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ProfossionalPaper No~18 ) . f D, Petrography and Mineralogy, 24 

Sene3 J • t dPh . "8 ~ E, Ohem1s ry an ys!Cs, o ·' . \ 

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\, ... '" '\ ' . 

DEPARTMEN'I: OF THE INTEIUOR 

' UNITED STATES GEQLOGICAL SURVEY 

"'-. CHARLES J), WALCOT'!', J)mECTOR 

l 

\. 

\ 

CHEMICAL CO~IPOSITION OF IGNEOUS ROCICS -. 

\ . \ 

' ' 

EXPRESSED BY ~lEANS OF DIAGllA~~S., "r: 

" . ./ , .... ,. 

, WITH REFERENCE TO ROCK CLASSIFICATION ON A QU,h.iri;TATIVE 

-~ CHEMICO-MlNERALOGICAL B,~~U.~.\:, . . _ 

\ ~ llY -' / 

·( 

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1 

.JO'-\EPH P A:Xi~ON IDDINGS 

WASHINGTON 

GOVERNMENT PRINTING OFFICE 

1903 

C 0 NT EN T S. 

l'age. 

Letter of transmittal. ..................... ' .... _. _ .... _ .. _ ..... _. _ ..... _ •..•••. _ .•..... _.. 7 

Introduction .............................................. _ ........•. _ .... _.... . . . . . . . . . . 9 

Historical review .................... _ ... , ............................. _ .. _ .. · ..... _ .. _.... 10 

Purpose of the_diagrams ···-······-·.·-····-················---·-····-··-·················-· 16 

Construction of the diagrams ." ...... _ .................. _ .. _ .... _ .. _ .. _ .. _ ........ _ . . . . . . . . 17 

Rock analyses used 'in constructing diagrams ......... __ ........ _ ....... _ .. _ ....... _ . _ . . . . . ~1 

Discussion of the diagrams ................ _ ....... _ ...............•.. _ ........... _ . _ . . . . . . 63 

General diagrams ............................ _ ........... _ ..•. _. _ .. _ .... _ .. _ .. _... . . . . 63 

Variations in composition._ ... ,_ .. _ .. _ ............ _ .•... __ ... _._ .. _ ......... _ ... _. 63 

Transitions and extremes .... -. __ . _ ........ _. _ .... _ .. _ .. _ ..... _ .. _ .. _ .. _ . ____ .. _.... 64 

Relative abundance of different kinds of rocks .. _ .. _ ........... _ ... _ ..... _ .. _ .... _ 65 

Absence of clustering .....•. _ .... _. __ . : . .... _ ............. _ .•.. __ . _ .. _ .... _....... 66 

Similarity of rocks from different petrographical provinces ..... _................... 66 

Classification of igneous rocks. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68 

Classified diagrams .. _ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . • . . . . . . . . . . . . . . . . . 70 

Diagrams of Cla.~s I .... , . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . • . . . . . . . . . . . . . . . . . . 71 

Diagrams of Class II. ....... _ . _ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . • . 76 

Diagrams of Class III . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77 

Diagrams of Classes IV and V ................ _ .. _ ............. _ ..•..•.... _ ..... _ . 79 

Correlation of igneous rocks dassified by th<J <iUantitative and the qualitative systems...... 81 

3 

ILLUSTRATIONS. 

PLATE I. General' diagram showing <;omparativc values of chief chemical components of over 

950 igneous rocks, and composite diagram showing ciist.ribution of Classes I, II, 

Page. 

liJ, and IV-V. ___ .... _. ____ . __ . _ .. ___ .. ____ . ____ . _. _. _____ .. _ ... ____ ....... _. _ 92 

Il. Diagram showing limits of orders and rangs for theoretically pure soda-salie rocks 

and potash-salic rocks ..•. _ .. __ .. _._ . ______ .. _ .. __ . _ .. _________ . _______ .. _____ . _ 92 

~II. Diagrams showing chemical variations for rocks of Class I._ .... ___ . _ .. -. ____ ... _.. 92 

IV. Diagrams showing chemical variations for rocks of Class II. _____ . __ . _____ . _ .. _ _ _ _ 92 

V. Diagrams showing distribution of analyses with respeet to silir~a ancl alkali-silica 

ratio for rocks of Classes III and 1 V-Y ___ ..•. _____ , . _ .. _ . ___ . _ . _ . ____ . _. _ _ _ _ _ _ 92 

Vf. Diagrams showing chemical variation for rocks of Class III. ___ ._. ___ . __ . ______ .. _ 92 

VII. Diagrams showing chemieal variation for rocks of Classes IV-\"---------~--------- 92 

VIII. Diagram showing distribution of analyses with respect to silica and alkali-silica ratio 

for 2,000 igneous rocks .. ___ ._._. ___ ....... __ ....... __ ._._ .. __ .. _. _ .. ___ ....... _ 92 

5 

LETTER OF TRANSMITTAL 

Dm•ARTMENT OF THE 1NTERIOR, 

lJNITEn STATES GEoLoniCAL SuRVI<W, 

Wasl1.1·ngton, D. C., j~[a.y 126, 1908. 

Sm: I have the honor to transmit herewith a mannsot'ipt by .Toseph Paxc;::.: 

Iddings entitled " Chemical composition of igneous rocks expressed by means o_i' 

diagrams, with reference to rock classification on a quantitative chemico-mineralogical basis," and to recommend that it be published as a Pro-fessional Paper. 

The signifimtncc o-f it .large ·number of ehemical analyses of igneous rock~;, 

with their many variable elementB, each having a great range, is somewhat diilieult of comprehension to all geologists and petrographers who have not devoted 

much time to their study. Mr. Iddings presents a method oi' expressing the 

most significant -factors in each analysis by a Himple diagram, and by grouping 

these individual diagrams on a certain principle he has sueceed<~d in representing 

the great variation in composition and the chemical relationships o£ almost the 

entire rang;c of igneous· rocks in a way that is comprehensible at a glance. The 

facti'l thus brought out are discussed by him in their bearing on petrographi(' 

system. As a successful attempt at ·the elucidation oi' a complex problem thP 

paper i:-; o-f importance to all students of igneous rocks. 

Very respect-fully, 

Hon. CnARLl<'S D. WALCOTT, 

\V HIT MAN CROSS, 

Oeoloq1;8t ·in Cnm'ge, Sed/on of PetJ'ology. 

Directm' United States Oeolo.q?:cctl Survey. 

7 

CHEMICAL COMPOSITION OF IGNEOUS ROCKS EXPRESSED BY MEANS 

OF DIAGRAMS, WITH REFERENCE TO ROCK CLASSIFICATION 

ON A QUANTITATIVE CHEMICO-MINERALOGicAL BASIS. 

By ,JOSEPH pAXSON IDDINGS. 

INTRODUCTION. 

The value of graphical methods for expressing . relative quantities has been 

well established in all kinds of statistical exposition and discussion. Their use in 

conveying definite conceptions of relative quantities of chemical and mineral components of rocks is becoming more and more frequent, and the value of the 

results in some cases can not b~ overestimated. This is especially true when a 

series or group of rocks is being considered. The intricate variations in the 

amounts of numerous mineral components, or of chemical components, baffle most 

attempts to comprehend their interrelationships by simple contemplation or by 

study of the numbers in which they may be expressed. Many facts and relations 

arc overlooked which arc readily observed when diagrams are used to represent 

numerical figures. Moreover, visual memory is sufficiently developed in most 

persons to enable them to carry in mind simple geometrical forms, where it does 

.not permit them to recollect manifold assemblages of oft-repeated numbers. 

Mental impressions of simple diagrnms are, therefore, more definite and lasting 

and enable the student to store up a much greater amount of quantitative data 

than he could otherwise acquire. 

Evidence of the ~ppreciation of this fact by petrographers is found in the 

increasing nse of diagrams in petrographical litei·ature, and a brief sketch of 

the growth and elaboration of graphical methods for prcsm1ting quantitative 

petrographical data will serve as an appropriate introduction to the subject in 

hand. From this notice will be excluded those diagrams which f:lerve to connect 

the names of rocks in series after the manner of expressing genealogical relationships, in which diagrams the space relationships are not strictly quantitative. 

Such diagrams have been used by George H. 'Villiams, H. 0. Lang, and other 

petrographers. 

9 
10 CHEMICAL COMPOSITION 0~' IGNEOUS ROCKS. 

HISTOHICAT, REVIJ<.JW. 

Among the earliest diagram:-; employed to represent relative quantities of 

rock constituents are those used by Reyer in 1877." They are more or less 

·generalized expressions, in one instance of the varying proportions of the chief 

oxide components in rocks and meteorites; in another of the varying amounts of 

the commoner rock-making minerals capable of being developed in rock magmas 

with different silica content. The diagrams used are rectangles subdivided by cmved 

lines corresponding to the variations mentioned. Other diagrams express the 

variations of different kinds of rocks with respect to silica; the relation between 

specific gravity, silica percentage, and texture of mineralogically similar rockt->; 

and the relative abundance of rocks of different compositions and textures. 

Subsequently in his work, Theoretische Geologie/ ·he reproduces two of 

these diagrams and introduces others showing the proportions of chemical 

components in two series of minerals (:feldspars and pyroxene:-;) and othc1·s 

showing the proportions of the -chief minerals in three kind~ of rocks. One 

diagram consists of adjacent, long, narrow rectangles, each divided into 

rectangular parts proportionate to the percentages of the oxide constituents in 

certain kinds of rocks, :from granite to gabbro, and in five types of meteorites . 

• T udd, c in his book on Volcanoes, in 1881, makes use of a diagram to 

represent_ the varying amounts of chemical clements in rocks and meteorites. It 

is similar in form to one used by Reyer, already deseribed . 

. In 1890 the author<t constr1.1cted diagrams to exhibit the variation in chemical 

composition of rocks forming geologically related groups or series. In these 

diagrams the quantitative data represent specific a'nalyses of different rocks in 

each series. The oxide constituents of each rock are referred to rectangular 

coordinates, the silica being plotted as abscissas, and the other oxides-alumina, 

ferric and :fer;rous iron, magnesia, lime, soda, and potash-being plotted as 

ordinates. Straight lines connecting successive loci of any one oxicle, as those of 

alumina, indicate the variations in the amount of each constituent in the rock 

senes. This is the chief feature brought out by these diagrams, the range and 

character of the variations being shown. 

Similar diagrams have been used by Dakyns and Teall e to illustrate the 

chemical variations in the plutonic rocks o£ Garabal Hills and Meall Brace, 

n Re;rer, E., Beitrag znr :Fysik der Ernptionen, Vienna, 1877. 

b Reyer, E., Theoretische Geologie. Stuttgart, 1888. 

c Judd, J. W,, Volcanoes. New York, 1881, p. 322, fig, 88. 

dlddings, J. P., The mineral composition and geological occurrence of certain igneous rocks in the Yellowstone 

National Park: Bull. Philos. Soc. Washington, vol.ll, January, 1890, pp. 207 and 211; also in Twelfth Ann. Rept. U.S. Geol. 

Survey, 1892, pp, 629 and 6<19; llion. U.S. Gcol. Survey, vol. 32, pt. 2, pp, 119 and 136; Origin of igneous rocks, BulL Philo,, 

Soc. Washington, vol. 12, June, 1892, and in Jour. Geol., vol.1, 1893, p, 173. 

e Dakyns, J. R., and Teall, J, .L H., Quart. Jour. Geol. Soc. London, vol. 48, 1892, p. 116. 
HISTORICAL REVIEW. 11 

Scotland; hy Vv ashington to exprer:;s the chemical variation m the volcanic rocks 

of }!~gina and Methana, Gre~ian Archipelago,a and in the roeks of Magnet Cove, 

Arkansas;b and by Cross c to show the chemical composition of the rocks of the 

Rosita Volcano, Colorado. 

Harker <l has employed the same form of diagram, hut. has used atomic ratios 

of the chemical elements instead of the oxides, to show the variations in the rocks 

of Carrock Fell, England. Subsequently he modified it slightly by using percentages of the oxide components instead of their molecular proportions to discuss 

the possibility of distinguishing igneous rock series from mixed igneous rocks.e 

Loewinson-Lessing·f has also made use of this method of exhibiting the 

variability of chemical composition in eruptive rocks, illustrating the great 

divergence in the composition of rocks dassed under one name in the qualitative 

system and also the differences in composition of average magmas. 

In 1900 Pirsson r1 pointed out the possibility of relating the variations in the 

·chemical composition of rocks of one geological body to their position in that 

body by introducing their space relations into this form of diagram. He accomplished it by letting the abscissas represent distances in the rock hody between 

the various rocks analyzed. By this modification· of the diagram just described, 

he showed that: the variations in chemical <:omposition in such cases follow very 

regular laws, and with one or two elements determined in a variety of the rock 

the remainder may be found by means of the diagram. 

Similar diagrams have since been used by \'Vashington in discussing the 

differentiation in the rocks of Magnet Cove."' 

Pirsson bas also used a somewhat similar diagram to represent the variations 

in mineral composition of rocks of Y ogo Peak, Little Belt Mountains, Montana. i 

In 1896 Becke.i represented the chemical composition of igneous rocks hy 

diagrams of two kinds, constructed in a manner different from that of those just 

described. The first is a modification of a three-coordinate diagram for three 

variables, whose sum is a constant, based upon an equilateral triangle. The 

three factors chosen are Ca, Na, K. The zero point of the coordinate axis is 

the center of the triangle. From this point three axes run to the corners of 

the triangle, one for each of 'the elements, Ca, Na, K. The spot within the 

"Washington, H. S., Jour. Geol., vol. 3, 1895, p. 160. 

1> Washington, H. S., Bull. Geol. Soc. America, vol. 11, 19UO, p. 404. 

cCross, W., Seventeenth Ann. Rept. U.S. Geol. Survey, pt. 2, 1896, p. 324. 

dHarker, A., Quart. Jour. Geol. Soc. London, vol. 51, 1895, p. 146. 

e Harker, A., Jour. Geol.;·vol. 8, 1900, pp. 389-399. 

f Loewinson-Lessing, F., Compte rendu Congres Geol. International, Seventh session, St. Petersbourg, lRU\1, Pis. I, II, 

und III. 

y Pirsson, L. V., Twentieth Ann. Rept. U.S. Geol. Survey, pt. 3, 1900, p. 569 et seq. 

h Washington, H. S., Bull. Geol. Soc. America, vol. 11, 1900, p. G51. 

i Op. cit., p. 568. 

JBecke, F., lllin. Pet. :Mltth., vo\.16, 1897, p. Hlf>-320. 
12 CHEMICAL COMPOSITION OF IGNEOUS ROCKS 

triangle determined by the values of Ua, Na, K, in a given ro~k analysis is the 

locus of the analysis (Analysenort). The various posjtions of these spots indicate 

the relative amounts of the elements named in the rocks compared. The other 

chemical elem.ents in the rocks are represented on a second diagram supposed to 

stand at right angles to the plane of the first. It is drawn with rectangular 

coordinates, the abcissas being proportional to the ratio Ca +<;a+ K' and the 

ordinates representing the values of Si, Al, Fe, Mg. Each of these elements is 

locatetl by a spot in the diagram. 

In .January, 1897, Michel Levy a devised diagrams to exhibit certain chcmicomineralogical characters of igneous rocks, a single· diagmm representing an individual rock. The 'component oxides arc first distributed into two groups, those 

that may combine with Al20 3 to form feldspars and those that may not. All 

the Al 20 3 is set aside for feldspars, and to it is allotted K20, Na20, and 

sufficient CaO to satisfy it. An excess of CaO is placed with iron and magnesm. Silica may he introduced into the diagram or omitted, and in a subsequent publication" in the same year is expressed only in numbers stating the 

percentage. Rectangular coordinates are used and the values of the components 

are laid off on two axes intersecting at the zero point. Below this point is 

plotted the percentage of potash, and also that of iron oxide. To the right of 

the zero point is plotted the percentage of soda which may combine with alumina. 

In this direction, also, may be plotted the percentage of silicn. Above the zero 

point is plotted the lime which may combine with alumina, and al:so the percentage of magnesia. If there is more lime than will sntisfy the alumina remaining 

after potash and soda hnve been satisfied, this lime is plotted to the left of the 

zero point. Triangles are constructed by connecting the end of the potash line 

with that of the soda line, and the ;;oda with feldspathic lime. Magnesia is connected with nonfeldspathic lime, and this with iron. Two triangles to the right 

of the y axis give an indication of the feldspathic constituents of the rock. The 

other two triangles to the left of the y axis represent the nonaluminous constituents. Modifications of the diagrams enter when there is an excess of ~alumina 

over alkalies and lime, and again when alumina is less than the alkalies. 

Michel Levy in the publication last cited also employs diagrams showing 

curves of variation for the percentages of the chemical components when subdivided in the manner just described. 

These triangular diagrams have been used by Lacroix; in describing the basic 

rocks accompanying the lherzolites and ophites. of the Pyrenees, c and also in his 

------------'--~------ -----~-~--------------

a Levy, A. Michel, Bull. Serv. Carte geol. France, vol. 9, No. 57, 1897, p. 38 and Pis. VII, VIII. 

b Levy, A. Michel, Bull. Soc. geol. Frnnce, 3d series, vol. 25, 1897, Pis. X to XV. 

c Lacroix, A., Compte rendu Congrt's Geol. International, Eighth session, Paris, 1901, Part II, pp. 834, 835. 
HiSTORICAL REVIEW. 13 

work on the alkaline rocks .of the petrographical province of Ampasindava, 

Madagascar." 

In May, 1897, Brogger 0 presented a modification of the individual diagrams 

·devised by Michel Levy. This was done in illustrating the chemical composition 

of the group of rocks associated with the laurdalite of the Christiania region. 

Brogger's diagrallll'> are composed of four coordinates in a plane intersecting in 

a common zero point. One is horizontal, another vertical, and the other two 

inclined, one 60° to the right, the other 60° to the left of the vertical _axis. On 

these axes are plotted the molecular proportions of the chief oxide components 

of a rock. On the upper vertical axis are plotted t.he molecules of CaO, on the 

lower vertical axi:'l the Al20 3 • On the' horizontal axis right and left is plotted. 

the Si02 , half and half. On the upper right inclined axis is plotted MgO; on the 

upper left one, the FeO + Fe20 3 , indicated separately. On the lower right inclined 

axis is plotted K20, and on the lower left one Na20. The extre:~;nities of adjacent 

axes are connected by lines. These diagrams show at a glance the relative proportions of the molecules of the oxide constituent~'\ of each rock. The amount of 

CaO capable of being coml;Jined with Al20 3, not combined with K20 and Na20, 

can be readily found by measuring the lengths of the several axes. The introduetion of the silica and alumina adds to the instructiveness of this form of 

diagram. 

Diagrams of this type htwe been employed by Hobb:s c to express the average composition of groups of rocks classed together under various divisions of 

the qualitative system in general usc at the present time. In these diagrams the 

inclined axes stand at 45° to the vertical axis. 

Hackman d has made usc of both the Becke and -the Brugger diagrams to 

express chemical relations among the rocks associated with ijolite in Kuusamo, 

Finland. 

Rosen busch e uses narrow rectangular diagrams to express the relative proportions of the chemical elements (11£etallatome) in two series of 26 rocks; one, a 

foyaitc-themlite series, the other a granitodioritc and gabbro-peridotite series. 

- In February, 1898, the authorf in an essay on rock classification, and later 

in another essay, made usc of diagntms exhibiting the variations of rock analyses 

with reference to percentage of silica and alkali-silica ratio. These are constructed by using the silica percentages as abscissas, the zero point being to the 

a Lacroix, A., Nom•. Arch. Museum HisL Nat., 4th series, I, Paris, 1902, p. 180 et ~eq. 

b Bri:igger, W. C., Die Eruptivgcstelne des Kristinniagebietes. III. Vf!lenskabssclskabet~ Schriftcr. I. 1\lath.-Natlln-. 

Kl. 1897. No.6. Christiania, 1898. 

c Hobbs, W. H., Jour. Gcol., vol. 8, 1900, pp. 1-31. 

d Hackman, V ., Bull. Com. _Geol. Finlande, vol. 11, Helsingfors, 1900. 

e Rosen busch, H., Elemcnte dcr Gesteinslehre. Stuttgart, 1898. 

f Iddings, J.P., Jour. Geol., vol. 6, 1898, .pp. 92-111, 219-237. 
14 CHEMICAL COMPOSITION OF IGNEOUS ROCKS. 

right of the diagram, and 100 to the left. The ordinates -represent the ratios 

obtained by dividing the sum of the molecular proportions of the alkalies, K2 0 

and Na20, by that of silica. The locus of each an~1lysis is indicated by a round 

spot or by figures of other shapes. 

In the same year, 1898, Michel Levy a presented a new mode of coordination 

of diagrams to represent rock magmas, based in a measure on those just published 

by the author, to some features of which Michel Levy took exception. The:;e 

diagrams by MiChel Levy give the loci of rock analyses referred to two coordinates in the plane of drawing, and also to a third axis projected on the same plane. 

The abscissas (re) represent the siliea percentages in the "white components" 

(elements blancs) of tbc rocks compared. The ordinates (y) represent the sum 

of the percentages of K20, Na20, and the CaO which may enter feldspar combined with Al 2 0 3 • The third coordinates (z) represent the pereentages of MgO, 

FeO, Fe~0 , CaO, and Si02 in the ferromag·nesian components of the rocks. The 

loei of the analyses are rixed by the -rectangular coordinates w and y. Their 

relation · to the axis z is inclieated by their position with reference to diagonal 

lines representing the projected traces of certain planes with an inclined plane 

through z. 

The usefulness of this diagram, which appears when the compositions of 

restricted groups of rocks are illustrated, is seriously impaired by repeated overlapping when many kinds of roeks arc taken into accoimt. The method. undertakes 

to distribute the analyses with respect to the relative abundance of the white 

(leucocratic) components-quartz and feldspathic minerals-and the dark (mclanocratic) ferromagnesian components in the first instance, and also with respect to 

the silica eontent of the lencocratic components. 

It is clear that rocks containing various amounts of nephelite, hiueite, and 

anorthite molecules with elosely similar percentages of silica _will be mingled 

together in the same part of the diagram, and that rocks with preponderant. 

ferromagnesian minerals, since they are plotted wholly on a basis of characters 

belonging to the subordinate feldspathic minerals, will be indiscriminately mingled 

in one portion of the diagram. 

In 1899 Loewinson-Lessing,O in his stuclies of eruptive rocks, an abstract of 

which was presented, without diag-rams, to the International Geological Congress 

at St. Petersburg in 1897, makes use of two forms of diagrams, one after the 

method of the author, already alluded to, and another based on the method of 

relative rectangular areas used by Reyer. The diagram represents the various 

molecular proportions of the ehemical components of a rock, or may represent 

the average of a group of rocks. It is a rectangular area divided by horizontal 

a Levy, A. Michel, BulL Soc. gcoL France, 3<1 series, voL 26, 1898, Pis. III to Vl. bLoc. eit. 
HISTORICAL REVIEW. 15 

lines into spaces whose vertical dimensions correspond to the proportions of SiO, 

H20 3, RO, and R20 in each case. These rectangles arc subdivided by vertical 

lines into spaces whose horizontal dimensions correspond to the proportions of 

Al20 3 and Fe20 3 in R20 3 , of FeO, CaO, and MgO in RO, and of K20 and Na20 

in R2 0. 

In 1900 Miigge" devised a form of diagram to express the proportions of 

the chemical components of rocks, based upon some features of Michel Levy's 

and Brugger's diagrams. Several modifications of the diagram were suggested 

by Mi1gge. It will be sufficient to describe the form used by him to illustrate 

the composition of a number of selected rocks. The relative quantities of the 

oxide components, expressed molecularly, are plotted on four eoordinate axes in 

one plane intersecting in a zero point and making· equal angles with one another. 

One is vertical, one horizontal, and two inclined at 45°. The silica is represented 

by an octagonal area, constructed by plotting one-eighth of the total silica plus 

and minus on each axis. The other components are plotted outside this area on 

particular axes by adding their values to the silica already plotted. K20 is 

plotted on the t;pper left inclined axis, Na20 on ·the upper right one, MgO on . 

the lower left inclined axis, CaO on the lower right one. FeO is plotted on the 

lower Yertical axis, followed by Fe20 3 in the same direction. Al20 3 is divided 

into three parts, when sufficient, the first, equal molecularly to K2 0, is plotted 

to the left on the horizontal axis. A second, equal to the Na20 is plotted 

upward on the_ vertical axis, and the remainder of the Al 20 3 is plotted to the 

right on the horizontal axis. vVhcn there is less Al20 3 than K20 + Na20, enough 

Fe20 3 is added to A1 2 0 3 upward on the vertical axis to equal Na20. In this 

mttnner the relative amounts of potash-alumina molecules, soda-alumina molecules, 

and lime-alumina molecules are indicated. 

In 1900 and 1901 Osann b made usc of several types of diagrams to illustrate 

chemical characteristics of igneous rocks -in his essay on a chemical classification 

of igneous rocks. 

One is a triangular diagram somewhat similar to that used by Becke, exhibiting the distribution of analyses with respect to three coordinate axes making 

equal angles with one another. The three chemical factors of rocks employed in 

their comparison are chemico-mineralogical to some extent. One factor (A) consists of the sum of the percentages of K2 0 and Na20 which may be combined 

with Al2 0 3 in equal molecular amount. A second factor (C) rcpre~Sents the perecntage of CaO which may be combined with Al 20 3 in equal molecular amount. 

The third factor (F) represents the sum of the percentages of the remaining CaO, 

« Miigge, 0., Neues Jahrb. 1\fin., ·aeoL imd Pa1., 1900, voL 1, pp. 100-112, Pis. V-VIL 

b Osann, A., Min. Pet. Mitth., voL 19, 1900, Pis. IV-VIII, XXV; vol. 29; 1901, Pis. VIII-XIV. 
16 CHEMICAL COMPOSITION Olf IGNEOlTS ROCES. 

MgO, FeO. The sum of these is as>Sumed t.o be a constant, and their relative 

proportions are determined on a basis of 20 units. "\Vith these three variables 

the position of a rock analysis within the equilateral triangle is located. 

A second form of diagram expresses the variation in silica and alkalinity in 

certain rocks by means of lines connecting loci of analyses referred to two rectangular coordinates, the abscissas corresponding to the alkalinity, and the ordinates to the silica percentage. Another diagram of the same type exhibits the 

variability of different kinds o£ rock with respect to the relative proportions of 

soda and potash. 

A third form of diagram is composed of narrow J,"ectangles, whose lengths 

correspond to the range of variation in silica ratios for different kinds of rocks. 

The rectangles are placed by the side of one another, with their longer diameters 

adjusted to one ordinate representing values of silica ratios. 

In 1902 Reid" used an equilateral triangle whose sides are divided into 100 · 

parts, as a basis on which to plot the oxide components of igneous rocks. 

PURPOSE OF THE DIAGRAJ\18. 

A study of the various· diagrams that have been employed by petrographers 

shows that their value depends upon the readiness with which their significance 

may be grasped and the use that is made of them. The first condition varies 

directly as the simplicity of the method of construction, both as to geometrical 

form and as to the factors on which they are based. The simpler the form of the 

diagram and the more characteristic its shape, the more definite the visual 

impression and the stronger the hold on the mind. It is also self-evident that 

the simpler the factors entering into it the better. The quantitative values of 

single rock components are simpler conceptions than intricate ratios and functions 

involving several different rock components. Moreover, a diagram is comparatively 

worthless unless' it can be made to convey some definite impression not otherwise 

obtainable,· or obtainable only with difficulty. Its employment should have some 

specific object. It is hoped that the diagrams presented in this paper will justify 

themselves and will produce certain definite impressions on the minds of petrographers who may study them. 

The author's first purpose in constructing the accompanying diagrams is to 

express in the simplest graphical manner the chief chemical composition of all 

kinds of igneous rocks in a form that will permit the student to compare them 

at a glance and obtain a comprehensive view of the whole range of differences. 

The diagrams are intended to exhibit the manifold character of the variations 

of the chemical components of rocks, and their extent. They are to show the 

a Reid, J. A., Bull. Dept. Geol. Univ. California, vol. 3, 1902, p. 18. 
OONSTRUCTION OF DIAGRAMS. 17 

gradual character of the variations; the transitions from rocks of one composition 

to those of another; and the distribution of the. rocks throughout the range ,.of 

their variations. 

They are to demonstrate the absence of clusters . of analyseR in definite parts 

of the whole system and the absence of "natural" subdivisions of rocks on a 

basis of chemical composition. 

They ·are to show the possibility of continuous series of rocks with diverse 

compositions, and to illustrate the chemical identity of roch belonging to different 

genetie families. 

Finally the diagrams exhibit the eharacter of the quantitative c\assification of 

igneous rocks proposed by Cro:;s, Iddings, Pirsson, and vVashington, the range 

of composition of the five classes, as well as of the orders; rangs, and subrangs. 

CONSTRUCTION OF 'l'HE, DIAGRAMS. 

As will be seen by looking at the plates, the diagi·ltm:-~ · [trc combinations of 

two ~inds already in use. They consist of assemblages of individual rock diagrams, 

which are modifications of those devised by Mi~hcl Levy and Br<>gger, the individual diagrams being arranged in a multiple diagram previously used by the 

author. The first are used to exhibit the chief ehemical _components of each 

rock taken into consideration; the second, to arrange these in an orderly manner 

for eomparison with one another. 

The small, individual diagrams are modified forms of those by Brogger. They 

are planned to exhibit the relative amounts of the ehief oxide components of 

igneous ·rocks, namely: Si02, AJ20 3, Fc20 3+Fe0, MgO, CaO, Na20, K20, and 

also Ti02 • Other components are usually so slight that they arc negligible in 

diagrams of such small seale. Owing to the fact that the small diagrams are 

arranged in the large diagram according to the silica, it is not necessary for the 

purposes of this paper to introduce Si02 into the construction of the individual 

diagram. The relative amount of SiO~ is expressed by the position of the small 

diagram in the htrge one. This simplifies the small diagmm. 

Tpe chemical eomponents of rocks may be compared with one another as 

oxides of metals or as metals. As oxides, the form in .which they are expressed 

in ehemical analyses of rocks, they may be compared by means of percentage 

weights or of molecular proportions. As metals they would be compared by 

ll10lecular or atomic proporti~ns. 

The use of oxides instead of metal elements is the more convenient method 

of comparison. It bears a more obvious and direct relation to the rock analysis 

:tnd requires less effort to apply. It is as valuable in the discussion of ehemicomi ncralogical relationships as the usc of metal elements. It has, therefore, been 

adopted in eonstructing these diagmms. 

14474-No. 18-03--2 
18 CHEMICAL, COMPOSITION OF IGNEOUS ROCKS. 

The value of basing the comparisons upon molecular proportions instead of 

percentage weights re~o;ts upon the fact that the chemical equivalency of the components b molecular or atomic, and that in this form they may be readily converted into mineral molecules for purposes of discussion and rock classification. 

For purposes of comparison in diagrams of this type it is not necessary to 

reduce the original analysis to a sum of exactly 100. So far as the small individual diagrams are concerned the amount of change produced in the lengths of 

the lines would not be appreciable. Further, all elementary lines in one diagram 

would be affected in like proportion and the shape of the figure would remain 

unchanged, e.ven could the alteration in the length of the lines be made visible. 

It would affect to a variable degree the position of the small diagrams within 

the large one in the direction of the silica abscissa, which will be discussed later. 

The smal1, individual diagrams are constructed to exhibit the molecular 

proportions of the component oxides: Al20 3, Fe20 3+Fe0, MgO, CaO, Na20, K20, 

and Ti02 • These are derived directly from the rock analysis by dividing the 

percentage weight of each oxide by its molecular weight. There is no further 

reduction. They are used in the proportions in which they are found in the rock, 

the assumption being that equal weights of different rocks are being eompared. 

Following Br6gger's method, the several \'ttlues of these oxides are plotted 

on coordinate axes in one place, intersecting at a common zero point. But the 

arrangement is different. For convenience in drawing on square-ruled paper 

the axes ehosen are vertical, horizontal, and two at 45° to these. The simple, 

approximate relation between the ~;ides and hypothenuse of a 45° triangle, namely, 

that when the hypothenuse is 10 units the sides are 7 units each (more exactly 

7.071) allows the values to be readily plotted by assuming the diagonal of each 

square of the ruled paper to he 5 and the side 3~. With larger diagrams and 

more exact requirements more accurate methods of plotting may he employed. 

Since the small diagrams are to he compared by means of the multiple one, 

the position of. the Broggcr diagrams is inverted to conform more closely to the 

manner of constructing the large diagram. In the multiple diagram the more 

alkalic, and consequently more alkalicfeldspathic, nicmbers of the serie:-; of rocks 

compared occur in the npper part; the le~o;s alkalic, and more ferromagnesian, in 

the lower part. so the alumina and aJkalies are placed in the upper part of the 

individual diagrams, the iron and magnesia in the lower. The mode of eonstruetion is as follows: Al2 0 3 is plotted upward on the· vertical axis; K20 upward to 

the left on one inclined axis; Na2 0 upward' to the right on the other inclined 

axis; CaO is plotted downward· on the vertical axis; MgO downward to the 

right;. Fe0+2F~ 3 downward to the left; and Ti02 , when present in appreciable 

amot.int, is plotted to the left on the horizontal axis. The end of the Al20 3 

ordinate is connected by lines with the ends of the K20 and Na20 ordinates, 
CONS'rRUCTION OJ<' DIAGRAMS. 19 

producing two triang-les having a common side-the Al20 3 ordinate-and one 

angle the same in each-45°. Consequently the areas of the two triangles are 

proportional to the lengths of the K20 and Na2 0 ordinates. The relative imprcs- · 

sions produced by these two triangles, colored. green and yellow in the diagrams, 

arc quantitatively the same as the relations between the molecular proportions of 

K20 and Na20.in the rock.· 

The end of the CaO ordinate is connected with the ends of the MgO and 

Fc0+2Fe20 3 ordinate, making two triang·les, colored blue and red in the diagrams, 

whose areas bear the same proportion to one another as the mtio between the 

molecules of MgO and the iron converted to FcO. 

When Ti02 is represented, the end of its ordinate is connected with that of 

the FeO ordinate. 

The FeO and Fe2 0 3 are combined chiefly for simplicity, and the Fe20 3 is 

reduced to FeO because there is then a more uniform basis of comparison and a 

means of avoiding the analytical defects or errors in the determination of the 

two oxides of iron. The combination · preventt> a proper conception of the 

possibilities of mineral molecular combination so far as the iron is concerned, 

but this is beyond the adaptability of the diagrams in a strict sen:;e. 

It is evident that diagrams constmeted on the molecular proportions of 

the oxide components of rocks may he easily converted into others, based on the 

proportiol1s of the metal elements, by doubling t.he lengths of the three upper 

ordinates, Al 20 3 , K20, Na20. The upper half of each diagram would be double 

its former size, while the angular shape of the whole would remain the same. 

The multiple diagram, by which the small individual ones are arranged for 

comparison and study, is constructed in the manner already described in the 

article on rock classification previously cited. It is intended to exhibit the distribution or variation of igneous rock analyses with respect to the silica and 

alkalies. The reasons for choot>ing these two factors are: First, the important role 

played by silica, the most abundant chemical component, and that which is dominant in the development of quartz, orthoclase, albite, leucite, or nephelite, orthorhombic pyroxene or olivine; second, the equally important role played by the 

alkalies in ·conditioning the character of the feldspathic mineral eomponents of 

rocks, whieh arc the preponderan.t ones -in the great majority of cases; third, 

the fact that the other chemical components-lime, mq,gnesia, tmd iron oxidesustain to a considerable extent a reciprocal relation to those just mentioned. 

The greater the silica the less the content in lime, mag-net>ia, and iron oxide. 

The same is true in general for the ttlkalies and these oxides. 

One of the chief purposes of the diagram is to distribtite the rocks in an 

orderly manner, so that unlike ·rocks shall be separated from one another as 

widely as possible and gradations between the extremes shall be made evident. 
20 OHEMIUAL COMPOSITION OF IGNEOUS ROCKS. 

The silica is made the abscissa because it is the greater component and has 

the widest range. It is plotted in percentages instead o£ molecular proportions 

because the process is simpler, and as it is not brought into immediate quantitative relations to the linear elements o£ the individual diagrams there is no occasion 

for its quantitative linear comparison with them. Moreover, the large diagralll 

could not be constructed on the same scale of units as· the individual diagram:;. 

It is therefore simpler and more convenient to use the percentage o£ silica given 

in the analyses. 

The vertical ordinates represent the ratio between the sum of the molecular 

proportions of the alkalies (K2 0 + Na20) and of the silica- (K20stoNa20). This 2 

ratio was selected because o£ the relation between the development o£ the alkalifeldspathic minerals in highly feldspathic rocks and the ratio between the alkalies 

and silica in their magmas; the more siliceous ones yielding more orthoclase or 

albite, the less siliceous ones more leucite or nephelite. It. is not a definite 

relationship in rocks generally, and, as Michel Levy has pointed out, the 

character of the diagram would not have been altered materially had the vertieal 

ordinates been made to correspond directly to the sum of the alkalies. In this 

case the curved lines which represent the loci of pure quartz-albite-nephelitc 

rocks and quartz-orthoclase-~eucite rocks would be straight lines instead .of 

hyperbolas, as in the diagramB here used. There would be a slightly different 

vertical spacing o£ the analyses on individual diagrams. They would be spread 

more on the left side of the ordinate of 60 per cent Si02 , and condensed more 

on the right o£ it. The multiple diagrams would be more simply constructed. 

Otherwise the results would be alike. 

With diagrams ·constructed by using ratios between two or more rock 

components it matters not whether the analyses discussed by it are reduced to 

anhydrous compounds, or whether their summation is exaetly 100. The ratio 

between the alkalies and silica is not affected by readjusting the analysis. The 

ordinate of an analysis so located is riot changed by readjw>ting the percentages 

in the analysis, but the abscissa would be affected by ehanging the Hilica 

percentage. The position of an analysis would be :-;hifted ·horizontally to the left. 

or right according as the percentage of. siliea is raised or lowered. 

The zero point of each individual diagram is loeated in the multiple diagram 

by referenee to the silica percentage and the alkali-siliea ratio of the analysis 

it represents. In some instances several individual diagrams belong so close 

together that they would overlap, so as to prevent their shapes from being easily 

seen. One or more of them is l)lovcd to the nearest nvailable space in the 

multiple diagram. From this it h~1ppens that the distribution o£ the analyses m 
ROCK ANALYSES USED IN CONSTRUC'.riNG DIAORAMS. 21 

the large diagram is not strictly correct in the more crowded portions of it. 

A more exact representation of the distribution is given in another form of 

multiple diagrams on a smaller scale, in which round spots take the place of 

the individual diagrams. 

ROCK ANALYSES USED IN CONSTRUCTING DIAGRAMS. 

Having described the methods by which the diagrams are constructed, a 

more important matter to be considered is the data to be used-the rock analyses 

to be compared. by them. 

Analyses have been selected from all sources available, but not all analyses. 

It is important that they be correctly made and frqrn good material. These 

. conditions, however, can not always be recognized or known without cnreful 

study of the publications in which the analyses appear, and not always then. 

The ·collection is not above criticism in this respect. However, care was exerCised to omit obviously defective analyses, as well as those from plainly declared 

altered rocks, except in cases where the altered form may be assumed to correspond approximately to the fresh rock, with the addition of water of hydration. 

For the strongly' ferrornagnesian rocks such analyses have been taken sometimes 

in default of better. 

The analyses represent as many varietie8 of igneous rocks as could be found; 

with as wide a range as possible. Many an11lyses closely similar to those introduced into the large diagrams have been omitted be~ause there was not space 

for them. Consequently the diagrams do not show the proper proportion8 between 

the commoner and rarer varieti~s of rocks. This can be shown by plotting the 

loci of all acceptable analyses by means of spots in a multiple diagram of fairly 

large scale. · This has been done in constructing the diagram on Pl. VIII, which is 

composed of 2,000 analyses. 

It was thought unnecessary to reprint the analyses themselves, for the reason 

that nearly all of them will be found in the collection of rock analyses made by 

Dr. Henry S. Washington and published by the United States Geological Survey," 

and' a large part of them also in Bulletin of the United States Geological Survey 

CNo. 168. Many of them will be found in Rosenbusch's Elemente der Gesteinslehre. 

So that these collections should be used in connection with the diagrams. For this 

reason reference is given in many cases to these publications, and to others 

where numerous analyses are assembled, instead of to the original sources, as 

the more convenient method of finding them. 

A list of the analyses used in the diagrams is given. Their positions on 

the diagrams may be found by means of the silica percentage a11d alkali-silica 

a Chemical analyses of igneous rockR from 1884 to 1900: Prof. Paper U. S. Geol. Survey No. 14. 
22 CHEMICAL COMPOSITION OB' IGNEOUS ],WOKS. 

ratio, which are stated in Bach case, besides the position giyen them when phteed 

differently. 

They are classified according to the quantitative classification, and the. author 

wishes to expre:-os his thanks to Dr. Washington for the hbor he has bestowed 

on the comparison of the list with his eollection and for the correction of errors 

that appeared in the list. He is indebted to him also for valuable additions to it. 

The list is far from complete, and petrographers may add to it and to the 

diagrams data which should have been included. But it seems as though enough 

has been introduced to aecomplish the put·pose for which the diagrams we1·e 

prepared. 

in order to shorten the refcrenees in the lists~ a nnmber of abbreviations 

are used whieh are given· alphabetically. 

ABBREVIATIONS l~MPLOYED IN BIBLIOGRAPHIC RljFERENCES. 

A. G __________________ .American Geologist. Minneapolis. 

A. J. s _________________ American Journal of Science. New Haven. 

A. W. B _. _____ . ______ .Sitzungsberichte rler Kiinig. Preuss. Akad. der I_Vis8ensch. Berlin. 

A. W. W ____________ : __ Sitzungsberichte der K. Akad. Wissensch. Wien. 

B. C. G. F _____________ Bulletin de la Commission geologique de FinlaiHle. Helsingfors. 

B. G. 8. A _____________ Bulletin of. the Geological Society of America. Rochester. 

R. IlL A----- .· _________ Bergens Museums Aarbog. 

Bull. 168 _______________ Bulletin of the U. S. Geological Survey, No. 168. Washington, 1900. 

C. G. L ________________ Congres geologique. International, Compte Rendu, VIII session. Paris. 

E. K. ______ .... · ........ Die Ernptivgesteine des Kristianiagebietes, IV. C. Brugger. Christiania. 1, 

1894; II, 1895; III, 1898. 

G. C __ ...... _. _ .. _ .. ___ Untersuchung einiger Gesteinssniten gesanunelt in Celebes, von P. and F. 

Rarasin. C. Schmidt, Wiosbaden, 1901. 

G. F. S. F._. __ .. __ . __ . Geol. .Foren. i Stockholm Fiirhandl. 

I. R. A . __ . __ . ____ .. ___ The igneous rocks of Arkansas: vol. 2 of Ann. Rept. Geol. Surv. Arkansas . 

• T. G . __ .. _ .... _____ .... The Journal of Geology. Chicago. 

0. N. ___ ... ____ ... ___ .. Recherches geologi11ues et petrographiques sur l'Oural clu Nord, Duparr• 

et Pearce. Part I. Geneva, 1902. 

:M . .M .................. .IIfateriaux pour la Mineralogic de Madagascar, A. Lacroix. Nouvelles 

Archives du Museum. 4th series, Vol. J. PariH, 1902. 

N. J ................... Neues Jahrbuch fiir Mineralogic, Geologie, etc.;. 

Q. J. G. 8 ___ ..... _ .... Quarterly Journal of the Geological Rociety of I,ondon. 

Rosenbusch, EI. ........ Rosenlmsch. Elementc der Gesteinslehre. Stuttgart, 1898. 

R. T ___________________ Roth's tables of rock analyses. Beitrtige zur Petrographic fler Plutonischen Gesteine. Berlin. 

S . .II'L Q ________________ School of Mines Quarterly. New York. 

T . .IIf. P. M _______ .. ___ Tschermak's Min. u. Petr. l\fitth. Vienna. 

W. T _ .. _ .. _ .. __ .... __ .. Washington's tables of che~ical analyses of igneous rocks from 1884 to 1900. 

Professional Paper U. S. Geological Survey, No. 14, Washington, JHO::!. 

z. D. g. G ...... _ .... _. Zeitschrift d. Deutsch en geol. Gesellschaft. Berlin. 

Z. K _. ____ .. _ . _ ... _ . _ .. Zeitschrift fiir Krystallographie. 

Z. P. G . _. _ ....... _ .. _. Zeitschrift fiir Praktische Geologie. Berlin. 

Fortieth Par •••••••••••• U. S. Geol. Expl. Fortieth Parallel. Washington. 
Bili~a 

content. 

ROOK ANALYSES USED IN CONSTRUCTING DIAGRAMS. • 

CLASSIFIED LIST OF ANALYSES USED IN CONSTRUCTING DIAGRAMS. 

Alkali-silica 

ratio. 

CLASS I. PERSALANE. 

ORDER 3. CoLUMBARE. 

RANG 1. ALASKASE. 

SuBR.iNG- 1. --. 

(T. 3, 1, 1.) 

Author's name. Lo~ality. Reference. 

23 

---1-------l--------l:-----~~---------1------------

79.25 0. 057 

79.75 0.062 

78.86 .07~ 

76.10 . 085 

75.39 .080 

74.40 . 079 

80.24 0.070 

79.57 . 070 

77. li8 .077 

77.68 .07f> (77.1i) 

77.59 .059 

. 079 (.078) 

. 080 

.080 

Porphy&y ............. Harz Mountains ...................... R. T., 1861, i. 

SURRANG 2. JIIAGDERURGOSE. 

(I. 3, 1, 2.) 

Quartz-porphyry ..... Blowing Rock, Watauga County, N.C. Bull. 168, 52.- W .. T. 

l<'elsite-porphyry ..... Fichtelgebirge, Bavarht .............. R. '!'., 1879, XX. 

(}ranite ............... Crystal Falls district, Mich ........... Bull. 168, 61i.~W. '!' • 

Rhyolite .............. Silver Cliff, Colo ...................... Jlnll. lf.S, 149.-W. T. 

Granite .............. ·. Pikes Peak district, Colo ..... , ........ Bnll. 108, H2.-W. T . 

SUBRANG 3. ALASKOSE. 

(I. 3, 1, 3.) 

Granite ............... Wexford, Ireland ..................... R. T., 1861-2. 

Rhyolite .............. Montgomery County, N.C ............ Bull. 11i8, 53.-W. '1'. 

Granitite ............. Eldorado County, C11l ................ Bull. 168, 199.-\Y. T. 

Quartz-porphyry ..... 'l'rybcrg Fall, Black Forest ........... N.J., 1883,11, 29.-W. '1'. 

Khyolitc .............. Hanraki Goldfield, New Zealand ..... Q .. J. G. S., 1899, LV, 467.-W. '1'. 

Alaskite .............. Tordrillo Mountains, Alaska ......... Bull. 168, 228.-W. 'l' . 

Qu~trtz-porphyry ..... Kro!tkollen, Norway ................. Z. K., XVI, 77.-W.'T . 

Aplite ................ Butte, Mont .......................... Bull. 168, 118.-W. T. 

77.33 

7i.20 

77.05 

77.03 

77.02 

76.87 

76.73 

76.10 

75.84 

75.52 

74.70 

74.24 

73.11 

.081 (76.&-.082) Granititc ............. Pikes Peak district, Colo ............. Bull. 168, 142.-W. 1' . 

83.08 

82.80 

76.00 

75.19 

. 077 (77.1) Granite .... : .......... PlatteCanyon,Colo ............ ~ ..... Bull.168,164.-W.T. 

.078 Aplite ................ Butte, 1\lout .......................... Bull. 168, 118.-W. T. 

. 077 (7ti. 6) 

. 063 

. 081 

. 080 (75. 7) 

.083 

. 069 

. 082 (73. 0) 

0.054 

. 049 

. 067 

. 076 (75.1) 

Aplitic granophyre ... Hennum, Norway .................... Z. K., XVI, 77.-W. '1'. 

.Mnscovite-gmnite .... Omeo, Victoria ....................... Trans. R. S. Vict..-W. T . 

Tordrillitc............ Tordrillo Mountains, Alaska . • . . . . . . . Bull. 168, 229.-W. T . 

Obsidian ............... Obsidian Cliff, Yellowstone Park ..... R\tll. 168, 104.-W. T. 

..... do ..................... do ........................ ~....... Do. 

Rhyolite .............. Plumas County, Cal .................. Bull. 168, 178.-W. '1' . 

Pitchstone ............ Rosita, Colo .......................... Jlull. 168, 150.-W. '1' . 

SUBRANG 4, --. 

(I. 3, 1, 4.) 

Spherulitic rock ...... Wales ................................. Teall, British Pctrography,339. 

Perlite ................ Monte 1\Ienone ....................... R. '1'., 1869, XC . 

Granite ............. :. Plumas County, Cal .................. Bull. 168, 187.-W. T . 

Rhyolite .............. ll!adison Plateau, Yellowstone Park .. Bull. 168, 105.-W. T . 
24 CHEMICAL COMPOSITION OF IGNEOUS ROCKS. 

Claslfijied li.~t of nnaly8es tt.~ed in con.~trucl'ing diagrams-Continued. 

Silica 

content. 

A lkali-silico> 

rlitio. Author's nan1e. 

SURRANG 5. WESTPHALOSE. 

(I. 3, 1, 5.) 

Locality. Hefcrcncc. 

----~--~- ---~--~-- -----------'------\----------

8;), 57 0. 053 

-'0.42 .059 

ii. 32 .Oll1 (.083) 

73.15 0.055 

73.07 :07,1 

72.68 .054 

70.59 .057 

79.95 0.049 

77.34 • OG9 

76.12 .059 

75.89 .oo9 (75. n 75.34 • 07G 

75.21 .072 

74.61\ .074 

74.41 ,oa7 

74.34 .072 

73.62 . 079 (73. ;) 

72.37 .058 

72.15 .067 

72.04 . 058 

72.01 .073 

71.45 .Of>-! 

78.75 0.052 

77.35 . 052 

74.65 . 064 

74.13 . 077 

73.08 . 080 (72. 9) 

72.8~ .056 

74. 791 0. 0()7 

Quartz-keratophyre .. Westplmlia ........................... N.J., 1893, VIII, G1G.-W. '!'. 

..... do ..................... do ................................ N.J., 1893, VIII, 632.-W. T. 

Granite ................ RorldO, Sweden ........ : .............. W. '!,. 

RANG 2. ALSRACHASE. 

SUBRANG 2. l\IrHALOSE. 

(I. 3, 2, 2.) 

Rhyolite .............. Nagy-MihtLly,'Hungary .............. W. T. 

..... do ................. Washoe, Nev ......................... Bull. 168, 174.-W. T . 

. . .. . do ................ Nagy-Mihaly, Hungary ............... W. T. 

..... do ..................... do ......................... ;...... Do. 

SUBRANG 3. TEHAMOSE. 

(I. 3, 2, 3.) 

! Felsite-porphyry ..... Bohemia ............................. R. T., 1884, XVIII. 

Aplite ................ Kirnechth~l, Vosges ................. Rosen!Jusch, EL, 207 . 

Gmnitite ............. Riesengebirge, Silesin ................ N.J., 1898, XII, 233.~W. T. 

i Rhyolite .............. Mount Sheridan, Yellowstone Park .. Bull. 168, 105.-W. T. 

: ..... do ................ Elephants Back, Yellowstone I'nrk.. Do. 

· Grauit.ite ............. Riesengebirge, Silesia ................ N.J., 18981 XII, 233.-W. T. 

: Rhyolite.............. Tehama County, Cal................. Bull. 168, 178.-W. T. 

I Granite ............... Riesengebirge, Silesia ................ N.J., 1898, XU, 233.-W. 'J'. 

Rhyolite.............. Butte district, Mont.................. Bull. IUS, 119.~\V. '1' .. 

..... do................ Tehama County, Cui................. Bull. 168, liS.~W. T. 

Gmnit.itc ............. Riesengebirge, Silesia ................ N.J., 1898, XII, 232.-\V. 7'. 

..... do ..................... do . . • • .. . • . • .. . . • . .. . .. .. . .. • • .. .. Do . 

..... do ..................... do................................ Do. 

Quartz-porphyry ..... Eureka, Nev .......................... U.S. G. S., Mon. XX, 228. 

Granitite ............. Sykesville, Md ................. : .. ... Bull. 168, 47.-W. T. 

SUBRANG 4. ALSBACHOSE. 

(I. 3, 2, 4.) 

! Granite ...... : ........ Storgord, Finland .................... R. T.,l8G9, XL. 

, ..... do ................ Riesengebirge, SileshL ............... N. J,, 1898, XII, 233.-W. 1' . 

1 Granitite .................. do . . .. . . . . . .. . .. . .. .. . .. .. . • . . .. .. Do. 

I Als!Jachite ............ Melibocus, Odenwald ................ Rosenbusch, El., 207.-W. '1' • 

: Rhyolite .............. Waihi, Ranraki, New Zealand ....... Q. J. G. S., 1899, LV, 467.~W. T . 

I Granitite ............. Riesengebirge, Silesia ................ N.J., 1898, XII, 232.-W. T. I 

SUBRAl'IG 5. YUKONOSE. 

(I. 3, 2, 5.) 

I 'l'onn.lite-n.plite ....... j Yukon River, Alnska ................. , Bull. 168, 229.-W. T. 
lWCK AN~I~YSES USED IN CONSTRUCTING DIAGRAMS. 

silica 

content. 

Alkali-Rillcn 

ratio. 

Class(fied l:i.~t of nnaly.~P..~ u.~ed -in const1·ucting d:ia.gram.~-Continued. 

RANG ~- RIESENASE. 

SlJBRANG 2. --. 

(I. R, 3, ~-) 

Author's name. Locality .. Reference. 

72.11 . 0.041 "Sehliere" in granite !Uesengebirge,' Silesia ................ N.J., 1898, XII, 235.-W. T. 

71.14 .055 •roscanite ............. Rocca Strada, Italy ................... J. G., V, 363.-W. T. 

66.86 .052 Granite-porphyry .... Nieder Modan, Hesse ................. W. T. 

76.82 0.037 

75.27 . 036 

75,21 .048 

73.00 .049 

72.92 .040 

72.71 .038 

69.04 . 047 

71i.l3 ·I 0. 055 (76. 2) 

72.81 . 011 

72. 24. 0. Oii2 

66.99 . 051 

!\8. 871 0. 02R 

SUBRANG 3. RIESENOSE, 

(I. 3, 3, 3.) 

Gmnitite ............. Riesengebirgc, Silesia ................ N.J., 1898, XIT, 23:J.-W. T. 

Cirnnite . ..... ·,· .... _ ...... . do .......................... _ .... . 

Gmnitite .................. do ............................... . 

Toscrrnitc ............. Ro~ca Strad,a, Italy ...... _ ............ . 

Granit.itc .. .. .. .. .. .. . Riesengebirgc, Silesia ............... . 

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

..... <lo ----------------1-----do .............. _ ................ .. 

8UBRANCi 4. --. 

(I. 3, 3, 4.) 

Do . 

Do. 

J. G., V, 363.-W. T. 

N .. T., 1898, xn, 232.-W. '1'. 

Do . 

N.J., 1898, XII, 234.-W. T. 

I

I Grnnitc ....... -- .... --1 Riescngcbirgc, Silcsirr ......... ! ..... -1 N.J., 1898, XII, 233.-W. '!'. 

Gmnitite .................. do ................................ N . .!., 1898, XII, 232.-W. T. 

8UBRANG 5. VULCANOSE. 

(1. 3, 3, 5.) 

Quartz-diorite- p or- Calaveras County, Cal. ............... Hnll. 168, 203.-W. T. 

11hyry. 

Vnlcanitc .......... ,. Vnlcano, Upari ...................... B. G. S. A., V, 001.-W. '1'. 

RANG 4. ----. 

SUBltANG 2. --

(I. 3, 4, 2.) 

\ "S~:hliere" in granite\ Iiiescngebirge, Silcsia ................ N.J., 1898, XII, 235.-W. T. 

25 
26 CHEMJCAJ, COMPOSITION OF IGNEOUS ROCKS • 

. Clct8.~ified li~t of wnnlyses 11sed i:n const:ructing cUagramR-Continued. 

Silic~t · content. 

Alk~tli-silic~t 

ratio. 

0RDF.H 4. BRITANNARE. 

RANG 1. LrPARASE. 

SUBRANG 1. J,EBACHUSE. 

(I. 4, 1, 1.) 

AnLhor'R name. Loc~tlity. Reference. 

-----------------1-------------·1----------

69.06 0.117 (69.3) Qu~trtz-orthocl~tsitc ... Thliringerw~tld, 1'rn""i" .............. W. T. 

68.13 .107 Quartz-porphyry .... , Hummel berg, Prussia................ Do. 

SUBRANG 2. 0MEOSB. 

(I. 4, 1, 2.) 

75.20 0.096 Rhyolite ............. Silver Cliff, Colo ...................... Bul_l. 168, 149.-W. 'l'. 

75.07 .084 ..... do ..........•....• Pine Nut Canyon, Ncv ................ Fortieth Pnr., I, 652. 

74.62 .095 ..... do ................ Humboldt Sink Group, Nev .... •...... Do. 

74.24 .089 Rnpnkiwi ............ Livlnnd, Finland ..................... R. T., 1873, X. 

71.09 .112 Aplite................ Satteljoch; Prcdnzzo, 'l'yrol .. .. . .. .. . K. A. W. W., CXI, I, 266. 

70.91 .. 121 Gr~tphic granite ...... Omeo, Victoria ....................... Trans. R. S. Vict.-W. T. 

68.99 .115 Pitchstone .... .. . .. .. Ponza, Italy .......................... R. T., 1879, LII. 

68.87 .084 Granite ............... Omeo, Victoria ....................... Trans. R. S. Vict.-W. T. 

SUBRANG 3. LIP AROSE. 

(I. 4, 1, 3.) 

77.61 0.088 Granite ............... Cape Ann, Mass ...................... J. G. VI, 793.-W. '1'. 

76.49 .092 l'aisanite ............. Magnolia, Mass ........................ J. G. VII, 113.-W. T. 

76.33 .092 Graphic gmnite ...... Hochland. ............................ R. T., 1869, XJ,TI. 

76.30 .088 Alaskite .............. Alaskn ............................... Bull. 168, 228.-IV. T. 

76.20 .091 Obsidian ............. Obsidian Hill, N.Mex ................ Bull. 168, 172.-W. T. 

76.05 .092 Apliticgranophyre ... Konerudwege,Norway ............... Z. K., XVI, 77.-W. '1'. 

75.71 . 094 (75. {i) Rhyolite ............. Great Paint Pots, Yellowstone Park .. Bull. 168, 105.-W. T . 

75.4-1 .091 Comendite ........... Jskagan B~ty, Siberia ................. A. J. S., XII, 1902, 180.-W. T. 

75.44 .089 Rhyolite ............. FrSh Creek Mountains, Nev.......... Fortieth l'ar., I, 652. 

75.30 . 082 ..... do ................ Rimini, Mont ........................ Bull.168, 119,-'W."T . 

75.17 . 085 Granitite ............ _ Pikes Peak district, Oolo ............. -Bull. 168, 142.-W. T . 

74.90 -~ "Rhyolite .............. Castle'Monntain district, Mont ...... Bull. 168, 129.-W. T. 

74.87 . 084 Granite ............... Brookville, Md ....................... Bull. 168, 46.-W. T . 

74.76 . 098 Comendite • . • . . . . . • . • Comende, San Pietro, Sardinia....... Rosen busch, El., 257.-W. T . 

74.4.'; . 090 Rhyolite .............. Chalk Mountain, Colo ............... Bull. 168, 156.-W. T . 

74.05 .096 Obsidian • .. .. .. .. .. .. Mono Craters, Cal. ........... ,....... Bull. 168, 219.-W. 'l'. 

73.93 .100 Granite ............... Quincy, 1\fass ........................ i .r. G., VI, 793.-W. T. 

73.69 . 100 Granite-porphyry ..... Mount Ascutney, Vt ................. Bull.168, 25.-W. T . 

73.51 .094 (73.4) Granitite ............. Pikes Peak district, Colo............. Bull. 168, 142.-W. T. 

73.35 .106 Paisanite ............. Mosques Canyon, Tex ................ T. !If. P.M., XV, 439.-W. T. 

73.09 . 085 Granite-porphyry ..... Albany, N.H ......................... A. J. S., XX,1881, 25 . 

73.03 .104 Syenite-porphyry ..... Mount Ascutney, Vt .................. Bnll. 168, 24.-W. '1'. 

72.88 . 093 Aplite-granite ........ Castle Mountain district, Mont ...... Bull. 168, 129.-W. T . 

72.48 ,099 Granite .................... do................................. Do. 

72.35 . 093 ..... do ................ Ironton, Mo .......................... Bull. 168, 60.-W.·T . 

72.26 .101 ..... do ................ Albany, N.H ......................... A. J. S., XXI, 1881,25. 

72.06 .107 ..... do ................ Stony Creek, Conn ................... B. G. S. A.,){, 375.-W. T. 
' 

ROOK ANALYSRS USF.D IN CONSTRUCTING DIAGT{AMf:!. 27 

C'lrtR.~ffied l·ist of anaZIJse.~ u.~ed in C01Mf.ructi.ng diagramR-Continued. 

SUBRANG 3. LlPAROSE--Continued. 

Silica Alkali-silica 

\ 

eon- ratio. tent. Author's name. Loculity. Reference. 

------------------

71.90 .102 Granititc ............. :Mount Ascutney. Vt .................. Bull. 168, 24.-W. T. 

71.88 .095 Porphyry ............. Ironton, 1\'fo ..... : .................... Bull.l68, 60.-W. T. 

71.67 .101 Quartz-porphyry ..... Castle J\1ountain district, Mont ..... _ Bull. 168, 129~-W. •r. 71.56 .086 Pitchstone ............ Silver Cliff, Colo ...................... Bull. 168, 150.-W. T. 

71.49 . 109 Quartz-porphyry ..... Gislernd, Norway .................... Z. K., XVI, 46.-W. T . 

71.07 .087 Granite-porphyry ... , Albany, N.H .................... __ ,._ A. J. S., XXI, 1881,25. 

70.92 . 096 (70. 7) Rhyolite ............. U}P._~. Geyser Basin, Yellowstone _Bull. 168, 104.-W. •r. 

70.23 .113 Keratophyre ......... Marblehead Neck, Mass .... _ ..... -- .. Bull. 168, 34.-W. T. 

70.09 .092 Orthoclase-porphyry. Cornon, Tyrol. ....................... R. T., 1879, XXVIII . 

70.01 . 113 Obsidim1 .. .. . .. . . .. .. Palmerola, Italy...................... R. T., 1879, LII. 

69.91 .119 

69.89 .098 

68.95 .144 

68. 7l .114 

JEgiri~e-gmnite ...... 

1 

Miask, Ural J\Ionntains ........ , .... __ A. J. S., XIII, 1902, 180.-W. T. 

Rhyohte ............. Nathrop, Colo ........................ Bull. 168, 164.-W. T. 

Grnrudite ............ W. Aker, Norway ..................... E. K., J, 199.-W. T. 

Quartz-pantellerite .. Vieja :Mountains, San Carlos, Tex .... Bull. 168, 61.-W. T. 

68.65 .110 (68.5) Granite-Ryenite-por- Little Rocky :Mountains, Mont ....... Bull. 168, 134.-W. T. 

phyry. 

68.34 .129 Quartz-syenite ........ Bearpaw Mountains, 1Iont ........... Bull. 68, 135.-W. T. 

66.40 . 097 (66. 7) Quartz- syenite· por- Fjelebua, Norway .. _ .......... .'...... Z. K., XVI, 46.-W. T. phyry. 

. . SUBRANG 4. KAU,ERUDOSE. 

(I. 4, 1, 4.) 

75.92 0. 093 (75. 8-. 094) Granititc ·····--···--- Pikes Peak district, Colo .. _ ... _ ...•.. Bull. 168, 142.-W. T. 

7a.61 .089 Rhyolite ····-·····-·· Oyacachi, South America ... _ ..... _ .. R. T., 1879, :.rv. 73.50 . 095 (n. 8) Quartz- bearing 

tonitc. bos- Ampangarinana, Madagascar ........ M. M., 55. 

72.56 . 099 (72. 8) Hhyolit!c pitchstone . Castle Mountain district, ·Mont ...... Bull. 168, 129.-W. T. 

i2.46 . 09:, Rhyolite .............. Gnomani, Ecuador, South Ame-rica.-.. R. T., 1879, LIV. 

71.65 . 119 Soda granite .......... Hougnatten, Norway.-_._ ..... _ ... __ . K K., I, 198.-W. T. 

SUBRANG 5. NOYANGOSE. 

(I. 4, 1, 5.) 

77.60 

75.78 

0.087 (77.9-:086) Quartz-keratophyre .. Omco, Victoria ....................... ! Rosenlmsch, El., 260.-W. '1'. 

Rice Point, Duluth, Minn ............ ~ 21st Ann. Rept., si1rv. Minn.,41.- W.T. 

Berkeley, Cal. .•. _ ...... _ .... _ ..... _._ RosenbiL•ch, ~:1., 260.-W. T • 

.091 Grnnitc .............. . 

75.16 . 097 Soda-rhyolite.~ ...... . 

RANG 2. TOSCANASE. 

SURRANG 2. DEJ,LENOSE. 

(I. 4, 2, 2.) 

69.19 0.102 Granite ............... Tryberg Fall, Schwarzwald .......... N.J., 1883, II. 

68.36 .078 Dellenitc .. . : ......... Dellen, Helsingland, Sweden ........ K K., II, 59.-W. T. 

66.24 . 093 Toscanite .. • .......... J\1onte Cucco, Italy ................... J. G., V, 362.-W. T. 

65.19 .093 ..... do ................ Tolfa, Italy........................... Do. 
• 

28 

Siliea 

content. 

76.48 

76.03 

76.00 

75.97 

75.74 

75.08 

75.01 

74.95 

74.60 

74.49 

74.37 

73.84 

73.70 

73.64 

73.51 

73.38 

73.12 

72.57 

72.40 

71.85 

71.79 

71.78 

71.53 

71.12 

71.08 

70.87 

70.75 

70.56 

70.54 

70.45 

70.29 

69.96 

69.95 

69.94 

69.6~ 

69.52 

69.45 

68.88 

68.68 

68.60 

68.58 

68.55 

68.42 

68.40 

68.36 

67.45 

67.44 

67.12 

67.04 

66.60 

CHEMICAL OOMPOSI1'ION OF IGNJWUS ROCKS. 

Clcts~rijied li.<t of (tnaly~es 1.tsed in cvn~truding diagrmns--Continued. 

Alkali-silica 

ratio. 

0.087 

. 081 

. 087 

. 079 (76. J-.078) 

. 086 

.084 (75.0) 

.086 (75.1-. 088) 

. 088 

. 081 

.088 (74.6) 

. 085 

. 083 

• 092 

. 083 

. 097 

. 080 

. 087 

. 090 

. 086 

. 087 (72.0) 

. 082 (71. 7) 

• 085 

. 070 

. 098 

. 084 (71:0) 

.092 

. 080' 

.105 (70. 7) 

. 107 

.084 

. 101 

. 089 

. 098 (70.1) 

. 092 

. 087 

. 108 

. 097 

. 100 

.077 

.107 (68. 7) 

.100 

.095 

. 083 (68.2) 

.112 (68.2) 

. 10.'\ 

.084 

.104 

• 082 

.107 

.111 

Author's name. 

Aplite .....•.........• 

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

Granodiorite-aplite ... 

Aplite ................ 

Granite ............... 

Obsidian ....... ----- Alaskite ..... _ ........ 

Rhyolite .. : ........... 

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

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

Granitite ............. 

Rhyolite-perlite ...... 

Granite ............... 

Rhyolite .............. 

Obsidian ............. 

Granite ............... 

Quartz-porphyry ..... 

Gmnite ............... 

Rhyolite .............. 

..... do ............... : 

Granitite ............. 

Granite ............... 

Granitite ............. 

Rhyolite .............. 

Granodiorite ......... 

Rhyolite ...... · ........ 

Granite ............... 

Rhyolite .............. 

JEgii~te-gmnite ...... 

Granite ............... 

Rhyolite ....•......... 

Dacite ...•...•........ 

Quartz-porphyry ..... 

Granite ............... 

Granite-porphyry .... 

l'rachyte ............. 

Rhyolo-trachytc ...... 

Quartz-syenite-purphyry. 

Granite ................ 

Granite-porphyry .... 

Granite ... _ ........... 

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

Quartz-monzonite .... 

Granite ............... 

Nordmarkite ......... 

Granodiorite ......... 

Granite-syenite- p or- phyry. 

Granite ............... 

Quartz-syenite -por- phyry . 

Akerite ............... 

SUBRANG 3. ToSCANOSE. 

(I. 4, 2, 3.) 

Locality. 

Dargo, Victoria ....................... 

Sierra, Co'unty, Ca.1. .. ................... 

Downieville area, Cal ................ 

Sierra County, Cal. ................... 

Lier, Norwu.y ......................... 

Lagunn cle l\h.ricunga, Chile . ........ 

Alaska ................................ 

Montezuma Mountains, Nl~Y ......... 

Shasta County, Cal ................... 

Thomas Range, Utah ................. 

Crazy llfountains, Mont .............. 

l\Iidway llnsin, Yellowstone Park .... 

Peterhe11d, Scotland.: ................ 

L11ssen trail, Tehama County, Cal. ... 

Modoc County, Cal. .................. 

L11ke Rasl11ngen, Sweden ............ 

Little Belt Mountains, Mont ......... 

Guilford, Md ......................... 

Mount Stover, Cal. ................... 

Tower Creek, Yellowstone'rark ...... 

Woodstock, Md ....................... 

Cottonwoocl Canyon, Utah ..........• 

Riesengebirge, Silesia ................ 

Ponza, Italy .......................... 

El Capitan, Yosemite, Cal. ........... 

Pennsylvania Hill, Silver Cliff, Colo~ 

Amador County,. Cal ................. 

Ponza, Italy .......................... 

Luken, Norwttr ...................... 

Dorseys Run, l\Id ...... , .............. 

Harlequin Canyon, Nev .............. 

Washoe, Nev ......................... 

Butte district, Mont .................. 

Ironton, Mo .......................... 

Little Belt Mountains, Mont ......... 

Pikes Peak district, Colo ............. 

Sunset Peak, Mont ................... 

Squam Light, MtiSS ................... 

Eureka, Nev .......................... 

Little Belt Mountains, l\Iont .......... 

West Humboldt Mountains, Nev ..... 

Shap, England ....................... 

Hailey, Idaho ........................ 

l\Iillstone Point, Conn ..............•. 

Gloucester, Mass ...................... 

Eldorado Canyon, Cal ...••.....•..••. 

Little Belt Mountaii!s, Mont ......... 

Boulder, Mont ........................ 

Little ·Belt Mountains, l\Iont ......... 

Gloucester, Mass ...................... 

Reference. 

1'rans. R. S. Vict.-W. '1'. 

Bull. 168, 19'2.-W. T . 

J. G., VII, 160.-W. 'f. 

Bull. IuS, 192.-W. 'r. 

Z. K., XVI, 77.-W. T. 

Z. D. J., G. LI, 4. 

Bull. 168, 228.-W. T. 

Fortieth Par., I, 652. 

Bull. 168, 178.-W. '1' . 

Bull. 168, 168.-W. T. 

Bull. 168, 120.-W. T. 

Bull. 168,108.-W. T. 

R. '1'., 1884, XIV. 

Bull.168,178.-W. '1'. 

Bull. 168, 217.-W. T. 

W.T. 

Bull. 168, 125.-W. T. 

Bull.168,46.-W.T. 

Bull. 168, 178.-W. T. 

Bull. 168, 104.-W. T. 

Bull. 168, 46.-W. T. 

Fortieth Par., J, 110. 

N.J., 1898, XII, 232.-W.T. 

R. T., 1879, LII. 

Bull.168,207.-W. T. 

Bull. 168, 149.-W. '1'. 

Bull. 168, 200.-W. T. 

Z. K., XVI, 57.-W. T. 

llull. 168,47.-W. T. 

Fortietll Par., I, 652. 

llull. 168, 174.-W. 1'. 

Rull. 168, 119.-W. T. 

Buli.168,60.-W.T. 

Bull. 168, 125.-W. T . 

Bull. 168, 145.-W. '1'. 

Bull. 168, 106.-W. T. 

J. G., VII, 109,-W. T. 

U.S. G. S., Mon. XX, 228. 

Bull. 168, 125.-W. T. 

Fortieth Par., I, 110 . 

Q. J. G. S., 47, 276 

Bull, 168, 137.-W. 'f. 

B. G. 8. A., X, 375.-W. T. 

J. G., VI, 800.-W. T. 

Bull. 168, 199.~W. T. 

llull. 163, 127.-W. '1'. 

Bull. 168, 118.-W. T. 

Bull. 168, 127.-W. T. 

J. G., Vl, 798.-W. T. 
ROCK ANALYSES USED IN CONSTRUCTING DIAGRAMS. 29 

ClWJsified list of a-nalyses used in comtructing diagrams-Continued. 

SURRANG 3. ToSCANOSE-Continucd. 

Silica Alkali-silica con~ ratio. ·tent. Author's name. Locality. Reference. 

----·---------·-----------------------

66.12 . 123 (66.3) Trachyte ............. Wieber Mountain, Colo .............. Bull. 168, 145.~W. T . 

65.58 . 094 ..... do ................ Monte Amiata,.ltaly ................. Rosen busch, El., 269.-W. T . 

65.32 . 096 ..... do ..................... do................................ Do . 

65.05 . 092 Toscanite .................. do ................................. J. G., V. 362.-W. T . 

64.76 . 094 Trachyte .................. do ................................ Rosen busch, El., 269.-W. '1' . 

64.64 .114 (64. 5) Syenite .... · ........... Little Belt ~Iountuins, Mont ......... BulL 168, 125.-W. T. · 

64;62 . 118 Diorite ............... Mount Ascutney, Vt .................. Bnll.168, Z,'i.-W. T . 

64.57 . 095 Toscanite ............. Br.icciano, Italy ...................... J. G., V,362.-W. T . 

64.49 . 103 Porphyrite ........... Cmzy 1\lountotins, Mont .............. Bull.l68, 120.-W. T . 

62.33 . 110 Latite ................ Cl~~f.r Meadow, Tnolnmne County, Bnl\.168,205.-W. '1' • 

SURRANG 4. LASSENOSE. 

(I. 4, z,.L) 

----------c-------~-c----- --·-------..,.---------------'-

75.50 0.083 Rhyolite ............. Obsidian Cliff, Yellowstone Park .... Bull.168, 104.-W. T. 

73.27 . 077 Granite ............... Florence, 1fass ....................... Bull.168,30.-W.T . 

. 73.00 . 075 ..... do ................ Rocklin, Cal. ......................... Bull.168,l98.-W. T . 

72.59 . 083 Obsidian ............. Willow Park, Yellowstone Park ....... Bnll.168, 104.-W. T . 

71.74 . 075 Granitite ............. Riescngebirge, Silesia ................ N .. 1., 1898, XII, 282.-W. T . 

71.19 . 073 Quartz-porphyrite .... Calaveras County, Cnl. ." .............. Hull.l68, 203.-W. T . 

70.36 . 082 Graiwdioritc ......... Enterprise, Butte County, Cnl........ Bull.168, 190.-W. T . 

69.93 . 109 Granite-porphyry .... Crazy Mountnins, Mont .............. Hull. \68, 120.-W. T . 

69.66 . 084 Dacite .. : ............. Lassen Peak,.Cal ..................... Fortieth Par., I, 652 . 

69.56 . 076 ..... do ................ Colombia, South America .... :....... J. G., 1,171.-W. T . 

69.51 . 083 ..... do ................ Lassen Peak, Cal ..................... Bull.168,179.-W.T . 

69 .. 00 . 126 Quart>-lindoitc ....... W. Aker, Norway ... : ................. E. K.,I;-198.-W.T . 

68.72 .084 (68.8) Dacite ................ La"en Pcotk, .Cal ..................... Bnll.168, 180.-W. '1'. 

68.65 . 084 Quartz-monzonite .... Sierra County, Cal .................... Bull.168, 192.-W. T . 

68.32 . 086 Dacite ................ Lassen Peak, Cal .. · ................... Bull.168, 179.-W. T . 

68.10 . 088 ..... do ........ ~ ....... Shasta County, Cal ................... Bull.168,180.-W. T . 

67.89 . 088 Andesite ............. Buntin·gville, Cal. .................... Bul1.168, ISL-W. T . 

67.55 . 087 (67.2) Pitchstone ............ Butte district, Mont .................. Bull.168,119.-W. T . 

67.49 .085 (67.6) Dacite ................ Sepulchre Mountain, Yellowstone Bull.l68, 91.-W. T. 

Park. 

67.49 .112 Mica-dacite .......... Silver Cliff, Colo ... , .................. Bnll.168, 149.-W. T. 

67.42 .116 Augite-soda-granite .. Kekeqtutbie Lttke, :Minn ............. A. G., XI, 385.-W. T. 

67.01 .120 Alaskite-porphyry .... Alaska ............................... Bull. 168, 228.-W. T. 

66:46 .104 Dacite ................ Rosita, Colo ............... , .......... Bull. 168, 149.~W. T. 

66.30 .098 Dacite-porphyry ...... Shasttt County, Cnl................. ... Hull. 168, 177.-W. T. 

66.28 .094 {66.5) Porphyrite ............ Crazy Mountains, Mont .............. Bull. 168, 120.-W. T. 

6~.H7 . 099 Feld,par-porphyry . . . Castle Mountain district, Mont....... Hull. 168, 130.-W. T . 

65 .. 78 . 121 Mica-andesite ........ San Mateo Mountain, N. 1\lex.· ....... Bul\.168, 170.-W. T . 

65.64 .108 Ande,ite-porphyry ... Gray Peak, Yellowstone Park ........ Bull. 168, 107.-\\'. T. 

64.98 .109 Oligoclasite .......... Preston, Norway ..................... B. M.A., 1898, VII, •17.-W. T. 

62 .. 58 . 109 Syenite-porphyry ..... Yogo Peak, Mont ..... : ............... Bull. 168, 127.-W. T . 

SUBRANG 5. MARlPOSOSE. 

(I. 4, 2, 5.) 

74. 21 I 0.100 

67.88 .084 (67.8) 

I 

S•oda-.granite ......... ! Mariposa ~onnty, Cal .. ;·:·--·_- ...... 1 B~tl,l: 168, 207,:_W. '1'. 

G-ranttc. ~-~ .......... _ Cavaura Rtver, Bnt1sh lTUlantL .. •• __ . ''. I. · 
30 CHEMICAL COMPOSITION OF IGNEOUS ROCKS. 

ClWJsijied list of analyses used -in constructing diagrams~Continued. 

RANG 3. CoLOHADAs~;. 

SUHlL-\Ntf 3 .. .AI\UATOSE. 

(I. -1, 3, 3.) 

Silic!t Alkali-silica con- ratio. tent. Author's name. Locality. Reference. 

1------1--------1-~-------~--1------------

68.97 0.075 

6,';,53 .085 

65.36 . 085 

65.13 • 082 

63.17 .088 

61.93 . 085 

68.41 0.084 

68.10 .065 

68.12 .078 

67.30 . 075 

66.94 .070 

66.65 .C82 

66.65 .074 

65.71 .065 

65.66 . 072 

65.63 .080 

65.60 .086 (65. 7) 

64.85 . 084 

64.61 • 088 

64.52 .080 

64.48 . 076 (64. 7). 

64.27 .081 

64.24 . 07~ (64.1) 

63.81 .079 

63.42 .098 

63.30 .087 

62.91 .094 

62.85 .085 

61.42 .078 

69.66 0. 074 

69.34 . 066 

65. 81 I 0. 047 

Granite .•............. Lower Elsass, Vosges ................. Rosen busch, El., 78. 

Trachyte •...•........ l\Iont'e Amiatc, Italy . . . . . . . . . . . . . . . . . Rosen busch, El., 269:-W. T. 

Quartz-porphyrite .... l\Iuunt Cllrbon, Colo .................. Bull. 168, 160.-W. 'l' . 

Andesite-perlite .••.•. 

1 

Eurekll, Nev .......................... U.S. G. S., l\Ion. XX, 264.-W. T . 

Dacite ................ Pergamon, Asia Minor ............... A . .1. S., III, 1897, 45.-W. T. · 

Andesite ............. Kara Tush, Asia Minor ............... A. J. S., III, 1897, •15.-W. T . 

SUBRANG 4. YELLOWSTONOSE. 

(I. 4, 3, 4.) 

Dacite ................ Colombia, South America ............ J. G., I, 171.-W. 'l'. 

Diorite .. .. .. . . .. .. . .. Ono, Cal.............................. Bull. 168, 177.-W. T. 

Andesite ............. Shasta County, Ca.l .... _ .............. Bull. 168, 183.-W. T . 

·Dacite ................ Colombia, South America ............ .1. G., I, 171.-W. T. 

Andesite ............. Sierra County, Cal. ................... BulL 168, 193.-W. T. 

Quartz-diorite- ..... do ................................ l:!ull.16S,192.-W.T. 

porphyry. 

Granodiorite ......... Nevada City, Cal ..................... BulL 168, 194.-W. T. 

Banatitc ............. ·. Banat, Hungary ...................... Rosenbusch, EL, 140. 

Dacite ................ Sepulchre Mountain, Yellowstone BulL 168, 91.-W. T . 

Purk. 

Andesite .............. Fan Creek, Yellowstone Park ........ Hull. 168, 107.-W. T. 

Quartz-mica-diorite .. Electric Peak, Yellowstone Park ..... Bull. 168, 88.-W. T. 

..... do ..................... do .................. :............. Do . 

Andesite ............. Crescent Hill, Yellowstone Park ..... Bull. 168, 108.-W. T • 

..... do ................ Mount Shastu. Cal. ................... Hull. 168, 176.-W. T. 

..... do ..................... do................................ Do . 

..... do ................ Sepulchre l\fountain, Yellowstone BulL 168, 91.-W. T. 

Park. 

Dacite-porphyry ...... Shasta County, Cal. .................. Hull.168, 177.-W. T. 

Ducite................ Mill Creek, Shasta County, Cui....... Bull. 168, 180.-W. T. 

Qua r tz-d i o ri tc- Crandall Basin, Wyo ................ , Bull. 168, 94.-W. T. porphyry. 

Andesite ............. Mount Ruse, Washoe, Nev ......... .. 

Granitite ............. Dorscys Run, l\Id ................... .. 

(?) Porphyrite-diorite Mount llfurcellina, Colo ............ .. 

Porphyrite . .. .. . .. . .. Storm Ridge, Colo .................. .. 

SURRANG 5. AMADOROSE. 

(I. 4, 3, 5.) 

Fortieth Par. I, 604. 

Bull. 168, 47.-W. T. 

Bull. 168, 160.-W. T. 

Do. 

Quartz-diorite-aplite. Amador County, Cui ................. Bull. 168, 201.-W. T. 

Granite ............... Sagunaga Lake, l\Iinn ................ 21st Ann. Rept. Geol. Surv. Minn., 

43.-W.T. 

RANG 4. ---. 

SuBRANG 3. --. 

(I. 4, 4, 3.) 

I. 

Granite ............... , Hochwald, Vosges .................... , Rosenbusch, Steiger Schiefer· 

(Strassburg, 1877), 167. 
ROCK ANALYSES USED I~ CONSTRUCTING DIAGRAMS. 31 

Clasmjied ti8f uf analyses 1tsed in constructing diagrams-Continued. 

ORDER 5. CANADARE~ 

RANG 1. NoRD)tARKASE. 

SUBRANG 3. PHLEGROSE. 

(1. 5, 1, 3.) 

Silica Alkali-silica. COil~ 

tent. ratio. Author's name. Locality. Reference. 

--------

66.13 0.130 Quartz-syenite ........ Fjelebua, Norway .................... Z. K., XVI, 46.-W. T . 

66.03 . 132 (6.'i.9) 1'mchytc ............. Game Ridge, Custer County, Colo .... BulL 168, 117.-W. T. 

65.43 .13l Syenite ............... Mount Ascutney, Vt .................. Bull. 168, 24.-W. T. 

64.88 .128 

64.04 . 160 

Syenite-porphyry ......... do ....•...................... -····\ Bull. 168, 25.-W. T. 

Nordmarkitc, ......... Tonsenas, Norway ...........•........ Z. K., XVI, 54.-\V. T . 

63.71 . 159 Pulaskitc ...........•• Salem Neck, Mass .........•...•...... J. G., VI, 806.-W. T . 

62.30 . 142 Bostonite ............. Gran, Norway ..•.•.•............•.... E. K., III, 204.-W. T . 

61.92 . 151 Pulaskite............. Lokobe, Madagascar.................. M. M., 204 . 

61.88 . 176 Trachyte ............. Marecocco, Italy..................... A. J. s., VIII, 18~9, 289.-W. T . 

61.62 . 170 (61. 2) .•... do ................ Monte Rotaro, Italy.................. Do . 

61.45 . 143 (61. 3) ..... do ................ 1\laros,Celebes .• , .....•••............. G. c., 16 . 

61.05 . 166 Solvsbergite .......... Coneylsland, Mass ................... J. G., VII,ll8.-W. T . 

60.33 .193 Trachyte ............. Monte NiiOvo;Itttly .................. A: J. S., VIII, 1899, 287.-W. T. 

60.13 . 165 Nephelite-sycnite .... Fourche Mountain, Ark ......... .' .... J. G., IX, 610.-W. T . 

60.02 . 147 Syenite-keratophyre. Harz Mountains .................... :. R. T., 1884, XXII . 

59.79 . 186 Trachyte, ............ 1\IonteNuovo, Italy .................. A. J. S., VIII, 1899, 287.-W. T . 

59.70 . 164 N ephe!ite-s)·cnite .. . . Fourche Mountttin, Ark.............. I. R. A., 88.-W. T . 

58.75 . 176 Umptckite ........... Cotbol>'rio, Brazil ..................... T. M.P. M., XX, 24g.-w. T . 

57.18 . 171 Trachyte ............. Highwood Mountains, Mont ......... Bull. 168, 131.-W. T . 

SUBRANG 4. NORD>IARKORE. 

(I. 5, 1, ·1.) 

66.50 0.162 Lestiwurite ........... Kvelht, Norwtty ...................... E. K., III, 216.-W. T. 

66.22 .1-19(60.4) Q.nurtz-syenite- par- Re11rpaw Mountains, Mont ........... Bull.168,135.-\v. T. 

phyry. 

66.06 .1iib Liparite ... _ .......... Hoben burg, near Bonn, Prnssitt...... R. T., 1884, XLVIII. 

6n.51 . 143 Phonolitic andesite .. San Mateo Mountains, N.Mex ....... BulL 168, 170.-W. T . 

65.43 .140 (65.1) ):<ordmttrkite .......... Shefford Mountain, Quebec ........... r. G., XI, 271. 

64.92 . 146 Quartz-solvsbergite ... Gran, Norway.: ...................... E. K., I, 78.-W. T . 

64.54 . 1.57 

64.33 . 151 . 

63.76 . 161 (63.4) 

63.20 . 161 

I 

P•:la~kite .... :··· ...... Lovasbucht, Norway ................. E. K., Ili,198.-W. T . 

Acmote-trach)tc ...... Cmzy Mountains, Mont .............. Bull. 168, 123.-W. T . 

Syenite ....... ; ....... Ahvenvaara, Finland ...... · .......... B. C. G. F.,ll, 34.-W. 'f . 

Nordmarkite ......... Tonsenas, Norway.................... Z. K., XVI, 54.-W. 'f . 

63.09 . 164 (63.6) l'ulttskitc •............ Sttlem Neck, :I! ass ..................... 1. G., VI, 806.-W. T . 

62.1J .156 Acmite·trachyte ...... Crazy Mountains, 11ont .............. Bull.168, 123.-W. 'f. 

61.67 1 . 169 Keratophyre ......... Harz Mountains ...................... R. 'f., 1884, XXII . 

61.54 .180 Phonolite .. ___ ....... Zittau, Saxony ....................... R. T., 1861, 23. 

61.08 . 185 ..... do ................ Black Hills, S.Dak ................... A. J. S., XLVII, 189<!, 344.-W. T . 

60.39 . 184 Litchfieldite ...... : ... Litchfiel<l, Me ........................ Bul1.168, 21.-W. T . 60.11 . 161 (59. 9) Rostonite ............. Hedrum, Norway .................... E. K., lii, 204.-W. T . 

60.05 . 157 (60. 3) Tingnaitc ............ Gales Point, Mass .................... J. G., VTI, 481.-W. T . 

59.62 . 173 Nephclite-syenite .... Snline County, Ark ................... I. R. A., 135.-W. T . 

.'i9.31 . 174 Foraite ............... Greut Haste Island, Mass ............. J. G., VII, 481.-W. T . 
CHEMICAL COMPOSITION OF IGNEOUS ROCKS. 

Classified list of analyses use(l ·in con8trttcting diagrams-Continued. 

8iliea 

content. 

Alkali -silica 

ratio. 

67.53 0.165 

66.09 .162 

58.48 0.16/i 

58.21 .142 

57.32 • 156 

55.17 • 150 

65.54 0.135 

62.64 . II9 

61.87 .145 

61.55 .141 

60.89 .131 

60.20 .165 

60.03 .154 

59.51 .158 

59.23 .149 

57,15 .149 

56.45 . 175 

55.52 .146. 

65.41 0.139 

64.80 .125 

64.63 . 132 

63.49 . 133 

61.47 . 120 

61.43 . 133 

61. 0.5 . 147 

60.98 . 142 (59, 9) 

60.72 . 142 

60.45 . 168 

60.24 . 170 

59.96 . 165 

59.:l8 . 125 

58.94 .109 

58.88 .141 

58.82 .155 

57.59 .139 

57.44 .157 

8UBRANG 5. TUOL!TMNOSE. 

(I, 5, I, 5.) 

An thor's name. Locality. Reference. 

Albitite ............... Tuolumne County, Cal ...... ·' ....... Rull. 168, 204.-W. T. 

..... do ................ Koswinsky, Untl 1\Iountaius .......... 0, N., 169. 

RANG 2. PtJLJI.SKASE. 

SUBRANG 2. VULSINORE, 

(I. fi, 2, 2.) 

Lencitc-tracbyte (?) . ·I Rocca 1\fonfina, Italy ................ . 

Vulsinite ............. Bolsena Monfina, Italy .............. . 

..... d~) .. _ .............. / Vetrella, Italy ...................... .. 

LenCite-trachyte ..... 

1 

San Rocco, Italy ..................... . 

SUBRANO 3. PULASKOSE. 

(I. 5, 2,"3.) 

J. G., V, 370-W. T. 

.T. G., V, 358.-W. T, 

Do. 

J. G., V, 370.-W. T. 

Quartz-syenite........ Highwood llfountains, Mont......... W. T. 

Andesite(?) .......... Pikes Peak di,trict, Colo ............. Bull. 168, 145.-W. T . 

Tr{tchyte ............. Ischia, Italy .......................... R. T., 1873, XXXVIII. 

..... do ..................... do . .. . .. .. .. .. . . .. . .. .. .. .. .. . . .. . R. T., 1873, XXXVI. 

Quartz-banakite ...... Ishawool). Canyon, Wyo .............. Bull.l68, 102.-W. T. 

Pulaskite ............. Fourche Mountain, Ark .............. J. G., IX, 609.-W. T. 

..... do ..................... do ................................ I.R.A.,88.-W.T. 

Leucitc-tracllyte..... Viterbo, Italy ........................ J. G., V, 370.-W.1'. 

Nephelite-syenitc .... }'ourehe Mountain, Ark .............. I. R. A., 88.-W. T. 

Trachy-dolerite . .. . .. Mttros, Celebes .............. , ....... ,. G. C., 14. 

Soda lite-syenite . . • . . . Square Butte, Mont.................. Bnll.l68, 134.-W. T . 

Bostonite ............. Gcntungen, Celebes .................. G.C.,20. 

SUBRANG 4. LAURVIKOSE. 

(I. 5, 2, 4.) 

Trachyte ............. Game Ridge, Custer County, Colo .... Bull.l68, 147.-W. T. 

Domite ............... Puy de Dome, France ................ R. T., 1869, CX.VIII. · 

Quartz-syenite ........ Fourche 1\fountain,.Ark ..... "·: ...... , T. R. A., 96.-W. T . 

Andesite....... . . . . . . Custer County, Colo.................. BulL 158, 148.-W. 1' • 

..... do ................ Pantellaria, Italy ..................... Z. K., VIII, 155 . 

..... do ..................... do ................................ Z. K., VIII, 164 . 

Trachyte............. Ischia, Itttly.......................... R. 1'., 1873, XXXVIII . 

Augite-porphyrite .... Henry llfountains,-Utah .............. Bull.168, 167.-W. T . 

Rhombenporphyry ... Notterii, Norway ..................... z. K., XVI, 35.-W:. T • 

Nordmarkite ......... Aneriid,Norway ...................... Z.K.,XVI, 54.-W.T • 

Augite-andesite . . . . • . Pantellaria........................... Z. K., VIII, 155 . 

Puhtskite ............. Sheffordllfountain, Quebec .......... J.G.,XI,271 . 

Ti:insbergite .......... Tonsberg, Norway .................... E. K., iii, 375.-W. T . 

Andesite .............. Silver Cliff, Colo ...................... Bnll.l88, 148.-W. T. 

Luurvikite ........... Laurvik, Norway ..................... Z. K., XVI, 30.-W. T. 

Rhombenporphyry ... Tiinsberg, Norw~ty ................... z. K., XVI, 35.-W. T. 

..... do ...... , ......... Notterii, NorwttY,..................... Do. 

PUlaskite ............. Mount Johnson, Quebec ............. J. G., XI, 271. 
ROOK ANALYSES USED IN CONSTRUCTING DIAGRAMS. 33 

Classified list of analyMs used in constructing diagrmns-Continued. 

SUBltANG 4. LAURVIKROSE-Continued. 

---.--------,--------------,--------------------,-----------

Silica Alkali-silica con- mtlo. tent. 

57.as . 153 (57.1) 

57.12 .138 

56.85 .144 

56.25 .155 (55. 9) 

56.19 • 156 

'54.00 . 162 

62. 90 I o. 135 

60.13 .164 

Author's name. Locality. Reference. 

Rhombenporphyry ... Nottero, Norway ..................... Z. K., XVI, 35.-\V. T . 

L11urvikite ........... Fredriksviim, Norway ............... Z. K., XVI, 30.-W. T. 

..... do ........ _....... Nottero, Norway .. .. .. .. .. .. . .. .. .. .. Do. 

Micromonzonite ...... Ambodimadiro, Madagascnr ......... M. 1!., 204. 

Tcphritic trachyte .... Columhretcslslands, Spain .......... T.l\I. P.M., XVI, 314. -\\'. T . 

Rhomhenporphyry, .. Brumunthal, Norway ................ Z. K:, XVI, 28.-W. T . 

SUBRANG 5. --. 

(I. 5, 2, 5.) 

I 

Diorite ............... \ Jahlanica, Herzegovina .......... -.. :.! W.T. 

Keratophyre_ .......... New Haven, Conn ................... A. J. S., III, 1897, 291.-W. T. 

RANG 3. ---. 

SUBRANG 2. --. 

(I. 5, 3, 2.) 

59.331 0.135 (59. 5) ~ugite:;::~~~Fa::~i district, British Guiana .. --I W. T. 

-----~-------~-------

59. 261 0.139 

58.281 0.1!2 

55.01 0.086 

54.62 . 098 

54.45 .122 

53.53 . 090 (53.6) 

53.43 . 099 

53.42 . 096 

52.61 . 092 

49.78 . 091 

47.2~ .056 

47.32 0.048 (47.4) 

46.24 .044 

45.78 .036 

SUBRAi-W 3. --, 

(I. o, 3, 3.) 

\Andesite ............. , Table Monntain,-Colo ................ j Bull. 168, 141.-W. T. 

SUBRANG 4. --. 

{I. 5, 3, 4.) 

I Diahase-porphyrite ... , Crazy Mountain~, Mont········-·····! Buil.168, 121.-W. T. 

RANH 4. LAHRADORASE. 

SUBRANG 3. LARRADOROSF.. 

{I. 5, 4, 3.) 

Anorthosite .......... Turtschinka, Wolynien, Russia ...... W. T. 

..... do ................ New York State ...................... N.J., 1893, VITI, 494 . 

..... do ................ Rawdon, Canada..................... Do. 

..... do ................ PokoHi., Finland ...................... W. T . 

..... do ................ Labrador, Canada .................. ~. N.J., 1893, VIII, 494.-W. T . 

..... do ................ Ogne, Norway ........................ B. M.A., 1896, V, 96.-W. T . 

..... do ................ Ekersund, Norway ................... B. l\L A., 1896, V, 79.-W. T . 

..... do ................ Carlton Peak, 1\linn .................. Am. Geol., XXVI, 281.-W. T . 

..... do ................ Beaver Bay, Lake Superior ........... U.S. G. S., Mon. V, 438. 

RANG 5. CANADASE. 

(I. 5, 5.) 

Anorthosite . . . . . . . . . . South Sherhrooke, Ontario........... Am. Geol., XXIV, 280.-W. T. 

..... do ................ Seine River, Canada .................. J. G., IV, 909.-W. T. 

..... do ................ l\Ionhegan Isle, Me ................... Am. Geol., XXVI, 340.-W. T. 

14474-No. 18-03-3 
34 

Silica I conlent.· 

60.42 

59.20 . 

58.89 

58.72 

58.00 

55.87 

55.38 

53.56 

53.09 

CHEMICAl~ COMPOSITION OF IGNEOUS ROCKS. 

• 

Clas8ijied list of analyses tlsed in constructing diagrams-Continued. 

Alkali-•ilica ratio. 

0.184 

. 189 (59.1) 

. 180 

. 199 (fi.~. 8-. ~00) 

. 199 

'201 (.'\fi. ~) 

.207 

. 229 (53.1) 

. ~26 

·ORDER 6. RussARE. 

RANG l. MIASKASE. 

SUBRANG 3. BEEMEROSE. 

(I. 6, 1, 3.) 

Author's name. Locality. Reference. 

----------------~----(-----------

Nephelite-syenite .... ·Moita, Foya, Portugal. ............... 'l', M.P. lll., XVl, 225.-;--W. 1'. 

.Microditroite ......... Nosy Komba, Mttdagasear ............ M. M., 169. 

Leucite-tinguaite- Picota, Portugal. ..................... T.M.P.l\f.,XVI,252.-W.;r . vitrophyre. 

Ditroite ......... _..... Nosy Komba, llfadagn•car............ l\L l\L, 204 . 

Phonolite ............ l\Iaros, Celebes ....................... G. C., 18 . 

Leucite-phonolite .... Lake Bmcciano, Italy ................ J. G., V., 370. -W. '1'. 

Foyaite ............... East Cape, Siberia.................... A. J. S., XIII, 190'2, 176. -W.T. 

Nephelite-syenite .... Becmerville, N.J ..................... Bnll.lG8, ~9. -W. T. 

Jcoyaite ............... Magnet Cove, Ark .................... J.G.,IX,G1l.-W.T. 

SUBRANG 4. MIASKOSE. 

(I. 6, l, 4.) 

60.02 0. 202 

59. as .189 

Phonolite ............ Cripple Creek, Colo .... _ ................ Bull.168, 143. -W. T. 

Trach ytic phonolite ...... .do .. . .. . . .. .. .. .. .. .. .. .. . .. .. .. .. Bnll.168, H4.-W. T. 

59.00 

58.98 

58.78 

58.77 

58.74 

58.70 

58.64 

58.62 

58.61 

. '>8.61 

58.51 I 58.25 

58.20 

58.10 

57.86 

56.75 

56.67 

56.43 

56.40 

50.30 

56.26 

55.95 

55.93 

55.92 

55.21 

55.01 

54.92 

54.22 

54.20 

53.95 

53.65 

52.73 

.. 196 

. 219 

. 213 

. 211 (59.1) 

l'lwnolite .· ................ do ................................ Bull.l68,143.-W.T. 

..... do ..................... do................................. Do . 

..... do ..................... do................................ Do .. 

Foraitc ............... Salem Neck, Mass ..... : .............. J. G., VII,481.-W. T • 

. 205 Nephelite-syenite .... Salina County, Ark ................... I. R. A., 139. -W.T. 

.190 Acmite-trachyte .... :. Crazy Mountains, Mont .............. Bull.168,123.-W.T. 

.195 (.196) Phonolite ............ Cripple Creek, Colo ................... Bull.168,143.-W. T. 

.191(58.5-.1!\e) .... _.do ................ NosyKomba,M~tdagascar ............ M.l\L,169. 

.194 (58.3) Foyaite ............... Heum, Lougenthal, Norw~ty ......... E.K.,III,3i7.-W.T. 

.21il(58.5) ..... do ................ NosyKomba,Jifuda$'ascar ............ l\L11I.,169 . 

. 216 (58. 2) Phonolite ............ Velay, France ........................ R. '!'., 1879, LVIII. 

.197 (57. 7) Microfoyaite ......... Nosy Kmnba, M~tdagascar ............ M.lii., 169. 

.190 I Ditroite .................... do .. .. . .. .. .. .. .. .. .. .. .. .. .. .. .. . Do. 

.191 (57.9) ..... do ..................... do ................................ 11Llii.,204. 

.214 (57.8) Phonolite ............ Black Hills, S.Dak ................... Bull.l68, 84.-W. T. 

.228 

. 226 (56. 3) 

. 195 (56. 3) 

. 201 

. 235 

.199 (56. 8) 

.256 

. 203 (55. 6) 

. 198 (f>'i. 8) 

. 226 

.211 

• 243 

. 224 

.237 

.246 

• 231 

.202 

Tinguaite ........ : ... Pickards Point, Mass .................. T. G., VII, 481.-W. •r. 

Nephelite-syenite .... Picota, Portugal.. ....... : ............ T.l\1. P.lii., XVI, 228.-W. T . 

·Phonolite ............ lleg!m, Germany ..................... R. T., 1884, LIV . 

Nephelite-syenite .... Poutelitschorr, Kola, Finl~tnd ........ Rosen busch, El., 126.-W. T . 

Ditroite .............. Ditro, Siebcnburgen, Hungary ....... Rosenbnseh, El., 126 . 

Miascite.............. Mount Sobatchia, Siberia .. .. .. .. . .. . W. T. 

Phonolite .. .. .. .. . .. . Borczen, Bilin........................ R. T., 1869, XCVI. 

Trachytic phonolite .. Columbretesislands .................. T. M.P. 1\I., XVI, 314.-W. T . 

Phonolite ............ Hegau, Germany ..................... R. T., 1884, LIJ . 

..... do ..................... do............................... R. T., 1879, LVIII. 

..... do ..................... do ................................ R.T.,l884,.LII. 

Nephelitc-aplite ...... Cabo Frio Island, Brazil. ..... · ........ T. M.P. M., XX, 288.-W. T . 

Phonolite ............ Sonthboro, Mass ...................... Bull. 168, 33.-W. T . 

Nephelitc-syenite .... Picota, Portugal.. .................... T. M.P. l\L, XVI, 218.-W. 1'. 

Phonolite ............ Sardinia .............................. R. T., 1879, LVIII. 

..... do ................ ,1\Isid Gharian, Tripoli. ............... R. T., 1884, LIV . 

Heromte ............. Heron Bay, Canada .................. .J. G., VII, 435.-W. T. 
.. 

ROCK ANALYSES USED IN CONSTRUC~ING DIAGRAMS. ·35 

Silica 

content. 

Alkali-silica 

ratio. 

60.29 0.197 (60.5) 

53.7610.207 (53.6) 

56.04 0.201 

55.·10 .184. 

54.68 .-176 

54.. 61 .197 

54.46 .186 

55. 50 1 o. 248 

;4.351 0.092 

70.30 .128 

72. 121 0. 070 

Classified list of analyse.~ used in constrttcting diagmm.~-Continued. 

SUBRANG 5. MARIUPOLOSII. 

(I. 6, 1, 5.) 

Author's name. Locality. Reference. 

Mariupolite .......... Nikolajew, Russia .................... T. ::11. P.M., XXi, 244.-W. T. 

RANG 2. VIEZZENASE. 

SUBBANG 3. -· --. 

(L 6, 2, 3.) 

I Nephelite-tinguaite .. , Magnet Cove, Ark ..... : .............. , I. R. A., 266.-W. T. 

SURRANG 4. VIJIZZENOSE. 

(I. 6, 2, 4.) 

Nephlite-rhomben- Vasvik tunnel, Norway ....... , .. .' .. ~ Z. K., XVI, 38.-W. T. porphyry. 

Andesite ............. Palma, Sicily .... · ••• : ................. R. T.,1879, LXVI. 

Nephclite-syenite .... Brookville, N.J ...................... Bull. 168, 39.-W. T.· 

..... do .......... , ..... Caldas de Monchiquc, Portugal. ..... N.J.; B. B., III, 271.-W. T. 

Tinguaite ............ Umptek, Kola, Finland .............. Rosenbusch, El., 215.-W. T. 

ORDER 7. TASMANARE. 

RANG 1. LAUGENASE. 

SUBRANG 4.· LAUGENOSE. 

(I. 7, 1, 4.) 

I Foyaite ............... , Brathagen, Norway .................. , E. K., III, 176.-W. T. 

CLASS II. DOSALANE. 

ORDER 3. HISPANARE. 

RANG '1. VARINGASE. 

SUBRANG 3. V ARINGOSE, 

(II. 3, 1, 3.). 

I I 

Grorudite ............ Varingskollen, Norway .............. . I z. K., XVI, 66.-W. T. . Pantellerite .......... Pantellaria .................... _. ...... Z. K., VIII, 173.-W. T. 

8UB'RANG 4. --. 

(II. 3, 1, 4.) 

I Felsite ................ , Cudgegong River, New South Wales, I W. T. 

. Australia. . . t 
36 

Silica 

eontent. 

Alkali-silica 

ratio. 

66.88 0.020 

70;15 0.109 

69.61 . 129 

69.02 . 121 

68.33 .137 

66.50 . 123 

61.83 . 102 (62. 2) 

71. 35 0.116· 

67.89 .116 

67. (8 .131 

67.18 .122 

66.57 0.103 

63.97 . 105 

62.51 • 090 

61.93 . 104 

59.24 . 095 (59. 5) 

65.50 0.107 

64.47 . 098 

63.50 . 101 

61.56 .102 

56.59 . 083 

CHEMICAL COMPOSITION OF IGNEOUS ROCKS. 

Gla83ified list of analyus used in constructing diagramB--Continned. 

Author'A name. 

RANG 4. -· --. 

SUBitJ.NG 3. --. 

(II. 3, 4, 3.) 

Loeality. Reference. 

Quartz-diorite . . . . . . . . Little Falls, l\Iinn.................... R. T., 1879, XXXVI. 

ORDER 4. AUSTRARE. 

RANG 1. p AN1'ELLERASE. 

SUBRANG 3. GRORUDOSE. 

(II. 4, 1, 3.) 

Grorudite ....••....•. Grussletten, Norway--···-·-·····-··· K K., I, 199.-W. T. 

Pantellerite .......... Pantellaria ... : ...•....•.•............ Z. K., VIII, 173.-W. T . 

.: ... do.• ................•.•• do ............•••..•••............ Z: K., VIII, 182.-W. T . 

••.... do ...••............•••• do .....•....•..................... Z. K., VIII, 170.-W. T, 

Grorudite . .. .. . . . . . .. Grussletten, Norway ................. E. K., I, 199.-W. T . 

}:'orphyritc ........... Siipplingen, Magdeburg, Prussia ..... W. T . 

SUBRANG 4. p ANTELLEROSE. 

(II. 4, 1, 4.) 

Grorudite ............ Kallerud, Norway .................... E. K., I, 199.-W. T. 

Pantellerite .......... Pantellaria ........................... Z. K., VIII, 186.-W. T. 

..... do ..................... do................................ Do. 

..... do ..................... do ............................... . Do. 

RANG 2. DACASE. 

SUBRANG 3. ADAMELLOSE. 

(II. 4, 2, 3.) 

Granite-porphyry .... Kirche Wang, Silesia ................. Rosen busch, El., 195. 

Quartz-mica-diorite . . Crandall Basin, Wyo................. Bull. 168, 9·1.-W. T . 

Syenite ............... Reichenstein, Silesia ................. N.J., 1890, I, 206.-W. T . 

I 

Granitite ...... :······1 L~veline, Vosges .. _. .................. ! Rosenbusch, El., 78 . 

Trachyte-andesite .... Highwood Mountams, l\Iont. ........ Rull. 168,131.-W. T. 

SUBRANG 4. DACOSE. 

(II. 4, 2, 4.) 

Andesite ............. Sepulchre Mountain, Yellowstone Bull. 168, 91.-W. T. 

Park . 

Granitite ............. Crazy Mountains, llfont .............. Bull. 168, 120.-W. T. 

Dacite ................ Chiles, Colombia, South America .... .T. G., I, 171.-W. T . 

Andesite ............. Tower Creek, Yellowstone Park ..... Bull. 168, 108.-W. T. 

Quartz-diorite., ...... Sauk Center, Minn ................... R. T., 1879, XXXIV . 

---'------'-------~-~---·--~·--~-~-----------
ROCK ANALYSES USED IN CONSTRUCTING ·DIAGRAMS. 37 

Cla.Bxified li.~t of arwly.~e-~ itxed in constructing dingrmns-Continued . 

. RANG 3. TONAI,ASE. J 

SUB RANG. 3. HARZOSE:. 

(II. 4, 3, 3.) 

Silica Alkali-silica COil· ratio. tent. Author's name. Locality. Reference. 

---------- -~~---- ~------ --------------

64.34 0.081 Granite ............... Butte, Mont. ......................... Bull. 168,117.-W. T. 

63.85. .080 Granodiorite ......... Grnss Valley, Cal. .................... BulL 168,194.-W. T. 

63.06 ,069 (63.2) "Schlierc" in granite. Riesengebirgc, Silesia ....... , ........ N.J., 1898, XII, 236.-W. T. 

61.73 . 088 Syenite ............... Hodritch, Hungary ................... R. T.,l869, LX . 

61.64 . 078 Quartz-monzonite .... Red Rock Creek, Butte, Mont ........ BulL 168, 118.-\V. T . 

60.68 . 090 (GO. 7) Andesite ............. Mount Pagos, Asia Minor._ ........... A. J. S. III, 1897, 43.-W. T . 

60.17 . 090 Latite ................ Tin tic district, Utah .................. BulL 168, 166.--;-W. T . 

59.76 . 094 Monzonite .. : .............. do .. . .. .. .. .. . .. . .. .. . . . .. . .. .. . .. Do . 

57.80 . 063 Quartz-pyroxene-dio- Sonorn, Tuolumne County, CaL ...... Bull. 168, ~04.-W. T . 

rite . 

57.69 . 064 (58. iJ Mica-diorite.......... Gippsland, Victoria................... E. K., U, 87.-W. T. 

57.26 . 076 Quartz-mica-diorite .. Sierra County, CaL ................... BulL 168, 192.-W. T . 

SUBitANG 4. TONALOSE. 

(II. 4, 3, 4.) 

66.91 0.055 Tonalite .............. Adamello Stock, Tyrol ............... Rosen busch, El., 140.-W. T. 

65.83 . 080 Granite ............... Granite Creek Station, Nev: .. .. . .. .. . Fortieth Par., I, 110 . 

65.39 ,1)81 Dacite ................ Cumbal, ColC?mbia, South America ... J. G., I, 171.- W. T. 

65.11 . Oh3 Quartz-mica-diorite .. Electric Peal<;, Yellowstone Park ..... Bull. 168, 88.-W. T . 

64.81 . 073 Porphyrite .. _ ......... Leadville district, Colo ............... Bull. 168, 155.-W. T . 

64.12 . 077 (.076) Quartz-noritc ......... 'fyrol ................................. Rosen busch, El., !40 . 

64.07 . 083 Quurtz-mica-diorite .. Electric Peak, Yellowstone Park ..... Bull. 168, 87.-W. T . 

63.56 . 084 Hornblende-dacite ... Colombia, South America ............ J. G., I, 171.-W. T . 

63.47 . 075 Andesite ............. Suppans Mountain, Tehama County, Bull. 168, 182.-W. T . Cal. 

63.28 .077 . ..... do .. .. .. .. .. .. .. .. Mount Hood, Oreg ·................... ~'orticth Par., I, 604. 

63.16 .089 Trachyte ............ ~ Henry Mountains, Utah .............. Bull. 168, 167.-W. T. 

63.03 .070 Andesite .... · ......... Mount Shasta, Cal............... .. .. Bull. 168, 176.-W. T. 

62.71 .084 Diorite ............... Gunnison County, Colo ............... Bull. ·168, 159.-W. T. 

62.65 .095 Hornblende-porphy- Herman Peak, Colo .................. Bull. 168, 164.-W. T. nte. 

62.62 . 070 Quartz-mica-diorite .. Mariposa Coni1ty, Cal ................ Bull. 168, 209.-W. T . 

62.4·1 . 071 Andesite ............. Shasta County, Cal ................... Bull. 168, 181.-W. T . 

62.09 . 070 H~[t~~lende-porphy- Nevada City, Cal ..................... Bull. 168, 194.-W. '1' . 

61.58 . 074 (61. 8) Andesite ............. Mount Shnsta, Cal. .................. _ Bull. 168, 176.-W. T . 

61.40 . 048 Syenite ............... Riesengebirge, Silesiu ................ N. J.,1898, XU, 234.-W. T .. 

61.22 • 089 (61.4) Micu-diorite .......... Eleetric Peak, Yellowstone Park ..... Bull. 168, 87.-W. '1' . 

61.17 . 077 Andesite ............. Shastu County, Cal ................... Bull. 168, 183.-W. T . 

61.16 .093 Andesite-porphrry ... Crundall Basin, Wyo................. Bull. 168, 94.-W. '1'. 

61.09 . 070 Andesite ............. Colombia, South America ............ J. G., I, 171.-W. T . 

61.04. .090 ..... do ..................... do ........ ·........................ Do. 

60.93 . 073 ..... do ................ Tuscan Buttes, Cal ................... Bull. 168, 181.-W. T . 

60.30 . 088 (60.4) ..... do ................ Sepulchre Mountain, Yellowstone Bull. 168, 90.-W. '1' . Park . 

60.20 .068 . .. .. do................ Pilot Peak, Plumas County, Cal. ..... Bull. 168, 188.-W. T. 

60.05 .079 ..... do ................ Colombia, South America ............ J. G., I, 171.-W. T. 

60.04 .078 (60.3) ..... do ................ Shasta County, Cal ................... Bull. 168, 181.-W. T. 

60.02 . 074 (59.8) · ..... do ................ Sierra County, Cul. ................... Bull. 168, 193.-W. T . 
38 CHEMICAL· COMPOSITION OJ<' IGNEOUS ROOKS. 

Classifierlli.~t of anal!fses·u,qed in constructing diagram.~-Continued. 

SUBRANG 4, TONALOSE-Continued. 

Silica Alkali-silic~t con- mtio. tent. Autl~or's name. Locality. Reference. 

-------

59.97 . 076 Diorite .. .. .. .. .. .. .. . Vildarth~tl, Tyrol..................... Rosen busch, El:, 140. 

59.84 . 080 Andesite .............. Near Lassen Peak, Cul ............... Bull.168, 183.-W. T . 

59.77 .088 Average of 680 ignc- America .............................. Bull. 148, 12.-W. T. ous rocks. 

59.48 .082 

59.34 .075 

59.19 .094 I 

Andesite ......... _ ..... Red Bluff, Mont ............... · ....... BulL 168, 114.-W.T. 

..... do ................ Sierra.County, Cal. ...... ,., ........... B;,ll.l68, 193.-W. T. 

Diorite ................ Sun llfiguell\foJintains, Colo ......... 'Bull.168, 164.-W. T_. 

58.67 . 065 Dolerite .. .. . .. .. .. . .. Eskdale, Scotland ................... . 

58.63 . 079 (58. 9) Diorite ................. unalaska Jslund ...................... Bull.168, 2'26.-W. T. 

58.46 • 083 (58. 7) Average of 397 igne- Great Britain ......................... Geol. llfag., 1899, 220.-W. T. ous rocks. 

58.08 . 075 (58.~) Andesite .............. Neur Lassen Peak, Tehama County, Bull. 168, 182.-W. T. . Cui. . . 

56.61 .08~ ..... do ................ Sepulchre Mountain, Yellowstone Bull.168, 90.--;-W. T. .Park. 

56.28 .065 Diorite ............... Electric Peak, Yellowstone Park ..... Bull. 168, 87.-W. T. 

55.83 . 069 (55. !I) Andesite .............. Sepulchre Mountuin, Yellowstone Bull. 168, 90.-W. 1'. Park. 

SUBRANG 5. PLACEROSE. 

(II. 4, 3, 5.) 

64.671 0.064 

60.40 .068 I 

Granit_e ............. ,.\ ~lacerCou_nty, Cal ... · ................ ,.Bnll.168, 198.-W. T. 

. Andes1te .............. St. Augustme yolcuno, Cook Inlet. .. Bull. 168, 226.-W. T. 

---------- ~ ~-----

RANG 4. BANDASE. 

SUBRANG 1. SAGAMOSE. 

·(II. 4, 4, 1.) 

--~-----,-------------

55.481 0.023. I Tonalite .............. , Hokizawa, Sa~ami, Jupun ............ ~ W. T. _L_ ___________ ___ 

SUBRANG 3. BA~IDOSE. 

(II. 4, 4, 3.) 

61.58 0.057 Diorite ............... Kadiaklsland, Alaska ............... Bull.168, 227.-W. T. 

59. 66 . 052 ~Andesite ..... '....... Bandui San, Japan................... W. T. 

56.74 .047 Dialn~se·porphyry .... Mount Morrison, Colo ................ Bull.168, 141.-W. T. 

56.51 .068. (51i.7-.0(i6} Quartz-basalt. ........ Near Lassen Peak, Cal ............... Bull.l68, 185.-W. T. 

56.41 .Ofi2 Diorite ....... · ...... :. Georgetown, D. C ... :· ................ Bull. 168, 44.-W. T. 

56.31 . 044 "Schlicrc" in granite Riesengebirge, Silesia ................ N.J., 1898, XII, ~35.-W. T. 

55.97 .052 ·Diorite ............... 

1 

Triadelphia, 1\fd ... _ ................... Bull.168, 44.-W. T. 

51. 62 1 o. 015 

RANG 5. ---. 

SUBRANG 3. --. 

(II. 4,5, 3.) 

I Diorite .............. ·I Kugelholmson, Sweden ........... ~ --I R. T., 1879, XXXII. 
~OCK ANALYSES USED IN CONSTl;tUCTING DIAGRAMS .. 

Clos.~ijierllist 1(( ana.ly~es used in constnwting_-cliay1'ams-Continued. 

0RDF.R 5. GERMANARE. 

RANG 1. U)!l'TEKASE. 

SUBltANH 2. HIGHWOODOSE. 

(II .. 1, 1, 2.) . 

----~-------------~---------------~-------------------------

Si!ic1t 

content. 

Alkali-silica 

ratio. Author'R 1utn1c. I,ocality. Reference. 

-----------1------- ---------- ----------------,----

61.28 0.126 

58.04 .166 

Syenite ...... _ ......... Tuolumne County, Cal. .............. Bull.168, 204.-W. T. 

Trachyte ............. Highwood Mountains, Mont. ........ l~n11. 168, 131.-W. T. 

----'------'----------"-----------------------------------

SUBRAN<l 3 •. ILMENOBE. 

(II. 5, 1, 3.) 

39 

62.99 0.139 Umptekite ........... Beverly, Mass ............ · ............ ! T. M.P. M., XX, 248.-W. T. 

57.91 .181 Sod~tlite-trachyte~ .... Monte Santo, Naples, Ilftl;-........... [ A. J. s., VIII, 1899, 290.-W. T. 

_5_5_.2_6__,__·~1-7_1 _____ -'-Le--u_c_.i_te_-t_r_n_c_h_yt~. Viterbo, Ital~-~==--:~:.J J. G.~70.-W. T .. ______ . _ 

(II. 5, 1, 4.) 

----;------------;---------------------------------------- ------- ------

64.28 0.156 S(ilvsl>ergite .......... Andrews Point, M11ss .................. 1. G., VII, 481.-W. T. 

63.71 . 152 Umptekite ........... Kola, Finland ................. : ...... Rosen busch, El., 112.-W. T . 

62.70 . 162 Solvsl>crgite .......... Laugendal, Norw11y .................. E. K., I, 199.-W. T . 

60.50 . 159 Hedrumite ........... Ostii, Norway ......................... E. K., Til, 377.-W. T . 

59.66 . 180 Nephelite-sycnite .... Crazy Mountains, Mont .............. BulL 168, 123.-W. T . 

59.01 . 171 ..... do ................ Red Hill, N.H ....................... Bull. !68, 23.-W. T . 

58.90 . 181 Nephelite-sulv,berg- Aklungen, Norway ................... E. K., I, 199.-W. T . ite. 

58.81 . 163 Soda-syenite .......... Lanp•tadeid, Norw11y .......... · ...... B. ~1. A .. 189R, VII, 48.-W. T . 

58.46 . 162 

57.52 .1~2 

Nordmarkite ......... Cabo Frio, Brazil. ...... _. ............. T. M.P. M .. XX, 244.-W. T . 

Uedruinite ........... Brathagan, Norway ................... E. K., Ill, 190.-W. T. .1' 

57.00 . 170 Heumite ................... do ................................ K K., III, 116.-W. T . 

RANG 2. MoNZONASE. 

SUBRANG 2 .. CI>IINOSli:. 

(II. 5, 2, 2.) 

56.39 0.110 (56. 6) .Mica-tmchyte ........ Monte Catini, ltnly ................... A. J. S., IX, 1900, 47.-W. T. 

55.85 . 157 Lc)lcite-phonolitc .... Bolsena, Italy ........................ J. G., V, 370.-W. T . 

55.46 . 107 Citniniic.............. Monte Cimino, Italy ................. A. J. S., IX, 1900, 44.-W. 1' . 

55.21 . 151 Leucite-trachytc ..... Viterbo, It11iy ....................... J. G., V, 370.-W. T . 

51.05 . 125 Durl>nchitc ........... SehwMzwnld, Baden ................. W. T . 

SUBRANG 3. MONZONOSE. 

(II. 5, 2, 3.) 

61.65 0.113 Syenite ............... Yogo Peak, Little Belt Monntnins, BulL 168, 125.-W. T. Mont. 

60.56 .. 1~7 Granite ............... Elliott County, Ky ................... BulL 168, 56.-W. T. 

59.78 . 140 Syenite ............... Cuelcr County, Colo .................. Bull. 168, 151.-W. T. 

58.18 .134 Kersantite ............ Titn, Chile .... .' ....................... Z. D. G. G., Ll, 4.-W. T. 
40 CHEMICAL COMPOSITION OF IGNEOUS ROCKS. 

Clas8'ijicd liHt of (tnalyse.~ 11sed im, con.~tructing .diagrams-Continued. 

SUBRANG :l. MONZONOSE-Continued. 

Silica Alkali-silica con- ratio. tent. 

Author's name. Locality. Reference. 

58.00 0.142 Pnlaskite ............. Laugcnthal, Norway ................. E. K., III, 375.-W. T. 

57.97 . 116 Diorite ............... Mount Ascutney, Vermont. .......... BulL 168, 25.-W. T . 

57.73 .147 Trachyte .. .. .. .. . .. .. Ischi6, Italy.......................... H. T., 1873, XXXVIII. 

57.48 . 118 Andesite ............. Pikes Peak district, Colo ............. BulL 168, 145.-W. T . 

57.29 . 134 Quartz-banakite ...... Head of Ishawooa River, Wyo . . . . . . . Bull. 168, 102.-W. T . 

56.75 . 149 Ciminite .............. Arso, Ischia, Italy: ................... A. J. S., VIII, 1899, 290.-W. T . 

55.35 . 100 Mica-basalt ........... Santa Maria Basin; Arizona .......... Bull. 168, 173.-W. T . 

55.23 . 143 Trachyte ............. Highwood l\Iomitotins, Mont ......... BulL 168, 131.-W. T • 

04.86 .114 Shoshonite ........... Indian Peak, Wyo .................... BulL 168,100.-W. T . 

04.42 . 109 (54.0) Monzonite ............ Yogu Peak, Mont ..................... BulL 168, 128.-W. T. 

04.20 • 106 ..... do ................ 1 Munzoni, TyroL ..................... K K., II, 24.-W. '1' . 

52.81 .124 (52. 6) ..... do ................ Bearpaw llfountains, Mont ........... BulL 168, 135.-W. T. 

52.80 • 150 Shonkinite-monzonite Maros, Celebes .. . .. . .. .. . .. . .. .. . .. .. G. C., 25 . 

52.63 • 133 Banakite . . . . . . . . . . . . . Hoodoo Mountain, Wyo ... !.......... BulL 168, 101.-W. 1' . 

52.33 • 147 ..... do .. .. . .. .. .. . .. .. Head of Ishawooa River, Wyu .. .. .. . Do . 

52.14 . 116 Syenite............... Heidelberg, Baden ............. ;..... R. T., 1879, XXIV . 

51.82 . 134 Head of Lamar River, Yellowstone BulL 168, 101.-W. T . Park. 

51.46 . 131 Ishawooa Canyon, Wyo ............. . Do. 

SUBRANG 4. AKEROSE. 

(II. 5, 2, 4.) 

61. 87' 0.119 Syenite ............... Castle 1\Iountnin district, Mont....... BulL 168, 130.-W. T. 

-61.63 .125 Nephelite-syenite .... Mulatto, Tyrol .. .. .. .. .. .. . .. .. .. .... K. A. W. W., CXI, 1, 21i0. 

61'.26 . 11)4 Andesite ............. Colombia, South America ........... J. G., I, 171.-W. '1'. 

61.08 .114 Porphyrite .. .. .. .. .. . Crazy Mountains, Mont ............ ;. Bull. 168, 120.-W. T. 

60.44 .110 Diorite-porphyry ..... La Plata !tiountains, Colo ........... _. Rull.168,162.-W. T. 

59.56 .125 Akerite ............... Vettakollen, Norway ................. Z. K., XVI, 50.-W. 1'. 

58.28 .155 Syenite ............... Crazy Mountains, Mont ............... Bull. 168, 121.-W. T.~ 

57.01 .124 

56.79 .118 

56.75 .108 

56.02 .119 

55.95 .135 

Andesite ............. Si~verC!iff, Colo .... ~ .............. ,--1 Bull.168,148.-W. T. 

Akerite ............... Vcttakollen, Norwny ................. Z. K., XVI, .'iO.-W. T. 

Porphyrite ........... Crazy Mountains, Mont. ............. ! Bull. 168, 121.-W. T. 

Andesite ............. Tual, Luzon, P. !. ............. : ...... N.J., B. B., I,l881, 482. 

Ditroite .............. Nosy Komba, Madagascar ............ M. M., 204. 

55.53 .115 Diorite .. .. .. . .. .. .. .. La Plata Mountains, Colo............ BulL 168, 162.-W. T. 

54.69 .136 (54.6) Porphyrite ........... Crazy Mountains, Mont .. : ........... Bull. 168, 121.-W. T. 

53.80 .144 Diorite ............... Silver Cliff, Colo .................... :. BulL 168, 147.-W. ·r. 

53.60 .124 Basalt ................ Reinhardswald, Prussia .............. W. T. 

53.15 .129 Essexite.............. Shefford Mountain, Quebec.......... J. G., XI, 265. 

.'i3.12 .171 Tephritic-trachyte ... Columbretes Islands .................. T. 1\I. P. M., XVI, 314.-W. T • 

51.42 .130 (51. a) Basalt .. .. . .. .. .. . .. .. S. Rhone . .. .. .. .. . .. . .. . .. .. .. .. .. . .. R. T., 1879, LXXII. 

51.22 .162 Minette .............. Brathagen, Norway .................. E. K., III, 376.-W T 

RANG 8. ANDASE. 

SUBRANG 2: --. 

(II. 5, S, 2.) 

_o_7._3_1_,j_o_._oo_4 _____ ._i_c_im_· _in-it_e_ ....... -~.J ~oute Cimin.o, Italy--~----- ... j A. J. s., JX, 1900, 44.-W. 'I'. 
ROCK ANAI,YSER USED IN CONSTRUCTING DIAGRAM8. 41 

Cla&~ijied l·ist of aualyse.~ ·used in crmsh'ucting diagrams-Continued. 

SUBHANG 3. SHOSHONOSE. 

(II. 5, ~. 3.) 

Silica Alkali-silica con- ratio. tent. Author's name. Locality. Reference. 

---1----------------- 1---~----------

59.41 0.102 

58.51 . 09.'i (58.8) 

57.97 .083'(57.8) 

56.90 .097 

li6. 78 . 093 

56:19 .092 

56.05 .107 

55.69 .100 (55.(i) 

54.56 ,076 (.07o) 

54.14 .077 

53.4S .104 

52.93 .132 

52.59 . 099 (52. 7) 

52.49 .102 

52.33 .103 

52.11 .897 (51.8) 

51.00 .115 

50.98 .120 (50. 7)' 

50.08 .137 

50.06 .110 

49.69 .107 

48.25 .118 

17.50 .117 

45.53 .HO 

58.45 0.080 

58.42 .099 

58.05 .083 

57.64 .104 (57.~) 

57.59 . 070 (57.8) 

o7. 38 . 071 (57.1) 

57.32 . 098(57.5) 

57.26 .102 

57.25 .067 

57.17 .079 

57.11 .084 (57.5) 

56.91 ,085 

56:70' . 074 (56.6) 

56.49 .112 (57.1) 

56.21 .104 

56.19 .076 

56.09 .080 

56.07 .091 (55.9) 

55.93 .103 (55.8) 

55. !)'2 .095 

55.80 .076 

55.84 .093 

Andesite ............. Cabo da Oata, Spain ................. . 

1\Iica-diorite .......... Crystals Falls, Mich ...... _ .. _ ....... . 

Diorite .............. : Crazy Mountains, Mont ............ .. 

Syenite ............... Denver Basin, Colo ................. .. 

Latite .............. ; . Clover Mcadow, Cal. ............... .. 

..... do------·-··- .... 'fablc~fountain, Tuolumne Cmtnty, 

Cal. 

Z. D., g. G., XLIII, 719.-W.. T. 

Bull. 168, 67.-W. '!' . 

Bull. 168, 122.-W. T. 

Bull.16S, 140.-W. T. 

Bull. 168. 205.-W. T • 

Bull. ~68, 20o.-W. T· . 

Shoshonite ........... Two Ocean Pass, Yellowstone Park .. Bull. 168, 100.-W. T. 

Vulsinitc ............. Rocca Monfina, Italy ..... _ ........... J. G., V, 358.-W. T. 

Andesite ............. Radicofani, Italy ............ _ ........ A. j, S., TX, 1900, 52.'-W. T. 

..... do ..................... do................................ Do. 

Shoshonite ........... Beaverdam C~eek, Yellowstone Park. Bull. 168, 100.-W, T. 

Banakite .................. do ................................ Bull. 168, 102.-W. '1'. 

Bttsalt ................ Table Mountain, Colo ................ Bull. 168, 140.-W. T: 

Shoshonite ........... Pyramid Peak, Yellowstone Park .... Bull. 168, 100.-W. T. 

Augite-porphyy ...... Cottonwood Creek, Mont ............. Bull. 168, 112.-W. T. 

Basalt ................ Crandall Basin, Wyo .. : .............. Bull. 168, 92.-W. T. 

Monzonite ............ Highwood Mountains, Mont ......... Bull. 168, 133.-W. T. 

Mondhaldeitc ........ Mondhalde, Kaiserstuhl, Baden ..... W. T. 

..... do ..................... do·.:.............................. Do. 

Shoshonite ........... Lamar River, Yellowstone Park ..... Bull. 168, 100.-W. T. 

Basalt ................ Denver Bttsin, Colo ................... Bull. 168, 140.-W. '!'. 

Dolerite ................... do................................ Do. 

Labrador-porphyrite. Gran; Norway ........................ Q. J. G. 8., L, 33.-W. T~ 

Lcucite-monchiquite. Bohemian Mittelgebirge ............. Rosenbmch4 El., 235.-'--W. T. 

SUBRANG 4. ANDOSE. 

(II. 5, 3, 4.) 

Diorite· ............... Pen Maen Mawr,~- Wales ........... Q. J. G. 8., XXXIII. 42-l. 

Andesite ............. Taal, Lnzon, P. I. .................... N.J., B. B., I, 1881, 481. 

Diorite ............... Electric Peak, Yellowstone Park ..... Bnll.168,87.-W. T. 

Augite-porphyrite .... Crandall R&sin, Wyo .. : .............. Bull.l68, 93.-\\'. T. 

Quartz-basalt ......... Silver Lake, Lassen, Cal.............. Bull, 168, 185.-W. T . 

Pyroxene porphyr~· .. Electric Peak, Yellowstone Park ..... Bull. 168, 87.-W. T. 

:Monzonite ............ Crandall Basin, Wyo ................. Bull.168, 93,-W. T . 

Diorite .................... do ...... :......................... Do. 

I 

Quartz-basalt. ........ Cinder Cone, Lassen, Cal. ............ Bull. 168,184.-W. '!'. 

Andesite............. Sepulchre :Mountain, Yellowstone Bull. 168, 90.-W. T. Park. 

l ... ,·_clo ................ Mill Creek, Lassen, Cal. .............. Bull. 168, 182.-W. '!'. 

..... do ................ ! Colombia, South America ............ J. G., I, 171.-W. T. 

Quartz-bamlt ......... Cinder Cone, Lassen, Cal ............. J. G., I, 184.-W. T . 

Diorite ................ I,ittle Falls, Minn .................... R. T., 1879,XXXIV. 

Gabbro-diorite ........ Crandall Basin, Wyo ................. Bull. 168, 93.-W. '!'. 

Andesite ............. Buffalo Peaks, Colo ................... Bull.168, 153.-W. T. 

Diorite ............... Campo Major, l'ortugal._. ............ E. K., II, 37.-W. 'L 

Andesite ............. Bogosloflsland ...................... Bull. 168, 227.-W. T. 

Gabbro-diorite ....... Crandall Basin, Wyo .............. , .. Bull. 168, Q3.-W. T. 

Andesite ............. Sepulchre Mountain, Yellowstone Bull. 168, 90.-W. T. Park. 

Diorite (norite) ...... Klausen, Tyrol ....................... E. K., II, 37.-W. T. 

Norite ................ ~IontrosePoint, N.Y ................. W.T. 
CHEMICAL COMPOSITION OF IGNROUS ROOKS. 

Cla.~.sijierlli.~t ri analy.ses UHerl in cm1stracting rliag/'(/.17/~-Continned. 

SUBRANU. '1. A NDOS:E-Continned. 

~-----,-------c--------~-------------------------

.Silic_a · Alkali-silica con- ratio. tent. Author's name. Locality. Reference. 

.. 55.20 0. 075 (~5. 4) Andesite ............. Butte County, Cal .................... Bull. 168, 182.-W. T. 

55.13 . 107 Diorite ............... Neihurt, Mont ........... : ............ Bnll.1G8, 127.-W. 'l' . 

54.62 .075 Andesite ............. J,uzon,P.I. ........................... N.J.,B.B.,J,1881,471. 

54.56 . 108 Diorit~·porpltyrite .... Cra~y l\fount~tins, Mont .............. Bull. 168, 121.-W. '1' . 

54.52 .092 Diabase .............. Diabase Hi1Is,Nev ...................... Portieth Pu.r.,II,812. 

53.94 . 086 Dolerite ................ · ... do................................ Do. 

53.8U . 099 Basic amlcsitic glass .. Indhm Rjdge, "iVyo ................... Bull.168, 92.-W. T . 

53.71 .ous 1\fica·/{abbro.......... Crandall Basin, Wyo................. Do. 

53.48 :o89 Quartz-diorite ........ Crazy Mountains, Mont .............. Buii.1G8, 121.-W. '1'. 

53.10 . 134 (53. 2) Covite ............ _ ... Nosey Komba, Madagascar .......... _ M. J\I., 204 . 

52.97 1107 Basalt ............ _ ... Pikes Peak district, Colo ............. Bull. 168, 141i.-W. 'l'. 

52.91 . 119 Diabase-syenite-par- Holmestrand, Norway ... _ ............ Z. K., XVI, 28.-W. '1' . phyry . 

52.63 . 082 (52. 7) Bttsalt ................ Shasta county, Cal ................... Bull.16~18u.-W. '1'. 

52.38 . 093 ..... do_ .......... _ .... Rio Graude,N. J\Iex .................. Bull.168, 169.-W. 'l' . 

52.37 . 084 ...... do ... _ ............ Ab,saroka Range, Yellowstone Park .. Bnll.l68, 109.-W. T . 

52.37 . 082 (51. 8) .... :<lo, ............... , Rio Grande, N. Mex .................. Bnll.168, 169.-W. '1' . 

52.27 . 095 ..... do ..................... do.:.............................. Do . 

52.12 .095 Diorit'i , ... __ ......... _ Mount Ascutney, Vt .. , ............... Bull.168, 25.-W. T. 

52.09 . 085 Basalt, ................ Cranrhtl! Basin, Wyo ................. Buli.168,92.-W.'l' . 

'51. 57 . 090 ..... do ................ Rio Grande,N.J\Iex .................. Bull.168,1G\I.-W.T . 

51.54 .110 

50.99 . 101: I Andesite ............. Bogosloflsland, Alaska .......... _ .... Bull.168, 227.-W. '!'. 

Camptonite :--------- Ishawooa Cnnyon, Wyo .............. Bull.168,110.-W.T. 

50.97 . 112 (50. o) Kcrsantite ......... , .. Guai_Ita,Chile ........................ Z.D.g.G.,LI,4 . 

50.73 . 099 Diorite .... __ ......... Crazy Mountains, Mont ............. _ Bull. 168, 122.-W. '1' . 

50.56 .OiU Basalt ................ Plumas County, Cal. ................. Bull.l63, 189 . .:..W. T. 

. 49._40_ . 087 Facies of monzonite .. Predazzo, Tyrol _ ...... _ .............. E_. K., II, 102.-W. '1' . 

49.24 . on (49. 7) Dolerite .. .. .. .. .. .. .. Ferdinandea .. .. .. . .. .. .. .. .. .. .. .. .. 'l'. J\L P. IlL, 1883, 393 . 

49.04 .110 Basalt ... : ............ Buffalo Peak, Colo' ................... 'Fortieth Par., I, 676. 

48.90 .ouo Diorite ............... Schwarzenberg, Vosges ............... Rosen busch, El., 140. 

48.85 . 131 Essexite .............. J\IountJohnson, Quebec .............. J. G., XI,265 . 

48.76 .105 Basalt ............ ~ ... Pikes Peuk district, Colo ............. Bull; 168, 145.-W. T. 

48.18 ·. 093 Olivine-diabase ...... Biella, l'iedmont ..................... R. '1'., 1884, XLII. 

48.0tl . 084 Kersantite ............ Laugendal, Norway .................. E. K., III. 376.-W. T. 

44.85 . 110 Nephelite-tephrite .. : J\Iittelgebirgc, Bohemia .............. Rosenbnsch, El., 346.-W. T . 

SURRANG 5. BEERBACHOSE. 

(II. 5, 3, 5.) 

55.08 o. 081 Andesite-basalt ....... Shasta County, Cal. .................. Bull.168, 176.-W. T. 

52.58 . 073 Andesite ......... _... S. W. Tillis............................ Z. D. g. G., XXIX, 823. 

47.21 .109 Beerbachite .......... Odenwald, llesse ..................... Rosen busch, El.. 219.-W. ~'-

RANG 4. HESSASE. 

SUBRANG 3. HESSOSE. 

(II. 5, 4, 3.) 

57.47 0.072 B11salt .. __ ........... _ Cascade Range, Oreg ................. Bull. 168, 223.-W. T. 

li6.94 .074 Anorthosite .......... Elizabethtown, N.Y ... : ............. Bull.168, 37.-W. T. 

55.53 .062 Andesite ............. Plumas County, Onl .................. Bull.168, 181.-W. 'l'. 

55.14 .075 Secretion in dacite ... Lassen l'ettk, Cal. .................... Bull.168, 179.-W. T. 
ROCK ANAI-YSES USED IN OONSTRUCTING DIAGRAMS. 

Classifiecll:i.<t o.f analyse.< 1.wecl in constructing 1z.iagra.m.~--'--Continued. 

RANH 4. HEssAsE-Continued. 

SUBRAl'G H. HESSOSE-Continned. 

Silica Alkali-silica -con- Author's name. Locality. Reference. tent. ·ratio. 

53.91 0.066 

53.35 .Oii3 

53.181 . 082 

53.00 .070 

52.95 . 073 (52. 7) 

52.16 . 074 

52.05 . 075 (51.7) 

51.27 . 064 

49.93 . 074 

49.88 ,057 

49.80 .049 

49.15 .095 

48.29 . 039 

47.94 .060 (47.5) 

47.88 • 065 

46.71 .036 

46.45 . 047 

45.20 . 071 

44.72 .047 

43.42 . 044 

43.19 . 094 

44.041 0. 027 

43.41 .020 

51.751 0.147 

57.63 0.198 

&7.46 . 196 (57. 3) 

53.09 . 226 (53.2) 

52.91 . 224 

51.94 . 157 

Dolerite ............. . 

Secretion in dacite .. . 

Anorthosite . 

Plt~mas County, Cu.l ................. . 

Lnssen Peak, Cul.., ................. . 

Whiteface Mountain; Adirondacks, 

N.Y. 

Bull. 168, 189.-W. T. 

Bull. 168, 180.-W. T; 

Bull. 168, 36.-W. T: 

. . Roscnbusch, El.,l40. · 

Bull. 168, 186.-W. T . 

Predazzo, Tyrol ...................... E. K., II, 25.-W. T . 

Ouray County, Colo .................. Bull. 168, 161.-W. T . 

Little Falls, Minn .................... R 1'.,,1879, XXXIV.· . 

Paterno, Ett~a, Sicily................. R. '1'., 1884, LXXX . 

Olivine-gabbro ....... Pigeon Point, Minn .................. Bull. 168, 76~-W. T. 

Gabbro............... Crystal Falls,_ Mich................... Bull. 168, 67. c.. W. T. 

..... do ................ Duluth, Minn ........................ Rosen busch, El., 151. 

Gabbro:diorite ....... Minnesota Falls, Minn ................ Bull.168, 83.-W. T . 

Basalt.' ................ Shasta County, Cal ................. ,. Bull. 168, 176.-W. T. · 

Gabbro ............... Elizabethtown, N.Y .................. Bull. 168,.37.-W. T . 

Olivine-g~tbbro ....... Lungenlois, Austria .................. R. T., 1879, XXXVIII. 

..... do ................ Minnesota ............................ B,ull. 168, 82.-W. T . 

Diorite ............... Tuc d'Ess,'Pyrenees .................. C. G. I., VIIl, 1901, 832.-W. T . 

Corsite ............... Poudiere; Auvergne.' ................. R. T., 1879, XXXVI. 

GR\Jhro-diorite ........ llchestcr, Md ......................... Bul\.168, 44.-W. T . 

B~tsalt.. ... .... .. .... . Westphali~t ........................... R. T., 1879, LXXIV . 

RANG 5. 00R8ASE. 

(II. 5, 5.) 

I 

Di~r~te .............. ·1 Stone Run, Md .... · .................. ·1 Bull. ~68, 4o.-W. T. 

Ohv1nc-gabbro ....... Tuolumne County, Cal. .............. Bull .• 68, 206.-W. T. 

ORDER 6. NoRGARE. 

RANG 1. LAURDALASE: 

SUBRANG 2. FERGUBOSE. 

(II. 6, 1, 2.) 

I Ps.cmlolencitc-syenite I Highwood Mountains, Mont ......... , Btlll. 168, 133.-W. T. 

SUBRANG 3. JUDITHOSE . 

. (II.' 6, 1, 3.) 

Tinguaite ............ Judith Mountains, 1\Iont ........... :. A. J. s., II, 1896, 192.-W. T. 

..... do ................ Bearpaw Mountains, Mont._ .......... Bull. 168, 136.-W. T . 

Foyaite ............... Magnet Cove, Ark .................... ·J. G., IX, 611.-W. T . 

Leucite-tinguaite ......... do ................................ I. R. A., 287.-W. T . 

Trachyte ............. Highwood Mountuins, Mont. ........ Bull. 168, 131.-W. T . 

43 
.. 

44 CHEMICAL COMPOSITION 01!' IGNEOUS ROOKS. 

·Ctassijied'list of analyses uud in constructing diagrams--Coutinued. 

Silica 

content . 

---

59.88 

56.58 

56.35 

55.90 

55.65 

55.18 

5-1.55 

5-1.04 

53.81 

53.73 

51.95 

50.96 

47.61 

45.16 

52.05 

51.35 

50.24 

50.15 

Alkali-silica 

ratio. 

0.188 

.242 

. 211 

. 209 

• 22f> 

.182 

.192 

. 233 

.192 

. 214 

. 155 (51. o) 

.229 

.190 

.195 

0.132 

. 165 

. 153 ( 49. 9-. 154) 

. 142 (49.8) 

. 49.70 .167 

47.8 .204 

SUBRANG 4. LAURDAL05E. 

(II. 6, 1, 4.) 

Author's name. Locality. Reference. 

Hcdrumite ........... Hedrum, Norway .................... E. K., III, 377.-W. T. 

Tinguaitc ................. do ................................ E. K., I, 199.-W.1': 

Laurdalite ........... Farris, Norway ....................... E. K.,III, 375.-W. T . 

Tinguaite ....... , .... Foya, Portngul ....................... T. M.P. l\L, XVI, 262.-W. T . 

..... do ................ Hedrum, Norway .................... E. K., 1,199.-W. '1' • 

Syenite .................... do ................... : ............ E. K., III, 375.-W. T. 

Luurdalite ............ Lougendal, Norw11y .................. Do. 

Leucite-tinguaite ..... Magnet Cove, Ark .................... I. R. A., 287.-W. T . 

Syenite-pegmatite .... Stoksund, Norway .................... Z. K., XVI, 116.-W. T. 

N ephelite-syenitc .. .. Transvaal .. .. . .. .. .. .. . .. .. .. .. .. .. .. Rosenlmsch, El., 126.-W. T . 

Soda-minette ......... Langesund~fjord, Norway ............ E. K., II, 376.-W. T . 

Leucite-nephelite- Magnet Cove, Ark .................... I. R. A., 276.-W. T. 

syenite. 

Tingu11ite .. .. .. .. .. .. Two Buttes, Colo................... .. l:lnlL 168, 165.-W. T. 

Olivine-laurdalite .... Fttrris, Norway ....................... E. K., III, 375.-W. T. 

RANG 2. EssExAsE. 

SU.I!RANG 3. BOROLANOSE. 

(II. 6, 2, 8.) 

Monzenite ............ Highwood Mountains, Mont. ........ Bull. 168, 133.-W. 1'. 

Nephelite-felsite ...... Magnet Cove, Ark .................... I. R. A., 263.-W. T . 

Leucite-tephrite ...... Bolsena, Italy ........................ J. G., IV, 56l.-W.1' . 

Shonkinite .......... ·. Maros, Celebes .............. : ........ G. C., 24 . 

Covite ................ Magnet Cove, Ark .................... .J. G., IX, 612.-W. 1' . 

Borolanite ............ Lake Borolan, Scotland .............. Rosen busch, El., 126.-W. 1'. 

--'------...'------~-.!..----·--,--------·----------

SUBRANG 4. ESSEXOSE, 

(II. 6, 2, 4.) 

.?5. Oi 0.162 R.hombenporphyry ... Stoksund, Norway ................... Z. K., XVI, 116.-W. T . 

54.34 .li3 Nephelite-syenite .... ·Cripple Creek, Colo .................. Bull. 168, 144.-W. T. 

51.90 .210 Laurdalite ............ Lunde, Norway .......... , ........... E. K., III, 375.-W. T. 

51.10 .173 Covite ................ Nosy Komba, Madagascar~ ........... M. M., 204. 

-50:50 . 143 Nephelite-mon•onite. Rongstock, Bohemia ................. T. M.P. llf., XIV, 98, 99.-W. T . 

50.26 .210 Nephelite-syenite· Viezzena, Tyrol ...................... K. A. W. W., CXI, I, 275. porphyry . 

49.90 . 155 (49.3) Leucite-kulaite ....... Kula, Asia Minor .................... J. G., VIII, 613.-W. 1'. 

48.69 .151 ( 49. 0-.150) Olivine-essexite ...... l\Iount Johnson, Quebec ............. J. G., XI, 265. 

48.46 • 243 Heumite . .. .. .. .. .. .. Lougendal, Norway.................. E. K., III, 376.-W. T . 

,~8. 35 . 161 Kulaltc ............... Kula, Asia Minor .................... J. G., VIII. 613.-W. T . 

47.94 .150.(48.3) Essexite .............. Salein Neck, Mass .................... Rosen busch, El., 172.-W. T. 

47.67 . 150 (48.0) ·l'heralite . .' ......... · .. Alabaugh Creek, ll!ont ............ :--· Bull. 168, 124.-W. T . 

46.48 • 162 Monchiquite ......... Rio de Janeiro, Brazil ................ Rosen busch, El., 235.-W. T . 
ROCK ANALYSES USED IN CONSTRUCTING DIAGRAMS. 

Clasoified list of analyses .used ·in constructing diagrams-Continued. 

RANG 3. SALEMABE. 

SUliiRANG 4. 8ALEMOSE. 

(II. 6, 3, 4.) 

Silica Alkali-silica con- ratio. tent. Author's name. Locality. Reference. 

--------1---------1-----------'--------- -------~----

50.47 0.132 

49.95 . 132 

48.50 . 138 

46.40 . 151 

45.32 .no 43.66 • 142 

47. so 1 0.137 

4~. 761 0. 086 

45.11 .090 

51. 931 o. 278 

54.14 0.238 

52.25 . 255 

51.94 . 208 (51.6) 

50.63 .271 

48.86 .234 

50.32 0.157 

49.73 .158 ( 49. 6) 

47.89 .161 (47.8) 

Augite-diorite: ....... Silver Cliff, Colo ................ __ .... Bull. 168, 147.-W. '1'. 

1\licroessexitc .. _ .. --. Nosy Kamba, Madagascar .. _ .... ___ .. 1\f. 1\1., 204 . 

Essexite ............. Jangoa, 1\fadagascar...... .... .... .... Do . 

Augite-diorite ........ Ullernas, Norway .................... Z. K., XVI, 49.-W. T . 

Hornblen<lti-gabbro .. Salem Neck, Mass ..................... -J. G., VII, 63.-W. T. · 

Essexite .............. Cabo Frio Island, Brazil ............. Rosen busch, El., 172.-W. T . 

SUBRANG 5. --. 

(II. 6, 3, 5.) 

I Basalt ................ , Pedregal, Mexico ...... _ .............. , w. T. 

---~------------

RANG 4. --. 

SUBRANG 3. --. 

(II. 6, 4, 3,) 

I Gabbro ............... , Rosswcin, Saxony .................... ! N.J., 1893, II, 503.-W. T. 

Diorite ............... Lindenfcld, Hesse.................... W. T. 

0RDE1' 7. lTALARE. 

RANG 1. LUJAYRASE. 

SUBRANG 3. JANEIROSE. 

(II. 7, 1, 3.) 

·1 Leucite-tinguaitc ..... J Bearpaw Mountains, 1\font ....... : .. ·l Bull. 168, 136.-_,_~·_:_ .. _T_. __ _ 

SUBRANG 4. LUJAVROBE. 

(II. 7, 1, 4.) 

Lujavrite ............. Tscha~natschorr, Finland ............ Rosenbusch, El., 126.-W. T. 

Chibinite ............. Umptek, Finland ..................... Fennia, XI, 2, 132.-W. T . 

Camptonitictinguaite Picota, Portugal. .. : .................. T. M.P. M., XVI. 272.-W. T . 

Nephelite-porphyry.. Laugendal, Norwuy .................. E. K., III, 157.-W. T. · 

Alloehetite ........... Allochet, Monzoni, Tyrol ............ A. W. W., 1902, Anz. XXI. 

RANG 2. VuLTURASE. 

SUBRANG 2. ---, 

(II. 7, 2, 2.) 

Basanite .............. Vesuvius ............................. R. T., 1861,25. 

Leucitc-tephritc ...... Bracciano, Italy ...................... J. G., V, 370.-W. 1'. 

Leucit!te .................. do .. .. .. .. .. .. .. .. . .. .. .. .. .. .. .. . lJo. 

\ 

45 

I 

I 

\ 

' 
46 

Silica 

content. 

Alkali-silica 

ratio. 

48.03 0.167 

CHEMICAL COMPOSITION OF IGNEOUS ROCKS. 

ClaBsijied list. of analyse8 used 'in constructi.ng diagrams-Continued. 

8UBRAN<7 3. -.--. 

(II. 7, 2, 3.) 

Author's name. Locality. Reference. 

B....,sanite ........ :····· Granatello, VeRnvitis ................. 1 R. T.,l861, 25. 

SuBRANG 4. VuLT~RosE. 

(IJ. 7, 2, 4.) 

42.461 0.229 ~----~ ;.:;:;~·=Ffi,ltaly=~=···········: ..... J Rosenlmsch. El., :157. 

47.40 1 0.130 

50.00 0.267 

46.48 268 

RANG 3. ---. 

SUBRANG 3. -·--. 

(II. 7, 3, 3.) 

ORDER 8. CAMPANARE. 

RANG 1. ---. 

SUBRANG 3. --. 

(II. 8, 1, 3.) 

Tingnuite .... _ ....... !. Jleemerville, N: .J ..... -.............. . 

J.Jcucititc ~. _........... Etinde Volcano, Kamerund, Africa .. 

Bull.lllus. Comp. Zoo!.', XXXVIII, 

1902, 276.-W. T. 

W.T. 

----'--------"--------------------·-------'----------------

SURRANG 5. --. 

(II. 8, 1, 5.) 

47.431 0. 333 . I Soda-sussexite ........ J Peni]<:kavaara, }'inland.: .. -......... , B. C. G. F., XI, 22.-W. T. 

RANG 2. VEsUVAS;E. 

SUBRANG 2. VERUVOSE. 

(II. 8, 2, 2.) 

---,----·-----.---------------'---------.---'---------

47.71 0.157 Lencite-basanite ..... Lava of 1631, Vesuvius ................ W. T. 

47.6~ .1ii7 ..... do ................ Lavu of 1872, Vesuvius ................ W. T. 

47.53 .149 Lcucilophyr" ......... Vesuvius .... , ... _ ................. --- R. T., 1884, LVI. 

46. 36 . 160 ( 46. 2) ..... do ..................... do ..................... -.......... R. T., 1884, LVIII. 

ORDER 9. LAl'PARE. 

RANG 1. U RTASE. 

SUBRANG 3. ARKANSOSE, 

(II. 9, 1, 3.) 

44.40 I 0.2.52 ___ ...:.I_A_r_k_it_e ................ , Magnet Cove,,:;;.,,_, ... _ .......... , J. G., IX, 616.-W. T. 
I 

. ~ 

ROCK ANALYSES USED IN CONSTRUCTING DI.A.GR.A.liiS. 

Silica 

content. 

Alkali-8ilica 

ratio. 

45.46 0. 397 

45.43 . 391 

45.28 . 418 

·13.02 . 37R 

68.751 0.144 

73. 60 1 o. 091 

53.39 0. 068 

53.35 . 067 ( ,'J2. 8) 

Classified list of analyses 11~ed in con.structing diagram.~-Continued. 

SUBRA,.;G 4. URTOSE ... 

(II. 9, 1, 4.) 

Author's name. Reference. 

Urtite ................ Luj~tvr Urt, Kola, Finland ........... ·G. F.'S. F., XVIII, 46i . .:_\r. T ... 

..... do ..................... do................................ Do. 

..... do ..................... do................................ Rosen busch, El., 126.-W. T. 

Iiflf~~,richinncphe- Kuuo"J.mo,_ Finland ....... : .......... R C. G. F., XI, 17.-W. T. 

I 

CLASS III. SA.LFEMANE. 

0HDEl{, 3. ATLANTARE. 

RANG 1. RocKALLASE. 

SUBRANG 2. --. 

(HI. 3, 1, 2.) 

I P~tntellerite .......... , Pantcllaria ........................... , Z. K., VIII, 179.-W. T. 

sunnAKG 5. RocKALLOSE. 

(UI. 3, l, 5.) 

ORDER 4. v AALARE. 

RANG 3. V AALASE. 

SUBltANG 4. V AALOSE. 

(Ill.. ·1, 3, 4.) 

Quartz-gabbro ........ Harz .................................. R. T., 1S84, XXXIV, 

Basalt ................ Teanaway River, Kittitas County, Bull. 168, 225.-W. T. Wash . 

52.67 

52.22 

. 047 (52.9) Olivine-diabase ...... Cape Colony, Africa .................. N.J., 1887, V, :!49.-W. T. 

.048 (51.9-.0ii1) Olivine-disbase-por- ..... do. .............................. .. phytite. Do. 

56.181 o. 036 

45.75 .027 

.. 47.00 l 0.008 

RANG 4. ---. 

SURRA~G 3. --. 

(IIT. 4, 4, 3.) 

I 

Diorite._ ............. :, WRshington, D~ c .... _ ................ l Bull.168,44.-W.T. 

MelaphFe ........... Holmestmnd, Norwa) ............... Z. K., XVI, 27.-W. T. 

RANG 5. --. 

(III. 4, 5.) 

I Olivine-gRbbro-dia-j S6Jvsberget, Norway .....•....... ····I Z. K., XVI, 27.-W. T. base. · 
48 

Silica 

content. 

Alkali-silie" 

ratio. 

54.17 0.160 

54.08 .163 

53.70 .160 (53. 6) 

50. 231 0. 150 

50.41 1 0.113 

48. 981 0.107 

48.95 .097 

47.561 .099 

47.32 .090 (47.5) 

CHEMICAL COMPOSITION OF IGNEOUS ROCKS. 

Classified list of analyses tmd in constructing diagrams-Continued. 

ORDER 5. GAUJA.RE. 

RAKG ] . 0RENDASE. 

SUBRAKG I. 0BENDOSE. 

(III. 5, 1, 1.) 

Author·~ name. Locality. Reference .. 

Orcndite ............. Leucitc HiliB, Wyo ................... Bull. 168, 86.-W. T. 

•.... do ..............•...... do................................ Do. 

Wyomingite ........• +····do •..•............................ Bull. 163, 85.-W. T. 

SUBRANG 2. --. 

(III. 5, 1, 2.) 

I Wyo~ingite ......... :l Leucite Hills, Wyo ···················I Bull.l68, 85.-W. T. 

RANG 2. KrLAUASE. 

SUBRANG 2. PROWERSOSE. 

(III. 5, 2, 2.) 

I Syenitic lamprophyre I Two Bnttes, Colo ......•........... --·1 Bnll.168, 165.-W. T. 

SUBRANG 3. LAMAROSE, 

(Ill. 5, 2, 3.) 

I 

Shonkinite ........... 1 Yogo Peak, Mont ..................... , Bul1.168, 128.-W. T. 

Absarokite ........... Hoodoo Mountain, Wyo .............. Bull. 168, 99.-W. T. 

I

. Mica:pi~rophyr~ ...... ·1 Nor!~ of Prug, Bohemia ............. ·1 R. T., 1879, XLVI. 

. Leu Cite absarokite ... Sunbght Valley, Wyo ................ Bull. 168, 97.-W. T. 

SUBRANG 4. KILAUOSE. 

(Ill. 5, 2, 4.) 

46.521 0.085 (4.'i.2) I Bast~lt ················/ V~lcano ~utte, Castle_llfountain' ····j Bull. 168,130.-;:-W. T. 43.35 . 099 Augitite .. . . .. .. . .. .. . M1ttelgcbuge, Bohemm.............. Rosen busch, El., 363. 

----~---------~-----------

RANG 3 .. CAMPTONASE. 

SUBRANG 2. ABSAROKOSE. 

(III. 5, 3, 2.) 

49.71 0. 090 AbMrokite ........... Cache Creek, Yellowstone Park ...... Bull. 168, 99.-W. T. 

19.03 . 082 Lcucite-husanite .· .... Rolsena, Italy ........................ J. G., V, 370.-W. T. 

48.36 . 080 Absarokite ........... Clark Fork, Wyo ..................... Bull. 168, 99.-W. T. 
ROCK ANALYSES USED IN CONSTRUCTING DIAGRAMS. 49 

Class(fied li~t of analyses used ·in constructing diagrams-Continued. 

SUBltA~G 3. KF.NTALLE~OSE. 

(III. !\, 3, 3.) 

Silica Alkali-silica con- ratio. tent. Author's name. ~ocnlity. H.efer~ncc. 

--1--------------·----·--

52.09 0.074 Kentallenite . o o 0 ••••• Glen Shira, Argyllshire, Scotlmul .... Q. J. G. S., TNI, 537.-W. T. 

ul. 76 .083 Absarokite ........... Ab~arok>L Wtnge, '\"ellowotonc Park .. Bull. 1U8, 9~.-W. T. 

51.65 .107 L:unprop.hyre -------- Cottonwood Canyon:, :Mont. .......... Bull.1ti8, 112.-W. T. 

50.82 .075 ..... rlo ................ Antelope an<l South Boul<lcr creeb, Bull. 168, 113.-W. T. :Mont. 

50.35 .101 01ivinc-niOllzonitc ... Smiilingen1 Sweden .................. E. K., II, 46.-\V. ·r. 

SUBRANG 4. CAMPTO~OSR. 

(IT I. 5, 3, 4.) 

51. 56 I o. 067 

53. 56 . on I 

Q~art,-basu:to.- ...... -1 Ci~der Conc,Cal .. _ ............. . 

M•cll·porph)r) ...... Cr.mdall Basm, W; o .......... . 

Diorite .... _.......... Little Falls, ~finn .............. . 

.. --j Bull. 168, 185.-"~ ----

.. Bull. 168, n -W. T. 

52. 3.5 • OG7 N .. 1., 1877, 12~. 

51.81 0 077 Gabbro-porphyry..... Crandall Basin, \\'yo 0 •••• _ ••••••••••• Bull. 168, 9·L-W. T. 

51.23 .076 Diabase .......... 0 ••• Hallcherg, Sweden ................... Rosenbuech, El., 3~:!. 

49.35 .074 Dolerite .............. Puntellaria .............. ___ ........ T. M. I'. M., 1883,393. 

48. GO .095 (4~.4) Nephelite-lmsalt. ..... 'Elkhead 1\Ionntains, Colo...... Fortieth Par.,- 1., 676. 

48.22 .084 Camptonite........... Mount Ascutney, Vt .................. Bull. 168, 26.-W. T. 

47.91 .086 .Basalt ....... _ . . . . . . . . \Vashoc, N ev .................... _ ... . 

47.90 .094 Essexite .............. Tortehohnen, Norway ................ E. K., II, 375.-W. 'L 

47.28 .083 Leucite-absarokite ... Ishawooa Canyon, Wyo .............. Bull. 168, 99.-W. T. 

47.16 . 077 Gabbro ............... Elizabethtown, N.Y .................. Bull. 168, 37.-W. T. 

·16.74 .089 ..... do ................. ___ .do ............ 0 ............. 0. .... Do. 

. 45.30 .107 Basalt ................ ll!ountTrumbnll, Ariz ............... Bull. 168, 174.-W. T . 

40. GO .078 Camptonite ........... :i\Iaena, Urm1, Norway ................ E. K., III, 376.-\V. T. 

SUBRANG 0. ORNOSE. 

(lii. 5, 3, 5.) 

54.1410.07-1 

46. 11 . 081 ( 0 077) I 

Tachylite ........... --1 Hanover ........................... ---1 R. T., 1879, LXXIV. 

Orniiite ............... Orni.i, Sweden ........................ G. F. S. ~'.,XV, 108.-W.T. 

SUBRA~G 2. --. 

(III. ;;, 4, 2.) 

50.031 0.062 (49. 4) I L~mproph;Te ....... ·1 Son~h Boulder Creek, Mont ........ 0-1 Bull. 168, 113.-;v. T. 

46.86 . 065 Dutbuse-p•lchstone ... ::\lemlen, Conn........... . ......... Bull. 168, 3fi.-\\. T. 

---~----------~------------

SUBRANG 3. AUVERGNOSE. 

(lli. "· 4, 3.) 

fi3.13 0. 053 Diabase ............... Jersey City, N. J.;c ................... A. J. S., IX, 1875,187. 

52.42 0 016 ..... do ................ Wintergreen T,ake, ComL ............. A.J. S., lX, JF75, 189. 

52.68 . 0:'>7 Dolerite .. _-_.......... Mount Holyoke, ~lass................ A. J. S., IX, 1875, 186. 

51.78 .0-14 Diabase . . . . . . . . . New Haven, Conn.................... Do. 

51.46 . Oo7 Gabbro ............... Sturgeon Falls, ::\lich ................. Bull. 168, 70.-W. T. 

14:4 7 4--No. 18--03-4 
50 CHEMICAL COJIIPOSITION OF IGNEOUS ROCKS. 

Classified list of analyse.~ usr:rl in const1'ucting dia[Jr<tms_:__Continuecl. 

Rilica 

eontent. 

---

51.36 

50.8V 

·10.~7 

49.6;! 

•19.18 

48.23 

4~.04 

47.93 

47.90 

47.i\4 

·17.45 

47.29 

-15.66 

44.90 

4-1.97 

44.77 

43:50 

42.77 

42.68 

42. oo 

Alkali-silica ratio. 

---------

0.040 

. 053 

.06~ 

. 05;\ (49./i) 

. 035 

.03-1 

.045 

. on (47. 7) 

. 04o (·17. -!-. 0·10) 

'070 ( 47. ~-- 079) 

.082 

. 029 

. 049 

. 033 

. 072 

.057 

.062 

.063 

.015 

. 053 (. 0<>5) 

SUBKANG 3. ATTVF.HGNORE-Cnntinnecl. 

Author's name. Locality. Reference. 

Basalt·--------------- Orange, N.J .......................... Hull.168, 39.-\V. T. 

..... do................ Lnssen Peak, Cal . .. .. .. . .. .. .. . .. .. .. Bnll. lGS, 186.-W. '1' . 

..... do ...... ____ : _____ Pan tell aria .......................... -~ '1'. )L P._ M., 1883., 3!l3, 

Diabase .............. MountAscntney, Vt .................. Bull.168, 21;.-w. T . 

Basait ................ Disko, Greenlaml .................... T. 11!. P. J\I., 1874, 1~U . 

Norite ................ Crystall<':tlls, Mich ................... 1 Bull.l68, 67.-\Y. '1'. 

Basalt ................ Ovifak, Greenland ................... / '1'.1\Ll'. M., 187·1, 1~1. 

__ ... do __ .. __ .......... l'ayncs Creek, Cnl. ................... i Bul-l. 16~, 186.-W. T . 

Djabn::-;e ···-···------- Pcnokee-GogeiJk Runge, Mieh ....... i Bull. HiS, 73.-,V. '1'. 

Basalt--------------·- Grant~ N. ~lex ........................ Bull. Hi8~ 170.-\V.1\ 

Gabbro .. . .. .. .. . . .. .. Saleix, I';-rcnees .. .. . .. .. .. . .. .. . .. .. C. G. I., VITI, 1901, 83~.- W. '1'. 

Prroxene-uriegite .... Lher,, Pyrenees ...................... C. G. I., VIII, 1901, 83~.-W. T . 

Olivine-gllbbro ....... Birch Lake, 1\Iinn ."..... .... ..... .. Bull. 168, 8l.-W. T . 

Pyro-'-t•ne-;uiegitc .... Tuc rl'Ess, Prrenees............... C. G. J., VIII, 1901, S33.-W. T. 

Gabbro ............... mizubcthtown, N.Y ................. .Bull. 168, 37:-W. T . 

Basalt ................ Kosk Creek, Cal...................... BulL 1~8, 186.-W. T. 

Homblende-monehi- 1\Iagnct Cove, Ark .................... Rosenbnsch, El., ~31\.-W. T. quite. 

Olivine-diabase ...... Campton, N. H .. __ .............. A. J. S. XVII, 187V, 150. 

Ariegite ...... __ .... _. Escourgeat, Pyrenees .... _--_-_ ...... _ C. G. I. 1 VITI, 1901, 833.-\Y. T_ 

V'ourchite -----------· Fonrrhc l\Iountltin, Ark ______________ T. R. A., 108.-\V. r_r_ 

RANG 5. KEDA BEKA~E. 

(Ill. 5, 5.) 

---.,------"7"-------~----- ------------------

i8. 0'2 0.010 1 Noril~---------------- MeKinseys Mill, Mel. ................. llull.168, 45.-W. T. 

47.09 . 014 1\ncg1te -----------·-- Lrhcrz, Pyrenees. _____________________ C. G. I., Vlll. lt,Ul. 83:L-\V. '1'. 

44.76 . 020 Hypersthene-gabbro. Wethererlvilk, 1\Id ................... Bnl1.1u8, ·H.-W. T. 

44.64 . 017 (4iJ.1) Kedabekite ........... Kerlabck, Ru,;sia ..................... W. T . 

H-38 . 019 (43.8) Aricgitc ------·------- Lher.z, Pyrenees ... ------------------- C. G. I., VII, HWI, ~a3.-\V. T . 

44.11 . 012 Kedabekile ........... Kedabek, Russia ..................... W. '1' . 

42.32 .025 Ariegite .............. Lherz, Pyrenees .... c ................. C. G. T., VIII, 1901, 8:13.-W. 'J'. 

38. V5 . 029 ..... do ..................... do . .. . .. .. .. .. .. .. .. .. .. . .. .. . . . .. Do . 

0Rv~m H. PoRTUGAuE. 

RANG 1. \VYOMINGA~E. 0 

SUBRANG 3. --. 

(IIJ. r., I, :q 

_5_o_._oo__,_j_o_._n_o ____ __.!_s_h_m_'kinite ........... , He:irpaw !\fountains, lllont.:.:.:=-1 Bull.168, 13G.-W. T. 

SUBRANG 4. --. 

(III. 6, 1, 4.) 

' 

48.39 0.121 (48.5) Analcite-ba,alt'. ...... Little Belt 1\Iountaim, l\lont ......... Bull. 1G8, 128.-W. T. 

·10. 72 .166 1\Ionchiquite ......... Fohbcrgc", Baden-------------------- W. T. 

42. ilO .157 Nephelinite .......... Katzeubnckcl, Odenwald ....... __ ... Hosenbnsch, El., 3o7. 

40.03 .140 (40.2) Camptonile .......... Oxford, N.J ... :...................... Rosc'nbusch, El., 235.-W. 1'. 
l':,OOK ANALYSES USED IN CONSTRUCTING DIAGRAliiS. 

Classified Ust of analyses 11sed ;,n constrncting diagrams-Continued. 

RAN<1 2. Moxemqu·A~E. 

SUBRANG 3. SHONKINOSE. 

(IlL 6, 2, :l.) 

-----.-------.---------------

Silicn 

content. 

A I kali-silica 

ratio. Author's name. Reference. 

51 

--------------------------------------------

49.5'.) 0.13~ Lencite-syenite ....... Highwood ~Ionntnins, ~font ......... Bnll. 168, 132.-W. T. 

-!S.Ofi .142 (4S.5) Shonkinilc ........... Maros, Celebes ....................... G. C., 2:1. 

47.98 . 136 Leucite-baS>tlt. ....... High woo<! Mouutains, ~font ......... Bnll. 168, 132-W. T . 

46.73 .088(45.9) Shonkiitite ........... Square Butte, )font................. 1:1. G. S. A., VI, 41-l.-W. T 

45.1~ . 101 (44.~) Nephelite-lmsalt ..... Breitfirst, Hesse ...................... Rosen busch, EL, 357 . 

43.85 . 150 Lcucite-nlOiwhiqnite. ~fittelgebirgc, Bohemia ... _. __ .... _ .. Ro~cnbu~eh, .El., 235.-\\', T . 

--...C...------'-----------'----;----------------------

SUJlRANG 4. MONCHIQUOSE. 

(TlL G, 2, •1.) 

----,-------.---------,-------------------------

•18.43 0.114 Hornblemle-vogesite. Hohwald, Elmss .. .. .. . . .. .. .. . .. . .. . Rosenbuseh, EI .. 231. 

47.82 . 121 Monehiquite ......... High woo<! Mountains, -~Iont ......... Bnii. 168, 132.-\V. T . 

45.n9 . 110 (45.-8) ATiltlcite-basalt ....... Pike• Peak district, Colo ............. Bull. 168, 146.-W. T. 

45.56 . 154 Nephelite-tephrite ... Herrnberg, TeLHchen, Bohemia ...... W. T . 

44.M . 124 Limburgite ....... : ... Held burger Feste, S. Thii-ringen ..... Rosenbu8ch, El., a63 . 

•13. 84 .119 Leucite-ba8anite ..... B!ankenhornberg,Kaiser.;tuhl,Bnden W. T. 

----'--------'------------'--------

RANG 3. LDfHURGASE. 

SURRANG 3. OUROSE. 

(ITT. 6, 3, 3.) 

46.65 0.11<1 Labradorite-porph)Ty Wildkuar, Trrol. ..................... R. T., 1879, XLIV. 

43.7-1 .108 llfonchiquitc ......... Rio do Onro, BraziL .................. Ru~cnbust:h 1 E1. 1 235.-\V. T. 

·12. 46 . 068 ..... do ........ , ....... Willow Creek, ~Iont .................. Bull. 168, 130.-W. T. 

SURRANG 4. LIMBURGOSE. 

(III. 6, 3, 4.) 

--------------.-------.-----------·-------------

46.60 0. 11~ ( 46. 3) Ncphelitc-gttbbro .... Nosy Komba, Madagascar ............ M. M., 204. 

46.35 . 086 Ncphelitc-basanitc ... Riimhild, S. Thiiringen .............. Rosen busch, El., 3-16 • 

-14.82 . Oi3 ( 44. fl-. 074) Paleolimburgite ...... A~acama, Chile ...................... Z. D. g. G., Ll, •1. 

43.65 .071 (43. 8) Olivine-gabbro-dia- Bmndbcrget, Gran. Norway ......... Q. J. G. S., L, 19.-W. '1'. base. 

43.50 . 107 Augititc .............. Limberg,Baden ...................... W.T . 

41.01 . 08~ Hornblende-basalt ... , Sp<trbrod, Rhone ..................... N .. !., 1882, II, 155 . 

•10. 70 . 08·1 (40.5) 

40.10 . 109 (40.•1) 

37.90 . 005 

Limburgitc .......... I Obcrcrsteinhcrg, Lausitzcr Moun- Rosenbuseh, El. 363 . 

I 

tain~, Pru~~ia. 

Ijol!te ................ Ampasibitika, Madagascar........... M. ~I.. 204 . 

. Horublen~litc ........ Brandberget! Gran, Norway .......... Q. J. G. S., L, 19.-W. T . 

8UBRANG 5. -· --. 

(III. 6, 3, 5.) 

41. 9·1 1 0.121 \ Cllmptonite .......... , CamptonFalls, N. H ................. J A. J. S., XVII, 1879,.150. 
52 CHEMICAI.- COMPOSITION OF IGNEOUS ROCKS. 

Classified list of nnalyses used in con~i1'1lCting diagrams-Coutinucd. 

Silica 

con· 

tent. 

Alkali-silica 

ratio. 

39.84 0. 046 (•10.4) 

45. 40 1 o. 0~3 

RANG 4. ---. 

SUB!tANG 1. --. 

(III. 6, 4, 1.) 

Auth(Jr's name. Locality. Hefereltce. 

Hornblende-gabhro _. Piedmont, Italy ................... -.. Rosen busch, El., 151. 

SUllRANG 3. --. 

(Ill. 6, 4, 3.) 

I Dioritic gabbro .. ·····I Nosy Komba, Madagascar ........... ,~0-4-.---------· 

ORDER 7. KAMERUNARE. 

RANG.l. JVLu.IGNA~~J. 

SUBRANG 3. --. 

(III. 7, 1, 3.) 

_4_7_.s_5_._l_o_.1_4_4----~•-IS_'_e_r_h_e_li_te_·_m_a~lignite .. jl'oohbah Lnke: Ontario .............. ~ Hosenb~seh, El., 176.~W. T. 

SUBRANG 4. MAL!GNOSE. 

(II, 7, 1, 4.) 

51.88 0.180 Garnet· pyroxene· Pooh bah Lake, Ontario .............. Rosen busch, El., 176.-W. T. mal ignite. 

51.38 .193 Amphibole-malignite ..... do................................ Do. 

44. 61} .186 Theralite ............. Crazy Mountains, l\Iont........... ... Bull. 168, 124.-W. T. 

42.02 .161 (41.8) Ijolite·porphyry ...... Alnii, Sweden ........................ N. J.,1S97, II, 99.-W. T. 

RANG 2. KAMERUNASE. 

SUBU.ANO 3. --. 

(III. 7, 2, 3.) 

46. 041 0. 127 I I,cucite-basalt ........ , Highwood Mountains, Mont ......... , null. 168,132.--W. T. 

--------

SUBRANG 4. KAMERUNOSE. 

(III, 7, 2, 4.) 

47.10 0.178 Hcumite .............. Laugendal, Norway .................. E. K., ITI, 376.-W. T. 

46.53 .123 Therulite ............. Umptck, Finland ..................... Rosenbusc]J, El., 17G.-W. T. 

45.77 . 163 Farrisitc .............. Farris, Norway ....................... R. K., III, 376.-\V. T . 

44.31 . 147 Therniite ............. Gorrlons Butte, Mont ................. Bull. 168, 124.-W. 'r . 

42.77 .143 (43.0) llfonchi(tuite ......... Kiechlillsbcrgen1 Badcn .............. ,V.1\ 

42.65 . 133 (43.3) Basalt ................ Cape Verde, Africn .................... R. T., 1884, LXXIV . 

·10.10 . 167 (40. 3) Lcucitc-nephclinitc .. Etindo Volcanv, Kan1ernn, Africa .... W. T . 

39.97 .183 (40.2) 

39.30 .165 (40.8) . ~~~~~~~;~~~--r~·::::::: l: :: :~~::: ::::::::::::::::::::::::::::: ~~: 
ROCK ANALYSES USlW IN CONSTRUCTING DIAGRAMS. 

Clas1lijied l·ist of analyBes used ·1:n construct1:ng cNagrmns-Continued. 

Silica 

content. 

Alkali-silica. 

ratio. Author's name. 

RANG 3. ETINDASE. 

SUBRANG 4. ETINDOSE. 

(III, 7, 3, 4.) 

Locality. I Reference. 

---·----·1---------1--------- --1----·---·--·-·· .. 40.52 0. 097 

39.33 .109 

38.46 .143 (38. 9) 

46.51 t o. 167 

Hessc-Dar_mstadt. .... : ............... 

1 

Rosenbnsch, El., 357. 

1\httelgcbnge, Rohemm .............. 1 Do. 

Mulatto, Prcdazzo, Tyrol. ........... ·I K. A. W. W., CXI, I, 234. 

Nephelile-basalt .... _. 

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

Camptonitc ......... . 

I 

ORDER 8. BOREMARE. 

RANG 1. CHOTASE. 

8UBRANG 2. CHOTOSE. 

(III. 8, 1, 2.) 

53 

I Lencitite ............. ~ Bearpaw Mountains, Mont ........... ~ ~~~:1.68,136.-W.T. -------

RANG 2. ALBANAS!o]. 

8UBRANG'2. ALBANOSE. 

(liT. 8, 2, 2.) 

47.4710.137 ---~-Lcncite-tephritc ...... l Vesuvius, lavaol1760 ................ 1 R.T.,1884,LVL 

45.99 .168 (46.1) I,encitite ............. Capo di Bove, Italy ................... A . .T. S.,IX, 1900,53.-W. T. 

SuBaANG 3. --. 

(III. 8, 2, 3.) 

41.241 0.141 \ Nephelinite ........ --I Laacher See, Rhine province ....... ·I Rosen busch, El., 357. 

--~-----~-

SUBRANG 4 .. COVOSE. 

(III. 8, 2, 4.) 

43.18 0.186 Themlite ............. Crazy Mountains, l\font .............. Rosenbmch, El., 176. 

42.06 . 132 Lim~urgite .... , ...... Habichtswald, Hesse ................. Rosenbusch, El., 363 . 

41.74 . 204 Ijolite ................ 1\fagnetCove,Ark .................... J.G.,IX,618.-W.T. 

40.15 . 204 (40. 3) Nephelinitc .......... Etindc Volcano, Kamernn, Africa ... W. T . 

38.39 .150 ..... do ..................... do................................ Do. 

ORDER 9. FINNARE. 

RANG 1. !JOLASE. 

SUBRANG 2. MADUPOSE. 

mr. 9, 1, 2.) 

42. 651 0. 139 I Madupite ............. l Lcncite Hills, Wyo.~.:~ ......... : .... ! Bnll.168, 85.-W. T. 
. 54 CHEMICAT~ COMPOSITION OF IGNEOUS ROOKS. 

Cla.s.s(fied liRt of w1aly.se.q ?t,qcrlin r•mJ . .stn .. wtinq diartrams-Continued. 

8UBRANG 4. IIYAAHOSE . 

. (III. 9, 1, 4.) 

s_ilica I Alkttli-sJ!ica con- ratio. tent. , Author'~ IUltnc. Locality. Reference. 

--1----~1------1-------~---1----------

45. u4 I o. 342 

4~. 70 I . 2ii7 

42.!8 . 268 

Ncphelite-porphyry .. Umptek, Finland .................... Fennin., XI, 2, 196.-W. T. 

Jjolite...... ... .. . . .. . Kunsmno, .!<'inland ................... B. C. G. F., XI, lu.-W. T. 

Nephelite-basalt ...... Baucrsberg, Bavaria ................. R. T., 1879, LXII. 

SUBRANG 5. !JOLOSE. 

(III. 9, 1, 5.) 

•12. 07 F ---I Jjolite -~-~nnsamo, Finland .................. ·I B. C. G. F., XI, 16.-W. T. 

51.83 

50. (i-t 

46. DO 

0. 00~ 

• 020 

. 030 

48. 6~ 1 o. 008 

CLASS IV. DOFEMANE. 

OnDER 1. HuNGARARE. 

SECTION l. MINNESOTJ ARE. 

RANG 1. MrNNESOTASE. 

SECTION 1. .1\HNNESOTIASK 

SUBRANG 2. COOKOSE. 

(IV. l, 1, 1, 1, 2.) 

Jlyroxcnitc _. Meadow Creek, .1\font ...... Bull. 168. 114.-W. T. 

Wchrlilc ............. New Braintree, Mass ................. Bull. JGH, 33.-W. 1' . 

Jlypcrsthcnc-;;ttbbro. Gunflint Lake, Minn ................. Bull. 168, 81.-W. T. 

SECTION 2. 

RANG].--. 

SECTION 2. --. 

SUBRANG 1. BELCHEROSE. 

(TV. 1, 2, l, 2, 1.) 

SUBRANG 2. --. 

(IV. 1, 2, 1, 2, 2.) 

---~--------,--------~-------

48. Ul 

46 .• 'iG 

46.56 

46.06 

44.94 

44.39 

0.013 

.050 

. 043 ( 1G. 9) 

.098 

.000 

.032 

Olivine-gabbro ..... _. Omngc Grove, Md .................... Bnll. 168, 14.-W. T. 

C:abhro ............ _ .. Pharkowsky-Onwal, Ural Mountains. 0. N., 145. 

..... do ................ Near Koswinsky, Ural Mountains.... Do . 

Missourite ............ Shonkin Creek, l\Iont. ................ Bull.168, 133.-W. T,. 

Wchrlitc ............. Koswinsky, Ural Mountains .......... 0. N., 173. 

Gabbro ............. _. Phn.rkowsky-Ouwal, Umll\Ionntains. 0. N., 145. 
tent. 

IWCK ANAT.YSF.S USED IN CONSTRUCTING DIAGRAMS. 

Clu.~sijiecl bist of mwlyBe.~ me£l ·in conRtrnctinu din_qram.•-Cont.inned. 

SECTION 3. HUNGARIARK 

RANG 1. vV ER RLASE. 

SECTION 1. WEURLIASE. 

8UBRANG 2. WE,HRLOSE. 

(IV. 1, 3, 1, 1, 2.) 

55 

--------

Alkali-silica rati<l. s:~~!~~~ I Author's name. I,ocality. Referenee. 

------1--

4S. 95 0. 040 

1G.13 . 001 

45. G8 .000 

47.75 

46.00 

44.99 

0. 027 

. 035 (4G.1) 

.028 

•14.fi!l 0.000 

RG. 80 , 049 

46. O:J I 0. 041 

41.fl() I O.OR6 

Wehrlitc .....•....••• Red Bluff, l\Iout.................. Bull. 168, 114.-W. T. 

Ilornhlcnd"-]Jieritc .. Meadow Creek, Mont................. Do. 

Lherzolite ..... _ .. ·.- .. Hahlisser, Piechnont, Italy ........... RosenlmRch, El., 1G5. 

-------

SECTION 2. --. 

SUBltANG 2. RosswErNosE. 

(IV. 1, 3, 1, 2, 2.) 

I Peridotite .......... .. 

l

llorn blemlitc ...... .. 

Wehrlite ........... .. 

Cathay Hill, M~triposa County, Cal ... l:lull. loS, 209.-W. T. 

Col d'Eret, P;·renees ................. C. G. T., VHf, 1901, 833.-W. T . 

Crystrtl Falls, Mich ................... Bn11.1G8, 67.-\V. T. 

. SECTION 4. --. 

RANG 1. CoRTLANDTASE. 

SECTION 1. CORTLANDTIASE. 

SU:SRANG 1. COH.TLANDTOSF.. 

(IV. 1, 4, 1, 1, 1.) 

I 

Lhcrzol_itc ............ l ~·~1erz, l'yrcnc_cs ................. _ ..... l C. G. T.: ~HI, 1~01 •• 83:>.-'--W. T. 

PcrJclnlltc ............ S; mcnsc, ~ \ ....................... Bull. ][,R, 38."7'\1. 1 .. 

SUBlt.ANG 2. CUSTEROSE. 

(IV: 1, 4, 1, 1, 2.) 

I Peridotite ---------·-·1 Silver Cliff, Colo ...................... ).Hnll'.1G8, 147.-W. T. 

SECTION 5. PYRE!'-HARE. 

RANG ~- LITERZASE. 

SECTION ·1. LHERZIASE. 

SUBRANG 1. LIIERZOSE. 

(IV. 1, 5, 1, 1, 1.) 

I Hornblcnde-lhcrzolitcl Caussou, l'yr"necs .. "" """"""--I c. G. r., 1901, vrrr, 833.-W. T. 

SURRANG 2. ARGEINOSE. 

(TV. 1, 5, 1, 1, 2.) 

l

llornblcndc-pcri<1o-! Argein, Pyren"-cs ..................... ! C. G. I., 1901, VIII, 833.-W. T. ~~ . 
56 cn:i;;MTCAL COMPOSITION OF IGNEOUS ROCKS. 

Clas8ijie!l list of rmalyses used in constractiny rlict.'Jrrrms-Continned. 

SECTION 3. VENANZ!ASE. 

SURRANH 2. VF.NANZOSE. 

(IV. 1, 5, 1, 3, 2.) 

---.,-------,---------,----------------,-------------

Silica 

content. 

Alkali-silica ratio. Author's nttme. Loc1tlitr. 

--1------1----------------------1-·--

41.43 0.152 

fi3. 051 0. 018 

4.'i. 051 0. 030 ( 45. 9) 

4fi. 041 0. 209 

Venanzite ... __ ... San Venanzo, Umbria, Italy .......... A. W. B., 1899, VII, 113.-W. T. 

ORDER 2. ScoTARJ<~. 

SECTION 1. --. 

RANG 1. ---. 

SECTION L --. 

SllBIIANG 2. --. 

(IV. 2, 1, 1, 1, 2.) 

I Augite-norite ......... 1 Ma<lmR, India ......... .. 

SECTION 3. RRANDBJ<~RGIASE. 

SUBRANG 2. BRANDBERGOS,E. 

(IV. 2, 1, 1, 3, 2.) 

.... j W.T. 

I Pyroxenite ........... 1 Rrandl.>crg, Norway ................ ·I \1. J. G. S., L, 31.-W. •r. 

SUBRANG 3, --. 

(lV. 2, 1, 1, 3, 3.) 

I Nephelitc-baRult ..... ·I Katzcnbnckel. Odenwnl<l, Baden . ~·I Rosen busch, El., 357. 

SECTION 2. PAOLIAHE. 

RANG 1. P AOin\SE. 

SEC1'JON 2. --. 

SUBRANG 2. --. 

I (IV. 2, 2, 1, 2, 2.) 

--~-----.----------- -------.,--------------- 47.41 I 0.031 I Augite-peridotite ..... tl'eekskill, N. L ...................... 1 A . .T. 8., XXXI, 1SSI>, 40.-W. 'l'. 

42.68 ' . 077 Hornblende-basalt . . . Hank, S. Rhone...................... Roscnhusch, El., 30~. 

40.42 . 038 Olivine-gabbro ....... Crazy Mountains, l\Iont .............. Bull. 168, 1~2.-W. T. 

40.15 . 000 K01<wite .............. Koswinsky, Uml ~fountains ......... 0. N., 119. 

39.5g .057 Nephelite-ba>mlt ..... Otten<lorf, Silesia ..................... R. T., 1884, LXIV. 

SECTION 3. l'AOLlASE. 

SUBRAJSG 2. PAOLOSE. 

(IV. ~. 2, 1, 3, 2.) 

41. 44 0. 000 ( 41. G) Koswite ....... _...... Koswinsky, Ural }.lountains.......... 0. N ., 119. 

38.39 . 031 (37. 5) Jacupirttngite ........ Magnet Cove, Ark .................... J. G., IX, 620.-W. T. 

R8. 38 . 022 ..... do .. . . . . . . . . .. . .. . Sno l'aulo, Brazil..................... Do. 

3G.fl1 . 075 Eleolite-mien-syenite. 11Ia9net Cnve, Ark.................... Do. 
ROCK ANALYSES URED IN CONSTRUCTING DIAGRAl\fS. 

Cla.~.~ijiP-(llist of mwlyses 1(.qed in constructimg_ diagram.,-Continucd. 

SECTION 3. TEXIARE. 

RANG 1. TEXASE. 

SECTION 1. l\IARQUETTIASE. 

8UBRANG 2. llrARQUETTOSE. 

(IV. 2, 3, 1, 1, 2.) 

57 

-------.~--------------------

Silica. 

eontent. 

Allmli-silien. 

ru.tio. Author's nnme. T. .. ocality. Reference. 

---------------------------------------1 

~9. a7 0. 017 

40. a~ o. oso 

39.92 .OG3 (-11.0) 

;19. 1(; .081 

3G. i\3 . 108 

38.341 0.10G 

37.98 .121 (37. 4) 

39.20 0. 056 (38. 6) 

37.96 .OG6 

Peridotite ............ Opin Lake, Mieh ..................... Bull. 168, 64.-W. T. 

--------·-'--------------

SECTION 2. UV ALDIASE. 

SllBRANG 2. UVAI,DOSE. 

(IV. 2, a, 1, 2, 2.) 

Kephclitc-bn,alt ..... Uvttlde County, Tex .................. Rnll. 1G8, fi2.-W. T. 

..... do ..................... do ................................ Bull.168,63.-'-W.T. 

..... do ................ Oberleinlciter, Raden ................ I!osenhusch, El., 3G7. 

Nephclite-m eli lite- Wartenberg, Raden .................. Rosen busch, El., RfiO. 

basalt. 

SECTION 4. --. 

RANG 1. CARSELASE. 

SECTION 2. CASSELIASE. 

SUBRANG 1. --. 

(IV. 2, 4, 1, 2, 1.) 

I.Jimburgitc .......... _ JUo de Jmwiro, Brazil ................ T. M. I'. l\1., XX1 304. 

Illelilite-ncpheli tc- Hollenberg, Westphali>t .............. Roscnbnseh, ~~I.. 3o7. basalt. 

SURRA NG ~- CASSELOSE. 

(IV. 2, 4, l, 2, 2.) 

Dike-rock . .... .. . . .. . Kola Peninsula, 'Finland ... .. 

Ncphelitc-ntclilite- Uvalde County, 'fex ....... . l.msult. 

SECTION 5. 

RANG 1. --. 

SECTION 1. KALTENIASE. 

SUBRANG 3. KALTENOSE. 

(IV. 2, 5, 1, 1, 3.) 

Fennin., 15, 2, 1899, '27.-\Y. T. 

Bull. 168. 63.-W. T. 

34.981 0.101 j.Mien-peri<lotitc ...... ·I Kaltcnthal, Hn.rzburg, Harz ~Its .... ·I Rosen busch, ~;1., lf•n.-W. T. _______ __. 
58 

SHieH. 

content. 

31.59 

CHEMICAL OOMPOSITION OF IONEOTJS HOCKS. 

Classified list o.f mJo.ly.~es uscrl ·i.n cmJst/·udi?.(! dia[JI'!IIJis-Continncd. 

Om>EI{ 3. SvEIUnARE. 

SECTION 1. BERGENIARE. 

RANG 1. BBHGJ~NASE. 

SECTION 1. HERGENJASE. 

RUBRANG ~. RER\.F.NOSE. 

(IV. o, 1, 1, l, 3.) 

------,--------·-----

SECTION 2. 

RAN<T 1. ---. 

SECTION 2. --. 

SUBRANG 2. --. 

(TV. B, 2, 1, 2, 2.) 

----,-------~ ---------·------------------,--------------·----· 

Neplwlite-mclilit<~- Burgstall, Raden ..................... Ro~cnlm~ch, El., ;)60.-,r. T. basalt. ~s. ~o · o.1n 

3S. 18 . 036 (?)Pyroxenite ........ Prcdazzo, ~ryrol ------ E. K., li, 7G.-W. 1'. 

SECTION ·3. A VEZACIASE. 

~UllRAXG 3. A VEZACOSE. 

(TV. 3, 2, 1. B, 3.) 

0RDEU 4:. ADIRONDACKARJ<J. 

Suborder 2. Adirondaokore. 

RANG ] . ADIRONDACKASK 

SECTION I. ADlRONDACKL\SE. 

SUBRAXG 3. --. 

(IV. 4, 2, 1, 1, 3.) 

24. 741 0. ooo Iron ore ............ --I Ulfu, Swedcm ........................ -I s. J\1. (/., XXI, r.o. 

22.871 .000 Iron ore ..... , ......... ! Cumberland Hill, H. I ............... 

1

1 S. J\L Q., XXI, 60. 

14.95 .000 ..... do ................ Laanghult, Sweden.................. Dn. 

----~------~--------~--~ 

SUBRAXG 4. --. 

(IV. 4, 2, 1, 1, 4.) 

--.--~~-~---c-------'-------c- ---~---------;------------

21.42 0. 033 Iron ore .............. Elizubcthlown, N.Y ................. S. !II. Q., XX, 3.J3. 

ll. 73 • 055 ..... do ..................... do~............................... Do. 

10.37 . 057 ..... do ................ Frontenfw Countr, Ontario---------- S.l\I. Q., XX, 331. 
ROCK ANALYSES USED IN CONSTRUCTING DIAGRAMS. 

C/assijietllist of tt.nalyse.s usP-d. in eonstruel.i.ng diar;rmn.s~Continued. 

Silica 

eon~ 

tent. 

Alkft!i-Rilica rn,tio. 

17.90 0.000 

13.35 . 000 

Suborder 3. Ohamplainore. 

RANG 1. CHA~fPLAINASE. 

SECTION f CHAMPLAINIASE. 

At1thor's name. 

SUBRANG 4. --. 

· (IV. 1, 3, 1, 1, 4.) 

Loca!Hy. Refcrmicc. 

Iron ore........ Split Rock mine, N.Y ................ S.M. Q., XX, 343. 

..... do ................ Tunnel Hill, N.Y.................... Do. 

ORDEn 5. 

Suborder 2. --. 

RANG 1. ---. 

SECTION 1. --. 

-SUBRANG 4. --. 

(IV. fi, 2, 1, 1, 1.) 

1~. 77 I 0.0:\9 -=-~ Iron o:..:_:_·=·~Pinc I.ake, Ontario ................... j S.M. Q., XX, 331. 

JO. 2G I 0. 000 

I 

9. 791 0. 000 (9. 5) 

fi5.52l 0.000 

55.23 . 000 

SUBRANG 5. --. 

(IV. 5, 2, 1, 1, 5.) 

\ Iron ore .............. j Iron Mountain, N.'Y ................. j S.M. Q., XX, 343. 

SECTION 2. --·. 

8UBRANG 4. --. 

(IV. fi, 2, 1, 2, 4.) 

I Iron ore ............ J ~~illford Pit, K. Y .................... j S.M. Q., XX, 3<!4. 

CLASS V. PERFEMANE. 

OI{DER 1. MAORARK 

SECTION 1. OAROLINIARE. 

RAXG 1. \V BDS'rEHASE. 

SECTION 1. MARTCIASK 

SUBRANG 1. MARICOSE. 

(V. 1, l, 1, 1, 1.) 

\ 

Lherzolite ............ \ Loc~tno, Piedmont .................... I Rosen busch, El., JGo. 

1')-rnxcnit" ........... M~tricc, district, Transvnrrl. ........... A. J. 8., VII, 1899, 318.-W. T. 

59 
60 

Silica 

content. 

Alknli-silic11 ratio. 

CHEMICAL OOM'POSITTON OF IGNEOUS ROOKS. 

Classified list of analyses nsed in con.~trncting diagmms-Continued. 

SECTION 2. WEBSTERIASE. 

SUBRANG ]. \YEBSTEROSE. 

(V. 1, 1, 1, 2, 1.) 

Author's name. Locality. Reference. 

-------------------1·------------1----------'---

55. H 0. 005" Websterite ....... _ .... W,ebster, N. C ........................ Bull. 168, 53.-W. T. 

53.98 . 000 ..... do ..... ,.......... IIebbvillc, Md ....................... Bull. 168, 43.-W. T. 

52.55 . 004 ..... do ..................... do ................................ Bun: 168, 43.-W. T. 

__c_------'------------'---------------'-'------------

li3. 21 ; 0. 003 

53.251 .000 (53.6) I 

50. so I 0. 000 (50. G) 

49.35 . 000 

SUBRANG 2. CECnOSE. 

(V. 1, 1, l, 2, 2.) 

I 

Websterite ....... ·····\ Cecil County, Md ................... ·1 Bull. 16S, 43.-W. T. 

Pyroxenite........... Mount Dinblo, Cal. ................... Bull. 168, 213.-W. T. 

SECTION 2. MARYLANDIAIU~. 

RANG 1. BAmnroRASE. 

SECTION 2. BALTJJIIORIASK 

SUBRANG 2. BALTIMOROSE. 

(V. 1, 2,'1, 2, 2.) 

I 

I~yrox_enite ........... , Johm~y Cake road, Md ... _ ..... ' .....• , Bull. 168, 42.-W. T. 

1~osw1te .............• Koswmsky, Uralllfountmns . . . .. . . . . 0. N., 119. 

SECTION 3. --. 

RANG 1. --. 

SECTION 2. --. 

SUilRANG 2. KOSWOSE. 

(V. 1, 3, 1, 2, 2.) 

-43.20 I 0~--~oswite~ .. ------1 Koswinsky, Ural Mountnins=----1 o_._N_·-_, _n_9_. ____ _ 

SECTION 4. --. 

RANG 1. ---. 

SECTION 1. --. 

SUBRANG 1. --. 

(V. 1, 4, 1, 1, 1.) 

~3~ 0.00 I Saxonitc ............. ~Riddles, Oreg ......................... ~ Bull. 108, 221.-W. T. 

~----~~----

~ 

SUBRANG 2, --. 

(V. 1, 4, I, l, 2.) 

_4_z._s_g_.l_o_._o_oo _____ l Peridotite_ .......... ·I Goose Bay, Straits of l\Iagclla_'_'_--_·_·_··_·.c.l_w ___ 'l_'_. ----------
ROOK ANALYSJ<;S USRD IN CONSTRUCTING DIAGRAMS. 

Silica Alkali-silica con~ ratio. tent. 

42.80 0.000 

40.11 .000 

39.99 .00 (39. 7) 

43.87 1 o. ooo 

31. 841 0. 000 

21. 251 0. 000 

Classified list of analyses 11sed in const1·ucl'i:ng diuyrams-Continued. 

SECTION 5. lVIAORIARE. 

RAKG 1. DUNASE. 

SECTION 1. DUNIASE. 

SUBRANG 1. DUNOSE. 

(V. I, 5, 1, 1, 1.) 

Author's name. Locality. Reference .. 

Dunitc _________ ...... Dun :Mountains, New Zealand-- ..... Rosentmsch, El., 1G5. 

Dunitc ..... _ ......... Corundum Hills, N. C ................ Bttll. 168, 51.-W. 1'. 

Harzuurgite .......... Olivine Hills Range, New Zealand ... Rosen busch, El., 165. 

ORDER 2. --~. 

SECTION 2. --. 

RANG 1. ---. 

SECTION 2. --. 

SUBRANG 2. --. 

(V. 2, 2, 1, 2, 2.) 

I Lherzolite ........ _ .... \ JohnnyCake road, Md .......... , . --·1 Bull. 168, 42. 

SECTION 5. --. 

RANG 1. ---. 

SECTION 1. --. 

SUBRANG 2. PERMOSE. 

(V. 2, 5, 1, 1, 2;) 

I Dunit" sideronitiqnc.j Koswinsky, Urall\lountltins ...... ---1 0. N., 128. 

\Iron ore 

ORDER 3. ---. 

SECTION 4. --. 

RANG 1. ---.. 

SECTION 1. --. 

SUBRANG 2. --, 

(V. 3, 4, 1, 1, 2.) 

........ j Taberg, Sweden ....................... \ S.M. Q., XXI, 60. 

61 
62 CHEMICAL COMPOSITION OF IGNEOUS ROCKS. 

Classified li:~t of annlyse.~ ·used in constructing diagrams-Continued. 

0RD~at 4. 

Suborder 2. 

RAN(-t 1. ---. 

SECTION 1. --. 

SUBRA~fi- 2. --. 

(V. 4, 2, J, 1, 2.> 

----~---- ----~ ----c--

Author'n 11ame. L(H.m.lity. Hefercuec. 

Jro11 ore .............. Cumberland Hill, H. I ............... S. ~f. (l., XX, 351. 

SUBRAXG 4. --. 

(V. 4. ~. 1, 1. 4.)_ 

~6.171 0.000 ---~~Iron ore ..... =.-~lglamala, Sweden.-·-·-=-~~ S. U. Q.,XXI, 60.~-- 7.52 .088 ___ _.do ............. ___ Horton, RenfrewCounty,Canarla ___ S. )f.()_, XX.33l. 

•J.osl o.on 

Suborder 2. --. 

RAN<! 1. --~. 

SECTION 1. --. 

SUBRANU 2. --. 

(V. 5, 2,1. 1, 2.) 

-illlagnetite-,pinelite .. 1 Routivam, Sweden:--- .. -------------1 Z. 1'. G. 

SUBRANG 3. --. 

(V. 5, 2, 1, 1, 3.) --1 7.52 0.080 --,~---~~--- Irou ore ___________ .. _ Leeds County, Ontario _______________ I S. ~I. Q .. XX, 331. 

_''-~8 _.ooo ___ l_du =-~--~~-~--~lnii, Sweden--~-~-~--- S.M. Q., XXI, t;o. -------

SUHRANG 5. --. 

(V. 5, 2, 1, 1, 5:) 

---~------.------~---~------~ --- --~ 

3. 67 o. 000 

2.02 .000 

1. •17 .'000 

Iron ore---------- .... 1\Iill Pond pit, N. Y ------------------ S.M. Q., XX, 3-14. 

_____ uo ____ ·- ______ ---· l\Iayhew Iron Runge, 1\Iinn _ ----· ---· s. M. Q., XX, 337. 

_____ rlo _____________ ... EagleLake'mine, Frontenac Comity, S.M. Q., XX, 331. 

Ontario . 

. ~7 __ .o_oo _____ ,__j-_----<lo -=~- :-lanford, N. Y -----------------------· ~- M. Q., XX,3-14. 

0.761 0.000 

SunounER 3. ---. 

RANG 1. ---. 

SECTION 1. --. 

SUllRANG 4. --. 

(V. 5, 3, 1, 1, '1.) 

I Iron ore---··----- ·---1 Ir:r1 Mountain~yu -----=-----1 S. l\1. Q., XX, 354. 
CHEMICAL COMPOSITION OF IGNEOUS ROCKS. 63 

DISCUSSION 01!' THE DIAGRAl\IS. 

GENERAL DIAGRAMS. 

On Pl. I are exhibited the comparatiye values of the chief chemical components 

of over 950 rocks. The rclati\'e molecular proportions of six oxides-Al 0~, 

K20, Na20, CaO, MgO, an<l FeO ( = Fc0+2Fe20J-are expreHsed by the shapes 

of the individual diagrams, the silica percentages are expressed by the relative 

lateral positions of these dittgrams, and the comparative richness in . ttlkttlies is 

shown by the shapes of the individual diag-rams aud is abo expressed by their 

relative vertical positions. 

In the uppe1' left-hand corner of the plate tt smaller multiple diagram shows 

the distribution of the analyse~; in a more concise manner, the several colors of 

the spot'l indicating the classes into which they may be subdivided, according to 

the quantitative systeu~; to be noticed more fully on page 68. 

VAlUATIONS IN COMPOSITION. 

From the large diagram it b seen how manifold ttnd intricate are the variation;; in chemical eompo;;ition of igneous rocks. The larger the yellow triangles, 

the richer the soda and alumina; the larger the green ones, the more the potash 

and ttlumina; the taller the upper hidf of the individual diagram, the more the 

alumina; the narrower and taller the yellow and green triangles, the greater the 

excess of nlumina over allmlies; the larger the b1 ue triangles, the more the magnesia 

alld lime; the larger the red triangles, the more the iron oxide and. lime; the 

longer these lower triang·lcs in the direction of the middle vertical line, the more 

the lime. Long·, nanow, iuelined, blue triangles indicate an excess of magnesia 

over lime; long, narrow, indined, red triangles, tm excess of iron oxide over lime. 

The vu.riation in the sizes of the individual diagrams, from the small ones at 

the Left to the large ones ttt the right, corresponds to the great difference in silica 

.content of the dift'crent rocks, as well as to differences in the components just 

named. Rocks with 75 per cent of silica have only 25 per cent of other constituent.s, wqile roeks with ±0 per cent of .silica have 60 per cent of other eomponents. 

·Moreover,· the relative number of molecules for given percentagcs'of mass increases 

with the decrease in molecular wcight of the component oxides. lt is to he 

observed that rocks high in silica are relatively high in alumiqa and the alkalies. 

The molecular weights of these are: Al2 0 3 , 102; K2 0; 94; Na20, 62. Rocks low 

in silica may be high in alumina and alkalies, or high in lime, iron oxide, ttnd 

nmgncsia. The molecnhtr weights of the htttcr are: FeO, '72; CaO, 56; MgO, 40. 

The lightness· of nmgnesia accounts for its greater proportion» in the diagmms 

than in the anal.Yses. 
64 CHEMICAL COMPOSITION OF IGNEOUS ROCKS. 

There are chemical variations which are somewhat regular, and others which 

seem irregular. First, it appears that the most silieeons rocks arc rich in alumina. 

and alkalies, and that lime increases at first more than iron and magnesia. But 

to this latter statement there are many exceptions. 

In rocks with intermediate silica, 50 to 60 per cent, there is a gradation 

from those rich in alumina and alkalies and low in lime, iron, and magnesia to 

those rich in the latter and poor in the former. But there arc rocks in this 

series high in alumina and lime and poor in alkaliei'l and iron and magnesia. 

The rocks low in silica, containing 35 to 50 per cent, have a wide range in 

variation, and attain the highest amount of magnesia. Those extremely low in 

silica, containing less than 30. per cent, are very rich in iron, with little or no 

alumina and alkalies, and little lime or magnesia. 

The diagrams of rocks with less than 28 per cent of silica are found on Pl. VII. 

They are not repeated on Pl. I, because of the inconvenience of a plate of such 

length. 

If the variations are studied in greater detail it is seen that in rocks having 

nearly the same silica and alkali ratios there i:> variation in the alumina, scarcely 

two rocks having the same amount. But there is more variation in the potash and 

soda. These values seem to be constantly shifting from place to place, with nothing 

suggesting a constant ratio between th~m. The great preponderance of soda is 

expressed by the predominance of yellow triangle:,; ovei· green ones. Dominantly 

potassic rocks are rare. They are more abundant among the more :>iliceous ones. 

Soda reaches its maximum in less siliceous rocks. Similar variability :>bows itself 

in the proportions of lime, iron oxide, and magnesia, whether these are subordinate 

or preponderant constituent::;. 

TRANSITIONS AND EXTUEMES. 

It is possible to select certain shaped diagrams as types and discover many that 

are approximately the same. But closer inspection showfl gradual variations froll!-

any two of these types to intermediate forms. And the general impression obtained 

from the whole assemblage is a regular variation from highly aluminous alkalic, 

yellow, and green figure::; to "highly ferromagnesian calcic, red, and blue ones, 

combined with a v13ry inegular variation in detttil among adjacent figures . 

. The extremes of chemical variation reached in igneous rocks are exhibited in 

some of the diagrami'J. However, all known extremes arc not expressed, beoouse 

chemical analyses are wanting in several instances. Thus the extreme of pure 

silictt attained by some intrusive dikes or veins of quart"' is not represented. Chemical analyses have not yet been made of such rocks, or of the highly quartzose 

pegmatitcs with more than 85 per cent o:f silica. When they have been made the 
RELA'.riVE ABUNDANCE OF DIFFERENT ROCKS. 65 

individual diagrams will extend to the extreme left-hand point of the multiple 

diagram. 

Individual diagrams, composed of only a green triangle, exhibit the composition of a rock almost wholly orthoclase and quartz. One that is simply a yellow 

triangle is an almost pure albite rock. An almost pure nephelite rock from 

Ontario haf' been described by Adams, but analyses of it have not yet been made. 

Diagrams consisting of only a narrow line represent an almost pure magnesium silicate, olivine, while those consisting of long triangles sloping to the left 

(Pl. VII) represent iron and titanium oxide-titaniferous magnetite. 

The extremes of variability expressed in mineral terms are known to be as 

follows: Igneous rocks wholly quartz, almost wholly feldspar, orthoclase, albite, 

labradorite, and other varieties of feldspar, and those wholly nephelite; rocks 

almost wholly enstatite, hypersthene, olivine, magnetite. From what is known 

of the variable mineral composition of igneous rocks it is clear that with more . I 

analyses to introduce into the diagrams the variations in the shapes of the figures 

would be increased. Enough are shown to demonstrate the gradual character 

of the variations in chemical composition, and the ti·ansitions from rocks of one 

composition to those of another. 

RELATIVE ABUNDANCE OF DIFFERENT KINDS OF ROCKS. 

The distribution of the individual diagrams in the multiple one, and of the 

spots in the small composite diagram of Pl. I, shows that those varieties of 

rocks having extreme · compositions, occurring in the margin of the multiple 

·diagram, are less abundant than those having more nearly an av-erage composition. This is still more evident when all those analyses are taken into account 

which were omitted because of lack of space for them. They will be found to 

belong to the central portion of the multiple diagram . 

. This is shown on Pl. VIII in a composite diagram exhibiting the variation 

in silica and alkali-silica ratio Qf 2,000 igneous rocks, which has been prepared 

by combining data found in this paper with those contained i.n the collection of 

analyses published by Washi.ngton,a to whom the author is indebted-for an opportunity to study the collection in proof sheets. There are mo1:e than twice as many 

rocks involve.d in this diagram as in that on :Pl. I, but the results are similar, and 

if the spots were replaced by individual diagrams the effect would be to doubly 

confirm all the conclusions drawn from a study of :Pl. I. Th~ construction of 

such a multiple diagram, however, is not feasible at this time. 

The average rock, as calculated by Clarke 0 from 680 analyses of American 

rocks, is shown by diagram at 59.77-0.088, and that calculated by Harker 0 

aOp. cit. b Bull. U. S. Geol. Survey, No. 148, p. 12. c Geol. l\Iag., 1899, p. 220. 

1447 4--No. 18-03--5 
66 CHEMICAL COMPOSITION OF IGNEOUS ROCKS. 

from 397 British rocks is shown by diagram at 58.7-0.083. These diagrams 

resemble those of rocks having like silica and alkali-silica ratios, and occur in 

the densest part of the assemblage. Other averages made from greater numben 

of analyses yield almost identical results. A later average, made by Clarke a from 

830 complete analyses of Amcri0an rocks combined with 180 additional determinations of silica, 90 of lime, and 130 of alkalies, produce an average magma with 

. 5H.71 per cent of silica, and other constituents very nearly the same as those 

expressed in the diagram. Washington b obtained a closely similar average magma 

from 1,811 analyses of igneous rocks from all parts of the world, having 58.24 

per cent of silica. The loci of the averages of American. and of British rocks 

are marked by crosses on the diagram on Pl. VIII . 

. These prove that the average of a large number of known rocks is like the 

commonest rocks; conversely, that the commonest rocks are like the average of 

all known rocks; fron;I. which it is possible to derive all kinds of igneous rocks 

by processes of separation, splitting up (spal&ung), differentiation. It does not 

follow from this that they have been produced from one common average magma, 

or even that they have been· produced in· this _ manner in actual fact; but such 

an origin is shown to be quantitatively possible and reasonable. 

ABSENCE OF CLUSTERING. 

A study of the diagrams of Pl. I and Pl. VUI fails to detect any clustering or .. 

grouping of analyses in definite parts of the multiple diagram, such as might serve 

as the basis for a chemical classification of rocks. This is the same as stating that 

there do not appear any "natural" recognizable subdivisions of rocks on a basis of 

their chemical composition. Variations in seven prominent chemical factors exist 

throughout the system of igneous rocks, the mathematical expression of which 

would be extremely intricate. The study of the chemical composition of igneous 

rocks by graphical methods does not reveal any simple method o£ grouping or 

~lassifying them on a basis of their chemical co~stituents alone. 

SIMILARITY OF ROCKS FROM DH'FERENT PETROGRAPHICAL PROVINCES. 

Further study of the diagrams and of the list o£ analyses shows the chemical 

similarity of many rocks that belong to different petrographical provinces. One 

illustration of this is taken from the best-known province, that of Christiania, 

made classic by the publications of Brugger. The diverse rocks of this region 

that are . genetically related may be found in various places in the list and in the 

multiple diagrams~ A comparison of the individual diagrams with those o£ 

a Clarke, F. W., Bull. U.S. Geol. Survey No. 168, 1900, p. 14. 

bWashington, H. S., Chemical analyses of igneous rocks from 1884 to 1900: Prof. Paper U.S. Geol. Survey No.l4, 1903, ~m . 
SIMILARITY OF NORWF.GIAN AND OTHER ROCKS. 67 

similar shape from other petrographical pn;>Vinces will demonstrate the truth of 

Bragger's statement that "the same group of differentiated rocks can be produced 

by sepa~ation :from mother magmas of quite · di.fl'erent chemical composition." a 

A list of. the chief cases o:£ similarity is given briefly, as follows: 

Table showing similarity between Norwcty rocks cmd those of other regions. 

---P;:::;:::s~~~~- ---N~a~k.-~------~U:,;;:-::;:-of other regions. 

I. 3, 1, 3. ...... .. .... .. .. . .. .. 77.20-0.080 77.05-0.080, Butte, Mont. 

76.73- .077 

I. 4, 1, 3... •.• . • • ••. . . . . .. . . . . 76.05- . 092 

71.49- .109 

I. 4, 2,3 ...................... 75.74-.086 

77. 03- . 080, Pikes Peak district, Colo. 

77.33- . 079, Alaska, and others. 

76. 20- . 091, New Mexico. 

1

75. 71- . 094, Yellowstone Park, and others. 

71. 67- . 101, Castle Mountain district! Mont. 

72.06- . 10i, Stony Creek, Conn. 

70. 23- . 113, Essex County, Mass. 

76.00- . 087, California. 

75.01- . 086, Alaska. 

74.95- . 088, Nevada .. 

70. 54- . 107 71. 88- . 095, Iron Mountain, Mo. 

70. 92- . 096, Yellowstone Park. 

68.36- . 105, Essex County, Mass. · 

I. 5, 1, 3 ................... _.. 66. 13- . 130 66. 03- . 132, Custer County, Colo. 

64.04- . 160 65.43- . 140, Mount Ascutney, Vt. 

I. 5,1,-L ..................... 64.92-.146 

64.54- .157 

65.51- . 143, New Mexico. 

63. il- .159,"Essex County, Mass. 

63.09- . 164; Essex County, Mass. 

62.17- . 156, Crazy Mountains, Mont. 

61.05- . 147, Ischia, Italy. 

I. 5,2,4 ...................... 59.38-.125 63.49-.138, Custer County, Colo. 

61. 43- . 133, 'Pantellaria. 

58. 94- . 109, Silver Cliff, Colo. 

5S. 28- . 112, Crazy 1\iountains, Mont. 

57.48- . 118, Pikes Peak district, Colo. 

I. 6, 1, 4 .... • .. .. .. •• .• •• .. .. 58.61- . 194 59. 20- . 189, Madagascar. 

II. 5, 2, 3 .......... _.... .• •. . 58.00- . 142 

II. 5, 2, 4 .. .. .. .. . . . . . .. . • .. . 59. 56- . 125 

56.79- .118 

58. 70- . 190, Crazy Mountains, Mont. 

58. 64- . 195, Cripple Creek, Colo. 

58. 62- . 191, Madagascar. 

58. 20- . 190, :Madagascar. 

59. 78- . 140, Custer County, Colo. 

58.42- . 099, Luzon, Philippine Islands. 

57.97- .116, Mount Ascutney, Vt. 

57.01- .124,_ Silver Cliff, Colo. 

aBrogger, W. C., Quart. Jour. Gcol. Soc. London, vol. 50,1894, p.-36. 
68 CHEMICAL COMPOSITION 01<' IGNEOUS ROCKS. 

Table 8howing similarity between Norway rocks and those of other regions-Continued. 

Place in classified list. Norway rock. Similar rocks of other regions. 

II. 5, 3, 4 . . . . . . • . . . . . . . . . . . . . 52. 91-(). 119 52. 97-o. 107, Pikes Peak district, Colo. 

53. 10- . 134, Madagascar. 

48. 06- . 084 49. 24- . 092, Ferdinandea. 

48. 90- . 090, Vosges. 

50. 56- . 07~, Plumas County, Cal. 

III. 5, 3, 4 ................... 47.90-.094 48.22-.084, Mount Ascutney, Vt. 

47.16- .077, New York: 

III. 6, 3, 4 . . . . • . . . . • . . . . . • . • . 43. 65- . 071 42. 03- . 053, Arkansas. 

IV. 2, 1, 1, 3, 2....... ... . . . . . . 45.05- . 030 46.56- . 043, Ural Mountains. 

46. 56- . 050, Ural Mountains. 

From this list it appears that among the various rocks, ranging from persalic 

to dofemic, that occur in the Christiania region there arc those whose chemical composition is very similar to p~rticular rocks found in the Ural Mountains, V 6sges 

Mountains, Ischia, Pantellaria, Ferdinandca, Madagascar, Luzon, Vermont, New 

York, Massachusetts, Connecticut, Missouri, Arkansas, Colorado, New Mexico, 

Nevada; Yellowstone National Park, Montana, California, and Alaska. These 

regions belong to diverse petrographical provinces, some of them very similar to 

that of Christiania, but others distinctly different. 

There are provinces in Finland, in Canada, and in parts of the United States 

closely resembling the Christiania province in the characters of their nephelitebearing rocks, but the regions are not identical in petrography. It is possible to 

find all degrees of similarity between petrographical provinces in various parts of 

the world, and the most intricate web of similar differentiation p!·oducts may be 

woven by their comparison. 

From the chemical character of igneous magmas, their content of like elements, 

· t4e chemical character of the rock-making minerals, the fixed composition of 

some of them, and the serial variation in the composition of others, the theory 

of differentiation leads us to expect diversity in the rocks of all petrographical 

provinces of such a kind that identical or closely similar varieties of rocks will 

occur in otherwise unlike provinces. 

CLASSIFICATION OF IGNEOUS ROCKS. 

From the foregoing considerations it is evident that if we attempted to classify 

igneous rocks on a basis of their groupings in petrographical provinces-that is, if 

we should unite in the first instance rocks that are said to be genetically relatedwe should separate in the system rocks of world-wide occurrence that are alike. 
CLASSIFICATION OF IGNEOUS ROCKS. 69 

It must not be forgotten that igneous rocks are not like biological organisms, 

and that we are constantly misleading ourselves by the use of biological terms, 

such as generation, consanguinity, and family, into imagining that the relationships 

of various rocks should be treated ·like the relationships of organisms. 

When we have had more experience in· the synthesis and the differentiation 

of molten rock magmas in chemico-physical laboratories; have handled them like 

other solutions of salts, which have been studied at lower temperatures;· have 

solidified them under diverse physical conditions, we shall no doubt free ourselves 

from the fascination of biology and look upon rocks as the chemist looks upon 

a solidified mass of mixed salts. Is it not possible, in the period of preparation 

of such properly equipped laboratories, to anticipate their psychological effects 

and to think of the study of igneous rocks, their magmas and relationships, as 

purely physico-chemical problems, involving the measurement and comparison of 

mass and force, and their definite quantitative ·expression~ 

It being evident from the diagrams that there are gradual transitions in the 

chemical composition of igneous rocks from one extreme to another, that there 

are no recognizable groupings of rocks or noticeable subdivisions of the chemical 

series, and that chemically similar rocks occur in genetically different families, 

it follows that the subdivision of all igneous rocks into groups for purposes of 

classification .must 'be along arbitrarily chosen lines. And the intricate character 

of the chemical variations, apparent in the diagrams, prevents a simple quantitative statement of any possible limits which may be selected fo;r subdivi.sions of 

the series, however arbitrarily chosen. A careful study of the diagrams will 

convince one of the truth of this statement. It is a problem involving at least 

seven variable factors, and in its exact statement still more. It is the problem of 

expressing quantitatively the chemical composition of solutions of mixed salts often · · 

containing identical clements. The most artificial method of statement would be 

to consider the element"l ~·egardless of the possible salts in solution. A less artificial method would seem to be one which takes into account the salts which may 

enter the solution or may separate from it. In r~ck magmas the salts in solution may properly be considered to have the composition of those minerals which 

separate and crystallize when the magmas solidify. But it is understood that 

salts in solution may become split tlp into molecules of simpler composition, may 

be partially dissociated into ions, and may be combined in more than one manner 

in the act of separating from solution Linder diverse conditions. 

When it is remembered that igneous rocks are solidified and for the most 

part crystallized mixed solutions, the expression of their chemical composition in 

terms of the separated salts or minerals developed in them is eminently r~asonable. These principles underlie the quantitative classification of igneous rocks 

proposed by Cross, Pirsson, "\V ashington, and the au tho:;·. 
70 CHEMICAL COMPOSITION OF IGNEOUS ROOKS. 

In expressing the chemical composition of the rocks in terms of the minerals 

developed it is advisable to reduce the complex possibilities by selecting the 

simpler and commoner minerals as standards of comparison. The details of the 

method must be learned from the published cssay,a to which the reader is 

referred 'if he is not already familiar with it. 

CLASSIFIED DIAGRAMS. 

The resulting chemical subdivision and grouping of igneous rocks by the 

method of quantitative classification recently proposed can be well shown graphically by the diagrams already described, The clearest exposition, however, 

requires a greater number of multiple diagrams than has been prepared, in order 

to separate all the divisions established by the classification. But the expense of 

publication has prevented the carrying out of such a plan, and so fewer multiple 

diagrams have been used, with a consequent loss of simplicity and a greater 

complexity than exists in the actual system of classification itself. The advantages to be derived from the exposition made, however, are sufficient to warrant 

its publication. It presents thP salient features and results of the classification 

in a manner which can not be conveyed by words. 

Multiple diagrams have been prepared to exhibit the grouping and variatior:.s 

in rocks belonging to the five classes of the quantitative system. Those of the 

first, second, and third classes are represented on three separate diagrams, 

while those of Classes IV and V are placed on one diagram because of their smaller 

number. . The diagram~ are presented in two forms-in one form spots represent 

the distribution of loci of analyses and their range of variation with respect to 

silica and alkalies; the other form is an individual diagram showing the variations 

with respect to the principal chemical components. (Pis. III, IV, V, VI, and 

VII.) 

The distribution of the analyses belonging to the five classes, with respect to 

silica and alkalies, is shown by the spotted diagrams on Pls. III, IV, and V 

and by the differently colored 'spots in the composite diagram on Pl. I, in which 

the yellow spots belong to Class I, the red spots to Class II, the blue ones to 

Class III, and the black ones to Classes IV and V. 

Since Ulas~ I is persalic, that is, is extremely rich in salic minerals-quartz 

and aluminous feldspathic minemls-most of these rocks occur in the diagram 

near the curved lines showing the positions of rocks composed wholly of quartz 

with albite or orthoclase, and albite with nephelite, or orthoclase with leucite. 

But rocks of this class include all those rich in alumina, which may form anorthite, a nonalkalic mineral. Consequently they also occur in the diagram remote 

from the curved lines, approaching· the locus of anorthite at 43.160.-0. 0. 

"Quantitative elussification of igneous rocks. Chicago, 190~. Also Jour. Geol., vol. 10, 1902. 
CLASSIFIED DIAGRAMS • 71 

. Class II is dosalic, that is, dominantly salic. There are less feldspathic minerals and more ferromagnesian ones, and since the latter are mostly low in alkalies, rocks of this class occur in the diagram farther from the limiting alkalifeldspathic curves than those of Class 1. 

As Class III is still richer in ferric minerals and lower in alkalies, rocks of this 

class occur still more removed from the curves just mentioned. The same is true 

to a greater degree for rocks of Classes IV and V. 

It is seen that the positions of these classes of rocks overlap one another 

more o~: less in the composite diagram on Pl. I, hence the confusion of individual 

diagrams in the large multiple diagram of Pl. I. 

DIAGRAMS OF CLASS I. 

Let us consider separ:Jtely the diagram;; of the different classes of rocks, beginning with Class I. The persalanes, represented by 412 individual diagrams, being 

characterized by preponderant salic .ninerals, are tlubdivided into nine orders, 

according to the proportions of quartz and feldspars and of feldspars and feldspathoids (lenads). The order highest in quartz, perquaric, is highest in silica, 

and that highest in lenads, perlenic, is lowest in silica. Consequently the· nine 

orders follow one another from left to right in the multiple diagram (Pls. II and 

Ill). The limits of the orders may be shown graphically for extreme cases, and 

may be interpolated for intermediate ones. Owing to the difference in the molecular weight of sodium and potassium, the limits for orders basPd on quartz and 

soda-feldspar (albite) and on quartz and potash-feldspar (orthoclase) do not coineide. lTurther, the greater chemical difference between the soda-lenad, nephelite, 

an orthosilicate, and the potash-lenad, leucite, a metasilicate, causes a still wider 

divergence between the boundaries of the orders based on albite and nephelite on 

the one hand and on orthoclttse and leucite on the other. That is to say, the 

limits between the nine. orders of pcrsalic rocks vary according as the alkalies in 

the rocks are soda or'potash. This is shown by the diagram on Pl. II. The black 

lines nearly at right angles to the upper curve mark the limits of the nine orders 

for ideal rocks composed wholly of quartz, albite, anorthite, or of soda-nephe1ite, 

albite, anorthite. The red lines transverse to the upper red curve mark the limits 

of the nine orders for rocks composed wholly of quartz, orthoclase, anorthite, or 

of leucite, orthoclase, anorthite. 

The division lines for soda orders start from points on the quartz-albite-nephelite 

curve situated where q: ab :: '7: 1; q: ab ::5: 3; q: ab ::3: 5; q: ab ::1: '7; ab.: ne :: '7: 1; 

ab : ne :: 5 : 3; ab : ne :: 3 : 5; ab : ne ::.1 : '7, and run to points on the quartz-anorthite 

line and the anorthite-nephclite line were q: an:: '7: 1; q: ap ::5: 3; q: an:: 3: 5; 

q:an::1:'7; an:ne::'7:1; an:ne::5:3; an:ne::3:5; an:ne::1:'7. The same may 
72 CHEMICAL COMPOSITION OF IGNEOUS RqCKS. 

be l:l~tid of the diviRion llnes for potash orders, substituting the names of orthoclase 

and leucite for those of albite and nephelite, respectively. 

The diagram on Pl. II shows that the first four orders in each case nearly 

. coincide, the boundary lines for potash rocks lying a little to the right of those 

'for soda rocks. That is, the limit for each 'quaric order of potash rocks reaches 

a little lower silica than that for the corresponding orders of soda rocks. 

The diagram also shows that the last four orders in each case differ more 

and more widely as they become more lenic. The range for the potash rocks is 

much more restricted than for the soda rocks, and the limits of orders for the . 

potash rocks are higher in silica than for ,the corresponding sorla rocks. This 

is because the potash lenad, leucite, is a metasilicate with 55.0 per cent Si02, while 

the soda lenad, nephelitc, is an orthosilicate with 42.3 per cent Si02 • 

Since most rocks contain both soda and potash, the limits for the orders will 

occur between the extremes illustrated on Pl. II, varying with the' ratio between soda 

and potash in each case. This explains the confused arrangement of the lenic orders 

in the upper right-hand portion of the diagram of persalic rocks on Pl. Ill. 

In this diagram the number of the Qrder of each rock is given by the first figure 

und9r its individual diagram. The number of the rang is given by .the second figure. 

A study of these numbers will show that in the left-hand portion of the large diagram there is general concordance among the individual diagrams with respect to 

orders and rangs, except near the borders between orders, and between rang·s. · But 

in the right-hand upper portion of the large diagram there is great confusion o:f 

orders. It will be noted that whem diagrams o:f different orders occur close together 

that 'with the higher number is the more potassic, other things being equal. The 

confusion would disappear i:f diagrams were constructed to exhibit the various subrangs. The correspondence between the distribution of the persalic rocks according 

to orders in the multiple diagram on Pl. III and the theoretical limits of the orders 

as shown on Pl. II is apparent. The orders form belts transverse to the curves 

which are the limits to ideally pure alkalic persalic rocks, namely, those consisting 

wholly of quartz, alkali-feldspar::;, or lenads. 

As the wholly alkalic rocks occur along the limiting curves just mentioned and 

those free rrom alkali occur on the bottom line of the diagram, i~ follows that the 

various rangs o:f persalic rocks occur at intervals between these limiting lines; the 

peralkalic nearest the upper curves, the percalcie nearest the bottom line. 

The boundary lines bet''leen the 5 rangs of persalic rooks are shown in the 

diagram on Pl. II. The blaek lines nearly parallel to the upper curve mark the 

limits for those based on soda alone; the reel lines for those based on potash 

alone. Since most rocks contain both alkalies the limit for rangs will shift 

according to the ratio between soda and potash in the rocks. The rangs form 

belts roughly parallel to the limiting curves and bottom line of the multiple 
CLASSIFIED DIAGRAMS. 73 

diagram. The limiting lines are drawn from the point of pure quartz, where 

they all become zero, to points on lines marking the middle of the perfelic order, 

5-that is, the lines for mixtutes of albite and anortk~e in the case of pure 

soda rocks, and that for mixtures of orthoclase and anorthite for pure potash 

rocks. The points on these lines occur in the first case where Na20:Ca0::7:1; 

Na20:Ca0::5:3; Na20:Ca0::3:5; Na20:Ca0::1:·7. They o~o.;ur in the second case 

where K20: CaO: :7:1, etc. From these points the limiting . lines pass to corresponding points on lines representing mixtures of nephelitc and anorthite and of 

leucite and anorthite. 

From Pl. II it is seen that the range of rangs is nearly concordant in the 

quaric orders of persalic rocks and more and rnore div ..:_,;ent in the more lenic 

orders according as. the rocks compared are more sodic or more potassic. This 

explains the apparent· confusions of rangs in the right-hand portion of Pl. III. 

There is a close correspondence between the distribution of the pcrsalic rocks 

according to rangs m the large diagram (Pl. III) and the theoretical limits of 

rangs shown in Pl. II. This is shown by the second figu--e under each individual 

diagram. 

The diagram on Pl. II exhibits the limitations of orders and rangs of the 

persalic rocks containing lenads. Th~se are seen at the right end of the diagram. 

The limiting lines representing combinations of nephelite and anorthite and of 

leueite and anorthite cut diagonally across the belts of. orders and rangs. Thus 

in soda rocks whose limits are shown by black lines order 9 has only 1·ang 1; 

order 8 contains r<~.ngs 1 and 2; order 7 embraces rangs 1, 2, and 3; order 6 has 

four mngs-1, 2, 3, and 4, while all five rangs occur in· order 5. In potash 

rocks, represented by red lines, the conditions arc not quite so simple, as is seen 

in the diagram. Each of the lenic orders has a little larger range in calcic 

content and includes a small amount of a more calcic rang than occurs in the 

purely soda rocks. 

There are variation:;; in composition in rocks not yet taken into consideration 

which further modify the distribution and arrangement of .D.e individual diagrams. 

Most rocks contain fernie ~omponents, and these are generally low in alkalies or 

free from them. With increasing amount of nohalkalic fernie components the 

limits of rangs in the multiple diagram shift downwar--1, for rangs are established 

on the ratio between salic alkalies and salic lime-that is, between the K20 and 

Na20 and the CaO in the standard feldspars and lenads. Consequently the inore 

·femic minerals present, the less salic, and the smaller the alkalies necessary to· 

maintain a given ratio with diminished salic lime. Hence the boundary ·line 

between rang 1 and n\ng 2 occurs fltrther below the limiting quartz-feldspar lenad 

curves the greater the amount of nonalkalic femic components in rocks. This is 

evident on comparing rangs in Pls. III and IV. 
74 CHEMICAL COMPOSITION OF IGNEOUS ROOKS. 

In the majority of rocks in which there is more alumina than alkalies there 

is usually more lime thari is sufficient to satisfy the excess of alumina, so that the 

ratio between salic alkalies and salic lime, which determines the rang, is 

dependent on the amount of alumina in the rock. From this it happens that 

rocks having like silica percentages and alkali-silica ratios, located near one 

another in the multiple diagram, may differ in rang because of differences in 

alumina. Other things being equal, those with higher alumina will have lower 

ratios between salic alkalies and salic lime; and conversely, those with lower 

alumina will have higher alkali-calcic ratios. And these diffei·ences may affect 

the rang of the rocks compared. Examples of this kind are more evident in 

diagrams of rocks of Class II, and are found at 56.3-0.065 and 56. 7-0;066, also 

56.6-0.074 and 56.9-0.074, on Pl. IV. 

Where the fernie components of persalic rocks are alkalic the rocks are always 

in peralkalic rang 1, so that the limit of. rang 1 is extended .downward in the 

multiple diagram. Tbe individual diagrams for rocks of this kind are characterized by comparatively short Al20 3 lines, less than the sum of K20 and Na20. 

The effect of increasing amounts of fernie components in persalic rocks upon 

the limits of orders is not so easily appreciated, the relations being less simple. 

If we compare two rocks with like silica and alkali percentages, which would \ 

occur near one another in the diagram (Pl. III), the more nonalkalic femic components the less salic; that is, the less alumina and the less anorthite. If the 

rocks are quaric the ratio between quartz and feldspar is increased by decreasing 

the anorthite feldspar. But the substitution of FeO, MgO, or CaO for Al~03 

would require more Si02 to form metasilicates than that required to form anorthite, consequently the free Si02 , quartz, would be reduced, but to a smaller 

amount than the feldspar is reduced, consequently the ratio between the quartz 

and feldspar would be higher in the rock with more nonalkalic fernie components. 

The limits between the quaric orders would shift to the right. 

If the rocks are lenic, containing nephelite, sodalite, or leucite, a reduction 

of anorthite feldspar would increase the ratio between lenads and feldspars. A 

substitution of FeO, MgO, or CaO for Al20 3 in amount equal to the CaO of 

presupposed anorthite would necessitate their conversion to m~tasilicates according to the method of the quantitative classification under discussion. This would 

require more silica than is required by anorthite, so that the amount of alkali feldspars would be reduced and the lenad-feldspar ratio further increased. In case 

the lime were replaced by magnesia and iron oxide and converted into orthosilicates there would be slight change in the silica available for the. salic components, because of the general preponderance o£ magnesia in such rocks, and its 

lighter molecular weight and consequent greater nnmber of molecules. Hence, 
CLASSIFIED DIAGRAMS. 75 

in most cases an increase of fernie components would increase the lenad-feldspar 

ratio, and the limits between lenic orders of persalic rocks would shift toward 

the·left. 

· In the less frequent cases in which alkali fernie components occm:, the limits 

bet.ween all orders shift to right or left according to the relative proportions of 

the alkali-fernie compoaents and aecording as they are acmite or are free from 

ferric iron. 

The occurrence of magnetite, ilmenite and other mitic components also modHies the position of the ordinal limits, but . in peralkalic rocks these constituents 

generally occur in such small amounts that their effects may be disregarded in 

the interpretation of the diagram under consideration. 

·with respect to subrangs it may be said that in the great majority of cases 

they cu.n be recognized by a comparison of the yellow and green triangles representing the relative amounts of soda and potash in the rock. For in most 

instances all of the alkali is salic. In other cases where part of it is femic, the 

ratio between the salic alkalies can be made out by a scrutiny of the triangles 

and a comparison of the amounts of alkalies and alumina expressed by the 

lengths of the potash, soda, and alumina lines. The ratio in this case would be 

K 20 

AI20 3 -K20. 

In general, where alumina is in excess of the sum of the alkalies, a comparison 

of the triu.ngles named, or of the lengths of the potash and soda lines, will 

determine the subrang to w~ich the rock belongs. Those in which NK 0o>~ are 

a2 1 

m . t . · b 1 th . h K O . 7 5 d . . b 2 h" perpo ,assw Ru rang ; ose w1t N;20 < l > 3 are opotassiC su rang ; w en 

KP 5 3 th b · 3 d' t · h K20 3 1 Na 't · d d' 

2

0-:: 3 > 5 e su rang 1s , so 1po assiC; w en Na20 < 5 > '7 1 1s oso rc, 

subrang 4; and with :~~ < ~ the sub rang is 5, persodic. 2 

These divisions apply only to the first three ~angs. In the fourth rang, :which 

is docalcic, there are only three subrangs, namely: 1, :~~>~ prepotassic; 2, 

KP 5 3 d' t .. 3- KP 3 . d' h h 

N 0 < 3 > ~ so 1po assiC, , N 0 < -5 preso 1c. T e fift rang being precalcic, a2 o, a2 , 

subrang::; are uot recognized. 

A study of the diagrams on Pl. III shows that soda preponderates over 

potash in most persalic rocks; that sodipotassic rocks, subra1~g 3, are the most 

numerous; that dopotassic rocks are rare, and perpotassic ones extremely so. The 

numbers of rocks in the 5 rangs are 3, 31, 201, 156, 21. 
76 CHEMIOAI, COMPOSITION OF IGNEOUS ROCKS. 

Variations in the fernie components, FeO, MgO, and fernie CaO, are noticeable 

m the individual diagrams and represent differimccs among the subordinate 

mineral constituents of the rocks. Their quantity is so small that they may be 

neglected in the magmatic classification of these persalic rocks. 

The diagrams plotted together demonstrate the gradual transition between 

orders of rocks of Class I, as well as between rangs and subrangs. And since 

any individual diagram may represent a large body of igneous rock or a small 

facies of one, and since any of the diagrams may represent rock bodies of considerable importance, it follows that all parts of the series may be of equal 

importance geologically or petrologically, and consequently rocks that happen to 

bel~ng on the border'·line of any set of &'Ubdivisions into which the whole rock 

series must be divided, for purposes of classification of any kind, may . be as 

important as those situated at the center of such an arbitrary division, and in 

some regions it will happen that such rocks arc the most important. 

When the student has become convinced of the continuity of the chemical 

series of igneous rocks he will not be surprised to discover that a rock of great 

importance belongs on the boundary of a class'ificatory division, or probably falls 

on both sides of a division line. It will no~ affect the importance of the rock or 

militate against the value of the system of classification. It will simply be a 

"natural" fact. And the ·system of classification will appear to him as "natural" 

as any other system which attempts to classify igneous rocks. 

DIAGRAMS OF CLASS II. 

The multiple difigram of 335 dosalic rocks of Class II (Pl. IV) may be 

readily interpreted by comparison ,with that of Class I (Pl. III). The spotted 

diagram to the left shows the distribution of the analyses with respect to silica 

and alkalies. The . rocks are for the most paf't lower in alkalies than those of 

Class I, b~cause the femic components are generally nonalkalic. The few· cases 

with rather high alkalies contain acmite molecules, which fact is indicated in the 

individual diagrams by pronounced iron oxide and soda and by low alumina. 

Several of these occur in the left-hand part of the multiple diagram at 74.35-

0.092; 69.02-0.121, etc. 

Tho dominant constituents in dosali c rocks being the same as those in the 

persalic rocks, nine orders have been esta~Iished, in the same manner as in Class I. 

Rangs and subrangs also correspond to those in Class I. So there is the same general arrangement of individual diagrams in Pl. IV, according to orders and rangs, as 

in the multiple diagram of Class I, with the modifications produced by increasing 

amounts of fernie eomponents, for the most part nonalkalic. The belts of orders 

are transverse to the limiting quartz-alkali-feldspar lenad/ curves. The limits of 
CLASSIFIED DIAGRAMS. 77 

rangs are lower than in the diagram of Class I. There is the same confusion of 

orders and. rangs along the division lines consequent upon variations in alumina and 

fernie components, and a like diversity of alkalies, shown by the yellow and green 

triangles, with a strong preponderance of soda over potash. ·The greatest number 

of rocks are dosodic. The numbers in each rang are: 0, 17, 126, 183, 9 . 

. With an increase in the fernie components the variations in iron oxide, magnesia, 

and lime become more noticeable and important, and it is necessary to recognize dis~ . 

tinctioris among the subordinate fernie components, that is, to note grads and subgrads. The nature of the grads can not be determined directly from the diagrams 

because it depends on the amount of available silica, which may be combined with 

fernie bases to form silicates, pyroxene, olivine, or akermanite, and also on the 

amount of ferric oxide and titanium oxide. The ferric oxide is blended with ferrous 

oxide in the diagrams and is not indicated graphically. Titanium oxide is so small 

in mostdosalic rocks that it is not introduced into the .diagrams in this Class II. 

It is to be noted, however, that the silica is sufficiently high to form silicates of 

almost all the fernie bases, and ferric oxide is in most cases low, so that the great 

majority of dosalic rocks belong to the prepolic grad 1, that in which the fernie silicates-pyroxene and olivine-preponderate over the fernie nonsilimites-magnetite, 

hematite, ilmenite, rutile, and the silico-titanate, titanite. 

As to the subgrad to which these rocks belong, by far the largest number contain 

ncnalkalic fernie components, and therefore fall in the premirlic subrang 1. A 

small number contain alkalic fernie components in. nearly the same proportions as 

nonalkalic ones, aQd fall in the alkalimirlic subrang 2. Some, characterized by 

highly alkalic fernie constituents, such as acmite, l:ielong to subrang 3. 

The multiple diagram for Class II (Pl. IV) exhibits similar transitions between 

orders and between rangs as those shown by the diagram for Class I, and permits 

the same conclusions to be drawn from it. The chemical series will appear more 

and more complete as more varieties of rocks are analyzed. 

DIAGRAMS OJ<' CLASS III. 

The chemical relations of the salfemic rocks, Class III, are expressed graphically 

0n Pl. VI. Two of them are so high in silica that they have been plotted on PI. 

IV with rocks of Class II. One is rockallose, with 73.60 Si02 , 0.091 ;il~~· It is 

intermediate between Classes III and II. The other is a pantellerite, with 68.7 5 

Si02 , 0.144 ~\~ • It is also intermediate between Classe:s III and II. 

The distribution of the rocks with respect to silica arid alkalie:s is shown in 

the upper diagram of Pl. V. The location of the analyses in the multiple diagram is still farther from the limiting curves than. in Class II; and the silica 
78 CHEMICAL COMPOSITION OF IGNEOUS ROCKS. 

ranges lower. The alkali-silica ratios reach high values in some cases. Ti02 is 

present in notable amount in a number of instances. 

It will be observed that the lower half of the individual diagrams is the 

larger in nearly every case, but the long, narrow, upper triangles indicate that 

ther.e is more alumina than alkalies, and that part of the lime is salic, so that 

the salie components are more nearly equal to the fernie than appears at first 

glance. 

There are but two rocks in quarfelic order 3, those mentioned abo've, and 

plotted on Pl. IV. Very few occur in order 4. The greatest number are perfelic, order 5, and the lenic orders are well represented. 

Most of the perfelic rocks are alkaliealcic, rang 3, or docalcic, rang 4. The 

few that are peralkalic or domalkalic are low in alumina, as, for example, 54.2-0.160 

and 45.2-0.085. It is noticeable also in the lenic salfemanes, orders 6, 7, 8, and 

9, that the domalkalic character of the salic minerals in a number of rocks is 

due to low alumina rather than to high alkalies, as 50.00-0.110, 46.00-0.121, and 

42.7-0.139. 

There are great variations in the shapes of the diagrams of rocks nea~ly 

alike in silica· and alkali-silica ratio. A few rocks are rich in potash, notably 

those from Leucite Hills, Wyoming, 54.08-0.163, and others. A greater number 

are rich in soda, occurring in the upper part of the multiple diagram. But the 

majority are sodipotassic and dosodic. 

Since in these . rocks the fernie minerals are equal or nearly equal to the 

salic, and in· some cases are more abundant, they are as characteristic of the 

rocks as the salic minerals. The salfemanes differ considerably with respect to 

these constituents, which is plainly shown by differences in the shapes of the 

lower part of the individual diagrams. Some are long in the direction of lime; 

others long in magnesia. Few have more iron oxide than magnesia. From this 

it follows that the grad, subgrad, and section of subgrad are as important in the 

classification of these rocks as are order, rang, and subrang. 

The grad of these rocks can not be determined from the diagrams because it 

depends upon the proportions of fcrro~agnesian silicates and nonsilicates determined by the available silica and the ferric iron not allotted to acmite. It is to 

be remarked that the great majority of salfcmic rocks included in the diagrams 

are dopolic, grad 2-that is, normative pyroxene and olivine dominate over magnetite, hematite, and ilmenite. In moHt of these rocks there is a notable amount 

of normative nonsilicates. The majority of these rocks are perpyric or dopyric, 

sections 1 and 2-that is to say, normative pyroxene preponderates over olivine. 

The character of the subgrad is indicated by the diagrams, since this depends 

upon the proportion of alkalies that enter the femic minerals. 'Vith few excep-
· CLASSIFilW DIA!}RAMS. 79 

tions the alumina is ·gr~ater than the sum of the alkalies, so that the fernie minerals are nonalkalic and the rocks . belong to the permirlic subgrad 1. The 

exceptions to this are the two rocks rich in acmite__:.rockallose and the rock near 

varingose. 

The diagrams also show that most of these salfemanes are domiric, sect~on 2, 

ferrous oxide and magnesia dominating over fernie lime. This, however, is not 

perfectly evident in the diagrams because of the lack of information concerning 

ferric iron· and the necessity of deducting salic lime from the total lime. 

Finally, when it is remembered that nearly half the molecules of iron oxide 

belong to ferric oxide, the diagrams show that in most cases the rocks are 

domagnesic, subsection 2, with magnesia dominant over ferrous iron. In a few 

instances they are permagnesic, which is indicated by long, narrow, blue triangles. 

DIAGRAMS OF CLASSES IV AND V. 

The diagrams of dofemic and perfemic rocks, Classes IV and V, are plotted 

together on Pl. VII. This has been done because of the comparatively small number of analyses of these rocks at hand and the desire to economize space. The distribution of these rocks with respect to silica and the alkalies is shown in the lower 

dia~ram on Pl. V. As. should be expected, these rocks are far from the quartzalkali-feldspathic curve, are low in alkalies, and extend to the lowest limit of silica. 

The diagram of one rock comparatively high in alkalies falls outside the area of 

Pl. VII, and is not represented. The rock is a nephelite-basalt from Katzenbuckel, 

Odenwald (45.0;1:-0.209). Individual diagrams belonging to rocks of Classes IV and 

V are designated by Roman numerals, IV and V, before Arabic ones denoting orders 

and sections of orders. 

The arrangement of the individual diagrams in the multiple one is in accord 

with the· general system adopted with special reference to the great majority of 

rocks, the more salic ones. The rocks of Classes IV and V are less than one-tenth 

of all that are represented in the diagrams. Their arrangement is related to one 

component of prime importance, silica. But alkalies are extremely subordinate 

and would not properly be chosen as a basis for their coordination were these rocks 

considered by themselves. ·However, their relations to the more salic r~cks are 

exhibited by retaining the same system of arrangement. 

The chief difference between the rocks of Classes IV and V lies in the amount 

of alumina, with which in general there is sufficient lime or alkalies to form salic 

feldspars or lenads. In one case only is the composition of the magma such as to 

require the assumption of salic corundum, the rock being magnetite-spinelite from 

Routivare, Sweden (4.08-0.092). Most all of the rocks containing alkalies belong to 

Class IV, but this class also embraces rocks without alkalies, the diagrams occurring 
80 CHEMlCA.L COMPOSITION. OF IGNEOUS ROCKS. 

on the zero line for alkali -silica ratios. Nearly all the rocks of Class V are so 

low in alkalies as to occur on the zero line. The higher ratios obtaining in several 

iron ores with 4 to 8 per cent of silica may easily be due to errors in chemical analysis, though, of course, they may be correct values. 

Since dofemic and :~erfemic rocks are divided into orders according to the 

relative proportions of fernie silicates and nonsilicates, and into sections of orders 

according to the proportions of fernie metasilicates and orthosilicates, it follows 

that the five orders and sections range according to the. silica content' of the rock 

from perpolic order :!., perpyric section 1, with highest silica, 55. 5, to permitic 

order 5, with lowest silica~ 0. 7. In like manner the various sections under each 

order range from higher to lower silica. These distinctions do not appear in the 

shapes of the diagrams, but in their lateral position in the multiple diagram. 

With respect to rangs it happens that without exception all the rocks represented in this collec~,on of analyses belong to permirlic rang J, the alkalies 

which occur in the . roQks ··being salic, which is shown in the diagrams by the 

alumina line mweeding the sum· of those of the alkalies. , 

Sections of rangs and · subrangs are based oil the proportions of fernie lime, 

magnesia, and ferrous. oxide, but the proportions of ferrous and ferric oxide are 

not indicated in the diagrams. It is to be noted, howev~r, that iron is generally 

subordinate to magnesia in most perfemic rocks with more than 28 per cent of 

silica, so far as they are represented in the collection of analyses; and when it 

is remembered that a. part of this iron is ferric, it will be seen that the proportion of ferrous iron is smaller than appears in the diagrams. 

While the lime is considerable in a large number of cases, it is very small 

in many of the rocks, and when salic lime is deducted it is found that the fernie 

lime is subordinate ·to the magnesia and ferrous iron in nearly every instance. 

A majority of the dofemic rocks, Class IV, are domiric, section 2 of rang 1. 

A smaller number are permiric, section 1 of rang 1. In nearly every case these 

rocks ar~ domagnesic, subrang 2. The iron ores of Class IV are perferrous, 

subrang 5. 

The perfemanes, Ciass V, with the exception of the iron ores, are permiric 

and domiric in about equal numbers. Lime is subordinate to magnetsia and iron. 

They belong to sections 1 and 2 of mng 1. In nearly every case these rocks 

are permagnesic, subrang 1. This is shown by the elongation of the magnesia 

line. The iron ores of. course are perferrous, subrang 5. The abrupt change 

from the titaniferous iron ores, below 27 per. cent silica, to the magnesium-rich 

rocks above this percentage of silica is very noticeable. It indicates that the 

intermediate transitional rocks which have been described by petrographers have 

not been analyzed. 
CORREJ.ATION OF ROCKS DIFFEREN'rT.<Y CLASSIFIED. 81 

The diagrams. of the different classes of igneous rocks established by the 

quantitative system illustrate the chemical characters of the rocks grouped 

together by this system, and show the degrees of similarity and the ranges of 

variation within the different divisions of the classification so far as they exist in 

the rocks represented by the 977 analyses in the collection. 

A greater number of multiple diagrams representing separate divisions of 

the system. will give more definite graphic expression to these minor groups of 

rocks. Their preparation and publication at this time. have not been feasible. 

It is possible,· also, to devise individual diagrams which shall express more 'or 

less definitely the norm of each rock, but these would of necessity be so intricate 

that a larger scale of drawing would be required, entailing serwus difficulties of 

publication. 

It is believed that the simpler individual diagrams and more composite 

multiple ones here presented will serve a b~tter purpose at this time in demonstrating g1'aphically some of the chemical facts and relationships that have. been 

used by Orosi', Pirsson, Washington, and the author as the foundation on which 

they have constructed the quantitative system of rock classification. 

CORRELATION OF IGNEOUS ROCKS CLASSIFIED BY 'l'HE QUANTITATIVE 

AND QUALI'.rATIV'"E SYS'.rEMS. 

The classified list of rocks already given shows the character of the correlation 

that may be ma~e of the two systems of classification. The variety of . names 

that appear within any one of the more. common divisions of the quantitative 

systems is due in part to differences in chemical composition, which are recog~ 

nized by subdivisions of the system of a lower order, as grad and subgrad. It 

is in part due to diversity of texture and mineral development, which is expressed 

in this system by terms qualifying the magma names. But it is also due to a 

great extent to essential differences in the bases of classification in the two systems and to the flexibility of qualitative definitions. 

A brief tabulated statement of the salient features of the correlation is given, 

with some general remarks concerni1~g the more common relationships. Greater 

detail must be gotten from the classified list and from the collection of rock 

analyses published by ·washington. 

14474-No. 18-03- -6 
CLASS I. PERSA LANE .. 

1. Vlctorare. ~- Belgare. I 3. Columbare. 4. Brltannare. · 5. Canadare. I 6. Uussare. 7. Tasmanare. 8. Ontarare. 9. --. 

Qunrtz-vcins. Qo,.rt.~"''"'"'""·i Oom<ro. I ''""'ro;;~~=;., ~--------'-:rs-·e_p_h_e_l_it-e--s--)--e-n-i-tc-.-------- Nephe\~\~~pegma-

--------l n. 1. Dnrgase. I n. 1. Alasknse. R. 1. Llparase. IU.l. Nurdm:trkase. R. 1. Mlaskase. R. 1. Laugenase. R. 1. --. R. 1. --. 

Quartz-pegmatite.! Aplite. Aplite. Syenite. Neph.-uplite. Foyaite. Ncph.-syenitc. Neph.-pegmatite. 

Granite. Gr:mite. I Quartz-syenite. Neph.-syenite. 

I 

Alaskite. Quart-z-syenite. Neph.-syenite. Foyaite. 

Tordrillite. Syenite-porphyry. Nordmarkite. Ditroite. 

I 

Quartz-porphyrr. Grorudite. I Pulaskite. 1\Iiascitc. 

Quartz-kern to- Qunrtz-pantellcr- Umptekite. Mariupolite. 

phyre. lte. I Albitite. Tinguaite. 

Rhyolite. Rhyolite. Solvsbergite. Heronite. 

Obsidian. I Paisanite. Keratophyre. Phonolite. 

I 

C. 2. Alsbncl•ase. 

Aplite. 

Granite. 

Alsbachite. 

Rhyolite. 

Comenditc. Bostonite. Leucite-phono}ite. 

Quartz- k e rtt to- Trachyte. phyre. 

Obsidian. Phonolite. 

B .. 2. Toscnnase. I R. 2. Pulasknse. 

Aplite. Quartz-syenite. 

Granite. I Ncph.-sycnite. 

Quartz-monzonite.

1 

Pulaskite. 

Granodiorite. Nordmarkite. 

Diorite. 1 Luurvikitc. 

Syenite. Sodulite-syenite. 

Quartz-syenite- Diorite. 

porphyry. Bo~tonltc. 

Rhyolite. Rhombeu por- Toscanite. phyry. 

Latite. Vulsinite. 

Dellenite. Kemtophyre. 

Dacite: Trachyte. 

Trachyte. Leucitc-trachyte. 

Andesite. Andesite. 

U. 2. Ylezzenasc. 

Kepb.-syen\te. 

Neph.-rhomben 

porphyry. 

K eph.-tingunite. 

Tinguaiu,, 
CLASS I. PERSALANE--Continued. 

1. Ylctorure. 2. Belgnre. 3. Columbare. I 4. Britannare. 5. Unnadure. fl. Russare. I 7. Tasmanare. 

1. s. Ontarare. n.--. 

Quartz-veins. Quartz-pegmatite. Granite. Syenite, anortho· Nephelite-s)•enite. Nephelite-pegrria· site. tite. 

----

lt.:l. Ule~enuse. n. a. Voloradase. 11.3.--. 

Granite. Granite. Syenite. 

Quartz-d io rile· Granodiorite. Diabnsc-porphyporphyry. Quartz-diorite. rite. . Toscanitc. Andesite . Banatite. 

Vnlcanitc. !)ioritc. 

Dacite. 

Andesite. 

Trachyte. 

lt. 4. Labrador· 

ase. - '· 

Anorthosite. 

R. o. Canadase. 

Anorthosite. I -
CLASS II. DOSALANE. 

1. 

I 

~t --. 

I 

3. Hlspanare. I 4. Austrare. 5. Germanare. 6. :Norgare. I. 7. ltalare. 8. Campanare. 9. J,appare. 

I 

Granite ·and quartz-diorite. Syenite, diorite, 

gabbro. N ephelite, syenite, and essexite. Leucite-basanite. l>rtite. 

R. 1. Yar!ngasc. IR. 1. Puntellerase. R. 1. Uinptekase. R. 1. Laurdalase. R; 1. LuJavrase. I R.l.-. R. 1. U rtase. 

Grorudite. Grorudite. Syenite. Neph.-syenite. Lujavrite. Soda sussexite. Urtite. Pan~ellerite. Pantellerite. Nordmarkite. Leucite-neph.- Chibinite. Tinguaite. Ijolite. Felsite. Umptekite. syenite. Allochetite. Leucitite. Arkite. 

Hedrumite. Pseudoleucite-sy- Neph.-porphyry. enite. 

Neph.-syenite. Laurdalite: Tinguaite. 

Heumite. Syenite. Leucite-tinguaite. 

Trachyte. Hedrumite. 

Sodalite-trachyte. Tinguaite. 

- Leucite-trachyte. Leuci te-tinguaite. 

R. ~. Dacase. R .. 2. Monzonase. R. 2. Essexase. R. 2. Vnlturase. R. 2. Vesuvase. 

Granite. Syenite. N eph.-syenite. Leucite-tephrite. Leucite-basanite. 

Quartz-diorite. Pulaskite. Neph.-monzouite. Basanite. 

Syenite. Monzonite. Laurdalite. Leucitite. 

Dacite. Durbachite. Essexite. Haiiynophyre.· Andesite. Neph.-syenite. Monzonite. 

Trachyte-andesite. Ditroite. Shonkinite. 

Essexite. Covite. 

Granite. Borolanite. 

Diorite. Heumite. 

Kersantite. Monchiquite. 

. . Min.ette . Theralite. 

Ciminitc. Kulaite. 

Akerite. Lencite-kulaite. 

Shoshonite. Tephrite. 

Banakite. Neph.-felsite. 

Trachyte. 

I""'"'"·""""""· Leucite-phonolite. 

Andesite. 

Basalt. 
·-

CLASS II. DOSALANE-Continuecl. 

1. 2. 7. Itulare. ·s. Campamt~e. I 9. J,appare. 

Syenite, diorite, Nephe1ito, syenite, and essexite. -~:~~e-b~:t~i~·.-~-- Urtite. 

3. Hlspanare. 

Granite and quartz-diorite. 

4. A.ustrare. 5. Germunare. 6. Norgarc. 

gabbro. 

1

. 

----------l-----------l---------~----------l-----------1-----~--~-----------------------------

R. 4. ---. 

Quartz-diorite. 

It. :!. Tonulasc. 

Granite. 

Q u artz-monzonite. 

Granodiorite. 

Quartz-diorite. 

Tonalite. 

Quartz-norite •. 

Syenite. 

Diorite. 

Dacite. 

La tit e. 

Andesite. 

Trachyte. 

Dolerite. 

R. 4. Bandase. 

Tonalite. 

Diorite. 

And,site. 

Quartz-basalt. 

U. :J. Andase. 

Sycnftc. 

Monzonite. 

Diorite. 

Gabbro. 

Norite. 

Essexite. 

Beerbachite. 

1\fondhaldeite. 

Kersantite. 

Andesite. 

Latite. 

Vulsinite. 

Ciminite. 

Shoshonite 

Banakite. 

Quartz-basalt. 

Basalt. 

Dolerite. 

Olivine-diabase. 

Leucite-monchiquite. 

Neph.-tephrite. 

R. 4. Hessase. 

Diorite. 

Monzonite. 

Anorthosite. 

Gabbro. 

Corsite. 

Andesite. 

Basalt. 

U. 0. ----. ' · R. I). t:orsase. 

Diorite. Diorite. 

Olivine-gabbro. 

It. :1. Snlemasl'. It. :1. ----. 

Diorit~. Leucitc-tephrite. 

Gabbro. 

Essexite. 

Basalt. 

R. 4. ---. 

Diorite. 

Gabbro. 

l 
CLASS III. SALF EM AN E. 

1. -- 2. -- 3. Atlantare. ... Vtutlare .. I 5. 'Gallare~ 6 • Portugarc. I 'i. Kamerunnre. I 8. nOhemare. I 

I !1. Fln11are. 

Diorite and gabbro. Lamprophyres and lcucite-nephelitc lavas. 

R.I. Rockall.:"·. R. 1. Ore11dase. R. 1. Wyomlngase. R. I. Mullgnase. I B. 1. Vhntase. I R. 1. Ijol:•••· 

Rockallite. Orenrlite. Shonkinite. Mnlignite. Lencitite. J\iadupite. 

Pantellerite. Wyomingite. Camptonite. Then11ite. I Ijolitc. 

Ncphelinite. Ijolite-porphyry. Nephelite- po rAnalcite-basalt. phyry. • 

' N eph.-basalt. 

u. 2. Kllaua,e. It. 2. ltloncJtiquase. U. 2. Knmerunn.Ne. U. 2. Alban:t.o"t~. 

Shonkinitc. Shonkinitc. Hcumite. Ijolitc. 

Syenite-hun pro- Le11citc-syenite. Theralite. N cpbelinite. pbyrc. I Monchiquite. · Monchiquite. Leucititc. . :11-Iica-picr(>phyre. Vogc"ite. Furrisitc. Thcralitc. 

Absarokite. Tcphritc. Leucite-basalt. Lcucite-tcphrite. Basalt. Leucite-basanitc. Leucite-ncphelin- Limburgite. Augitite. Lcucitc-basal t. ite. 

Nephelite-basalt. Haiiynophyre. 

Limburgite. I Basalt. 

I 

- R. 3. Vaalase. R. 3. eamptonase. R. 3. Llmburgase. R. 3. Etlndase. 

Quartz-gabbro. Kentltllenitc. J\ cph.-gabbro. Camptonitc. 

Olivine-diabaRC. OliYine- monzon- Jjolite. Neph.-baeult. 

Basalt. ite. ' Camptonite. Diorite. Monchiquite. Gabbro. HornblendeEsscxite. basalt. 

Cltmptmtite. 1\uph.-basariitc. 

Absarokite. . Limlmrgite. 

J.. .. euCite-Lasanite. I Augitite. 

Neph.-bttsalt. Hornblendite. 

Quartz-basalt. 
CLASS III. SALFEMANE-Continued. 

1. -- ~~ -- 3. Atlantare. ... Ynnlare . I fi. Gnllare. 6. Portug~tre. I 7. Kumcrunare. I 8. Uoh-emnrc. I 9. }'lunare. 

' 

Diorite und gabbro. Lamprophyres and lcucite-ncphelite lavas. 

u .... -- R. 4. Auvergnnse. U.4.--. 

Diorite. Gabbro. Gabbro. I Melllphyre. Noritc. 

Dolerite. 

Ariegite. 

Fourchite. 

1ionchiquite. 

Basalt. 

R.fi.--. H. 5. Ke<lnhekase.' 

Olivine-gabbro- Gabbro. 

diabase. Noritc. 

Ked11bckite. 

Aricgite. 
88 CHEMICAL COMPOSITION OF IGNEOUS ROCKS. 

CLASS IV. DOFEMANE. 

1. Hungurare. 

S. 1. llllnnesotlare. 

Gabbro. 

Wehrlite. 

·Pyroxenite. 

s. 2. 

Gabbro. 

Missourite. 

Wehr lite. 

Peridotite. 

S. 3. Hungurlure. 

Wchrlite. 

Peridotite. 

Hornblende-picrite. 

Hornblendite. 

Lherzolite. 

8.4.-·-. 

2. Scotare. 

G!Lbbro and peridotite. 

8.1. --. 

Augite~norite. 

Pyroxenite. 

Neph.-basult. 

8. 2. Paollare. 

Gabbro. 

Koswite. 

J acupin1ngi te. 

Augite-peridotite. 

Hornblende-basalt. 

Neph.-basult. 

s. a. 'l'exlure. 

Peridotite. 

Neph.-basalt. 

N cph. melilite-basalt. 

8.4.--. 

Peridotite. Liniburgite. 

Lherzolite. Neph.-mclilite-basalt. 

S. o. l'yrenlure. S. 5. --. 

Hornblende-peridotite. Mica-peridotite. 

Hornblende-lherzolite. 

Venunzite. 

3. 8verigare.' 

S. 1. Bergenlare. 

Ilmenite·norite. 

s. 2. 

(?) Pyroxenite. 

Avczacite. 

Neph. melilite-lmsalt. 

I 

4. Adlrondackare. 5. 

Iron ores. 

S. 2. Adlrondackorc. 8. 2. 

Iron ore. Iron ore. 

8. 3. Uhamplulnore. 

Iron ore. 

CLASS V. PERFEMANE. 

1. Maorare. 2.--. 

Peridotite and pyroxenite. 

S. 1. Uarollnlare. 

Websterite: 

.Pyl'Oxenite. 

Lherzolite. 

8. 2. Murylandlare; 

Pyroxenite. 

Koswite. 

s. 3. 

Koswite. 

8 .... 

Saxonitc. 

S. 5. Maoriare. 

Dunite. 

Harzburgite. 

8.2.--. 

Lherzolite. 

s.o: --. 

Dunite sideronitiquc. 

3. 4.--. 5. 

Iron ore!'!. 

s. 2. s ., 

Iron· ore. IroJl ore. 

s. 3. 

Iron ore. 

s .... 

Iron ore. 
CORRELATION OF ROOKS DIFFERENTLY CLASSIFIED: 89 

Approaching the subject from the standpoint of the qualitative, mineralogical 

system we are interested in the distribution of rocks in . the quantitative. system 

in the first instance according to their content of quartz, feldspar, feldspathoid, 

or ferromagnesian minerals.. We may consider the distribution of, first, rocks 

containing a notable amount of. quartz and their equivalent lava forms; second, 

rocks characterized by feldspar without notable amounts of quartz or feldspathoids; 

third, rocks containing notable amounts of feldspathoids; fourth, rocks composed 

chiefly of ferromag:nesian minerals. 

In general, it may be said. that the quartzose igneous rocks fall almost without 

exception in Classes I, II, and III, and .those in Class III are comparatively rare, 

so that most· quartzose rocks belong to Classes I and Il, and those with notable 

. amo~nt of quartz (~. > . i) are in orders 4 a~d 3, .very few occurring in orders 2 

and 1, and these only in Class I. 

Nearly all rocks known as' granite, granodiorite, quartz-monzonite, qua1;tz-. 

diorite, and the rare quartz-gabbros, together with their aphanitic and glassy equivalents, belong to order 4, Classes I and II, in most part, and to some. extent to 

order 3 in Class I, very few being found ·in this order· of Class II. · The most 

quartzose rocks belong to Class I .. 

Of the minerals associated with quartz the most abundant .and frequent are 

feldspars, usually preponderant, and these are distinguished in 'the qualitative 

system as alkalic, alkalicalcic, and.calcic. Since it is generally true that as magmas 

are richer in magnesium and iron they also contain more calcium, it follows 

that rocks richer in ferromagnesian minerals usually carry more calcic feldspars 

than rocks poor in those minerals. Consequently the greater number of quartzose 

rocks with alkalic feldspars occur in Class I, and the g'l'eater number with calcic 

feldspars are in Class II; and those' with the most ~alcic feldspar should occur · 

in Class III. To. this, of course, there are notable exceptions, especially where 

the .fernie mineral is not ferroruagnesian but arlkalic, as· acmite, in rockall6se. 

Most granites . are found in Class I, ·and most of the~e are in order 4, with 

dominant feldspars; fewer in order 3. Most of these persalanes are peralkalic 

and domalkalic, rangs 1 and 2. But in order 4 a considerable number are alkali-

·calcic, rang 3. The more alkaiic rocks are commonly sodipotassic, while the 

alkalicalcic ones are mostly dosodic; that is, with increase of lime the1~e is a 

diminution of potash. · 

These quartz-bearing persalanes include rocks that have been named aplite, 

granite, granitite, granodiorit~, quartz-monzonite, quart?-diorite, the phanerocrystallinc porphyries of these, and quartz-porphyry, rhyolite, dacite, and andesite, 

.together with those of special yarieties--alaskite, alsbachite, tordrillite, comendite, 
90 CHEMICAL COMPOSITION OF IG~EOUS ROOKS. 

paisanite, toscanite, and others. Some rocks that fall within the limits of. these 

divisions of the quantitative system bear names occurring mostly in other divisions, sneh as syenite, nordmarkite, diorite, andesite. These are in part intermediate rockl'! deserving double magma names; in part, those, like some andel'!ites, 

whose mineral composition is not completely determinable, and in which the 

qua~'tz content is obscure or uncrystallized. 

A much smaller ~umber of granites belong to Glass II, dosalancs. The most 

alkalic members of this clast'!, pantellerite and grorudite, are comparatively deb in 

ferric oxide. 

Most of the quaric rocks of Class II are alkalicalcic and dosodic." The 

greater number of them l:iea·r .the names quartz-diorite, diorite, and andesite. 

The quaric rocks i. · Class III are low in quartz, except in the rare varieties of pantellerite and rockallite. But in the other rocks, also rare, quartz 

oqcurs in smttll amount with alkalicalcic feldspars and calcic feldspars .. One of 

these rocks is quartz-gabbro, another a diorite, and several others olivine-bearing 

rocks, whose chemical analyses are such that they fall in order 4 of this class. 

Rocks characterized by feldspars without notable amounts of quartz or feldspathoids occur in perfelio order 5 of Classes I,. II, and III. 

Among the perfelic persalanes, Class I, the more alkalic rocks are commonest 

(syenites), alkalicalcic ones are rare, while docalcic ones are well known (anorthosites). As to the character of the alkalies, soda preponderates in most cases, 

dosodic rocks being more abundant than sodipotassic ones, which, however, are· 

common. 

The names borne by these rocks arc: Syenite, nordmarkitc, pulaskite, lam·vikite, bostonitc, trachyte vulsinite, andesite, keratophyre, and others. The most 

sodic rocks have been called albitite; the mosp calcic, anorthosite. Some of them 

have been called nephelite-syenite, phonolite, leucite-trachyte, and other names. 

The perfelic· dosalanes, Class II, are more common than the extremely feldspathic persalanes, and t 1

1e alkalicalcic ones ate more numerous than the domalkalic or docalcic forms, .but these are also well represented. Most of these rocks 

are dosodic, although many are sodipotassic. 

They appear under the names of syenite, . umptekite, monzonite, diorite, 

gabbro, norite, trachyte, ciminite, akerite, shoshonite, andesite, basalt, and others. . . I 

They also include some rocks called granite, nephclite-syenitc, leucite-trachyte, 

and kcrsantite. 

The perfelic salfemanes, Class III, are alkalicalcic and docalcic, and most of 

them are dosodic. They -embrace gabbro, norite,. ariegite, kedabekite, camptonite, dolerite, and basalt. The more potassi~ and sodipotassic rocks of this 

class and order have been called kentallenite, absarokite, and lamprophyre. A · 
CORRELA.TIO:N OF ROCKS DIFFERENTLY CLASSIFIED. ~1 

few peralkalic rocks belongin~ here occur at Leucite Rills, Wyoming-orendite, 

wyomingite. ' · 

The rocks characterized by notable amounts 'of feldspathoids or lenads-leucite, 

nephelite, sodalite-with the exception of a few that belong i~ Class IV, fall 

within the lenic orders 6, 7, 8, 9 of Classes I, II, and Ill. 

Lenic persalanes, Class I, are most abundant in order 6, with dominant 

feldspar, but they are known in each of the more lenic orders. They are mostly 

peralkalic and dosodic, some being sodipotassic. They have been named nepbelitesyenite, foyaite, ditroite, miascite, phonolite, and tinguaite. V ~:~ry few contain 

leucite. · 

The same is true for the lenic dosalanes; Class II. Most of them occur in 

lendofelic order 6, but the other lenic orders. are represented. . 

In order 6 they are mostly peralkalic and . domalkalic, and the majority are 

dosodic. They include nephelite-syenite, laurdalite, essexite, tinguaite, the~·alite, 

and 'others, besides some rocks called syenite, monzonite~ ql.orite, and gabbro:· 

Rocks of the remaining orders are peralkalic and dominantly sodic. A few 

rocks in order 7 are sodipotassic. 

Order 7 contains rocks called lujavrite, tinguaite, tephrite, leucitite, hauynophyre, and others. 

Rocks of orders 8 al).d 9 ai·e rare. The first embrace leucite-basl;tnite, leucitite, 

and tinguaite. The ninth order is represented by urtite, an ijolite rich in 

nephelite, and sodipotassic arkite. 

Lenic salfefil:anes, Class III, are about as numerous as lenic rocks in Classes 

I and Il. They are mo1:e uniformly distributed through orders 6, 7, and 8. 

Perlenic rocks, order 9, are rare. 

In order 6 there are more alkalicalcic rocks than in- the corresponding order 

of Class II. Most of the rocks are sodipotassic and dosodic. The rocks have 

b~en call_ed shonkinite, leucite-syenite, leucite-monchiquite, monchiquite, limburgite, 

basanite, and others. . 

In order 7 the rocks . are dominantly alkalic and dosodic. They embra:ce 

malignite, theralite, nephelite-basal~, nephelin\te, and others. . 

Order 8 is similar to order 7. The rocks are rarer and a fe~ .are dopotassic . 

. . They are tberalite, ijolite, nephelinite, leucitite, and others. 

The rocks of order 9 are peralkalic, and include dopotassic madupite of 

Lencite Hills, Wyoming; and dosodic 1jolite, nephelite-porphyry, and U:ephelite-

·basalt. 

Rocks with preponderant fernie constituents, the dofemanes, Class IV, and 

perfemanes, Class V, are disti_nguished from one . another by the presence in the 

former of a notable but subordinate amount of salic, feldspathic minerals and 
92 CHEMICAL COMPOSITION OJ!' IGNEOUS ROOKS. 

by their absence from the perfemanes. The dofemanes, then, contain either notable subordinate amounts of feldspar, leucite, nepheiite, socialite, or of aluminous . . ferromagnesian, alferric minerals. · 

In Class IV the five orders, based on the proportions of normative pyroxene 

and olivine, compared with magnetite, ilmenite, and other nonsilicates, are all represented. Orders J and 2 are most common. In each of these the more pyroxcnic 

sections are better· represented than the more olivinic. The rocks invariably · 

belong to the permirlic rang, 1; that is to say, the fernie minerals contain little 

or no alkali_. In most cases ferrous oxide and magnesia preponderate over lime, 

and in the majority of rocks magnesia· dominatCi;f over fer!ous oxide. 

In perpolic order 1 the rocks are known in the q,ualitative system as gabbro, 

olivine-gabbro, norite, koswite, peridotite, pyroxenite, jacupirangite, nephelitebasalt, nephelite-melilite-basalt, and limburgite. 

In polmitic order 3, with nearly equal silicate and nonsilicate minerals, the few 

·rocks ns -yet described have been called ilmenite-norite, pyroxenite, avezacite, 

and nephelite-melilitc-basalt. 

Orders ± and 5, with preponderant magnetite and ilmenite, embrace certain 

feldspathic iron ores from Sweden, Canada, and New York State. 

Rocks of Class V are comparatively rare; they have little or· no feldspathic 

minerals or aluminous ferromagnesian minerals. Most rqcks belong to perpolic 

order 1, and range from wholly pyroxenic to wholly olivinic kinds. A very few 

·rocks fall within each of the other orders. 

In order 1 the rocks have been called pyroxenite, websterite, kof?wite, peridotite, 

saxonite, harzburgite, and dunite.. • 

In order 2, with notable, .subor"djnate, nonsilic[!,te minerals, occur a lherzolite, 

and dunite rich in iron ore. 

In the other orders, 3, 4, and 5, the rocks are titaniferons iron ores, with variable 

amounts of" ferromagnesian silicates. In one instance the rock consists o:f m~gnetite 

a.nd spinel 

\ 
INDEX. 

A. P~tge . 

Augite-~tndesite ...........•.....•• ·. .. •• ..... . .. . . . . . .. . 32 

Augite-diorite . . . . .. . . . . .. . .. .. . . . . . . . .. . . . . . . . .. . . . . . . 45 

Augite-norite .......................................... 56,88 

Augite-peridotite ..................... : ................ 56,88 

Augite-porphyrite ..................................... 32,41. 

Augite-porphyry ......... :............................. 41 

Augite-soda-grunite . . . . . . .. . .. . .. . . .. .. . .. .. . . . . . .. . . . 29 

Augite-syenite......................................... 33 

Augitite ............ · ................................ 48,51,86 

Australia, rocks from.: .................... 23, 26, 27, 28, 35, 37 

Austrare ...................... ." .................. 36-38,84,85 

Austria, rocks from ...... 33, 34,37, 38,40, 41, 42, 43, 44, 45, 51,53 

Auverguase .................... : .................... 49-50,87 

Auvergne, rocks from .. . . .. . ......... .... .. • .. . . ...... 43 

Auvergnose ........................... · .......... , .• ' ... 49-50 

Average rock, composition of. ..................... 38,65-66 

Avezaciasc •.... ~ .............. ~ .... ·.................... 58 

•. Avezacite .............................................. 58,88 

A vezacose .. .. . .. . .. . .. .. . .. .. .. .. .. .. .. . .. .. . .. • .. . .. . 58 

. Page. 

Abbreviations, list of.................................... 22 

Absarokite .......................................... 48,49,86 

Absarokosc ........ · ........................... :........ 48 

Acmite-trachyte ....................................... 3l, 34 

Adamellose.. .... ....... ... . . ....... ..... .... .. .. .. . ... 36 

Adirondack~tre ................ : ... : .. .. : . . .... . . . .. . 58--59, 88 

Adirondackase ..... :. . . . .. . . . .. . . . . .. . . . . . . . . . . . . . . . . . 58 

Adirondackiase..... .. ....... .. .. . ... . ...... ..... . . .... 58 

Adirond11ckore ....... :: ............ · ................... 58,88 

Aegirite-granite .......... :. . . . .. . . . .. .. . .. .. . .. . . . . . . . 28 

Africa, rocks from ............................ 44, 47, 52, 53,59 

Akerite ............................................. 28,40,84 

Akcrose ... : .............................. ·.,............. 40 

Alaska, rocks from ............... 23, 24, 26, 28, 29, 38, •11, 42,67 

. ~:::~;':::::::::::::::: ::::::::::::::::::::::::::: ·;3, ~t::~~ Alaskite-porphyrr ................ ~... .. .. . . .. .. . .. .. .. 29 

Alaskose................... ...... .. .. .. .. ... .. . .. . .... . 23 

Albanase .............................................. 53,86 

Albanose .,.· ............. : .............. :.............. 53 

Albitite ............................................... : 32,82 

Allochetitc .................. .......... : ........... .... 45,84. 

Alsace, rockH from ... , .............. 2~, 30, 36, 42, 43, 51, 61,68 . 

B. 

Baden, rocks from ............... 39, 40, 41, 50, 51, 52, 56, 57,58 

Balth:wrase ..... _.: ........ ."............................ 60 

Alsbachase ..... , ...................................... 2( 82 Baltlmorlasc·........................................... 69 

'Alsbachite ............................................. 24,82 Balt)morose ......................... , ....... , .. .. . .. .. 60 

Alsbachose . . . .. .. . .. . .. .. .. . .. .. • .. .. . .. .. .. . .. .. . .. .. 24 Banakite ........................................ 40,41,84,85 

Amado rose ............... ~..... .. .. .. .. .. . .. .. . .. . .. .. 30 Banatitc .. · ........................... : ... ." ............ : 30,83 

America, North, average rock from................... 38 Bandase ............................................... 38, 85 

Ami~ttose .......................... :.. . .. .. • .. .. .. .. .. . 30 Ban dose . .. . .... .. . .. .. . .. .. . .. .. • .. .. .. .. .. . .. .. • .. .. .. 38 . 

Amphibole-malignite .................... ,., ... ·........ 52 

Analcite-basalt ......... : ........................... 50,51,86 

Basalt .............. 40,41,42,43,45,47,48, 49, 50~ 52, 84,85,86,87 

Basanite ..........................•.........• , ...•.. 45, 46, 84 

Andase ............ : .. .............................. 41l-42, 85 See alao Leucite, Nephelitc-basanitc. 

Andes: tc ....... 2~, 30, 32, 33, 35, 36, 37, 38, 40, 41, 42, 82, 83, 84, 85 Bavaria, rocks from ....... : .. ......................... 23, 5-l 

phonolitic . .. .. . . .. .. .. .. . .. .. . .. .. .. . .. .. . .. .. .. .. . 31 

Amlesite-porphyry .................... : ............... 29,37 

Bearpaw Mountains, Montana, rocks from ....... : .... 27,40 

Becke, F., diagrams used by, description of........... 11 

·Andesite-basalt ........................... ·............. 42 Beemerose .................. ~......................... 34" 

·Andesite-perlite....................................... 30 Beerbachite ............................................ 42,85 

Andcsitic glass ................ ·........................ 42 Beerhachose........................ . . . . . . . . . . . . . . . . . . • 42 

An dose ................................................ 41-42 Ilelcherose ....... : ..... ............ :............... .... 54 

Anorthosite .................................. 33,42,43,83,85 Befgare ............................................ ·.·.. ~2-63 

· ~~::~~c~;~;,;i~:::: :::::::::::::::::::::::::::: -~~~~~: ~~· 28'~! Bergenase ......................... :.. . .. . .. .. .. .. . .. .. 58 Bcrgeniarc ......................... :.-.................. 58,88 

A plitic granophyre .................................... 23,26 Bergeniase ....................... :. . . . . . . . . . .. . . . . . . . . . 58 

Argeinose ...... :....................................... 55 

AriE\gite .. · ................. : ........................... 50,87 

Bergenose .......................... , ._................. 58 

Bl~tck Forest, rocks from .. .. .. .. .. .. .. .. .. .. .. . .. .. .. . ~7--_ 

Arizona, rocks from ........ ___ ........ , ....... _ ....... 40,49 Bogoslof Island, Alaska, rocks from ................... 41;42· 

Arkansas, rocks from ...........•. 31, 32, 34, 35, 43, 46, 53, 56,68 Bohemare .......... ." ............................... 53,86-87 

Arkimwse............................................. 46 Bol)emi11, rocks from ................... 24, 41, 42, 44, 48, 51,53 

Arkite .............. :.: ................................ 46,84 Borolanite ............................................. 44,84 

Ascutney Mountain, Vermont, rocks from............ 67 Borolanose ....... :. .. .. .. .. .. .. . .. . .. . .. .. .. .. .. . .. .. . 44 

Asia, rocks from .......................... ,............ 56 Bostonitc ....................................... ." ... 31,33,82 · 

Asia Minor, rocks from ............................. 30,37,44 quartz-bearing .......................... :. .. . .. .. . 27 

Atlantare .............................................. 47,87 Brandbergiasc....... ............ ...... ........... .... . 56 

93 
94 INDEX. 

Page. 

Brandbergose.......................................... 56 

Brazil, rocks from ................... 31, 34, 39, ;!4, 45,51, 56, 57 

Britannare ....................................... 21\-30,82-83 

British Guiana, rocks from . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29, 33 

Briigger, W. C., cited on production of similar rocks 

from different magmas ............ :......... 67 

diagrams used by, description of .................. 13,18 

c. 

California, rocks'from .. .................... '. 23, ~4, 25,26, 27, 

28, 29, 30, 31, 37, 38, 39, 41, 42, 43, 49, 50, 55, 60, 67,68 

Campanare ...........•............................. 46, 84-85 

Camptonase .................................. : ..•.. 48-49, 86 

Camptonite ................................ 42, 49, 50, 51, 53, 86 

Camptonitic tingnaite.. ... . . . . . . . . . . . . . . . . . . . . . . . . . .. . 45 

Camptonose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 

Canada, rocks from ......... 31,32,33, 34, 40, 42, 44, 52, 58, 59,62 

Canadare ........................................ 31-33,82-83 

Cauadasc ................................. ·. . .. . . . . .. . .. 33, 83 

Cape Colony, rocks from............................... 47 

Cape Verde, rocks from ................................ 52, 53 

Caroliniare .. .. . . . . . .. . .. .. . . .. . . . . . . . . . . . . . . . . .. . . . -59-60, 88 

Casselase ............................................. : 57 

Casseliase........... .. . . . . .. . . . .. .. . . . . . .. . . ... .. . . . . . .. 57 

Casselose............................................... 57 

Castle l\fountains, rocks from .......................... 40,48 

Cecilose ...................................... ·.......... 60 

Celebes, rocks from ........................... 31, 32, 34, 40, <14 

Champlainase ........................ : . ... ' ........ .'... 59 

Ch~tmplainiasc ........................... :............ 59 

Champlainorc ......................................... 59,88 

Chibinite ............................... : .............. 45, 84 

Chile, rocks from ...... ; ......................... 28, 39, 42, 51 

Chotase .................................. , ............. 53, 86 

Chotose ........................... :. . . . . . . . . . . . . . . . . . . . 53 

Christiania region •. Norway, rocks from .. ; .... : ........ 67-68 

Ciminite. . .. . . . . .. . . . . .. . . . . . .. . .. . . .. . . .. . . . . .. . 39, 40, 84, 85 

Ciminose ........... :. .. . . .. . .. .. .. .. . . .•. .. .. .. . .. . . .. . 39 

Clarke, F. W., cited on composition of ~tverage rock ... 65,66 

Classification of igneous rocks, methods of: ........... 68-70 

Colombia, rocks from ........................ 30, 36, 37, 40,41 

Coloradase .................................... .' ........ 30,83 

Colorado, rocks from .................... :. 23, 26, 27, 28, 29, 30, 

31, 33;34, 37, 38, 39, 40, 41, 42, 43, 44, 45,.48, 49, 51, 55, 67,68 

Coloradose. ...................... .......... .... .. ... . .. 30 

Colmubare ....................................... 23-25,82-83 

Columbretcs Islands, rocks from ................... 33, 34,40 

Comendite~ .............................. .' ............. 26,82 

Connecticut, rocks from ...................... 26, 28, 33, 49,67 

Cookose ....................... :.::.::.................. 54 

Correl~ttioii of igneous J;OCks, tables showing .......... 81-92 · 

Corsase ................... : .. .......................... 43, 85 

Corsite.: .... :: ......... ,. ......... ·. : ........ :· .. : :.: ..... 43,.~5. 

Cortlimdtase ............................. .... :......... 55 

Corthmdtiase.............. ........ ...... .............. 55 

Cortliuidtose ................................ ~.......... 55 

Covife ................ :.. . .. . .. .. . .. . . . .. .. .. . .. .. .. 42, 44, 84 

Covose................................................. 53 

Cruzy llfountains, Mont-ana, rocks from............... 31, 

33, 39, 41, 42, 52, 56,67 

Cripple Creek, Colorado, rocks from................... 67 

Cross, Whitmun, diagrams used by; reference to...... .11 

letter of, transmittal by ......... : ..... ::.......... 7 

Oust erose ...................................... _ 55 

D. 

D>tease .................... : ............................ 36,84 

Dacite ............................ 28, 29, 30, 36, 37, 82, 83, 84,85 

sec"retion in ........................................ 42,43 

Page. 

Dacite-porphyry . . . .. . .. .. .. . . .. .. . . .. . .. . .. .. .. . .. .. .. 29, 30 

Dacose ............. : ................... :............... 36 

Dakyns, J. R., and Te~tll, J. J. II., diagrams used by, 

• reference to ...................... , ......... 10-11 

Darg~tse ...................................•..... :. . . . . . . 82 

Dargose ................ .'............................... 82 

Dellcnite ................... .' ........................... 27,82 

Delle nose .. .. . .. .. .. .. .. .. .. . .. .. . . .. .. .. .. . .. . .. .. . .. . 27 

Diabase ............................................. 42, 49,50 

Diabase-pitchstone . .. .. .. .. .. . .. .. .. .. .. . ... .. . .. .. . . .. 49 

Diabase-porphyrite ..................................... 33,83 

Diabase-porphyry...................................... 30 

Diubase-syenite-porphyry ............................. · 42 

Diagmms, clussifica.tion of. .......... : ................. 70-81 

clt1ssification of, Cl~tss I. ........................... 71-76 

Class·n ............................ : . .......... 71\-77 

Class III ....................................... 77-79 

Classes IV and V .............................. 79-81 

discussion of ...................................... 63-81 

previous use of .................................... 10-16 

Dike ·rock... .. . .. .. .. . .. . .. .. .. .. . .. .. . .. .. .. .. .. .. .. .. 57 

Diorite .............. :.~ ........... .' .......... ."......... 29. 

Diorite-porphyrite..................................... ~~~-~~~~~~~~-~~-~ ·12 

Diorite-porphyry . .. . .. . . .. .. .. . . .. .. .. . .. .. . .. . .. .. .. . 40 

District of Columbia, rocks from ...................... 38,47 

Ditroite ..................................... : .... 34,40,82,84 

Dofemane ........................................... 54-59, SA 

Dolerite ................................ 38, 41, 42, 43, 49, 85,81 

Domite ................................................ 32 

Dosalane .. .. . .. .. .. . .. .. .. .. . .. .. . . . .. . . . . . .. . .. . .. .. . 35-47 

Dunase ................................................ 61 

Duniase .......... ~ ............. .' ............. -...... .'.. 61 

Dunite ................................................. 61, 88 

Dunite sideronitiqile .................................. 61,88 

D.unose ................................................ 61 

Durbachite ........ · .................................... 39, 8.4 

E. 

Eleolitc-mica-syenite............. ... . . . . . . . . . . . . . . .. . . 56 

Elsass. See Alsace. 

Engl~tnd, rocks from ............................. ~.... 28 

Essexase ............................................... 44,84 

Essexite ............................. 40, 42, 44, 45, 49, 84, 85,86 

Essexose ................................ :. . . . . . . . . . .. . . 44 

Etindase .............................................. ·. 53,86. 

Etindose. ...... ..... ............ ......... ... .. . ... . .... 53 

Extreme types, discussion of .......................... u4-Q6 

F. 

Farrisite .. .. . . .. .. .. . .. .. .. . .. .. . .. . . . . .. . . . . . . . . .. .. .. 52, 86 

Feldspar-porphyry..................................... 29 

Felsite ................................................. 35,84 

Felsite-porphyry ....................................... 23,24 

J<'erdinandea, rocks from : .' ..... .- ....................... 42, 68 

Fergusosc...... ............ .... .................. ...... 43 

Fichtelgebirge, rock from .... : ................. ~...... 23 

Finland, rocks from .. 24, 26, 31, 33, 34; 35, 39, 45, 46, 47,52154,57 

Finn arc .......................................... 53-54,86-87 

Fourchite .............................................. 50,87 

Foyaite ....................................... 31, lH, 35, 43, 82 

France, rocks from ................... :. · 32, 34, 40, 43, 50, 55,58 

G. 

Gabbro ........................ 43, 45,49, 50, 54, 84, 85, 86, 87,88 

dioritic · ............................................ · 52 

Gabbro-diorite ......................................... 41, 43 

Gabbro-porphyry................... .. .. . . .. .. .. .. . .. .. 49 
INDEX. 95 

Page. 

Gallare ............................... ; .......... 48-50, 8&-87 

Garnet-pyroxene-malignite . . . . . . . . . . . . . . . . .. . . . . . . . . . 52 

Germanare ...... : ............................. · .. 39-43, 84-85 

Germany, rocks from .... 23, 26, 31, 34, 45, 49, 50, 51, 53, &4, 56,57 

Glrtss, andesitic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42 

Graham Island, rocb from............................ 42 

Granite ......... · 23, 24, 25, 26, 27, 28, 29, 30, 37, 33, 39, 82, 83, 84, 85 

graphic ............................. :. . . . . . . . . . . . . . 26 

Grunite-syenite-porphyry .............................. 27,28 

Granite-porphyry .......................... 25, 26,27, 28, 29,36 

Granitite ....................... 23, 24, 25, 26, 27, 28, 29, 30, 36,37 

Granodiorite .................................. 29, 30, 82, 83,85 

. Granodiorite-aplite . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28 

Granophy,.e............. .. . . . .. . . . . . . . . . . .. . .. . . . . . . . .• 23 

' Graphic granite........................................ 26 

Great Britain, roc.ks from •................. 23, 28, 38, 41, 44,49 

Greenland, rocks from.................................. 50 

Grorudite ..................................... 27, 35, 36, 82,84 

Giorudose............................................... 36 

H. 

Hackman, V., diagrams used by, reference to......... 13 

Hanover, rocks from................................... 49 

Harker, A., cited on composition of the average rock .. 65-66 

diagrams used by, reference to . . . .. . . . . .. . . . . . . . . . 11 

Harz 1\Iouptains, rocks from ..................... 23, 31, 17,57 

Harzburgite ........................................ , .. 61,88 

Hrrrzose ....... ·......................................... 37 

Hrriiynophyre .................................... 46, 52, 8·1, 86 

Hedrumitc .......................................... 39, 44,84 

Heronite ........................................... _ .... 34,82 

Herzegovina, rocks from .. .. .. .. . . .. . .. .. .. .. . .. .. .. .. 33 

Hessase ........ : .................... : . . : .... · ........ 42-43, 85 

Hcssose.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42-43 

Hesse, rocks from ............................. 25,42,45,51,53 

Heumite ...................................... 39, 44, 52, 84,86 

Highwood ·Mountains, Montana, rocks from .......... · 31, 

36, 40, 41, 43, 51,52 

Highwoodosc................................. ... . .. .. . 39 

Hispanare ........................................ 35-36, 84-85 

Hobbs, W. H., diagrams used by, description of....... 13 

Hornblende-basalt ........ · ...................... 51, 56, 86,88 

Hornblende-dacite . .. . . . .. . .. .. . .. .... . ... .... . .. .. .. . 37 

Hornblende-gabbro .............................. .' ..... 45,52 

Hornblende-lherzolite ................................. 55,88 

Hornblende-monchiquitc.............................. 50 

. Hornblende-peridotite ................................. 55,88 

Hornblcnde-picrite ............................. · ....... 55,88 

Hornblende-porphyrite .......................... : ... ·.. 37 

Hornblcnde-vogcsite................................... 51 

Hornblcndite .................................... 51,5f,86,S8 

Hungary, rock from ........ , .................... 24,30,34,37 

Hungarare .......................................... 54-56,88 

Hungariare ............................................ 55,88 

Hypersthene-gabbro ................................... 50,54 

I. 

Idaho, rocks from .................................... .. 28 

Iddings, J.P., diagrams employed in 1890 and 1898 by, 

description of. .......................... 10,18-14 

livaarose .. .. . .. .. .. . .. .. .. . .. . . .. . . . .. .. .. . .. . .. . .. . .. 54 

Ijolase .............................................. 53-54,86 

ljolite ..................................... 47,51,53,54,81,86 

Ijolite-porphyry ...................................... 52,86 

Ijolose .................... ! .. . . . .. .. .. .. . . .. . . .. . . . . .. . 54 

llmcnite-.norite ................................. : .. .... 58-88 

llmenose ................................ :.............. 39 

Page. 

Ireland, rock {rom..................................... 23 

·Iron :Mountain, Missouri, rocks from.................. 67 

Iron ore ....................................... 58, 59, 61, 62,88 

Ischia, Italy, rocks from ............................... 40,67 

Italy, rocks from ...................................... 25,26, 

27, 28, 29, 31, 32, 34, 35, 39, 40, 41, 42;43, 44, 

45, 46, 47, 48, 49, 50, 52, 53, 55, 56, 58, 59,67 

Italare ........................................... 45-46, 84--85 

J. 

Jacupirangitc.: ........................................ 56,88 

Janeirose . .. . . . .. .. . . .. .. .. . .. .. .. .. .. .. .. .. .. .. .. . . . .. 45 

Japan, rocks from ................................. :... 38 

Judd, J. W., diagrttm employed hy, reference to.. .. . . 10 

Judithuse.............................................. 43 

K. 

Kaiserstubl, rocks from . .. . . .. .. . .. . . . .. • . . . . . . . .. .. .. 41 

Kallerudose............................................ 27 

Kalteniase ...................................... · ..... .. 57 

Kaltenose... ....... .... ........ ........... ..... ... . .... 57 

~:::~~~::::::::::::::::::::::::::::::::::::::: :'. ~~~~~· ~t~! Kamerunose ................ :.......................... 52 

Kedabekase ........................................... 50,87 

Kedabekite ............................................ 50,87 

Kentallenile ........................................... 49,86 

Kenta!lenose . .. .. . . . .. .. .. .. . .. .. .. .. .. .. . .. . . . .. . . . .. 49 

Kentucky, rocks from................................. 39 

Keratophyre ........................................ 31, 33,82 

Kersantite ....................................... 39, 42, 84,85 

Kilanase ............................................... 48,86 

Kilauose .. :....... ..................................... 48 

Koswite ............................................ '56,60,88 

koswose............................................... 60 

Kulaite ............ :. . . . . .. . . . .. . . .. .. . . . . . . .. . . . . . . .. . 44, 84 

TJ. 

Labrador, rocks from .... c ........... : ................ . 

Labradorase .......................................... . 

Labrador-porphyrite .................................. . 

Labradorite-porphyry ............................... .. 

Labradorosc ......................................... .. 

33 

33,83 

41 

51 

33 

Lacroix, A., diagramB used by, description of ......... 12-13 

Lake Superior region, rocks from .... _....... . . . . . . . . . . 33 

Lam arose ........................ :. , . . . . . . . . ... . . . . . . . . . 48 

Lamprophyre .................................... 48,49,86,87 

syenittc ............... : .................. ,. .. . . .. .. 48 

La Plata l\fountains, rocks from....................... 40 

Lap pare ........ , ........ , ........................ 46-47, 8·~-85 

Lasscnose.·...... ......... .... . ...... ...... ... . ..... . ... 29 

Latite ......................................... 29,37,41,82,85 

· Laugenase. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35, 82 

Laugenose ............................................. 35,82 

Laurdalase ................... : ..................... 48-44, 84 

Laurdalite., ........................................... 44,81 

Laurdalose ............ : ~.............................. 44 

J~aurvikite ................. , ..................... 32, 33,82 

Lau~vikose ...... .- ................................... • 32-33 

Lebachosc ..................... , ......... ... .. .. .. .. .. 26 

Lestiwarite ....................... :.. .. .. .. .. .. .. .. .. .. 31 

Leucite-absarokite ..................................... 47,49 

Lencite-basalt.: .................................... 51, 52,86 

Lencite-basanite ........................... 46, 48, 51, 84, 85,86 

Leucitc-kulaite ........................................ 44,84 

Lcncite-monchiqnite .................................. 51,85 

Lcncitc-nephelite lavas .............. · .................. 86,87 

India, rock from ...................... : .............. .. 56 Leucite-nephelitc-s,-enitc ............................. 44,84 
96 INDEX. 

Page. 

Leucitc-nephelinite ... _ ................ __ ..... __ ... _ .. 52,86 

Leucitc-phonolitc .... ·.' .......................... 34, 39, 82,84 

Leucite-syenite .. .. .. . .. .. . . .. . . . . .. .. .. .. .. .. . .. .. .. .. 51, 86 

Lencite-tephrite ................... ' .... 44, 4li, 46, 53, 84, 85,86 

Le\Icite-tinguaite ................................ 43, 44, 45,84 

IJeucite-tinguaite-vitrophyre .... _..................... 31 

Lcucite:tmchyte.. .. . .. .. . . .. .. . .. .. .. .. .. . .. .. .. 32, 39, 82, 84 

Lcucite Hills, Wyoming, rocks from .. .. . .. .. .. .. .. .. . 48 

Lencitite ....................... : ............. .' 45, 46, 53, 84,86 

Leucitophyre ...................................... :.. . 46 

Levy, A. Michel, diagrams used by, description of ..... 12,14 

Lherzasc............................................... 55 

Lherziase . . .. .. . .. .. .. .. .. .. .. . .. .. . .. .. . .. .. .. .. .. .. .. 55 

Lherzolite ....................................... 55, 59, 61, 88 

Lherzose..... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . • • 55 

Limbnrgase ............................................ 51,86 

Lim bnrgite ................................... 51, 53, 57, 86,88 

Limlmrgose. ... .. ... .... . . .. ... .......... .... ..... ..... 51 

Liparuse ............................................... 26,82 

Lipari, rocks from . .. . .. . . .. .. .. .. .. .. .. .. . .. .. . .. .. .. . 25 

Liparite.......... .... ... .... ...... ..... . ... .... .... .... 31 

Lipurose ................ _. ~ ............ _ .............. _ 26,:27 

IAtchfielditc., ............. :........................... 31 

Little Helt l\fountains, Montana, rocks from .......... 39,50 

Little Rocky Mountains, .Montana, rocks from........ 27 

Loewinson-Lessing, F., diagrams used by, description of .............................. · ... : ·11,14-15 

Lujavrase .............................................. 45,84 

Lujavrite, schliere in .................................. 44,84 

Lujavrose.............................................. 45 

Luzon, rocks from ............................... 40,41,42,67 

M. 

l\Iadagascur, rocks from .. 27, 31, 33, 34, 40, 42, 4<1, 45, 51, 52, 67, 68 

l\fadupite ............................. : .. .............. 53,86 

Maduposc. ............... .... . ...... ..... .............. 53 

l\fagdeburgose......................................... 23 

}t-fagnetitc-spinelitc ... ........... _ ................... __ . \62 

Maine,rocksfrom .. : ........... : ...................... 31,33 

Malign use .. . . .. . .. . .. . . .. . .. .. .. .. . .. .. .. .. .. .. . .. .. .. 52 

Malignite. ... . . . . .......... .... .... . ... . ..... .......... 86 

Malignose ............................ : .. .............. 52,86 

l\Iaorure .. .. . . .. .. .. .. .. . . .. .. .. .. . .. . .. .. .. .. .. .. .. 59-61, 88 

M:wriare ................................ : .............. 61,88 

Mnriciase... ........ ..... ........ ... .............. ..... 59 

Muricose............. .... . ... .. .. .. .. .. .. . .. .. . .. .. . .. . 59 

l\furiposose.............. ..... .. .. .. .. . .. . .. .. ..... .. .. . 29 

Mariupolitc ............................. · ............... 35,82 

Mariupolosc .. .. .. .. . . .. .. .. . . .. . .. .. . .. . .. .. . .. .. .. . .. 35 

Marqilettiuse · ...... · ............ ,....................... 57 

Marquettose ......................... , ....... · ... ·....... 57 

Maryland, rocks from ........ , ... 24, 26, 28, 30, 38, 43, 54, 60,61 

M:uyhwdiare .......................................... 60,88 

Massachusetts, rocks from .. 26, 27,28, 31, 34, 39, 44,45, 49, 54,67 

Mcluphyre ............................................. 47,87 

Mexico, rocks from.................................... 45 

Miascite .................. : ............................ 34,82 

llfiaskase ............................................ 34-35,82 

Miaskose............................................... 34 

l\fic:>-andesitc ............. : ........................... . 

Mica-basalt ........................................... . 

llfica-rlucite ........................................... . 

Mica-diorite ......................................... .. 

~lieu-gabbro ......................................... .. 

Mica-peridotite ........................ _._ ............. . 

1\!iea-picrophyrc ........................... : .. ....... :. 

Mica-porphyry ... · ............. ~ ...................... .. 

Mica-trachyte ........................................ .. 

'· 

29 

40 

29 

37,41 

42 

57,88 

4$,86 

49 

39 

Page. 

Michel-Levy, A., diagrams used by, description of .... 12,14 

Michigan, rocks from ...................... 41, 43, 49, 50, 55,57 

1\ficroditroite .. .. .. . .. . .. .. .. .. .. . .. . .. .. . .. . . .. .. . .. .. 34 

l\Iicroessexitc... .. .. . . .. . . .. .. .. .. .. . .. .. . .. .. .. .. .. .. . 45 

11-ticrofoyaitc~. _ ......... __ .... __ ......... _.: __ ..... ___ ... 34 

l\Iicromonzonite ..... __ ................... ·-- ...... __ .. :13 • 

Mihalose............................................... 24 

Minette ................................................ 40, 84 

Minnesota, rocks from ......... 27, 29, 30, 33, 36, 41, 43, 49, 54,62 

Mlnnesotase .. .. .. . .. .. .. .. .. .. .. .. . .. .. . .. .. . . .. . .. . .. 54 

l\Unncsotiare ..................................... :.. . . 54, 88 

l\finncsotiasc . .. .. . . .. .. .. .. . . .. .. .. . .. .. .. . .. .. . .. .. . . 54 

Missouri, rocks from ................................ 26, 27,67 

!~~:~~~~~~a~~-:::::::::::::::::::::::::::::::::::::::::: ~~;~~ ' 

l\fonchiquitc ............................ 44, 50, 51, 52, ~4, 86, 87 

Monchiquose .. .. . .. .. . . .. .. . .. .. .. . .. .. .. .. . .. .. .. .. . . 51 

Montana, rocks from ......... 23, 24, 26, 27, 28, 29, 31, 33, 34, 36, 

37, 39, 40, 41, 42, 43, 44, 45, 48, 49, 50, 51, 52, 53, 54, 55', 56,67 

Jlfonthaldcite .......................................... 41,85 

l\fonzonase ............................................ 39,84 

Monzonite .............................. 37, 40, 41, 42; 43, 81,85 

facies of ......................... · .................. 42, 44 

l\fonzonose .. .. .. . .. .. . . .. .. . .. .. .. . .. . .. .. . .. .. . . .. .. . 39-40 

Mount Ascutney, Vermont, rocks from................ 61 

1\Iiigge, 0., diagrams used by, description of.......... 15 

Muscovite-granite ............... , . .. .. .. . .. .. . .. . .. .. . 23 

N. 

Naples, rock• from..................................... 39 

N ephelinite ........................................ : 50, 53, 86 

Nephelite-aplite ....................................... 34,82 

Nephelite-basalt ... · .................. 49, 50, 53,54, 56, 57, 86,88 

Nephelite-basanite .................................... 51,86 

Nephelite-felsite ....................................... 44,34 

Ncphelitc-gabbro ................ , ..................... 51,86 

Ncphelitc-malignite.. .... . .. .. ... .... ..... .. .. .. . .. .. . 52 

Nephelitc-melilite-basalt ........................... 57, 58,88 

Nephelitc-monzonite .................................. 44,84 

Nephclite-porphyry .............. · ............... 45,54,84,86 

Nephclite-rhomben-porphyry ......................... 35,82 

Nephclite-siilvsbergitc ............................. .'... 39 

Nephelite-sycnite ................... 31, 32, 35, 39,40, 44, 82,84 

Nephelite-sycnite-porphyry .. . .. .. .. ..... . .. .. .. .. .. .. 44 

Nephelite-tcphrite .................................. 42, 51,85 

Ncphelite-tinguaite ................................... 35,82 

N cvada, rocks from .............. 24, 25, 26, 28, 30, ;!7, 42, 49,67 

New Hampshire, rocks from ..................... '26, 27, 39,51 

New Jersey, rocks from .......................... 34, 35, 46,50 

New Mexico, rocks from .................. 26, 29, 31, 42, 50,67 

New South Wales, rocks from......................... 35 

New York, rocks from ...... 33, 41, 42, 43, 49, 55, 56, 58,59, 62,68 

New Zealand, rocks from ....................... c ... 23,24, G1 

N ordmarkase ....................................... 31-32, 82 

N ordmarkite .............................. 28, 31, 32, 39, 82,84 

Nordmarkose.. ............... ..... ...... ......... ..... 31 

Norgare .......................................... 43-45,84-85 

Norite ........................................... 41,50,85,87 

North America, average rock from.................... 88 

North Carolina, roqks from ......................... 23, GO, 61 

Norway, rocks from ...... : ................... 23,26,27, 28, 29, 

~~~~~~~~~~~~~~~~~~ 

Noyangose .. ~ ....... ~- .... -.... .. . . . . ... . . . . . . . . . . .. . . 27 

o. 

Obsidian ......... , ............................ 23, 26, 28, 29, 82 

Odenwalrl, rocks from ................................. ~4,50 

Oligoclasite..... .... . .. . . . . . . . .. . ... . . .. .. . . . .. . . .. ... 29 
/ 

INPEX. 97 

Page. 

Olivine-diabase ............................... 42,47, 50,85, 86 

Olivine-diabase-porphyrit<>............................ 47 

Olivine-essexite. ..... . . .. .. . .. . . . ..... .... . . .... . . . . . 4i 

Olivine-gabbro ............................... 43, 50, 54, 56,85 

Olivine-gabbro-<lial.mse ............................. 47, 51,87 

Olivine-laurdalitc . .. .. .. . .. .. .. .. .. .. .. .. .. .. .. .. . .. .. 44 

Olivine-monzonite ..................................... 49,86 

Omeose ......... ......... ... ... . ..... .. . ... . . .. .. . . .... 26 

Ontarare ........................ , ................. ~ .... 82-83 

.Ontario, rocks from ........................... 33, t>2, 58,·59, fi2 

Oregon, rocks from .................................... 42, 60 

Orendase .......................... : ................... 48, 86 

Orendite ................................................ 48,86 

Orendose .. . .. .. .. .. .. .. .. . . .. .. .. .. .. . . .. .. . .. .. . .. . .. 48 

Orni:iite . .. . .. .. .. .. .. .. .. . . .. . .. .. .. . . . .. .. . .. . .. . .. .. . 49 

Ornose ............ _..................................... 49 

Osann, A., diagrams n•ed by, description of .......... lf>-.16 

Ourose . .. .. . .. .. .. .. .. .. .. . .. . .. .. .. . . .. .. . . .. . . .. .. .. . 51 

P. 

Paisanite . .. .. .. .. . .. .. .. .. .. . .. .. .. .. .. .. .. .. .. . .. .. . 26, 82 

Paleolimburgite . .. .. . . .. .. . .. .. .. . .. .. . . .. .. . .. .. .. . .. .51 

Pantellaria, Italy, rocks from .......... 3~, 35, 36, 47, 49, 50,67 

Pan tell erase ................. · ...... :. .. .. .. . .. .. . . .. . . . 36, 85 

Pantellerite ................................... H5, 36, 47, 84,86 

Pantel! erose .. .. .. . .. .. .. .. .. .. . .. .. . . .. .. .. .. .. . . . .. .. 36 

Paolase .... ... __ . __ ............................... '..... 56 

Paoliare . . .. . . .. .. . .. . . .. .. . . . .. . . . . .. . . .. .. . . .. .. . . . .. 56, 88 

Paoliase . . .. . . .. .. .. . . .. . .. .. . .. . .. .. . . .. .. . .. . .. . .. . . . 56 

Paolose ................................................ 56 

Perfemane,..... .. .. .. . .. .. . . .. . .. . . .. .. . . . . .. . .. .. . 59-62, 88 

Pergamon, rocks from . .. .. .. . . .. .. . .. .. .. .. . .. . . .. . .. . 30 

Peridotite .......... : ...................... 54,55,57,60,86,88 

Perlite................................................. 23 

Permosc................................................ 61 

Persalane ........................................ 23-35,82-83 

Philippine Islands, rocks from .................. 40, 41, 42,67 

Phlegrose...... .. . . .. .. .. . .. .. .. . . .. .. . . . . . . . . .. . .. . . .. 31 

Phonolite ........................................... 31,34,82 

trachytic . .. .. . . .. .. .. .. .. . .. . . . .. .. .. . . . . .. . .. .. .. 34 

Piedmont, Italy, rocks from............................ 42 

Pikes Peak district, Colomdo, rocks from ........... 2H, 51,67 

Pirsson, L. v., diagrams used by, description of........ 11 

Pitchstone .. .. .. .. .. . .. . .. .. .. . .. . .. . . .. . .. .. .. . . 23, 26, 27, 29 

rhyolitic........................................... 27 

Placerosc . .. . .. . . . . .. .. .. . . . . . . .. . .. .. . .. . . . . .. .. .. .. . . 38 

Porphyrite .................................... 29, HO, 36, 37,40 

Porphyrite-diorite..................................... 30 

Porphyry .............................................. 23, 27 

Portugal, rocks from .......................... 34, 35, 41,44, 45 

Portugare ........................................ 50-52, 86-87 

Prussia;rocks from ..................... 26, a1, 36, 40, 48, 49,51 

Pseudoleucite-syenite ............ .- .................... 43,84 

Pulaskase ........................................... 32-33,82 

Pulaskite ..................................... 31,32,40,82,84 

Pulaskose. .. .. . . . .. .. .. . .. .. . . .. .. .. . .. . .. . .. . .. .. . . . .. 32 

Puy de Dome, France, rocks from. . . . . . . . . . . . . . . . . . . . . 32 

Pyrenees, rocks from .. .. .. . .. .. .. . .. . .. .. .. . . .. . 43, 50, 55, 58 

Pyrenaire ............................ , .............. 5&-56,88 

Pyroxene-ariegite .. .. .. .. .. .. .. .. .. .. .. .. . .. .. .. .. .. .. 50 

Pyroxene-porphyry..... .. . .. . .. . .. . . .. . . . .. . . . .. .. . . .. 41 

Pyroxenite ................................ 54, 56, 57, 59, 60,88 

Q. 

Quartz-banakite ....................................... 32,40 

Quartz-basalt ...... , .......................... 38, 41, 49, 85,86 

Quartz-diorite ............................ · .... 36, 42, 83, 84,85 

14474-No. 18-03--7 

Page. 

Quartz-diorite-aplite ...................... ,............ .HD 

Quartz-diorite-porphyry .......................... 25, 30, 83,85 

Quartz-gabbro ......................................... 47,86 

Quartz-keratophyre ................................ 24, 27,82 

Quurtz-lindoite . . . . . .. . . . . .. . . . . . . . .. . . . . . . .. .. . .. . .. .. 29 

Qm.rtz-mica-diorite .............................. 30,36,37,84 

Quartz-monzonite ............................ 28,29,37,82,85 

Quurtz-norite .......................................... 37,85 

Quartz-orthoclasite .. .. . .. .. . . .. . . . . .. . . . .. .. . .. .. .. .. . 26 

Quartz-pantellerite .................................... 27,82 

Q artz-pcgtnatite ................. :.................... 82 

Quartz-porphyrite ..................................... 29,30 

Quartz-porphyry ........................... 2:~. 24, 26, 27, 2R, 82 

Quartz-pyroxene-diorite ..... :......................... 37 

Quartz-solvsbergite .. .. .. . .. .. . . .. .. . . .. .. . . . .. .. .. .. .. 31 

Quartz-syenite ................................... 27, 31, 32,82 

Quartz-syenite-porphyry ......................... 27, 28, 31,82 

Quebec, rocks from ........................... 31, 32, 40, 42, 44 

R. 

Rapakiwi granite...................................... 2fi 

Reid, J. A., diagranu.;used by, description of.......... 111 

, Reyer, E., diagrams used by, dscription of. .... ·....... 10 

Rhode Isltwd, rocks from .............................. 58,62 

Rhombenporphyry .............................. 32, 33, 44,82 

Rhyolite ................................ 23, 24, 26, 27, 28, 29, 82· 

Rhyolite-perlite .............................. ,........ 28 

Rhyolitic pitchstone..................... . . .. .. .. .. .. .. 27 

Rhyolotrachyte . . .. .. . .. . .. .. . . . . .. .. . . .. . .. . .. . . .. .. . 28 

Riesenase .............................................. 25, 83 

RiesengcUirge, Silesin, rocks from ......... _ ..... 24, 25, 28,29 

Riesenose . . . . .. . . . .. . . .. .. .. .. .. . . .. . . . .. .. . .. .. .. . .. .. 25 

Rockall Island, rocks from . . . . . . . . . . . . . . • . . . . . . . . . • . • . ·47 

Rockallase ............................................. 47,86 

Rockallite ............................................. 47,8tl 

Rockallose............................................. 47 

Rosen busch, H., diagrams use( I Uy, refer.ence to ..... _. 13 

rock analyse" citccl from work by, reference to.... 21 

RosswcinoRc ......................... _ ...... _ ........ __ 55 

Rnssare ............................................. :H, 8~-83 

Russia, rockR fron1. ............... ...... 27,::H,33,35,42,f>4,HO 

s. 

Sagamose ........................................... .. 

Salemasc ............................................. . 

Salemose ............................................. . 

Salfemane ...... .' .................................... .. 

San Pietro, rocks from ................................ . 

38 

45,85 

45 

47-f>.l 

2ti 

Sardinia, rocks from .. ................................. 20, 34 

Saxonite ...................... .' ...................... · .. 60, ss 

Saxony, rocks from .................................... 31,'45 

Schwarzwald, rocks from.............................. 2i 

Schliere in granite ............................ : ..... 25, 37,38 

Scotare . .. .. .. .. .. .. .. .. .. .. .. .. .. . .. .. .. . .. .. .. .. .. 56-fii, ~8 

Scotland, rocks from ............................. 28, 38, 44, 4~ · 

Shonkinite ................................ 4<1, 48, 50, 51, 84,86 

Shonkinite-monzonite...... ... .. . .. .. . . .. . . ..... . . .... 40 

Shonkinose............................................ 51 

Shoshonite ...................................... 40,41,84,85 

Shoshonose.. ... ....... ....... ................ .... ..... .41 

Siberia, rocks from ..................................... 26, 34 

Sicily, rocks from .. · .................................... 35,43 

Silesia, rocks from . . . . . . . . . . . . . . . . . . . 24, 25, 28, 29, 36, 37 1 88, 56 

Silver Cliff, Colorado, rocks from...................... (i7 

Similarity of rocks from flifi"·eut regions, table showing ......................................... 66-67 
98 INDEX. 

Page. 

Soda-granite ..... --·--·---··· .......................... 27,29 

Soda-minette .................. _....................... 44 

Sodu-rhyolite . . . . . . . . . . . . . . . . . . . . . . . . . __ ............ 27 

Soda-sussexite ......................................... 46,84 

Soda-syenite ...................................... _.... 39 

Sodalite-trachyte ................................... _ .. 39, 8-l 

Soda lite-syenite ................................ _ ...... 32,82 

Solvsbergite ......................................... 31, 39,82 

South America, rocks from . . . . . . . . . . . . .. . . . . . . . . . . .. . . 27. 

28, 29, 30, 31, 33, 34, 36, 37, 39, 40, 41, 42, 4·1, 4n, at, 56, 57,60 

South Dakota, rocks from ............... _ ...... -.... _ 31, 34, 3f> 

Spain, rocks from ................................ 33,34,40,41 

Spherulitic rock ..................... _................. 2:l 

Svcrigare ................... . · .... __ ... _ ... _ ............ 58,88 

Sweden, rock from .................. 24, 28, 38, 49, 52, 58, 61,62 

Syenite ......... : ........ 29, 31, 36, 37, 39, 40, 41, 44, 82, 83, 84, s;; 

Syenite-kcrotophyre................................... 31 

Syenite-pegmatite .. -................................... 44 

Syenite-porphyry ................................ 26, 29, 31, 82 

Syenitic lamprophyrc ................................. 48,86 

T .. -

Tachylyte............................................. 49 

Tasmanare .............................. _ .......... 3~, 82-83 

Teall, .r. .T. H., und Dakyns, .T. R., cliugrums nRed by... 10 

'fehamo~c ..... _ ... _. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 

Tephritc ................ :.. . .. .. .. . . .. .. .. . .. . .. . . .. .. . 84, 86 

Tephritic truchyte. .. .. . . .. . . . . . . .. . . .. .. . . .. . . . . . . . .. . 33, 40 

Texas,rocksfrom .................................. 26,27,57 

Texuse................................................. 57 

Tcxiare .................. _ ......................... , ... 57,88 

Theralite ..................................... 44, 52, 53, 84,86 

Thiiringerwalrl, rock from . . . .. .. .. .. .. .. . . .. .. .. ..... 26 

Thuringia, rocks from................................. 51 

_ Tinguaite ........................ 31, 34, 3-\43, 4•1, 41i, 46, 82,84 

camptonitic ............................. '.......... 45 

Tonala•e ............................................ 37-38, 81) 

Tonalite ............................................ 37,38,85 

Tonalite-aplite . . . .. . . .. . .. . . . . . . . .. . . . . .. . . . . . . .. . .. .. 24 

'l'omtlose ............................................... 37-38 

Tiinsbergite ..... :. . . . . . . . . . . . . . .. . . .. . .. . . . . . . . . .. .. . . 32 

'l'ordriJlite .. .'.. .. .. . .. .. . . . .. . . . .. .. . .. . . . . . . . .. . . .. .. . 23, 82 

Toscanase .......................................... 27-29,82 

Toscanite ............ _ ........................ :!5, 27, 29, 8~~, 83 

Toscanose ............................................. 28-:-2~ 

Trachydoleritc . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 

Tm.chytc ............. 28, 29, ~0, 31, 32, 37, 3~, ·10, 43, 82,83, 84,85 

tephritie ........................................... 33,40 

Trachyte-andesite ..................................... ~6. 84 

Trachytic phonolite .. ·................................. 34 

Transitional types, <li•eussion of ....................... 64-65 

Transvaal, rocks from ................................. 44,59 

Transylvania, roeks from.............................. 34 

Tuolumnose ...... .'.................................... 32 

T) rol, rocks from ..... 26, 27, 37, 38, 40,41, 42, 43, 44,45,51, 53,58 

u. 

Umptekase ...... _ ..................................... 39,85 

Umptekitc ..... _ .......... _ ...................... 31, 39, 82,84 

Umptekose .................................... 39 

Unalnska, rocKs from.................................. · :)8 

Page. 

Ural ~founhtins, rock~ from ............ 27, 31, 5-l, 56, 60,61, 68 

Urtase .............................................. 46-47, 8-l 

Urtite ............................................... 47,84,85 

Urto•c .. .. .. . .. .. .. .. .. .. .. .. .. .. . .. .. .. .. .. .. .. .. .. .. . 47 

utah, rocks from ................................... 28,32,37 

Uvaldiase.............................................. 57 

Uvaldose ... _ .... _ ........ _ .. . . . . . . . . . . . . . . .... . .... . .. 57 

v. 

Vaalarc ............................................. 47,86-87 

Vaalosc ................................................ 47,86 

Vaalosc................................................ 47 

Variu.tions in composition of rock:;;, discussion of. ..... 63-64 

Vnringase .......................................... 35-36,85 

Varingose............. ................................ 35 

Venunziase ................ _ .................... ___ .... 56 

Venunzite ................................. · ............ 50,88 

'renanzose .... _. _.............. .. . . . . . . . . . . . . .. . . . . . . . . 56 

Verde, Cape, rocks from ............................... 52,53 

Vermont, rocks from ...... : ... 26,27,29,81,40,42,49,50,67,68 

Vcsnvase .............................................. 46,8-l 

Vesnvius, rocks fr'?m ............................... ~5,46, 53 

Vesuvose .. .. .. .. .. .. . . .. .. .. .. .. .. .. . .. . .. .. .. .. .. .. .. 46 

Victorare .. .. .. .. .. .. .. .. .. .. . . .. .. .. .. .. .. .. .. .. .. .. . 82---83 

Victoria, An~traliu, rocks from ............ 23,26,27,28,35,37 

Viezzenase ............................................. S.\82 

Vlezzenose.... .... .... ...... . . .. . . .. . ..... .. .. .... . ... . 35 

Vogesite ...................................... ,........ 86 

Vosges, rocks from ........................ 24, 30, 36, 42, 43, 68 

Vnlcanite .............................................. 25,83 

Vulcanose .... . ... .... .... .... ....... ..... . ............ 2o 

Vulsinite ........................................ 32,41,82,85 

Vulsinose ....... ....................................... 32 

Vulturase ........................................... 45-46,84 

Vulturose .................... ,......................... 46 

-w. 

Wales, rocks from ...................................... 23,41 

Washington, D. C., rockR from......................... 47 

Washington, H. S., acknowledgments to .............. 22,65 

cited on compositiou of the average rock.......... - 66 

diagrams used by, reference to.................... 11 

rock analyses cited from paper by, reference to... 21 

Websterase ............................................ 59-60 

Websteriase ........ :.... .. .. .. . .. .. .. .. .. . .. . .... . ..... 60 

Websterite ............................................. 60,88 

Websterose . .. .. .. . . . .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 60 

Wehr lase.............................................. 55 

Wehrliase... .... .. .. .... . . .. .. .. .. . .. . . .. .. . .. .. . .. . .. . 55 

Wehr lite ............................................ 54,55,88 

Wchrlose ................ .............................. 55 

W cstphalia, rock from ............ __ .. .. .. .. .. .. .. .. ~4. 43, 57 

\\'estphalose.................. .. .. .. .. .. .. .. .. .. . .. ... 24 

Wyoming, rocks from ....... 30, 32, 36, 37, 40, 41,42, 48,49,53, 62 

Wyom!ngase .......................................... 50,86 

Wyomingite ........................................... 48,86 

Y. 

Yellowstone Park, rocks from·········-----··········· 23, 

24, 26, 27, 28, 29, 30, 36, 37, 38, 40, 41, 42, 48, 49,67 

Yellowstonose . .. .. .. .. .. .. .. . . .. . .. . . . .. .. .. .. .. . .. .. . 3C 

Yukonose ......................................... ,.... 24 

0 
PUHLICATIONS OF UNITED STATES GEOVlGICH SURVEY. 

[Professional l'upcr l'o. 18.] 

The serial publications of the United States Geological Survey <:onsi~t of (1) Annual Report", 

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The 'Bulletins, Professional Papers, and ·water-Supply Papers treat of a variety of subjects, aud 

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SERIES D, PETROGRAPHY AND MINERALOGY. 

B 1. On hypersthene~andesite anrl on tric1inic pyroxene in angitic rocks, by 'Vhitman Cross, with a geological sketeh of 

Buffalo Peaks, Colorado, by S. 1''. Emmons. 1883. 42 pp., 2pls. 

R x. On secondary enlargements of mineral fmgments in certain rocks, by R. D. Irving and C. R. Van Hise. 1~84. 0<\ pp .. 

6 pis. (Out of stock.) 

R 12. A erystallographic study of the thinolite of Lake Lahontom, by E. S. Danll.. 1884. 34 pp., 3 pis. 

B 17. On the development of crystallization in the igneous rocks of Washoe, Nevada, with notes on the geology of the 

<listrict, by Arnold Hague and J. 1'. Iddings. 1885. 44 pp. (Out of stock.) 

B 20. Contributions to the mineralogy of the Rocky Mountains, by Whitman Cross >uld W. F. Hillebrand. 1885. 114 Pl•· 

1 pl. (Ont of stock.) 

B 28. The gll.bbros and ns.,ociaterl hornblende rocks occurring in the neighhorhood of Baltimore, 1htryland, by G. H. 

Williams. 1886. 78 pp., 4 pls. (Out of stoc}>.) 

B 3~. Peridotite of Elliott County, Kentucky, ·by J. S. Diller: 1887. 31 pp., 1 pl. 

B 59. The g>Lbbros and associated rocks in Delnwi1re, by F. D. Chester. 1890. 45 pp., 1 pl. 

B 61. Contributions to the mineralogy of the Pacific coast, by W. H. :Melville an<l Wnldemar Unllgren. 1890. 40 pp., 3 pl>. 

B 62. The greenstone-schist areas of the Menominee nnd Marquette region• of Michigan; a eontributiou to the snbJect of 

dynnmic metRmorphism in eruptive rocks, by G. H. Williams; with introduction by R. D. Irving. 1890. 241 pp., 

16 pis. (Out of stock.) 

B 66. On a group of volcanic rocks from the Tewan :Mountains, New .Mexi(!O, and on the occurrence of prima.ry quartz in 

certain basalts, by J. P. Iddings. 1890. 34 pp. 

B H. The minerals of North Carolina, hy F. A. Gent11. 1891. 119 pp. (Out of stock.) 

B 79. A late volcanic eruption in northern Californi>L and it• peculiar lava, by J. S. Diller. 1891. :13pp., 1i pis. (Out of 

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B 8\l. Some lava flows of the western slope of the l:lierra Nevada, California, Ly F. L. Ransome. 189~. 74 pp., llpls. 

B 107. The trap dikes of the Lake Champlain region, hy ,J. F. Kemp and V. \<'.~lasters. 1893. 62 pp., 4 pi,. (Outofstoek.) 

B 109. The eruptive and sedimentary rocks on Pigeon Point, 1\llnncsota, and their contact phenomenR, by \Y. S. B~tyley. 

1893. 121 pp., 16 pis. · 

B 1~6. A mineralogical lexicon of l''ranklin, Hampshi're, nnd HRmpden counties, -;\IIL"achusetts. Ly B. K. Emerson. 1895. 

180 pp., 1pl. 

B 136. Volcanic rocks o.f South :Mounttt.in1 I)enn.sylvanht, by Plureuce Ba .. o;;com. 1~96. 124 pp .. 28 }JlS. . 

B 150. 'l'he educational series of rock specimens collected and distributed by the United States Geological Survey, hy J. ~. 

Dil'ler. 1898. 400 pp., 47 pis. 

B 15i. The gneisses, gabbro-schists, and llSSOCiatcrl rocks of southwestern Minnesota, by c. w. Hall. 1899. 160 pp., ~7 plo. 

I' I' 3. Geology and petrography of Crater LH.ke N~ttional Park, hy .J. S. Diller and H. B. Patton. 1902. 167 pp., 19 pis. 

B 209. The geology of Ascutney Mountain, Vermont, by R. A. Dilly. 1903. 122 pp., 7 pis. 

Pl' 14. Chemical annlyses of igneous rocks published from 1884 to 1900, with a critical discussion of the ehamet"r and n,;e 

of analyses, by H. S. Washington. 1903. 495 pp. 

PP 18. Chemical composition of igneous rocks expres~cd by Inettns of diagrttms. with reference to rock chtl!!Sitication on a 

quantitative chemlco-mineralogicttl basis, by J.P. Iddings. 1903. 98pp., 8 pis. 
II PUBLICf\.TIONS OF UNITED STATES GEOLOGICAL SURVEY. 

SERIES E, CH:Kl\HSTRY AND PHYSICS. 

B 9. Report of work done in the Washington laboratory during the fiscal year 18R3-84, by F. W. Clarke and T. M. ·chatanl. 

18~4. ·!0 pp. (Out of stock.) 

H 1-J. Electrical and magnetic propertieH of the iron earhnrets, by Carl Barus and Vincent -Stn•uhal. 18Ro. ~38 pp. (Out 

of stock.) 

H ~i. Report of work dune in the Division of Chemistry and Physics, mainly during the year 1884-85. !Sou. 80 pp. 

H 32. List.' aml analyses of the minernl springs of the United St:ttes (:t preliminary study), by Albert C. Peale. 1886. 235 pp. 

(Out of stock,) · 

H o-5. !'hysical properties of the iron carhurets, by Carl Barus and Vincent Stroulml. 1886. 62 pp. 

1!36. Subsidence of tine svlid particles in liquids, by Carl llarus. 1886. 58 pp. (Out ofstoek.) 

F 42. Report of work done in the Division of Chentistry ancl Physics, mainly 1luring the fiscal yenr 1885-Sti, l•y ~-,. ,Y, 

· Clarke. 1887. 152 pp., l pl. (Out of stock.) 

H ·17. 'Analyl'!el-3 of waters of the Yellowstone Nationnll'ark, with an account of the methodH of nnalyscH employe1l, by 

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B 52. Subaerial deeay of rocks and origin of the red color of certain formations, by Israel Cook Russell. 188~ .. 65 pp., ;, pJx. 

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B 5-1. On the thermoelectric measurement of high temperatureH, by Carl Barux. 18~9. 313 pp., 11 pis. (Out of stock.) 

B o.5. Report of work done in the Division of Chemistry and Physics, mainly during the' fiscal year 1886-87, by F~ W. Clarke. 

1889. 96 pp. (Out of stock.) . 

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B 64. Report of work done in the Division of Chemistry and l'hysic_s, mainly during the fiscal year 1888-89, by F. W. Clarke. 

1890. 60 pp. . 

B o8. Earthquakes in California inl889, by James Edwurd Keeler. 1890. 25 pp .. 

B 73. The viscosity of solids, by CRrl Barns. 1891. xii, 139 pp., 6 pis. 

B 78. Report of work ilone in the Division of Chemistry and Physics, mainly during the fiscal year 1889-90, by 1<'. W. Clarke. 

1891. 131 pp. 

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1892. 77 pp. 

B \1~. '!'he compressibility of liquids, by Carl Barns. 1892. 96 pp., 29 pls. 

B 91. The mechtmi;m of solid viscosity, by Carl Barus. 18n. 13R pp. 

B 9o. Earthquakes in Califomia in 1890 1tn<l 1891, by Ed ward Singleton Hol<lcu. 1RH~. 3lpp. 

B 96. The volume thermodynamics of li<]nids, by Carl Barns. 1892. 100 pp. 

B 103. High tempera-ture work in igneous fnsion and ebullition, chiefly in relation to preKsnre, by Gu.rl Barus. 1Kmt [)7 

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llll~. Earthquakes in Californhc in l~n. by ClHtrleH 11. Perrine. 1893. 57 pp. 

R 113. Report of work done in the Division of Chemistrr an<l 1-'hysieH during the fiscal y1~nr~; l~Ul-~1~ aw.ll:-)IJ~-V3, hy J:i'. \V. 

Clarke. 1893. llf> pp. · 

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H 129. Eurthquakes in GRlifomin inl89,J, hy Charles D. Perrine. 18Uil. ~5 pp. 

B 147. Earthquakes in C:tlifornia in 1895, by Charles D. Perrine. 1896. 23 Jllj· 

B 148. Analyses of rocks, with a chapter on analytical methods, laboratory of the Unitecl 1-Hutes Geological o;urvey, l~~u lo 

1896, by .F. W. Clarke and W. F. Hillebmnd. 1897. 306 pp. (Out of stock.) · 

H 155 .. Earthquakes in California in 1896 and 1897, by Charles D. Perrine. 1898. 47 pp. 

ll1lil. Earthqtmkes in California in 1898, by Clutrles D. l'errine. 1899. 31 pp., 1 pl. 

B 167. Contributions to chemi,try and mineralogy from the laboratory of the United Stutes Ueologiealliurvey; Frank W. 

Clarke, Chief Chemist.. 1900. 166 pp. 

Jl168. Analyses of rocks, laboratory of the United States GeologiCitl Survey, 1880 to 18!19, tabulated by. I<'. \\'.Clarke." 1900. 

308 pp. (Out of stuck.) 

H 176. Some principles nnd methods of rock analysis, by W. F. Hillcbrall(l. 1900. 114 pp. 

B 181l. On pyrite anrl marcasite, by H. N. Stokes. 1900. 00 pp. 

B :..!07. The action of ammonium ~hiurirtc upon silicate::-;, hy }'. \V. Clarke anrl George Steiger. UIU:2. fl7 ~·l'· (01it of Htouk.) 

PP 1~1. Chemi<:al analyses of igneous rockR JHlblished from 181):1 to 1900, with n eritical rli:-:;eu~~ion of the character awl usc 

of ann.lyses, by H. K Washington. 1903. 49.5 pp. 

1--P 18. Chcmieul composition of igneons rocks expressed by 111ea11s of diagru.ros, with rcfereiwe to rock dn.~~itication on u 

qtmntitative ehernico·mineralogieal baeis, by J.P. Iddings. 1903. 98 pp., 8 pl,. 

Correspondence should be addresse<l to-

' THB Duu~urou, 

UNI1'J;]D S•J'ATJ;J:S GJoJOLUUli~AI" SUH\'Jo]Y,, 

\V A:SHINGTON, D. u. 

SEP'l'EMllEH, 1903.