b

: a=(001 

ft=(100 

e=(103 

2= (021 

. ft=(120 

6 = (100 

6= (001 

: «=(010 

: z=(010

) : (100 

:(101 

:(021 

^20 

: (101 

: (010 

: (010 

:(021 

:(120

).......................................

)......................................

)......................................

)......................................

).....................-.................

(

.

Measured.

0

76 

51 

69 

44 

68 

68 

68 

37-40 

39

Calculated.

0

75 

51 

67 

45 

66 

69 

67 

37 

38

/

30 

16 

51 

53 

16 

36 

38 

42 

17

A comparison of the forms observed on the two minerals is as follows:

Amblygonite. Fremontite. 

c{001} c{001 

6(010 

a aflOO

m

m

z

e

I

h

100

110

110

120

021

101

101

i 120 ! 

e{021}
THE CHEMICAL COMPOSITION OF NEPHELITE.

The chemical composition of nephelite has long been a much 

discussed problem among mineralogists. One general theory endeavors to harmonize the analytical figures with the calculated 

values by the assumption of a number of complex formulas. The 

very complexity of these formulas is sufficient to cast doubt on 

their correctness. Another view is that the groups Si04 and Si3 08 

can replace each other, in an isomorphous sense, so that by the 

presence of sufficient Si308 , replacing Si04 , the analytical figures 

obtained can readily be accounted for. Foote and Bradley* have 

proposed still another explanation, namely, that as a substance on 

crystallizing may form a "solid homogeneous solution with foreign 

matter," the mineral nephelite consists of a pure compound, probably NaAlSi04 , with a varying amount of dissolved silica. Such an 

interpretation certainly is suggestive, but before it can be accepted 

for nephelite it must be proved that the compound NaAlSi04 can 

dissolve silica. Furthermore, the fact that chemically the "dissolved 

silica" acts in an entirely different way from any known modification 

of silica must be satisfactorily accounted for.

The composition of nephelite can be readily explained without 

assuming complex formulas and without calling on the hypothesis 

of " dissolved silica." The mineral albite has the formula AlNaSi3 08 , 

and the corresponding isomorphous mineral anorthite has the 

formula AlCajSi04 . The soda anorthite, AlNaSi04 , has been prepared artificially, and Washington and Wright 2 have assumed its 

presence to the extent of 5.58 per cent in a feldspar (anemousite) 

consisting essentially of albite and anorthite in isomorphous mixture.

In the feldspars just named there are two types of compounds 

AlR/SiO4 and AlR'Si308 and their isomorphous relation, as earlier 

developed by Clarke,3 led to a simple interpretation of the composition of nephelite. These compounds occur in several modifications, 

which are isomorphous. This relation can be best shown schematically.

1 Foote, H. W., and Bradley, W. M., On solid solution in minerals, with special reference to nephelite: 

Am. Jour. Sci., 4th ser., vol. 31, p. 25,1911.

2 Washington, H. S., and Wright, F. E., A feldspar from Linosaand the existence of soda anorthite (carnegieite): Am. Jour.-Sci., 4th ser., vol. 29, p. 52,1910.

3 Clarke, F. W., The constitution of the silicates: U. S. Geol. Survey Bull. 125,1895.

97888° Bull. 610 16 10 145
146 MINERALOGIC NOTES SERIES 3.

Modifications of compounds AlR'SiO^ and AlR'Si3Os.

Compound.

AlNaSi04.........

AlKSi04 .........

AlGajSKV.......

AlNaSi308. ......

AlKSi3 08 .........

AlCajSijOs........

Hexagonal.

of _ nephelite; artificially prepared.

Kaliophilite. . .........

Present in small

amounts in the 

calcic varieties of 

nephelite.

mixture in nephelite.

Monoclinic.

;

CelsJan is the corresponding barium 

salt.

Barbierite..........

Orthoclase...........

Triclinic.

naturally only in 

mixture (carnegieite).

Anorthite.

Albite.

Microcline.

The mineral nephelite is then an isomorphous mixture of the 

compounds crystallizing in the hexagonal modification, which are 

ALNaSi04 (essential component), AlKSi04 (kaliophilite), and 

AlNaSi308 (best known in its triclinic form as albite).

To show that the explanation offered is in agreement with the 

analyses of nephelite it will suffice to quote two analyses, one by 

Foote and Bradley and one by Morozewicz (No. V in paper of Foote 

and Bradley). These have been chosen for the reason that they 

are among the best analyses and show a minimum amount of other 

bases, such as CaO and Fe2 03 . . The nephelite analyzed by Foote and Bradley consists, as calculated from their ratios, of the following compounds in the proportions 

indicated: 60 parts or 19.0 per cent of KAlSiO4 , 245 parts or 70.4 

per cent of NaAlSi04 , and. 21 parts or 10.6 per cent of NaAlSi308 . 

The comparison of the analysis with the figures calculated from 

this composition is very close, as is shown below.

Comparison of analysis of nephelite by Foote and Bradley with calculated values.

SiO

Al O

FeA............. .....................................

K20. ....................................................

Na-jO.. . ................................................

2

Analysis.

44.46

33.11

5.61

16. 32

.38

100. 84

Calculated.

44.45

} 33. 37

5.66

16.52

100. 00
THE CHEMICAL COMPOSITION OF NEPHELITE. 147

The analysis made by Morozewicz yields the following composition: 

62 parts or 19.7 per cent of KAlSi04 , 259 parts or 74.7 per cent of 

NaAlSi04 , and 11 parts or 5.6 per cent of NaAlSi308 . As in the other 

case, the comparison of the analysis with the values calculated from 

this composition shows a very close agreement.

Comparison of analysis ofnephelite by Morozeiwicz with calculated values.

Si02 . ..................................................

TiO

AI n

TV O

K20... .................................................

NasO. ..................................................

Analysis.

42. 71

.04

33.83

,40

5.86

.32

16. 46

.18

.06

99.86

Calculated.

43. 04

} 34. 20

5.89

} 16. 87

100. 00

The figures prove that the composition of the mineral nephelitc is 

best explained by assuming an isomorphous relation of Si04 and 

Si308 .

The remarkable fact that the compound KAlSi04 is always present 

in nephelite to the extent of about 20 por cent has not yet received 

any adequate explanation.
LARGE CRYSTALS OF BLOEDITE.

Some bloedite recently found by Mr. Hoyt S. Gale, of the Geological Survey, is remarkable for the large size of the crystals. An 

extensive deposit of soda forms a crust on Soda Lake, in Carrizo 

Plain, San Luis Obispo County, Cal. This deposit has been described

by Arnold and Johnson,1 who give a detailed 

analysis of the saline crust that shows it to 

be nearly pure sodium sulphate with 1.66 per 

cent of MgO. In the black mud below this 

crust were found the isolated crystals of 

bloedite, a hydrous magnesium sodium sulphate with 12 per cent of MgO.

The larger crystals have a dark, almost 

black appearance when the superficial covering of gray mud is removed, though the 

smaller crystals are nearly colorless, the black 

appearance being due to impurities. In 

places the larger crystals are likewise nearly 

colorless and translucent and in small pieces 

transparent. The clear and glassy fragments 

which do not show any cleavage greatly 

resemble quartz fragments.

The largest crystal at present on hand 

measures 16.5 by 10.5 by 3.5 centimeters and 

weighs 652 grams. The crystals are flattened somewhat parallel to 

the base and show the following forms:

Large: c{00l}, d{011}, m{110}.

Medium: n{210}, p{lll}.

Small: ?{201}, s{211}, it{Ill}, x{l2l).

The measurements were made with a contact goniometer and gave 

the following results:

1 Arnold, Ralph, and Johnson, H. R., Sodium sulphate in Soda Lake, Carrizo Plain, San Luis Obispo 

County, Cal.: U. S. Geol. Survey Bull. 380, pp. 369-371,1909.

148

FIGURE 96. Crystal of bloedite 

from Carrizo Plain, Cal. Forms: 

c{001>, <f{011>, ?«U10>, ?i{210}, 

?{201},p{lll>. The crystal is 

drawn with the base c{001> 

vertical.
LARGE CRYSTALS OP BLOEDITE.

Measurements of bloedite crystals.

149

Form.

m(110) : #(111). .......................................

c(011) : g(201). .........................................

c(001) : p(lll) ..........................................

n(210) : w'"(210). . .....................................

m(110) : m'"(110) ......................................

d(011) : d(0ll).. ........................................

c(001) : s(2ll).. ........................................

c(001) : M(lll).. . .......................................

Measured.

0

47

50

36

68

105

67

55

43

Calculated.

o /

46 42

50 06

36 55

67 06

105 58

66 46

55 16J

42 05

The form z(121) was determined by zonal relations.

A peculiarity noted on almost all the crystals examined is that the 

pair of faces of the pyramid #{111} are very unequally developed, as 

shown in figure 96. In order to show better the relative development 

of the faces, the drawing was made with the a and c axes interchanged, 

so that the basal pinacoid c{001} is shown in vertical position.

The analysis' made on selected pure material gave the following

values:

Analysis ofbloeditefrom California.

H20......................................................... 21. 37

MgO. - Jffc-................................................ 11. 93

Na20.. .^F-................................................ 18.26

S08 .......................................................... 48.11

99.67

These values are close to those that are required by the formula 

Na1Mg(S04),.4H10.
ALUNITE FROM MARYSVALE, UTAH.

The occurrence of alunite near Marysvale, Utah, has been fully 

described by Butler and Gale. 1 On some of the more coarsely crystalline alunite small cavities were noted in which were found crystals 

showing the base c{0001} and the rhombohedron r{10Tl}, both developed as large faces whose edges were in part truncated by narrow 

faces of s{0221}.

An analysis of a selected clear-pink, translucent, coarsely granular 

crystalline specimen gave the results shown below in column 1, 

whereas an analysis of the very compact fine-granular alunite rock 

(column 2), which has a decided porcelain-like appearance, showed 

that it was much impurer than the better-crystallized granular

material.

Analyses of alunite from Marysvale, Utah.

A1203 --. ------------------------------------

FeA- ........--...-.-.-...-.-...-.......-

K20........ ...... .........................

NaA - -- --- ............................

S03 ......... ...............................

P208 .......... ..............................

H220......................................

H20+............. ........................

Si02 ................ ................. .......

1. Coarse 

granular 

variety.

37.18

Trace.

10.46

.33

38.34

.58

.09

12.90

.22

100. 10

2. Compact, 

fine-grained 

rocl^^

 ^P34.40

Trace.

9.71

.56

36.54

.50

.11

13.08

5.28

100. 18

Calculated 

composition.

36.97

11.36

38.63

13. 04

100. 00

The first analysis, made on pure material, agrees well with the 

composition of the mineral as calculated from the formula 

3A1203 .K20.4S03 .6H20.

Laboratory experiments showed that the powdered mineral, when 

ignited, gives off all its water and three-quarters of its sulphuric acid. 

The remaining quarter is combined with the potassium as potassium 

sulphate and may be dissolved out with water. The residue consists 

of aluminum oxide plus the impurities, such as silica, which were 

present in the sample. The maximum amount of alumina found in 

the water leach of several experiments was 0.25 per cent. It is probi Butler, B. S., and Gale, H. S., Alunite, a newly discovered deposit near Marysville, Utah: U. S. Geol. 

Survey Bull. 511,1912.

150
ALUNITE FBOM MARYSVALE, UTAH. 151

able that a small amount of potassium sulphate was volatilized by 

the heat. The following results were obtained by igniting the powdered alunite and subsequent leaching with water:

Percent. 

Volatilized (H20, 13; S03 , 29; K2S04 (?), 2)........................ 44

Insoluble residue (A1203 )......................................... 37

Water-soluble residue (K2S04 )...................................... 18

99

It follows that about 92 per cent of the total potassium sulphate in 

the mineral was obtained in a water-soluble form by this treatment. 

A higher percentage can doubtless be obtained by regulating the 

heat, as it is believed that in the experiments some of the potassium 

sulphate was volatilized.

According to these experiments about 32 per cent of the ignited 

alunite consists of available potassium sulphate which can be extracted and recovered by simple water leaching and evaporation. 

The remaining 68 per cent consists of alumina (A12 03 ) plus the 

impurities of the mineral sample.
THE COMPOSITION AND RELATIONS OF CUSTERITE. 

OCCURRENCE AND ASSOCIATION.

Custerite lias been described by Umpleby 1 as occurring in a contact zone of granite porphyry with Mississippian limestone, 3£ 

miles southwest of Mackay, Ouster County, Idaho. The zone is 

worked for copper, and the ore minerals, principally chalcopyrite 

and its oxidation products, are intimately associated with garnet, 

diopside, magnetite, fluorite, and other contact minerals in bodies 

that are nearly coincident in extent with original limestone inclusions. In some of these inclusions none of the original limestone 

remains, though locally its bedded structure is preserved in the 

garnet-diopside rock, but in others a core of unaltered blue limestone 

grades outward through pale-blue, partly recrystallized limestone 

into white marble and on into a zone made up principally of garnet, diopside, and magnetite. The custerite was collected between 

the garnet-diopside and marble zones which fringe one of these 

inclusions.

PHYSICAL AND OPTICAL PROPERTIES.

The results of microscopic study indicate that custerite is monoclinic. Two cleavages were noted, one parallel to the base and the 

other parallel to a prism. The hardness is 5 to 6, the density 2.91. 

The crystals show lamellar twinning like albite. As determined by 

Umpleby and Larsen, the refractive indices are, for sodium light, 

« = 1.586±0.005, 0 = 1.589 ±0.005, 7 = 1-598±0.005.

Fuller description of the optical relation is given in the paper 

cited, in which the microscopic characterization of custerite is summarized as follows:

Custerite is characterized microscopically by its moderate index of refraction, 

low birefringence, polysynthetic twinning, maximum extinction angle of twin 

lamellae of 6°-7°, positive optical character, distinct dispersion of the optic axes 

with p<u, and three cleavages which intersect at high angles. There is no known 

mineral species from which it may not be readily distinguished optically. Its 

birefringence and twinning suggest albite, but its refringence is much higher. Its 

relief, lack of color, and cleavage in thin section might at first glance lead to its being 

mistaken for a colorless pyroxene, but its refringence and birefringence are lower, 

and its extinction angle is less than in all pyroxenes except segirite. It resembles 

hillebrandite in index of refraction and birefringence, but that mineral is orthorhombic, optically negative, and. occurs in fibrous forms. In relief and birefringence 

also it resembles eudialyte, which, however, is uniaxial and occurs in association 

with soda minerals.

i Umpleby, J. B., Schaller, W. T., and Larsen, E. S., Custerite, a new contact-metamorphic mineral: 

Am. Jour. Sci., 4th ser., vol. 36, p. 385,1913.

152
THE COMPOSITION AND RELATIONS OF CUSTERITE. 153

It is believed that custerite is a mineral of rare occurrence, for its optical properties 

are so distinctive that it would scarcely have been overlooked. In the hand specimen, however, it is so unpromising in appearance that thin sections of it may never 

have been cut. The mineral should be looked for in fluorine-bearing contact zones, 

apparently in the border phases of the metamorphisni.

CHEMICAL PROPERTIES.

PYBOGNOSTICS.

When heated gently in a closed tube, custerite turns a transitory 

yellow and phosphoresces with a golden-yellow light. As seen in 

a darkened room, the color of the glow is like that of a deep-colored 

golden beryl. On increasing the heat the phosphorescence is 

destroyed and water is given off. The mineral does not decrepitate. 

A white ring, due to the fluorine, is obtained by heating the mineral 

at a temperature sufficient to melt the glass tube. In the blowpipe

flame custerite fuses with difficulty to an opaque white enamel.

The mineral is very readily decomposed by acids, gelatinous 

silica separating so quickly when the powdered mineral is treated 

with HC1 as to form a stiff coherent mass. The separated gelatinous 

silica floats around in an excess of acid, the solution itself not gelatinizing on further boiling. Custerite therefore does not "gelatinize"

like natrolite.

QUANTITATIVE COMPOSITION.

The chemical analysis showed that water, fluorine, silica, and lime 

were the essential constituents, the small amounts of iron and magnesium present being probably due to magnetite and diopside, 

respectively. Fairly pure, fresh material, suitable for analysis, 

was available only in portions of 0.25 to 0.75 gram...

The analytical results obtained are shown in the following table:

Analyses and ratios of custerite.

Si02 .... .....................

CaO.............. ...........

H20........................

F

MgO................. .........

:i.

32.13

55.11

5.53

8.12

1.19

.85

2

32.20

5.06

1 1Q

1.14

Average.

32.17

55. 11

5.30

8.12

1 1Q

1.00

102. 89 

0=Fa -3.42

99.47

Ratios.

0.536

.984

.294

.427

.030

These results were verified by a partial analysis (water not being 

determined) of a different, somewhat less pure portion of the same
154 MINEBALOGIC NOTES SERIES 3.

specimen of custerite. The results obtained are: Si02 , 33.46; 

CaO, 53.93; F, 7.29; MgO, 1.41; magnetite, 2.13. Alkalies were not 

determined on any of the samples because of paucity of material. 

Some of the whiter, chalky-looking material gave less water than the 

fresh material, several different samples yielding from 2 to 3 per cent 

H20 instead of the 5 or 6 per cent given in the above analyses. 

Whether this represents an alteration of the custerite or a much 

impurer sample could not be determined on the scanty material 

available.

INTERPRETATION OF ANALYSIS.

The ratios derived from the above analytical figures can be interpreted by considering either that the small amount of magnesia 

belongs to the custerite or that it represents admixed diopside. 

These alternatives are shown in the table below."

Interpretation of ratios of custerite analysis.

Si02 ...........................

CaO.............................

MgO...........................

HoO................... ........

F."... .........................

Ratios.

0.536

.984

.030

.294

.427

Combining 

CaO+MgO.

2.00

} 3.78

1.10

1.59

Deducting 

diopside.

2.00

f 4.01

1.24

1.79

Combining 

water and 

fluorine.

2.00

4.01

\ 2. 14 H20

/ or 4. 27 F

. The formula derived for custerite is Ca2SiHF04 , with some of the 

fluorine replaced by water (hydroxyl). The composition may also 

be expressed as a mixture of the two compounds 2Si02 .4Ca0.2H20 

and 2Si02 .4Ca0.4F, with the first one slightly in excess. The relation of the fluorine to water (hydroxyl) can be much better shown in 

the .empirical formula, according to which the ratios reduce to 

Ca4Si2O6 (OH,F) 4 with the ratio of hydroxyl (OH) to fluorine (F) as 

2.48 : 1.79, or nearly 4 : 3.

No water was given off when custerite was heated to 110°, indicating that the water is an inherent part of the mineral. The temperature at which the water does go off was not determined, but the 

observation was repeatedly made that the phosphorescence phenomenon displayed itself and was destroyed by heat before the water 

was given off. Some powdered custerite, placed in a watch glass 

with several cubic centimeters of water, immediately gives a deep-red 

color with a few drops of phenolphthalein. This reaction was 

described by Clarke, 1 who has suggested that it is indicative of the 

presence of the univalent group CaOH. As the ratio of OH to F is

i Clarke, F. W., The alkaline reaction of some natural silicates: U. S. Geol. Survey Bull. 167, p. 156,1900.
THE COMPOSITION AND RELATIONS OF CUSTEBITE. 155

approximately 1:1, the formula of custerite may be structurally 

interpreted as a metasilicate, as follows:

/CaOH 

SiO/

XJaF

The ratio of hydroxyl (OH) to fluorine (F) being not exactly 1 : 1 

but more nearly 4:3, custerite may be more accurately considered as 

an isomorphous mixture of the following compounds, in the ratio 

indicated.

f /CaOH"! r /CaF~l 

4 SiO/ +3 SiO/ I 

\CaOH Vie

RELATION TO OTHER MINERALS.

There are only three minerals known to which custerite is related 

in composition. These are zeophyllite, cuspidine, and mUebrandite. 

The relation in composition can be best shown by directly comparing 

their analyses:

Comparison of composition of custerite with that of related minerals.

Si02 .... ..........

CaO. .......:.....

HaO... ............

F................

Rest...............

Deduct 0=F2 ....

Custerite.

32.17 

55.11 

5.30 

8.12 

2.19

102. 89 

-3.42

99.47

Zeophyllite.

38.84 

44.32 

8.98 

8.23 

2.62

102. 99 

-3.47

99.52

Cuspidine".

Franklin 

Furnace.

32.36 

61. 37

9.05 

1.46

104. 24 

-3.81

100. 43

Vesuvius.

32.80 

61.12

9.88 

.42

104. 22 

-3.98

100. 24

Hillebrandite.

32.59 

57.76 

9.36

.53

100. 24

Zeophyllite is the only one of the three minerals which contains 

both water and fluorine. The proportions of silica and lime are 

different from those in custerite, though structurally its formula 

may be written in a somewhat similar way. The mineral is described 

as rhombohedral, the crystals being composed of a uniaxial center 

surrounded by a biaxial border. On being heated the mineral 

becomes uniformly and permanently uniaxial. In crystal form 

and physical and optical properties there is no relation between 

zeophyllite and the other minerals chemically related to custerite. 

In its paragenesis zeophyllite is also totally different from custerite,
156 MINERALOGIO NOTES SERIES S.

being a zeolite-like mineral found in basalt with natrolite, calcite, 

apophyllite, analcite, etc. A specimen of zeophyllite obtained 

through the kindness of Dr. Koechlin, of the Vienna Hof-Museum, 

was tested for its alkaline reaction and found to .give only a very 

faint pink color with phenolphthalein.

The dual optical character of zeophyllite suggests strongly that 

it is polymorphous. Possibly the uniaxial compound is the zeolitelike mineral, bearing no relation to custerite, cuspidine, or hillebrandite. The biaxial compound, not found as such in nature, may 

possibly represent a compound similar in properties to custerite, 

cuspidine, and hillebrandite. Its formula, Ca4Si3H4F2On, can be 

written as that of custerite plus one part of metasilicic acid, thus: 

Ca4Si2H2F208 (custerite) 4- H2Si03 , but what significance, if any, is 

to be attached to this fact is not known. The formula of zeophyllite 

can be interpreted structurally in a way analogous to that of custerite:

CaF-Si03s

>Ca

Si03< + 2H2 0

>Ca 

CaF-SiO/

which would explain the fact that zeophyllite does not give a strong 

alkaline reaction with phenolphthalein but which seems inconsistent 

with the fact that less than 1 per cent of the water is given off at 

110°. Other structural interpretations are of course possible.

Cuspidine, found originally at Vesuvius, has recently been noted 

at Franklin Furnace, N. J., by Palache. At Vesuvius it was found 

as well-developed crystals in druses associated with augite, hornblende, biotite, garnet, sarcolite, hauyne, and calcite (derived from 

altered cuspidine). Granular aggregates resembling a fine-grained 

diabase, composed of cuspidine with augite and biotite, were also 

noted. Attention may also be called to the " cuspidine-like mineral" 1 found with green magnesia mica and white sodalite and 

occurring in rhombic prisms, apparently different from cuspidine. 

The composition of this material is not known, though Zambonini 2 

considers it identical with humite.

The density of the Franklin Furnace cuspidine is given as 2.965- 

2.989, and that of the Vesuvius cuspidine, as determined by Zambonini, as 2.962; the average being 2.97. The formula derived by 

Zambonini, Ca2 (CaF) 2Si207 , is in perfect accord with his own analysis 

and with Warren's analysis of the Franklin Furnace material. 

The presence of only 0.57 per cent of water (not determined according

1 Rath, G. von, Zeitschr. Kryst. Min., vol. 8, p. 45, 1884.

'Zambonini, F., Appendice alia Mineralogia Vesuviana: Accad. Sci. Napoli Atti, vol. 12, p. 44, 1912.
THE COMPOSITION AND RELATIONS OF CUSTEBITE. 157

to Warren's analysis) would suffice to bring the ratio of [F+ (OH)]: 

Si02 to 1.00 : 1.00 instead of 1.00 : 0.88, as calculated from his analysis. Structurally the formula of cuspidine can be interpreted as

Ca\x /CaF

>Si2O7< 

Ca/ \CaF

which dpes not show any direct relation to that of custerite.

Hillebrandite is genetically similar to custerite, being one of the 

products of contact metamorphism of limestone. A sample of hillebrandite kindly furnished for study by Dr. F. E. Wright yielded 

0.77 per cent of water at 110° and 9.64 per cent on ignition (calculated 9.45 per cent). The strong alkaline reaction with phenolphthalein as described by Wright was confirmed and suggests the 

presence of the CaOH group. From these results the composition 

of hillebrandite can be readily interpreted as a metasilicate with the 

folio whig structural formula:

/CaOH 

SiO/

\CaOH

This formula is identical in type with that of custerite and suggests 

at once that custerite is an isomorphous mixture of hillebrandite and 

a theoretic fluo-hillebrandite, in which all the hydroxyl is replaced by 

fluorine. This conception is simple and rational but is opposed by 

other considerations.

As cuspidine has been found at two widely separated localities, the 

inference may be justified that in the presence of much fluorine and 

little or no water a mineral of the cuspidine formula, 3Ca0.2Si02CaF2 , 

would always form instead of a fluo-hillebrandite with the formula 2Ca0.2Si02 .2CaF2 . In other words, fluo-hillebrandite seems 

to be unstable under the metamorphic conditions prevailing, though 

this inference rests solely on the fact that at the only two localities 

where a calcium fluo-silicate occurs a compound of different type 

(cuspidine) was formed. It seems likely, therefore, that, in view of 

the isomorphous replacement of fluorine and hydroxyl, the isomorphous series of which hillebrandite is the hydroxyl end consists of 

the two end members (CaOH) 2Si03 and (CaF) (CaOH)Si03 and not of 

the theoretic end members (CaOH) 2Si03 and (CaF)2Si03 .

The symmetry of hillebrandite and custerite is apparently different, 

though some of the properties of hillebrandite could not be as definitely determined as those of custerite. Hillebrandite is fibrous and 

orthorhombic, whereas custerite is granular and monochnic, with a 

close approach to orthorhombic symmetry, as is indicated by the 

nearly rectangular cleavages and low extinction angle. The custerite 

and hillebrandite compounds may both be dimorphous, only the two
158 MINEKALOGIC NOTES SERIES 3.

nonisomorphous end members of the four possible compounds being 

known.

The status of the relations of these minerals, so far as can be judged 

by the available evidence, seems to be somewhat as is given below.

Cuspidine: Ca4Si2F207 .

Theoretic fluo-hillebrandite: Ca4Si2F406 . Unstable, nonexistent.

Custerite: Ca4Si2F2(OH) 206 . Dimorphous; orthorhombic form isomorphous with 

hillebrandite (not known) and monoclinic.

Hillebrandite: Ca4Si2(OH)406 . Dimorphous; monoclinic form isomorphous with 

custerite (not known) and orthorhombic.

Zeophyllite: Ca4Si3H4F2On . Dimorphous; the known form not related to the 

above-named minerals.

The close chemical relation of these four minerals can be shown 

by writing their formulas so as to keep intact the common compound, 

Ca4Si2F207 .

Cuspidine..... Ca4Si2F207 .

Custerite..... .Ca4Si2F207 .H20'(or cuspidine plus water).

Hillebrandite. Ca4Si2(OH)207 .H20.

Zeophyllite....Ca4Si2F207 .H2O.Si02 (or cuspidine plus water and silica).

These relations suggest the existence of a hydroxy-cuspidine, 

Ca4Si2 (OH) 207 , and the derivability of custerite and zeophyllite (or a 

polymorphic form of the zeophyllite compound) from cuspidine by 

the actual addition of water and silica.

The essential properties of the four minerals considered in the 

preceding paragraphs are briefly tabulated below for future reference.

Properties of custerite and related minerals.

Composition. . . 

Symmetry .... 

Cleavage......

"PTd T<"1 Tl PfW

Density ...... 

Fusibility ....

Axial plane...

TnrlpY 'v

Index a ...... 

Birefringence . 

2E ...........

Sign...........

Extinction . . .

Custerite.

Ca4Si2H2F20 8 .. 

Monoclinic. .... 

Two, basal and

prismatic. 

5-6............

2.96........... 

Difficult. ......

Normal to basal cleavage. 

1.598..........

1.589..........

1.586.......... 

0.011.......... 

105°...........

Strong, p>u . . .

Positive ....... 64°

 polysynthetic.

Zeophyllite.

Ca4Si3H4F2Ou .. 

Rhombohedral . 

One, basal. ....

3..............

2.75........... 

Very easy......

Normal to 

cleavage. 

1.565..........

1.560.......... 

0.005.......... 

0-27*°.........

p<u ...........

Negative ......

Cuspidine.

Ca4Si2F207 

Monoclinic. ....

5-6............

2.97........... 

Difficult.......

{010}, normal 

to cleavage. 

1.602o.........

1.595®.. .......

1.5900......... 

0.012o......... 

110°...........

Crossed, very

distinct, p>u. 

Positive 0 . .....

5°. ............

.(100).

Hillebrandite.

Ca4Si2H4 010 . Orthorhombic. 

Prismatic (?).

5-6.

2.69. 

Difficult.

Par a 1.1 el to 

cleavage. 

1. 612.

1. 605. 

0. 007. 60-80°.

p<u.

Negative. 0°.

Z.

Data kindly furnished by Esper S. Larsen, measured on the'Vesuvius mineral.
THE COMPOSITION OF HODGKINSONITE.

OCCURRENCE AND ASSOCIATIONS.

The occurrence of hodgkinsonite at Franklin Furnace, N. J., is 

described by Palache 1 as follows :

Hodgkinsonite is a hydrous silicate of zinc and manganese crystallizing in the monoclinic system. It occurs in seams in massive granular ore of the typical willemitefranklinite mixture; the seams are generally very thin with but a film of the mineral 

which is always associated with white barite and not uncommonly with plates of native 

copper. Locally the film thickens to a narrow vein, and then the new mineral may 

show individuals up to 2 centimeters across, sharply angular in form and apparently 

with crystal faces but in reality determined in their outline wholly by the older platy 

barite which incloses them. The clear pink color and brilliant cleavage of hodgkinsonite together with the snow-white barite make such specimens both striking and 

attractive in appearance.

The crystals so far obtained have occupied cavities in the thicker 

veins and show evidence of solution, the faces being generally faceted 

and dull. The largest crystal seen measures about 1 centimeter in 

length. In the cavities hodgkinsonite is accompanied by black rhombohedral crystals of pyrochroite and scalenohedral crystals of calcite, 

both later in age and partly ihcrusting it. The hodgkinsonite crystals are implanted directly on willemite or franklinite, and in one 

specimen on manganese garnet. The association and mode of occurrence both indicate a pneumatolytic origin for the new mineral.

CRYSTALLOGRAPHY.

Hodgkinsonite was determined by Palache to be monoclinic with 

normal symmetry. The highly perfect cleavage, normal to the symmetry plane, has been taken as the basal pinacoid. In other directions the fracture is conchoidal. The habit of the crystals is acute 

pyramidal. The axial ratio 2 is a : & : c= 1.538 : 1 : 1.1075, 0 = 84° 35'. 

The forms determined are c{001}, m{.110}Z{210}, s{011}, o{021},

r{221},

, CHEMICAL PROPERTIES.

PYROGNOSTICS.

The mineral decrepitates when held in the blowpipe flame, wherein 

it fuses readily and quietly to a brown enamel. When heated in a 

closed tube it decrepitates strongly, splitting up into numerous thin

1 Palache, Charles, and Schaller, W. T., Hodgkinsonite, a new mineral from Franklin Furnace, N. J.: 

Washington Acad. Sci. Jour., vol. 3, p. 474, 1913.

2 Palache, Charles, Supplementary note on the crystal form of hodgkinsonite: Washington Acad. Sci. 

Jour., vol. 4, p. 154, 1914.

159
160 MINEEALOGIC NOTES SERIES 3.

cleavage scales which, on further heating yield water and become 

brown in color. The mineral is readily soluble in acid, yielding gelatinous silica.

QUANTITATIVE COMPOSITION.

The chemical analyses of hodgkinsonite were made on carefully 

selected cleavage fragments of a clear pink color and gave the following results. Quarter-gram samples were used, as the total amount of 

available material was only somewhat over a gram.

Analyses and ratios ofhodgJcinsonite.

Si02 .....................

MnO...................

ZnO.....................

CaO..... ................

MgO.....................

EvO...... ..............

1

19. 92 

20.39 

52.93 

.99 

.04

2

19.89 

20.97

(°) 

.88

3

19. 77

*>5. 77

Average.

19.86 

20.68 

52.93 

.93 

.04 

5.77

Ratios.

0.331 .291' 

.653 

.017 

.001 

.321

1. 02 

2.98 

.99

100. 21

a A duplicate determination of ZnO, of which a small amount was lost, gave 51.38 per cent.

6 Determined directly by fusing the mineral with sodium carbonate and collecting the water in a caluium 

chloride tube. A determination of the loss on ignition, corrected for oxidation of the manganese, gave 4.08 

per cent.

A doubtful trace of lead was encountered, but iron and chlorine 

were absent. No water was given off by the mineral at 110°.

The ratios yield the formula 3RO.Si02 .H20, in which R is chiefly 

zinc and manganese. If the manganese, calcium, and magnesium 

are arbitrarily taken together, then the ratio of MnO + CaO + MgO to 

ZnO is 309 to 653, or 1 : 2.11, or nearly 1 : 2. The formula may then 

be written Mn0.2ZnO.Si02 .H20, which may, as the water is all constitutional, be interpreted as Mn.(ZnOH) 2 .SiO4 .
CRYSTALS OF PISANITE FROM DUCKTOWN, TENNESSEE.

Some specimens of pisanite from Ducktown, Term., were sent to 

the writer for crystallographic study by Prof. F. R. Van Horn, of 

Cleveland, Ohio, who. has recently 1 given a full description of the 

occurrence and composition of the mineral. Several crystals were 

detached from the specimens and measured with'the following result:

bFlQURE 97. FIGURE 98. FIGURE 99.

FIGUKE 97. Crystal 1, pisanite from Ducktown, Tenn. Forms: m{110}, c{001>, «{I01}.

FIGURE 98. Crystal 2, pisanite from Ducktown, Tenn. Forms: 6{010>, ?n{110>, c{001}, o{011}, w{103},

w{103}, minute, figure 98. 

£{101}, minute but larger than w, figures 

97, 93, 99.

FIGURE 99. Crystal 3, pisanite from Ducktown, Tenn. Forms: &{010>, m{llQ}, c{001}, o{011>, t{101>, 

o{T21>.

Forms determined:

6{010}, very narrow, figures 98 and 99. 

c{001}, large, figures 97, 98, 99. Cleavage. 

m{110}, large, dominant form, figures 97,

98, 99. 

o{011}, small, figures 98 and 99.

<r{l21}, minute, figure 99. 

Average measured and calculated angles of pisanite from Duclctown, Tenn.

&{010}................................

c{001}........... ........................

m{110}..................... ...........

o{011}......... '.......................

w{103}. ...............................

*{101}....... ..........................

tr{12T:}.... ............................

Measured.

 0

o

0

89 

41 

9 

88 

89 

18

/

17 

23 

34 

35 

27 

21 

33

p

o

90 

15 

90 

57 

36 

47 

72

/

00 

54 

00 

19 

29 

06 

06

Calculated.

<t>

o

0 

90 

41 

10 

90 

90 

19

/

00 

00 

36 

07 

00 

00 

32

p

o

90 

15 

90 

57 

35 

47 

72

'/

00 

11 

00 

04 

48 

09 

46

i Van Horn, F. R., Notes on a new occurrence of pisanite and arsenopyiite, and some large staurolite crystals from the Ducktown district, Tenn.: Am. Jour. Sci., 4th ser., vol. 37, p. 40, 1914.

97888° Bull. 610 16 11 161
THE REFRACTIVE INDICES OF STRENGITE.

The only published figures for the refractive indices of stfengite, 

Fe203 .P205.4H20, which could be found are those given by Schroeder 

van der Kolk. l His figures are 1.81 +0.03, which can be stated, as 

Lacroix 2 did, in the form a = 1.81, 7 = 1.84. Determination of these 

values for a manganese strengite from California gave a = 1.70-1.71, 

7 = 1.72-1.73. Lacroix 3 determined the mean index of similar 

material (which he called angelardite) as approximately 1.70. It 

therefore seemed necessary to redetermine the refractive indices 

of typical strengite in order to bring the conflicting determinations 

in accord.

Professor Ledroit, of Mainz, very kindly presented several specimens of the mineral from the Eleonore mine, on the Dunsberg, near 

Giessen. The strengite forms small spherulites associated with beraunite (eleonorite), cacoxenite, etc. Crushed fragments of these 

spherulites .were used for determining the minimum and maximum 

refractive indices. The oil-immersion method was used, and the 

results obtained are as follows:

a (normal elongation of fibers)=1.71.

7 (parallel elongation of fibers)=1.735. *

7-«=0.025.

The figures given by Schroeder van der Kolk are therefore wrong, 

and it seems most probable that his figure 1.81 was miscopied for 

1.71. ' ° . 1 Tabellen zur mikroskopischen Bestimmung der Mineralien, p. 54,1906. 

 2 Lacroix, A., Min4ralogiede la France, vol. 4, p. 475,1910. 

s Idem, p. 523.

162
THE CALCULATION OF A MINERAL FORMULA.

In the calculation of the ratios of a mineral analysis, it is customary to select arbitrarily one of the constituents as unity or some 

multiple of unity and on this basis to calculate the ratios of the 

other constituents. As an example the analysis of pearceite from 

the Veta Rica mine, Sierra Mojada, Coahuila, Mexico, as recently 

given* by Van Horn and Cook, is reproduced below.

Analysis and ratios of pearceite.

s................. ..............................

As.............................................

" Ag. Arr 

............................................

Gu... ..........................................

Sb..............................................

Analysis.

17.46

7.56

59.22

15.65

.00

99.89

Ratios.

0. 5444 10. 80

. 1008 2. 00

«. 2744 7.886

6.1231

11

?,

8

a Considered asAg2. & Considered as Cu2.

The ratios' are sufficiently close to 11:2:8 to show that these 

are the correct values. The true ratios are very much closer to 

11:2:8 than those given by Van Horn and Cook, as will be shown 

below.

The first column from the ratios given above is reproduced below 

(1) with the figures for silver and copper combined, and all the 

figures multiplied by 100 for convenience. By taking the lowest 

number as unity it is readily seen that the approximate ratio is 

5£ : 1 : 4. On dividing the first value by 2 times 5£ (these numbers 

are doubled to avoid fractions) the second by 2 times 1 and the 

third by 2 times 4, the results under (2) are obtained. These numbers should be nearly the same. Their average is 4.986. Dividing 

now the ratios obtained from the analysis by this average we obtain 

the figures given under (3), which are much closer to 11, 2, and 8 

respectively than those given by Van Horn and Cook.

(1) . (2)

As. ................................... 10. 08-*-(2 XI) -5. 040

Ag2+Cu2 ............................... 39. 75-^(2X4) -4.969

Average=4. 986

(3)

10. 92

2.02

7.97

1 Van Horn, F. R., and Cook, C. W., A new occurrence of pearceite: Am. Jour. Sci., 4th ser., vol. 31, 

p. 518, 1911.

163
164 MINERALOGIC NOTES SERIES 3.

Ratios like those given above under (3), which vary considerably 

from the whole numbers they approximate, should not be compared 

as they stand. The figures should be reduced to multiples of approximate unity, which can then be directly compared, as the following 

table shows. In the last column only two decimals are expressed. 

If the third decimal is below 5, it is neglected. If it is 5 or above, 

the second decimal is increased 1.

S..........................................10. 92=11X0.993=11X0.99

As........................................ 2.02= 2X1.01 = 2X1-01

Ag2+Cu2 ................................. 7.97= 8X0. 996= 8X1.00

These figures show that the ratios deduced from the pearceite 

analysis are in fact very close to the whole numbers 11:2:8, a 

fact that is not brought out by the ratios 10.80 : 2.00 : 7.886 given 

by Van Horn and Cook, which were obtained by arbitrarily assigning 

a whole number to one of the values. The form of the last set of 

ratios given above expresses most accurately the relations calculated, 

from the analysis.

o