SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES • NUMBER 22

Mineral Sciences Investigations

1976-1977

Robert F. Fudali

EDITOR

SMITHSONIAN INSTITUTION PRESS

City of Washington

1979
ABSTRAC T

Fudali, Robert F., editor. Mineral Sciences Investigations 1976-1977. Smithsonian

Contributions to the Earth Sciences, number 22, 73 pages, 22 figures, 20 tables,

1979.—This volume is comprised of six short contributions reporting the results

of some of the research carried out by the Department of Mineral Sciences,

Smithsonian Institution, during the period 1976-1977. Included are: a comparison

of impact breccias and glasses from Lonar Crater (India) with very similar specimens from the moon; petrographic descriptions and chemical analyses of virtually

all the known pyroxene-plagioclase achondrite meteorites and a discussion of the

relationships within this class; a comparative chemical study of sixty Australian

tektites from widely separated localities; a description of a new, rapid technique

of sample preparation for whole-rock analyses using the electron microprobe; an

interlaboratory comparison of the precision and accuracy of electron microprobe

analyses; and a tabulation of the chemical compositions of some electron microprobe reference samples.

OFFICIAL PUBLICATION DATE is handstamped in a limited number of initial copies and is recorded

in the Institution's annual report, Smithsonian Year. SERIES COVER DESIGN: Aerial view of Ulawan

Volcano, New Britain.

Library of Congress Cataloging in Publication Data

Main entry under title:

Mineral sciences investigations, 1976-1977.

(Smithsonian contributions to the earth sciences ; no. 22)

"Six short contributions reporting the results of some the research carried out by the

Smithsonian's Department of Mineral Sciences."

Bibliography: p.

1. Mineralogy—Addresses, essays, lectures. I. Fudali, Robert F. II. National Museum of Natural

History. Dept. of Mineral Sciences. III. Series: Smithsonian Institution. Smithsonian contributions to the earth sciences ; no. 22.

QE1.S227 no. 22 [Q364] 560'.943 [549] 78-24474
Contents

Page

METEORITES

PETROLOGY, MINERALOGY, AND DISTRIBUTION OF LONAR (INDIA) AND LUNAR

IMPACT BRECCIAS AND GLASSES, by Kurt Fredriksson, Phyllis Brenner,

Ananda Dube, Daniel Milton, Carol Mooring, and Joseph A. Nelen .. . 1

CHEMICAL VARIATION AMONG AUSTRALIAN TEKTITES, by Brian Mason 14

T H E PYROXENE-PLAGIOCLASE ACHONDRITES, by Brian Mason, Eugene

Jarosewich, and Joseph A. Nelen 27

ANALYTICAL LABORATORY

FUSION OF ROCK AND MINERAL POWDERS FOR ELECTRON MICROPROBE ANALYSIS, by Peter A. Jezek, John M. Sinton, Eugene Jarosewich, and Charles

R. Obermeyer 46

MICROPROBE ANALYSES OF FOUR NATURAL GLASSES AND ONE MINERAL:

AN INTERLABORATORY STUDY OF PRECISION AND ACCURACY, by Eugene

Jarosewich, Alan S. Parkes, and Lovell B. Wiggins 53

ELECTRON MICROPROBE REFERENCE SAMPLES FOR MINERAL ANALYSES, by

Eugene Jarosewich, Joseph A. Nelen, and Julie A. Norberg 68

i n
Mineral Sciences Investigations

1976-1977

Petrology, Mineralogy, and Distribution of Lonar (India)

and Lunar Impact Breccias and Glasses

Kurt Fredriksson, Phyllis Brenner, Ananda Dube,

Daniel Milton, Carol Mooring, and Joseph A. Nelen

ABSTRACT

Chemically and mineralogically, the shock metamorphosed breccias and melt rocks at Lonar Crater

(India) are the closest terrestrial analogs to the

impact-generated rocks and soils of the moon. Comparative studies reveal a wide range of virtually

identical forms and textures between Lonar and

lunar samples. Thus, the advantage of knowing the

unshocked target rocks at Lonar, especially with regards to alternating layers of different competency,

may yield invaluable insights into lunar impact

processes. Also, chemical differences reported herein

between Lonar basalts and impact glasses suggest

some probable trends in lunar analogs. Conversely,

the isochemical nature of much of the Lonar glass

and basalt demonstrates that lunar glasses may often

be chemically equated to their parent rocks.

Introduction

As the importance of meteorite impacts as a

mechanism producing lunar land forms, rocks, and

Kurt Fredriksson, Phyllis Brenner, Joseph Nelen, Department

of Mineral Sciences, National Museum of Natural History,

Smithsonian Institution, Washington, D.C. 20560. Ananda

Dube, Geological Survey of India, Calcutta 13, India. Daniel

Milton, United States Geological Survey, National Center,

Reston, Virginia 22092. Carol Mooring, Department of Geology, University of Wisconsin, Madison, Wisconsin 53706.

soils is more clearly recognized, the existence of

Lonar Crater, India, is coming to be seen as one of

earth's more fortuitous catastrophes. This impact

crater is located in the Deccan Trap basalts of

India (19°58'N, 76°31'E), and affords unique opportunities for earthbound scientists to study analogs to lunar processes. We report herein a comparative study of the petrography, morphology, and

chemistry of shocked Lonar and lunar materials.

ACKNOWLEDGMENTS.—We are indebted to Walter

Brown, Andrea Eddy, Becky Fredriksson, and Julie

Norberg for technical and/or editing assistance.

Support from the Geological Survey of India, the

Smithsonian Research Foundation and Foreign Currency Program is gratefully acknowledged. One of

us (DM) received partial support under a NASA

contract. We also thank Laurel Wilkening and

Hans Suess for access to their unpublished radiometric data from Lonar.

General Geology

The Lonar crater is an almost circular depression,

1830 m in diameter, approximately 150 m deep.

Lonar Lake, a shallow saline lake, occupies most

of the crater floor. The rim of the crater is raised

approximately 20 m above the surrounding plain.

A smaller circular depression in the traps, 300 m in
SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

diameter and about 700 m north of Lonar Crater,

apparently is a second crater, probably excavated

after throwout from the main crater landed, but

during settling of fallout. Various data on general

morphology, conclusive evidence for the impact

origin, and preliminary studies of petrography,

stratigraphy, and the chemistry of the impact rocks

have been published elsewhere (Fredriksson et al.,

1973). Recent fission track dating of Lonar shockmelted glasses indicates an age less than ~ 50,000

years (Wilkening, pers. comm.). Carbon-14 dating

shows an age of more than 30,000 years for organic

material recovered 50 m down in one of the ~90 m

thick sediment columns in the lake (Suess, pers.

comm.). The crater's age then lies between 30 and

50 thousand years.

The Geological Survey of India has drilled a

series of five boreholes approximately on a line

trending NE-SW in the floor of the crater. Each

drillhole encountered 90 to 100 m of lake sediment,

which was found to contain small amounts of impact glass in the form of fragments and spherules,

and also rounded lithic fragments exhibiting varying degrees of shock metamorphism. This material

was probably eroded from the crater rim. After

penetrating the sediment, each of the drillings returned cores of coarser breccia apparently composed

of blocks up to meters in size which are unshocked

or slightly shocked and contain crude shatter cones.

Beneath the coarse breccia, the first four drillings

encountered a layer that yielded essentially no core

recovery, apparently because it was composed of

unconsolidated to extremely friable microbreccia.

The assumption was confirmed in the fifth hole for

which an improved core catcher was used, resulting

in approximately 100% core recovery. In addition,

one deep (~100 m) and several shallower holes were

drilled in the smaller crater and on its rim. Current

evidence indicates that the structure, although artificially modified by former dams and ditches, for

purposes of irrigation, is of impact origin.

Comparative Petrography, Morphology,

and Chemistry

The Deccan Trap basalts at Lonar exhibit two

main textural varieties: (1) "hard" trap which has

euhedral plagioclase phenocrysts with strong oscillatory zoning, often glomero-porphyritic, in an

aphanitic groundmass; and (2) medium to coarsegrained, slightly to moderately vesicular or amygdaloidal basalt which has weathered to "soft" trap.

Major minerals in both textural types are plagioclase (An 50-70) 33%-48%, clinopyroxene (augite

± pigeonite) 17%—34%, and opaques (ilmenite

and/or magnetite) 2%-12%. Olivine may be present in small amounts. Alteration minerals include

chlorite minerals, iron oxides, serpentine, and epidote. In addition, within both groups more coarsegrained sub-ophitic basalt may contain 20%-30%

interstitial fresh glass or palagonite.

In contrast, lunar basalts range in grain size from

coarse to fine to vitrophyric, and are often vesicular.

In coarse lunar basalts pyroxene may occur as poikilitic grains in plagioclase. Plagioclase constitutes

25%-3O%, clinopyroxene 45%-55%, and opaques

15%-2O% (including ilmenite, armalocolite, chromespinel, ulvospinel, rutile, metallic iron, nickel-iron,

and troilite). Minor olivine may also be present.

Many of the observed differences between Lonar

and lunar impact-produced rocks and glasses discussed below may be explained by the chemical

differences between the target basalts (see Table 1).

Shockwaves generated by a hypervelocity impact

cause a variety of deformations and changes in the

targets. Thus, slight shocking of Lonar basalt

(<250 kb) produces minor cataclasis in plagioclase

and pyroxene, wavy extinction in pyroxene, and

shock-induced twinning in plagioclase. Increasing

pressures within this range produce closely spaced

twins in pyroxene (this twinning seems to be related

to possible strong shear loci). Large plagioclase and

pyroxene crystals also tend to recrystallize or granulate into smaller domains, optically independent. In

some cases planar elements in plagioclase are also

produced, often accompanied by strong cataclasis,

warping of the grain, and reduced birefringence.

In "moderately" shocked basalt (~250-450 kb),

plagioclase is converted to disordered maskelynite

in which the original oscillatory zoning is preserved.

Moderately strong shocking (~450-600 kb) produces

microbreccia clasts in which maskelynite exhibits

incipient flow. With intense shock, (>800 kb), the

basalt may be converted to glass. The mechanisms

involved and necessary pressures for these various

transformations with special reference to Lonar

basalts have been studied in great detail by Kieffer

et al, 1976, and Schaal and Horz, 1977.

Ejecta on the rim of the main Lonar crater consist of two contrasting types of debris. The lower
NUMBER 22

TABLE 1.—Chemical compositions of some lunar and Lonar basalts; Lonar tabulations are electron

microprobe analyses, done by this laboratory, using powders fused to a glass with lithium tetraborate flux

Apollo 17 PET, 1973:659-692.

-Average of 9 basalt samples.

All Fe as FeO; average Fe2O3/(FeO + Fe2O3) = 0.42,

Constituent

SK>2

A12O3

FeO

MgO

CaO

Na2O

K2O

TiO2

75055,6

41.27

9.75

18.24

6.84

12.30

0.44

0.09

10.17

Apollo 17a

70035,1

37.84

8.85

18.46

9.89

10.07

0.35

0.06

12.97

70215,2

37.19

8.67

19.62

8.52

10.43

0.32

0.04

13.14

Average'3

Lonar

basalt

50.13

13.69

14.09c

5.80

10.20

2.52

0.55

2.72

Lonar

LNR

shocked

basalt

50.35

15.08

12.74C

5.99

11.55

1.70

0.25

2.31

unit ("throw-out") is crudely stratified and shows

no evidence of shock. The overlying unit ("fallout")

contains clasts from different bedrock units, Fladlelike bombs, glass spherules, and fragments. The

lithic clasts show varying degree of shock from

barely perceptible through medium to (rarely) intense. As a practical matter the ejecta can be assigned to only two bedrock units representing the

two basalt types described above: (1) hard, fresh

trap exposed in the upper 50 m of the crater wall;

and (2) soft, weathered trap exposed in the lower

50 m which presumably continues downward almost

to the lake level and is probably followed by another dense basalt. Ejecta patches dominantly of

one or the other unit are juxtaposed throughout the

ejecta blanket with, at best, a weak tendency toward inverted stratigraphy. The patches vary widely

in size, but are characteristically on the order of

100 m across near the rim and decrease to several

meters across near the outer edge.

The hard trap typically forms breccia of small

angular clasts; the soft trap is in large masses that

have much less internal disruption. Concentrations

of ejecta relatively abundant in glass and shocked

fragments were found up to ~2 crater radii from

the rim expecially to the E and ESE.

The ejecta blanket does not feather out evenly

at the margin, but breaks into clumps increasingly

scattered in ejecta-free terrain. Some of these are

composites of hard and soft trap or even polymict

breccias which, surprisingly, cohered during a flight

of two or more kilometers. Some clumps remain intact; others are spread out inside secondary craters

they have excavated. By analogy, secondary cratering on the moon depends neither on ejection of

large individual blocks nor absence of atmosphere

(Milton and Dube, 1977).

In Figures 1-6 the similarities between Lonar

and lunar shocked basalts and breccias are illustrated. Lithic clasts in the Lonar microbreccias

may exhibit severe cataclasis without reduction of

birefringence in the plagioclase, or may show little

or no cataclasis and still contain plagioclase completely converted to maskelynite. Deformation of

plagioclase in lunar breccias is directly analogous

to that found in Lonar samples including cataclasis,

increased density of twin lamellae, granulation or

development of a mozaic texture, development of
SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

FIGURE 1.—a, Lonar trench sample LRT 18VII-1, a medium-grained basalt with plagioclase

totally converted to maskelynite; pyroxenes exhibit moderate cataclasis; section is ~0.9 mm in

length, b, Apollo 17, #79155,68, a coarse-grained basalt with plagioclase partially converted to

maskelynite (lower right); pyroxene exhibits moderately strong cataclasis; length of section is

—3 mm.

FIGURE 2.—a, Lonar core sample LNR-2-317, ~460 m below crater rim; note contact between

coarse-grained ophitic basalt and area of strong brecciation; section is —0.9 mm in length.

b, Apollo 17, #78155,7; note contact between coarse-grained plagioclase and pyroxene crystals

and strongly brecciated area; section is ~0.9 mm in length.

planar features and conversion to maskelynite.

Lunar pyroxenes exhibit close-spaced twins, granulation, and wavy extinction as do their Lonar

counterparts ( Figures 1, 2).

Lonar microbreccias from both cores and trenches

consist of lithic and crystal fragments embedded in

a generally fine semi-opaque rock flour (Figures 3-5).

The lithic fragments vary in size from several centimeters to approximately 0.2 mm. Small lithic fragments tend to be more abraded than large fragments. Lithic fragments in a single thin section may

all exhibit similar shock characteristics or may exhibit a wide range of shock features (e.g., a slightly

shocked fragment juxtaposed to a moderately

shocked one). Fragments may also be very similar in

texture and grain size ("monomict" breccia) or extremely dissimilar ("polymict" breccia) within one

thin section. Occasionally, abraded breccia frag-
NUMBER 22

FIGURE 3.—a, Lonar core sample LNR-2-319 is a microbreccia with angular to subangular crystal

fragments and rounded lithic fragments; length of section is ~3.2 mm. b, Apollo 17, #73235,63,

also with angular to subangular crystal fragments and rounded lithic fragments; length of

section is —3.6 mm.

FIGURE 4.—a, Lonar core sample LNR-3-300, ~440 m below crater rim, has abraded lithic fragments in fine-grained rock flour; fragment at lower edge has plagioclase partially transformed to

maskelynite; section is 3.4 mm in length, b, Apollo 16, #68822,1; note abraded lithic fragments

in fine-grained rock flour and partially devitrified glass spherule; section is 0.9 mm in length.

merits are observed along with normal lithic fragments indicating a process of brecciation, consolidation, abrasion, and final disposition. Apparently,

one impact can produce a kind of the breccia-withina-breccia texture so common in lunar samples (Figure 5). One notable lithic fragment type consists

almost entirely of plagioclase; similar lunar "anorthosite" breccia clasts may, thus, not always represent individual rock types. Microbreccia rock flour

matrix material often shows evidence of flow, and

may contain turbid shock glass (Figure 6). Crystal

fragments in the matrix are usually angular to subangular and exhibit shock effects ranging from mild

to moderately strong. The unconsolidated variety

of microbreccia appears to contain little or no rock

flour matrix, a major component of consolidated

microbreccia, and instead, consists almost entirely

of small crystal fragments of a fairly uniform size.

Shock effects in these fragments are generally slight,

occasionally moderate. Lithic and breccia fragments
SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

FIGURE 5.—a, Lonar core sample, LNR-2-319A, with abraded lithic fragments in fine-grained

rock flour; note high degree of crystal angularity in matrix contrasting with roundness of the

lithic fragments; length of section is 3.4 mm. b, Apollo 16, #67943,1-J; note abraded lithic

and breccia fragments in fine-grained rock flour; length of section is 1.7 mm.

FIGURE 6.—a, Lonar core sample LNR-2-138, ~280 m below crater rim, is a layered microbreccia;

light areas are plagioclase crystal fragments; section is 3.4 mm in length, b, Apollo 17, #72215,7,

also a layered microbreccia; note subangular breccia fragment; section is 3 mm in length.

are small and uncommon. Crude stratification suggests flow or sedimentation rather than brecciation

in situ.

The material found in core 5 between ^200 and

300 m below the lake level ("no core" zone in previous holes) is indeed best characterized as microbreccia, although it is mostly unconsolidated.

Mineralogically it resembles the microbreccias described in the previous paragraph. Occasionally

more indurated (whether by shock or later diagenetic processes is uncertain) sections of core (up

to tens of centimeters) are found. Thin sections

show these breccias to resemble simple lunar soil

breccias and to contain unshocked to moderately

shocked minerals and rock fragments.

Lonar glass ejecta consist of bombs, spherules, and

fragments. Black glassy bombs, evidently still soft

when deposited, are 10-15 cm in diameter and generally have a dense outer shell and a vesicular core.

Spherules, millimeters in diameter and smaller, and

similar in appearance to microtektites, consist of

droplets of brown to colorless glass, often with flow
NUMBER 22

FIGURE 7.—a, Part of a glassy teardrop from Lonar trench sample LRT 18IVB-3 #2. SEM photo;

analysis in Table 3; note microcrater and mound of glass; sample is ~2 mm long, b, Apollo 17,

#74220,86 (>60 mesh) #1 , a teardrop-shaped spherule; note internal structure; SEM photo;

sample is 0.5 mm long.

FIGURE 8.—a, A cone-shaped fragment from Lonar trench sample LRT 18VA-4 #1 ; SEM phc.o;

note mound of glass, probably extruded upon cooling; sample is 1.3 mm long, b, Apollo 17,

#74220,86 (>100 mesh) #1 , a cone-shaped fragment; SEM photo; analysis in Table 4; saaple

is 0.6 mm long.

banding indicated by contorted schlieren. Feathery

recrystallization in the spherules occurs rarely.

Though most Lonar spherules seem to be compositionally homogeneous, several were found with

compositional zoning. The trends most often observed include progressive alkali depletion (particularly Na2O) accompanied by FeO enrich nent. from

the center to the edge of the spherules. Glass shards

and angular fragments mostly consist of turbid,

brown to colorless glass, often vesicular and containing contorted schlieren. The production of shock

melts requires intense shocking, >800 kb (Schaal

and Horz, 1977), and yet glass shards frequently include crystal fragments or rarely entire lithic fragments that are only slightly shocked.

Lunar glass spherules and fragments have been

studied by a number of authors (see especially

Carter, 1971). Figures 7-10 show some characteristic
SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

FIGURE 9.—a, A spherule from Lonar trench sample LRT 18IIIA-4 #1 ; SEM photo shows small

mound of glass possibly extruded as spherule cooled; analysis in Table 3; spherule is 1 mm in

long dimension, b, Thin section of spherule shown in a; note apparent inhomogeneity of internal

structure; the glass, however, has almost constant (basaltic) composition; the skeletal crystallites

decorating flow lines are titanomagnetite; length of section is 1 mm. c, Apollo 17, #74220,86

(]>100 mesh); SEM photo illustrates similarities in surfaces features of lunar and Lonar spherules

(also of many meteoritic chondrules); sample is 0.4 mm long, d, A thin section of sample shown

in c reveals a partially devitrified texture.

types illustrating the similarities between Lonar and

lunar glass particles. A few chemical analyses are

given in Tables 2-4.

A large number of electron probe analyses were

made to determine trends in composition among

Lonar basalts, "bombs," and the other glass particles. The glasses were subdivided into two somewhat arbitrary groups based on composition and/or

morphology: (1) "normal" glasses (Table 2), the

compositions of which were comparatively uniform

and resemble the basalts; and (2) "selected" glasses

(Table 3) mostly with compositions deviating from

the "normal" glasses. Observed trends were various

degrees of alkali, water, and sometimes silica depletion in the spherules and some "unusual" glasses.

The majority of analysed glasses, however, closely

approximate a homogeneous basalt melt although

they appear somewhat depleted in FeO + MgO and

enriched in A12O3 relative to the parent basalt

(Figure 11, Tables 1, 2). In addition, ferrous iron

is more prevalent in the glasses, indicating a

reduction upon melting of the parent basalt
NUMBER 22

FIGURE 10.—a, Almost perfectly round spherule from Lonar trench sample LRT 18VA-4 #2 ;

SEM photo; note microcrater; spherule is 0.8 mm in diameter, b, Thin section of Lonar trench

sample LRT 18IIA-3 #3 , a spherule similar to that shown in a; analysis in Table 3. c, Apollo

17, #74220,86 (>60 mesh), a spherule; SEM photo; note microcrater; sample is ~0.43 mm in

diameter, d, Thin section of spherule shown in c, showing almost complete devitrification; length

of section is 0.25 mm.

(Fe2O3/(FeO + Fe2O3) is -0.42 in the basalts, -0.37

in the glasses). According to Morgan (1978) the

heavy volatile elements Se and Cd are also significantly depleted in the glasses.

Lunar trends, though inherently more difficult to

discern (e.g., initially low alkalies) seem also to indicate a depletion in alkalies in glasses relative to the

parent basalts (Fredriksson et al., 1971). As at Lonar

some heavy volatile elements, such as Pb (Silver,

1975), may also have been redistributed in the lunar

rocks and soils by impact volatilization. If lunar

fractionation trends are indeed analogous to Lonar

trends (even ignoring the "unusual" Lonar glasses

which were likely produced by complete or partial

melting of individual phenocrysts) then lunar glass

fragment chemistry may or may not represent unaltered lunar rock types.

Interpretation of impact cratering and ejecta stratigraphy has been attempted throughout the Apollo

missions. The results of the present study are certainly relevant to such questions as the extent,

homogeneity, and composition of lunar ejecta blan-
10 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

TABLE 2.—Chemical compositions of Lonar "normal" glasses; electron microprobe analyses, this

laboratory

Constituent

SiO2

AI2O3

FeOa

MgO

CaO

Na20

K20

TiO2

LRT

19VB-1

52.02

13.84

13.58

5.43

10.27

2.30

0.63

2.69

LRT

19VB-1

51.65

14.89

12.76

5.12

9.94

2.56

0.53

2.09

LRT

19VB-1

52.61

14.36

12.91

4.95

10.40

1.99

0.47

2.27

D

215-4

50.48

13.99

12.96

5.46

10.13

2.59

0.53

2.23

SL-3

1.5-4

51.59

14.53

13.45

4.85

9.97

2.32

0.46

1.90

All Fe as FeO; average Fe2O3/(FeO + Fe2O3 ) = 0.37.

TABLE 3.—Chemical composition of Lonar "selected" glasses (note that LRT 18IVB-3 is a

"normal" glass); electron microprobe analyses, this laboratory

Constituent

SiO2

A12O3

FeOd

MgO

CaO

Na2O

K2 0

TiO2

LRT

19VIB-3

37.69

22.22

28.41

4.82

6.96

0.02

0.02

0.10

LRT

18HA-3a

49.1

12.8

16.5

7.24

9.0

1.76

0.28

2.34

LRT

18111A-4

 b

47.79

12.69

15.88

7.67

9.13

1.49

0.23

2.29

LRT

19VB-1

51.81

5.27

18.30

11.64

12.13

0.62

0.29

1.95

LRT

181VB-3C

51.78

13.43

13.55

5.08

9.41

2.31

0.65

2.38

aSee Figure 10b.

b See Figure 9a,b.

See Figure 7JI.

'All Fe as FeO.

kets. Thus the mechanisms involved in reworking

the lunar regolith (e.g., Gault et al., 1974) may

deserve reconsideration. Secondary impacts played

an important role in mixing and reworking preexisting Lonar soils with ejecta of both basalt fragments and loosely consolidated microbreccias. This

should be considered in the interpretation of the

evolution of the lunar regolith. Secondary cratering may also explain the discrepancy between the

long exposure ("suntan") ages of lunar soil relative

to excavated rock fragments (Gold and Williams,

1974). Detailed descriptions and maps of the Lonar

ejecta distribution are being prepared by the Geological Survey of India in cooperation with some of

us, and will be published elsewhere.

Some findings near the bottom of the fifth and

last drillcore may justify also a reevaluation of

current concepts of the impact effects in rock com-
NUMBER 22 11

TABLE 4.—Chemical compositions of selected lunar soil and glasses (Apollo 17); electron microprobe analyses, this laboratory; bulk soil analyses derived from 20 mg splits fused to a glass with

lithium tetraborate flux (A, B, C, and D designate individual glass analyses that appear to be

representative of distinctive groupings; it appears that the B glasses generally correspond to the

local bulk soils, but the other groupings are not readily identifiable)

Constituent

SiO2

A12O3

FeO

MgO

CaO

Na20

K2O

TiO2

Constituent

SiO2

AI2O3

FeO

MgO

CaO

Na20

K20

TiO2

Constituent

SiO2

AI9O3

FeO

MgO

CaO

Na20

K20

TiO2

Bulk Soil

41.4

12.8

16.3

9.9

10.6

0.28

0.15

7.2

Bulk Soil

41.2

13.0

15.7

9.9

10.7

0.39

0.10

6.4

Bulk Soil

42.0

15.1

14.3

10.0

11.1

0.44

0.20

4.7

700019,72

A

38.1

6 . 1

24.4

14.2

7.2

0.30

0.22

8.7

A

39.4

6.2

22.7

14.6

7.6

0.32

0.09

9.0

A

38.6

5 . 8

22.4

14.7

7.4

0.42

0.10

9 . 1

B

40.1

12.7

16.8

10.1

10.8

0.34

0.11

7.9

79035,29

B

41.9

13.8

15.8

10.0

11.3

0.33

0.11

7.4

79135,71

B

42.0

13.6

14.3

10.5

10.8

0.40

0.06

6.0

C

41.4

22.0

6.4

14.7

13.1

0.11

0.03

1.20

C

45.2

21.5

8. 1

11.7

13.3

0.04

0.01

1.16

74220,86

A

39.9

6.0

22.3

14.8

7 . 1

0.33

0.10

8.8

D

44.0

36.0

0 . 1

0 . 1

20.1

0.25

0.02

0.03

D

43.6

35.5

0 . 1

0.3

19.6

0.24

0.08

0.02

plexes with layers of different competency (chemically similar or not). At ~450 m below the rim solid

basalt was encountered as in previous drillings. At

about 470, 490, and 520 m, however, rock flour

layers apparently up to ~1 m thick were encountered between several meters of solid basalt with

essentially no shock features. The rock flours in

these horizons differ in grain size but are all relatively well sorted. Whether these loose layers represent a peculiar kind of shock veins or injected material or explosively disrupted porous or weathered

basalt layers of low competency is unclear. Ongoing

studies should yield a better understanding of this

and also give more realistic comparisons (scaling

factors) between real, large impacts and artificial experiments on small targets (e.g., Gault et al., 1974).
12 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

t.

25

2 4

- 2 3

22

21

2 0

O

18

G)

(VI

• Spherules

A Glass bombs

o Normal glasses

a Selected glasses

X Basalts

® Shocked basalt

x * x

D

o X

X *

a

Ao "o A X

• A

 A a A X

o

o

a °<f o o

o o

1.0

% Na2O

2.0 3.0

FIGURE 11.—Plot of Na2O versus FeO + MgO, both in weight percent, for Lonar basalts and

glasses; note that two "selected" glasses with high FeO + MgO plot outside the diagram.
NUMBER 22 13

Literature Cited

Apollo 17 Preliminary Examination Team (PET)

1973. Apollo 17 Lunar Samples: Chemical and Petrographic Description. Science, 182:659-672.

Carter, J. L.

1971. Chemistry and Surface Morphology of Fragments

from Apollo 12 Soil. Proceedings of the Second

Lunar Science Conference, 2:873-892.

Fredriksson, K. J., Nelen, A. Noonan, C. A. Anderson, and

J. R. Hinthorne

1971. Glasses and Sialic Components in Mare Procellarum

Soil. Proceedings of the Second Lunar Science Conference, 1:727-735.

Fredriksson, K., A. Dube, D. J. Milton, and M. S. Balasundaram

1973. Lonar Lake, India: An Impact Crater in Basalt.

Science, 180:862-864.

Gault, D. E., F. Horz, D. E. Brownlee, and J. B. Hartung

1974. Mixing of the Lunar Regolith. Proceedings of the

Fifth Lunar Science Conference, 3:2365-2386.

Gold, T., and G. J. Williams

1974. On the Exposure History of the Lunar Regolith.

Proceedings of the Fifth Lunar Science Conference,

3:2387-2395.

Kieffer, S. W., R. B. Schaal, R. Gibbons, F. Horz, D. J.

Milton, and A. Dube

1976. Shocked Basalt from Lonar Impact Crater, India,

and Experimental Analogues Proceedings of the

Seventh Lunar Science Conference, 2:1391-1412.

Milton, D. J., and A. Dube

1977. Ejecta at Lonar Crater, India. Meteoritics, 12:311.

Morgan, J.

1978. Siderophile and Volatile Trace Elements in "HighMagnesian" Australites and in Glasses From Lonar

Crater, India. In Lunar and Planetary Science, IX,

pages 754-756.

Schaal, R. B., and F. Horz

1977. Shock Metamorphism of Lunar and Terrestrial

Basalts. Proceedings of the Eighth Lunar Science

Conference, 2:1697-1729.

Silver, L. T.

1975. Volatile Lead Components in Lunar Regolith at the

Apollo Mare Sites. In Lunar Science VI, pages 738-

740.
Chemical Variation among Australian Tektites

Brian Mason

ABSTRACT

Microprobe analyses for major components of 60

australites from specific locations covering most of

the strewnfield show a wide range of composition.

Regional variations are seldom clearly defined, and

australites of closely similar composition may be

found at widely separated locations. Three distinctive geographic-compositional groups can, however,

be distinguished: (1) a group with high Fe and Mg

from the Lake Wilson-Mt. Davies region in northwest South Australia; (2) a group with high Ca/Al

ratio centered around Charlotte Waters on the

South Australia—Northern Territory border and extending into southwest Queensland; (3) a group

with high Al and low Si from Pindera in New South

Wales (australites from elsewhere in New South

Wales analyzed by other investigators also show this

feature). Australites show a relatively restricted composition range, whereas micro tektites from deepsea

sediments south and west of Australia show a much

more extensive composition range; thus claims for

a common origin of these contrasted materials are

not supported by compositional comparisons.

Introduction

Beginning in 1963 and continuing for some years,

Mr. R. O. Chalmers of the Australian Museum,

Dr. E. P. Henderson of the Smithsonian Institution,

and I travelled widely throughout Australia (except

Tasmania) for the purpose of collecting tektites

(australites) and establishing the limits of the

strewnfield. The results of these travels are reported

in Chalmers et al. (1976). An important result was

the acquisition of large collections from clearlydefined locations; one scientific drawback of many

Brian Mason, Department of Mineral Sciences, National

Museum of Natural History, Smithsonian Institution, Washington, D.C. 20560.

collections of australites is the vagueness of geographic attribution, such as "Nullarbor Plain,"

"Birdsville Track," etc. Our collections from clearly

defined locations (Figure 1) thus provide the opportunity to investigate compositional variations

within a specific location, and to make comparisons

between locations. By virtue of the fact that individual tektites are glassy objects usually of uniform

composition and that australites exhibit a limited

range of compositions (67%-79% SiO2), australites

are especially suitable for microprobe analysis.

TECHNIQUES USED.—From a single-locality collection, individual specimens were selected for analysis

by separation according to specific gravity. The specific gravity of australites (except for the rare and

enigmatic HNa/K group) ranges from about 2.36

to 2.52, and is inversely related to SiO2 content,

79% to 67% (Chalmers et al., 1976, fig. 17). Collections were processed by flotation in bromoformacetone mixtures of progressively increasing specific

gravity, and individual specimens were selected to

cover the whole range. This provided a group of

specimens fairly evenly spaced over the total range

of SiO2 content for that locality. A total of 60 specimens representing 11 localities were selected for

analysis.

A polished thin section was prepared from each

selected specimen. Another portion of the same

specimen was crushed and the refractive index of

the crushed material determined by the immersion method. This determination also provided an

opportunity to evaluate the homogeneity of the individual australite. Thin sections of australites frequently show schlieren of slightly differing refractive index (see, e.g., Chalmers et al., 1976, fig. 16).

Most of the analyzed australites showed only minor

variation (±0.001) in the refractive index of crushed

fragments, and this limited variation was confirmed

14
NUMBER 22 15

-14°

-22°

-30°

-38°

(

\

110°

1

120°

\

• EARAHEEDY

1

130°

MT.DAVIES*

HUGH

• L YINDARLGOOOA

120°

• L. WILSON

ES«

130°

I

1

140°

i

i

i

i

i

i

i

i

i

•CHARIOTTE WATERS SPURRIE

• MACUMBA 1

o. 1 »PINDERA

V#PIN E DAM

h V ) y • FROME DOWNS

^ A 1

I. /S «MANNAHILL

|40o \ ^

/

J

150°

1

1

150°

14°-

f 22° -

\

/ 30°-

/

38°-

FIGURE 1.—Map showing locations of analyzed australite collections.

by the limited variation between individual spots

in the microprobe analysis. A few, specifically some

with high SiO2 content (>75%), showed a greater

variation in refractive index, sometimes as much as

±0.003. Although Glass (1970) reports large compositional variations (SiO2 60%-85%) within a single

australite, it must be noted that he specifically selected small, rare inclusions (two high-silica and

three low-silica in two thin sections) to establish

this extreme range, and also that he states (p. 241),

"The bulk of the glass has an average composition

of about 76% SiO2."

The polished thin sections of the individual australites were analyzed with an ARL-SEMO electron

microprobe using an operating voltage of 15 kV

and a sample current of 0.15 /xA; a broad beam

(approximately 0.05 mm diameter) was used to

counter the local inhomogeneities discussed in the

preceding paragraph. A previously analyzed australite containing 68.35% SiO2 (Chalmers et al.,
16 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

1976, tbl. 8) was used throughout as a reference

sample. Measured intensities were adjusted by computer using Bence-Albee factors. The following

components were determined: SiO2, A12O3, FeO (all

Fe reported as FeO) MgO, CaO, K2O, Na2O, TiO2,

MnO; MnO is not reported in the analyses, since

it was uniformly at or near the lower limit of

measurability, approximately 0.1%.

Results

The analytical results are set out in Table 1 and

are plotted in Figures 2, 3. The results for specific

locations are discussed below.

EARAHEEDY.—The collection from this locality

comprised 97 specimens. The specific gravity range

was from 2.432 to 2.459, most specimens (87) falling

in the range 2.455-2.459. The four specimens analyzed (Table 1, columns 1-4) cover the full specific

gravity range, which is relatively small; the analyses

show a correspondingly small composition range.

LAKE YINDARLGOODA.—The collection from this

locality near Kalgoorlie comprised 61 specimens.

The specific gravity range was from 2.432 to 2.467,

with practically all the specimens (57) having specific gravities between 2.450 and 2.460. The three

specimens analyzed (Table 1, columns 5-7) cover

almost the full specific gravity range.

A considerable number of analyses of australites

from the Kalgoorlie region have been published,

most of them by Taylor (1962) and Taylor and

Sachs (1964). These analyses confirm the restricted

range of australite composition in this region. Of

Taylor's 13 analyses, 11 have SiO2 contents ranging

from 70.34% to 72.13%; the remaining two have

75.17% and 77.39% respectively.

HUGHES.—This collection, from the Nullarbor

Plain close to the South Australia-Western Australia border, comprised 248 specimens, ranging in

specific gravity from 2.398 to 2.473 (two specimens,

described in columns 9 and 11 of Table 1, had interior bubbles and their specific gravities were less

than 2.398). Of the total collection of 248 specimens,

203 had specific gravities between 2.440 and 2.460.

The three collections from Hughes, Lake Yindarlgooda, and Earaheedy all show very similar

specific-gravity distribution patterns, with a single

peak at 2.45-2.46 on the frequency curve. The

largest collection, that from Hughes, shows the

greatest range in specific gravity, as might be expected. Chapman et al. (1964) have shown that this

specific-gravity distribution pattern is uniform for

all collections they examined from the Kalgoorlie

and Nullarbor Plain locations. The Earaheedy collection shows that this uniformity extends far to the

north. Within this vast area australites with comparable SiO2 content generally show a close correspondence in other components; compare for

example in Table 1, analyses 1 and 5, 3 and 9,

7 and 12.

CHARLOTTE WATERS.—A small collection of 33

specimens from Charlotte Waters showed a wide

range in specific gravity, 2.390-2.483, with a rather

ill-defined frequency peak at 2.440. Chapman et al.

(1964), who examined a much larger collection

(420 specimens), found a specific-gravity range of

2.395-2.495, with a peak at 2.445. The analyzed

specimens (Table 1, columns 14-20) show SiO2

ranging from 69.0% to 77.6%; a significant feature

is a relatively high CaO content compared to australites of similar SiO2 content from the Nullarbor

Plain and Western Australia. Taylor (1962) and

Taylor and Sachs (1964) published six analyses of

australites from Charlotte Waters; SiO2 ranged

from 71.26% to 75.10%, CaO from 3.11% to 5.49%,

figures similar to those obtained in this investigation.

DURRIE.—This collection is of considerable interest, since it is closest to the northern and eastern

margin of the strewnfield. The 99 specimens in the

collection ranged in specific gravity from 2.384 to

2.489, with a mean of 2.440. Six specimens covering

the full range of specific gravity were analyzed

(Table 1, columns 21-26), and show a range of SiO2

from 69.2% to 78.9%. The compositions are similar

to those of Charlotte Waters, but extend to a higher

SiO12 content; it is significant that the low-SiO2

australites from Durrie also show the high CaO

contents of Charlotte Waters australites (cf. analyses

14 and 21).

MACUMBA.—This small collection (19 specimens)

is of particular interest because it has a wide range

of specific gravity (2.386-2.461), and the specificgravity distribution plot shows two peaks, one at

2.395 and one at 2.440 (Chalmers et al., 1976, tbl. 7).

This two-peaked specific-gravity distribution plot is

characteristic of australite collections from the Lake

Torrens-Lake Eyre region of South Australia and is

not found elsewhere. The six specimens analyzed

(Table 1, columns 27-32) cover an SiO2 range of
NUMBER 22 17

TABLE 1.—Analysis of 60 selected australites for major constituents and for specific gravity and

refractive index (locality of analyzed specimens, by column: 1-4, Earaheedy, USNM 5796; 5-7,

Lake Yindarlgooda, USNM 5733; 8-13, Hughes, USNM 2548; 14-20, Charlotte Waters, USNM

2537; 21-26, Durrie, USNM 5799; 27-32, Macumba, USNM 2535; 33-38, Pine Dam, USNM 5802:

39-45, Mannahill, USNM 4831; 46-51, Lake Wilson, USNM 2534; 52-56, Mount Davies, USNM

2536; 57-60, Pindera, USNM 2242)

Constituent

SiO2

AI2O3

FeOa

MgO

CaO

K20

Na2O

TiO2

Total

SG

n

Constituent

SiO2

A12O3

FeO

MgO

CaO

K2O

Na20

TiO2

Total

SG

n

1

69.9

14.5

5.24

2.34

3.24

2.74

1.54

0.80

100. 3

2.459

1.517

11

73.3

12.0

4.64

2.04

3.52

2.74

1.51

0.71

100.5

1.508

2

70.2

14.2

5.01

2.16

2.51

2.77

1.74

0.84

99.4

2.452

1.514

12

74.3

12.0

4.42

1.81

2.23

2.39

1.10

0.73

99.0

2.410

T.504

3

71.8

12.8

4.54

2.15

3.70

2.29

1.14

0.72

99.1

2.445

1.513

13

75.2

11.0

4.27

1,80

2.79

2.71

1.35

0.65

99.8

2.398

1.500

4

73.0

12.9

4.60

2.02

3.14

2.63

1.37

0.78

100.4

2.432

1.511

14

69.0

12.9

4.78

2.29

5.93

2.34

1.12

0.74

99.1

2.483

1.522

5

69.9

14.1

5.06

2.31

3.36

2.49

1.32

0.80

99.3

2.464

1.517

15

70.8

13.3

4.74

2.22

3.80

2.43

1.26

0.77

99.3

2.455

1.514

6

70.6

14.0

4.99

2.31

3.15

2.48

1.35

0.79

99.7

2.454

1.514

16

73.3

10.9

4.11

1.86

4.40

2.40

1.20

0.64

98.8

2.442

1.512

7

74.3

11.4

4.02

1.69

2.89

2.44

1.27

0.67

98.7

2.432

1.509

17

73.6

10.6

4.16

1.93

5.03

2.37

1.23

0.57

99.5

2.439

1.512

8

70.2

13.4

4.93

2.39

4.63

2.62

1.42

0.78

100.4

2.467

1.518

18

74.3

10.1

3.98

1.77

5.00

2.35

1.19

0.59

99.3

2.429

1.508

9

71.7

12.6

4.64

2.14

3.63

2.62

1.43

0.68

99.4

- -

1.515

19

75.6

9.95

3.91

1.70

4.19

2.39

1.16

0.54

99.4

2.417

1.506

10

72.4

12.7

4.55

1.98

3.20

2.71

1.43

0.70

99.7

2.445

1.513

20

77.6

10.6

3.65

1.58

2.17

2.23

1.08

0.60

99.5

2.390

1.499
18 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

TABLE 1.—Continued.

Constituent

SiO2

A12O3

FeO

MgO

CaO

K20

Na2O

TiO2

Total

SG

n

Constituent

SiO2

A12O3

FeO

MgO

CaO

K20

Na20

TiO2

Total

SG

n

21

69.2

12.9

5.26

2.42

5.79

2.36

1.08

0.74

99.8

2.489

1.522

31

76.0

10.1

3.76

1.64

3.31

2.34

1.20

0.59

98.9

2.406

1.504

22

70.3

12.5

4.72

2.28

5.81

2.41

1.28

0.69

100.0

2.473

1.519

32

77.3

9.48

3.55

1.46

3.10

2.33

1.20

0.53

99.0

2.398

1.503

23

71.7

13.1

4.90

2.10

4.05

2.40

1.20

0.72

100.2

2.452

1.514

33

68.9

13.8

5.10

2.35

5.19

2.60

1.43

0.74

100.1

2.476

1.520

24

73.1

12.8

4.73

2.04

3.12

2.45

1.31

0.74

100.3

2.429

1.510

34

70.1

13.4

4.91

2.26

4.18

2.54

1.36

0.76

99.5

2.466

1.518

25

76.1

10.9

4.44

1.65

2.40

2.55

1.15

0.68

99.9

2.404

1.504

35

72.0

12.9

4.74

2.21

4.05

2.45

1.28

0.71

100.3

2.454

1.514

26

78.9

10.0

4.08

1.49

1.89

2.36

1.00

0.59

100.3

2.384

1.499

36

74.2

12.0

4.52

1.94

3.06

2.25

1.09

0.57

99.6

2.416

1.507

27

70.9

10.8

4.42

2.03

5.91

2.44

1.27

0.58

98.4

2.461

1.515

37

76.3

10.9

4.42

1.70

3.00

2.55

1.25

0.66

100.8

2.400

1.502

28

71.4

12.9

4.65

2.12

3.51

2.44

1.37

0.77

99.2

2.454

1.514

38

78.3

10.3

3.83

1.31

1.57

2.44

1.14

0.61

99.5

2.371

1.496

29

72.3

10.8

4.24

1.82

5.10

2.51

1.33

0.64

98.7

2.442

1.513

39

69.5

14.5

5.04

2.41

3.97

2.48

1.22

0.77

99.9

2.468

1.518

30

74.9

10.1

3.90

1.80

3.97

2.41

1.21

0.58

98.9

2.422

1.507

40

70.6

14.1

4.92

2.28

3.59

2.35

1.13

0.72

99.7

2.460

1.515
NUMBER 22 19

TABLE 1.—Continued.

Constituent

SiO2

AI2O3

FeO

MgO

CaO

K20

Na20

TiO2

Total

SG

n

Constituent

SiO2

A12O3

FeO

MgO

CaO

K2O

Na2O

TiO2

Total

SG

n

41

72.3

12.5

4.55

2.02

3.71

2.49

1.26

0.71

99.5

2.446

1.513

51

74.9

10.9

4.75

2.41

2.68

2.37

1.11

0.64

99.8

2.415

1.506

42

73.5

12.5

4.45

1.85

3.49

2.41

1.25

0.67

100.1

2.434

1.510

52

69.0

13.2

5.50

3.30

4.14

2.33

1.17

0.75

99.4

2.493

1.523

43

75.2

12.0

4.28

1.70

2.11

2.52

1.13

0.69

99.6

2.399

1.501

53

69.9

13.2

5.76

3.13

3.22

2.52

1.26

0.72

99.7

2.477

1.520

44

76.0

11.7

4.08

1.64

2.07

2.32

1.09

0.67

99.6

2.391

1.500

54

70.6

13.1

4.99

2.47

3.59

2.66

1.41

0.74

99.6

2.460

1.515

45

76.8

11.5

4.32

1.54

1.60

2.55

1.10

0.65

100.1

2.377

1.498

55

71.4

12.5

5.33

2.96

2.92

2.37

1.21

0.66

99.4

2.445

1.512

46

68.7

13.0

6.10

3.53

3.91

2.28

1.29

0.79

99.6

2.489

1.522

56

73.0

12.2

5.25

2.99

2.87

2.16

1.10

0.66

100.2

2.425

1.506

47

70.7

12.8

5.85

3.33

3.28

2.16

0.97

0.72

99.8

2.466

1.519

57

67.3

15.9

5.57

2.68

3.22

2.78

1.38

0.85

99.7

--

1.519

48

71.1

12.0

5.39

2.92

3.59

2.37

1.18

0.65

99.2

2.446

1.513

58

68.2

15.7

5.37

2.57

3.08

2.56

1.30

0.83

99.6

--

1.518

49

72.2

11.8

5.33

2.70

3.40

2.48

1.16

0.64

99.7

2.437

1.513

59

68.9

15.3

5.27

2.33

2.99

2.61

1.13

0.83

99.4

--

1.518

50

74.1

11.6

5.26

2.98

2.51

2.08

0.91

0.65

100.1

2.420

1.507

60

69.3

15.4

5.25

2.45

2.90

2.55

1.38

0.82

100.1

--

1.518

A l l Fe a s FeO.
20 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

70.9%-77.3%, similar to but somewhat less extensive than that for Durrie. Other components are

comparable for those recorded for australites of

similar SiO2 content from Charlotte Waters and

Durrie; in particular, the low-SiO2 (<75%) australites from Macumba also show relatively high

CaO (except for analysis 28).

PINE DAM.—Australites from Pine Dam, near

Lake Torrens, show a specific-gravity range of

2.368-2.476, with peaks at 2.395 and 2.462

(Chalmers et al., 1976, tbl. 7). Six specimens, covering practically the full specific-gravity range, were

analyzed (Table 1, columns 33-38). These analyses resemble those of similar SiO2 content from

Macumba, except that they are generally lower in

CaO and higher in A12O3.

MANNAHILL.—A collection of 89 australites from

Mannahill was available for study. The specificgravity range was 2.377 to 2.468, with a single peak

at 2.419 in the distribution curve. This single peak

at 2.40 to 2.42 is characteristic of collections from

southeast South Australia and Victoria (Chalmers

et al., 1976, tbl. 7). Seven specimens, covering the

whole specific-gravity range, were analyzed (Table 1,

columns 39-45). The analyses are comparable to

those of Pine Dam australites with similar SiO2

contents, although the Mannahill australites appear

to have somewhat lower CaO contents.

FROME DOWNS.—A small collection (14 specimens)

from Frome Downs station was acquired after the

main part of this manuscript was completed. It is

of considerable significance because of its approximately equidistant position between three locations (see Figure 1) with distinctly different australite populations, as indicated by specific gravity

ranges and peaks (in parentheses): Mannahill

(2.377-2.468, peak 2.419); Pine Dam (2.368-2.476,

peaks 2.395, 2.462); Pindera (2.270-2.470, peak

2.450). The 14 Frome Downs australites have a

specific gravity range of 2.380-2.429; no peak is

evident, probably because of the small number of

specimens, but the mean is 2.402. The Frome

Downs collection clearly differs in specific gravity

range and therefore in chemical composition from

the Pine Dam and other collections in the Lake

Torrens region to the west, and to the nearest location in the east, the Pindera area in New South

Wales. A search of the region between Frome

Downs and Pindera in August 1978 found no

australite occurrence, although the terrain appeared

favorable in many places. I conclude therefore that

a significant chemical hiatus exists between these

two locations. The Frome Downs occurrence seems

to be the farthest north location for the low specific

gravity Victoria-type australites unmixed with the

higher specific gravity population, as around Lake

Torrens and Lake Eyre.

LAKE WILSON.—This location, in the far northwest of South Australia, is known to carry australites

of unusual composition. This was first recognized

by Taylor and Sachs (1964:250), who analyzed one

specimen and commented: "Sample No. 26 is unusual in possessing, in addition to the high value

for nickel, the highest amounts of Mg, Fe, Co and

Cr. The concentrations of the other elements are

normal for the silica content (69.8 per cent)."

Chapman et al. (1964) published a specific-gravity

distribution diagram for Lake Wilson australites

and noted that it was different from those of all

other australite locations, with a more extensive

specific-gravity range (2.395-2.505) and the highest

peak (2.465).

Six specimens from Lake Wilson were analyzed

(Table 1, columns 46-51), ranging from 2.415 to

2.489 in specific gravity and 74.9% to 68.7% in

SiO2 content. The data plotted in Figure 2 show

that the Lake Wilson australites are uniformly

higher in FeO and MgO than other australites of

similar SiO2 content. It was on this basis that

Chapman and Scheiber (1969) established their

HMg group of tektites; they recognized tektites

belonging to this group not only in Australia but

in Indonesia and at one locality in the Philippines.

Chapman and Scheiber (1969) and Chapman (1971)

published analyses of HMg australites from the

following locations: Lake Margaretha (25°26'S,

125° 14'E), West Serpentine Lakes (28°50'S, 128°35'E),

near Young Range (25°06'S, 125°15'E), and Giles

Creek (25°02'S, 128°18'E). These locations, together

with the Mt. Davies collection mentioned below,

define a triangular area straddling the South

Australia-Western Australia border and extending

over about 4° of both latitude and longitude.

Hughes, with australites of "normal" composition,

is about 140 miles south of West Serpentine Lakes,

and Earaheedy, also with australites of normal composition, is about 150 miles west of Young Range;

at Charlotte Waters, 300 miles to the east of Lake

Wilson, the australites are also of normal composition except for relatively high CaO. The HMg
NUMBER 22 21

tektites thus occupy a defined geographic field, and

although its limits remain to be precisely defined,

they do not appear to overlap into surrounding

areas of normal compositions.

MT. DAVIES.—Mt. Davies is a geographical area

centered around the Western Australia-South

Australia—Northern Territory conjunction, about

40 miles west of Lake Wilson. Many thousands of

australites have been collected from this area by

aborigines and sold through the Department of

Aboriginal Affairs, Adelaide. I obtained a small

collection of 12 specimens directly from the local

aborigines in 1965. Five of these were analyzed

(Table 1, columns 52-56), and these analyses are

very similar to those of the Lake Wilson australites

of comparable SiO2 content.

PINDERA.—This is an isolated location in northwestern New South Wales, rather far removed from

other areas of tektite concentration. Australites from

this location have a unique appearance, with pitted

surfaces resulting from the presence of small internal bubbles, a feature rare in australites from other

localities. As a result, specific gravities of Pindera

australites show a wide range (2.270-2.470 in a

collection of 155 specimens) according to Chapman

(in Chalmers et al., 1976, tbl. 6). This range is, however, almost entirely a function of bubble content,

since the ten specimens I analyzed all had very

similar compositions, with SiO2 ranging from 67.3%

to 69.3% and A12O3 ranging from 15.9% to 15.3%;

four of these analyses, covering the full range of

composition, are given in Table 1 (columns 57-60).

Chapman and Scheiber (1969) report a similar composition for the Pindera specimen they analyzed.

Chapman and Scheiber note that their Pindera

specimen and two other analyzed australites from

New South Wales have uniquely high A12O3 contents (>14.9%), and this may be related to their

unusually low SiO2 contents (66.8%-68.5%). Figure

2 shows that apart from the low SiO2 and high

A12O3 contents, the only other distinguishing feature in the analyzed Pindera australites is a relatively low CaO content. Nevertheless, it is possible

that the New South Wales portion of the strewnfield

does have a distinctive chemical composition; more

analyses from additional locations are needed to

establish this.

Discussion of Analyses

Most of the available analyses of australites have

been published by Taylor (1962), Taylor and Sachs

(1964), Chapman and Scheiber (1969), and Chapman (1971). Table 2 compares the results obTABLE 2.—Compositional range, in weight percent, of australites; (source

of data by column: 1, this paper, 60 analyses; 2, Taylor (1962) and Taylor

and Sachs (1964), 32 analyses for SiO,2, A1,,,O3, FeO and 43 analyses for other

components; 3, Chapman and Scheiber (1969) and Chapman (1971), 23

analyses)

Constituent

SiO2

A12O3

FeO

 a

MgO

CaO

K20

Na20

TiO2

67.3

9.5

3.55

1.31

1.57

2.08

0.91

0.59

1

- 78.9

- 15.9

- 6.10

- 3.53

- 5.93

- 2.78

- 1.74

- 0.85

2

69.6 -

9.35 -

3.83 -

1.49 -

2.13 -

2.07 -

1.05 -

0.55 -

78.7

14.0

5.38

2.49

5.09

2.57

1.52

0.90

3

66.9 -

9.9 -

3.57 -

1.31 -

1.72 -

2.00 -

1.00 -

0.48 -

79.7

16.1

6.06

4.28

5.62

2.62

1.58

0.93

All Fe as FeO.
22

SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

tained by these investigators with those reported

in Table 1. Table 2 excludes the HNa/K australites of Chapman and Scheiber; these are very rare 3

(Chapman and Scheiber found nine during the js

specific-gravity screening of approximately 47,000

tektites), and their identification as tektites has been

questioned by Chalmers et al. (1967:37-38).

The comparison shows that the ranges of composition for the major components are very similar q

in each of the three groups. It can therefore be ^

stated with some confidence that the compositional

range of australites is now well established, and

specimens falling outside this range are unlikely to

be found.

The extent of the variation in major components

is clearly demonstrated in Figure 2, in which the

percentages of the individual components in each <S

analysis are plotted against the SiO2 percentage of

that analysis. The first impression is the limited

scatter within each component. This is especially

characteristic for FeO, MgO, K2O, and Na2O (note

that the vertical scale for K2O and Na2O is twice

0

that for the other components, which tends to em- £

phasize the scatter for the alkalies). Another obvious **

feature is the general decrease in A12O3, FeO, MgO,

and CaO with increasing SiO2 content; however,

this trend is not marked for Na2O and may be

absent in K2O.

Taylor and Sachs (1964) computed correlation |

coefficients for their 32 analyses for which SiO2 determinations were available. The correlation coefficients with SiO2 were Al, -0.907; Mg, -0.955; Ti,

-0.842; Fe, -0.817; Na, -0.805; K, -0.764; Ca,

-0.221. For all these elements except Ca, the negative correlation is significant at less than 0.01 per

cent.

Chapman has used his analyses of Australasian

tektites to establish a chemical classification of these

objects. Within the Australian strewnfield he has 3

distinguished the following classes: normal, HCa, ^

HMg, HA1, HNa/K (not considered here). His definitions of these classes are not unequivocal; in fact

they vary somewhat from time to time, as the following quotations show.

Normal: The predominant type in Western Australia and

the Philippines, with a restricted range of CaO and MgO

respectively about 3.1% and 2.2% (Compston and Chapman, 1969:1024).

SiO2 70% to 73%, alkalies higher than in, for example, the

•*»**»%•**

©o

•

•

•

o

•

m

o

•

o

®

Earahxdy

L. Yindarlgooda

Hughtt

Charlotte Watert

Durri.

Macumba

Pin* Dam

Mannahill

Pind.ra

l.Wilton

Ml. Daviw

B*

FIGURE 2.—Plot of SiO, versus Na2O, K2O, CaO, MgO, FeO,

and A12O3, all in weight percent, for australite analyses in

Table 1.
NUMBER 22 23

HCa group (Chapman and Scheiber, 1969:6761).

GaO > MgO and Ni < 41 ppm (Chapman, 1971:6313).

HCa: CaO varying from about 2.0 to 10.0% and MgO from

1.3 to 2.5% (Compston and Chapman, 1969:1024).

FeO 3.5-4.9%, Ni 14-42, Cr 56-110, Co 7-18 ppm, Cr/Ni

2.0-4.9 (Chapman and Scheiber, 1969:6741).

LSG-HCa streak . . . stretching from Tasmania to Central

Australia .. . low modal SG (< 2.41); Na2O < 1.25%

(Chapman, 1971:6312).

Nearly HCa: CaO near lower boundary and with NasO >

1.25% (Chapman, 1971:6313).

HMg: MgO varying continuously from 1.5 to 8.0% and

comparatively restricted variation in CaO (Compston and

Chapman, 1969:1024).

MgO > 3.4%, Ni > 210 ppm, Cr > 210 ppm (Chapman,

1971:6312).

FeO 3.9-8.6%, Ni 91-390 ppm, Cr 100-460 ppm, Co 14-

63 ppm (Chapman & Scheiber, 1969:6741).

Nearly HMg: MgO > 2.8%, Ni > 200 ppm, Cr > 190

ppm (Chapman, 1971:6312).

HA1: A12O3 > 14.9% (Chapman, 1971:6312).

Some comments may be made on these criteria.

The criterion CaO >MgO given for normal australites applies to all australite analyses except for a

few in the HMg class. The criterion CaO varying

from about 2.0% to 10.0% and MgO from 1.3% to

2.5% for the HCa class applies to practically all

australites; reference to Table 1 and Figure 2 shows

only three australites with less than 2% CaO, and

the only australites with MgO >2.5 belong to the

HMg class. Australites generally contain less than

6% CaO; tektites with CaO greater than 6% seem

to be limited to the Philippines.

Chapman (1971) presented a map (his fig. 2) showing the distribution of his chemical classes of australites. Practically all his normal australites are

confined to Western Australia. The HMg australites

define a streak extending northwest from the Lake

Wilson-Mt. Davies region. The HCa australites define a streak from Victoria through South Australia

to Charlotte Waters and Henbury. The HA1 australites are found only in New South Wales, with the

exception of one from Tasmania.

Figure 2 provides the opportunity to try to fit the

analyses of this investigation into Chapman's classification scheme. The only class that can be unequivocally recognized is the HMg class; the analyses of australites from the Lake Wilson and Mt.

Davies regions are consistently higher in MgO (and

FeO) than other australites of similar SiO2 content.

The utility of an HA1 group is doubtful; few are

known, and their A12O3 content (>14.9%) being

coupled with low SiO2 content puts them on the

same Al2O3-SiO,2 trend as other australites (Figure 2). Figure 2 shows that some australites, specifically most of those from Charlotte Waters, Durrie,

and Macumba, are significantly higher in CaO than

the remainder. Thus an HCa class can possibly be

recognized, but as pointed out above the criteria

given for this class by Compston and Chapman

(1969) apply to practically all analyzed australites

except those of the HMg class.

Robert Fudali has demonstrated to me that a plot

(Figure 3) of AL>O3 versus CaO values from the

analyses in Table 1 shows a well-defined hiatus.

All the values plotting above the hiatus are of

australites from Charlotte Waters, Durrie, and

Macumba. This pattern defines a coherent and restricted geographical region extending from northcentral South Australia to adjoining southwest

Queensland. Not all analyses from these locations,

however, yield values that plot above the hiatus;

two of seven from Charlotte Waters, four of six

from Durrie, and one of six from Macumba plot

below it. The values which plot above the hiatus

probably all represent HCa australites according to

Chapman, but many of those plotting below the

hiatus also belong to this class. The values from five

analyses of HCa australites published by Chapman

and Scheiber (1969) have been plotted on Figure 3;

three (all from the Charlotte Waters area) plot

above the hiatus, one (from Victoria) plots below it,

and one (from near Macumba) plots just within its

lower limit.

One purpose of this research was to see whether

australites from a specific locality showed a distinctive range of chemical composition. Table 1 and

Figure 2 show that this is not generally the case,

although some regional trends can be distinguished.

The Lake Wilson-Mt. Davies group in the far

northwest of South Australia are uniformly somewhat higher in MgO and FeO than other australites

of similar SiO2 contents, but for the other major

components they fall within the range of most australites. The Pindera australites have uniquely high

A12O3 contents. Some but by no means all the australites from localities extending from Mannahill to

Charlotte Waters in South Australia and Durrie

in Queensland have high CaO (>4%); some of

these also have lower A12O3 contents than most
24 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

Earaheedy

L. Yindarlgooda

Hughes

Charlotte Waters

Durrie

Mocumba

Pin* Dam

Mannahill

Pindera

L. Wilson

Mt. Davies

12 13

% ALO,

14 15

FIGURE 3.—Plot of Al O3 versus CaO, both in weight percent, for the analysis

in Table 1 (c = HCa australites by Chapman and Scheiber (1969); diagonal

lines define locality-related hiatus).

other australites. Australites from Western Australia

and adjacent parts of the Nullarbor Plain tend to

be slightly higher in K2O and Na2O than australites

from other localities.

These results may be compared with the observations of Taylor and Sachs (1964:241). They detected

regional differences between average australite compositions from localities near Kalgoorlie, Charlotte

Waters, and in Victoria. They commented:

Compared to the Charlotte Waters group (II), the Kalgoorlie

group (I) have a distinctly lower average for SiO2 and are

higher in those elements which show significant negative

correlations with SiO2 . • . The Victorian group (III), although

containing low values for the alkali elements, are generally

intermediate in average composition. It thus appears that

two distinct groups, at Kalgoorlie and Charlotte Waters,

may be distinguished. Perhaps a mixture of these two types

is found in Victoria.

My results are consistent with these comments. I did

not analyze any Victorian australites, but many of

my analyses of Pine Dam and Mannahill australites

can be matched with published analyses of Victorian

australites.

Australites and Microtektites

In 1967 Glass announced the discovery of microscopic (< 1 mm diameter) glassy objects in deep-sea

sediments from south and west of Australia: "On

the basis of their geographical distribution, appearance, physical properties, and age of deposition, it

is concluded that the glassy objects discussed in this

report are microtektites, and that they constitute a

portion of the Australasian strewn field which

extends from Thailand to Tasmania" (Glass, 1967:

374). Not all tektite researchers have accepted the

identity of microtektites with tektites; a summary

of opposing viewpoints is provided by Chalmers

et al. (1976:16).

Cassidy et al. (1969) published microprobe analyses of 60 microtektites and Glass (1972b) reported

44 analyses of a particular variety which he calls

"bottle green microtektites." Cassidy et al. and

Glass both conclude that their chemical analyses

support the identification of these microtektites

with Australian tektites. A rigorous comparison,

however, of their analyses of microtektites with the
NUMBER 22 25

analyses of australites reveals many inconsistencies

and may negate their conclusion.

The range of composition of microtektites is

much wider than that for australites. For the principal component, SiO2, the range for microtektites

is 48.1% to 77.0%; of the 104 microtektite analyses

from the Australian region, only 46, or less than

half, fall within the SiO2 range of australites (66%-

79%). Cassidy et al. claimed that the "normal"

microtektites (excluding the bottle green ones)

showed concordant compositional trends with the

Australasian tektites and served to extend the

known composition range of tektites. Glass claimed

that the bottle green microtektites overlap and

extend all major-element trends found for the HMg

tektites of Chapman and Scheiber (1969). Even if

this claim were valid, the non-existence of australites with less than 66% SiO2 renders it of little

relevance.

When the data, however, for microtektites within

the australite composition range of 66%-79% SiO2

are studied closely, the correspondence between

° Aultralitn

• Normal microtoktitu

* Bottl* gra*n mkrataktlm

FIGURE 4.—Plot of FeO versus MgO, both in weight percent,

for australites (Table 1) and microtektites (Cassidy et al., 1969;

Glass, 1972b) (trapezoid defines scatter of australites).

australite and microtektite compositions can only

be described as poor. Discordances are particularly

prominent for Na,O (most microtektites have less

than 1%, most australites more than this amount);

for K2O, where only four microtektites fall within

the field for australites and two of these are discordant with australites in other components; and

for MgO, where practically all the bottle green

microtektites have much higher contents than the

HMg australites with which they are claimed to

correspond. The chemical discordance between

microtektites and australites is clearly displayed in

Figure 4, which plots FeO versus MgO percentage

for australites and microtektites. The australites

show a very limited range in FeO and MgO contents and an extremely strong positive correlation

between these two components. Note the contrast

in the microtektites, which show a very wide range

in FeO and MgO contents, and essentially no correlation between these components.

The extreme scatter of microtektite analyses, compared to the relatively restricted composition of

australites, argues against rather than for a common source material. If one is to claim that microtektites and australites are cogenetic, the evidence

must be from sources other than chemical composition.

Literature Cited

Cassidy, W. A., B. Glass, and B. C. Heezen

1969. Physical and Chemical Properties of Australian

Microtektites. Journal of Geophysical Research,

74:1008-1025.

Chalmers, R. O., E. P. Henderson, and B. Mason

1976. Occurrence, Distribution, and Age of Australian

Tektites. Smithsonian Contributions to the Earth

Sciences, 17: 46 pages.

Chapman, D. R.

1971. Australasian Tektite Geographic Pattern, Crater and

Ray of Origin, and Theory of Tektite Events. Journal

of Geophysical Research, 76:6309-6336.

Chapman, D. R., H. K. Larson, and L. C. Scheiber

1964. Population Polygons of Tektite Specific Gravity for

Various Localities in Australasia. Geochimica et

Cosmochimica Ada, 28:821-839.

Chapman, D. R., and L. C. Scheiber

1969. Chemical Investigation of Australasian Tektites.

Journal of Geophysical Research, 74:6737-6773.

Compston, W., and D. R. Chapman

1969. Sr Isotope Patterns within the Southeast Australasian Strewnfield. Geochimica et Cosmochimica Acta,

33:1023-1036.
26 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

Glass, B. P. Australian-New Zealand Sector, pages 335-248. Wash1967. Microtektites in Deep-Sea Sediments. Nature, 214: ington: American Geophysical Union.

372-374. 1972b. Bottle Green Microtektites. Journal of Geophysical

1970. Comparison of the Chemical Variation in a Flanged Research, 77:7057-7064.

Australite with the Chemical Variation among Taylor, S. R.

"Normal" Australasian Microtektites. Earth and 1962. The Chemical Composition of Australites. GeoPlanetary Science Letters, 9:240-246. chimica et Cosmochimica Ada, 26:685-722.

1972a. Australasian Microtektites in Deep-Sea Sediments. In Taylor, S. R., and M. Sachs

D. E. Hayes, editor, Antarctic Oceanology II: The 1964. Geochemical Evidence for the Origin of Australites.

Geochimica et Cosmochimica Ada, 28:235-264.
The Pyroxene-Plagioclase Achondrites

Brian Mason, Eugene Jarosewich, and Joseph A. Nelen

ABSTRACT

The pyroxene-plagioclase achondrites (also known

as eucrites and howardites, as calcium-rich achondrites, and as basaltic achondrites) form the largest

class of achondrite meteorites, and are of special interest because they are the closest meteoritic

analogs of lunar rocks. In this paper we provide

chemical analyses for 20 of them, and have selected

analyses of 31 others from the literature. Brief accounts are provided for them, together with microprobe analyses of their principal minerals, pyroxene

and plagioclase. We have adopted the structural distinction between eucrites (unbrecciated and monomict breccias) and howardites (polymict breccias).

Shergotty and Zagami, although eucrites by this

difinition, are distinct in their chemical and mineralogical composition, and the term shergottite

should be retained for them. A large number of

eucrites (which we call main-group) have almost

identical chemical and mineralogical composition;

they are silica-oversaturated, having excess SiO2 in

both the mode and the norm. Howardites are not

mechanical mixtures of eucrites and diogenites;

their individual mineral and rock clasts belong to

a differentiation sequence that is compositionally

more extensive than the eucrites and diogenites.

Introduction

The pyroxene-plagioclase achondrites are a group

of meteorites consisting essentially of pyroxene and

calcic plagioclase, the pyroxene usually dominant

over plagioclase. They compose a majority of the

achondrites, totalling over 50 of approximately 90

known. Prior (1920) grouped them together with

Angra dos Reis and the nakhlites as calcium-rich

Brian Mason, Eugene Jarosewich, Joseph A. Nelen, Department of Mineral Sciences, National Museum of Natural History, Smithsonian Institution, Washington, D.C. 20560.

achondrites. Urey and Craig (1953) preferred to

call the calcium-rich achondrites the basaltic-type

achondrites (now generally shortened to basaltic

achondrites), to emphasize their general similarity

to terrestrial basalts (although the latter are clearly

different in the amount and composition of the

plagioclase).

Prior recognized three classes of pyroxene-plagioclase achondrites: (1) eucrites or clinohyperstheneanorthite achondrites; (2) shergottites or clinohypersthene-maskelynite achondrites; and (3)

howardites or hypersthene-clinohypersthene-anorthite achondrites. (Clinohypersthene in Prior's usage

is the mineral now known as pigeonite.) In the

current British Museum catalog (Hutchison et al.,

1977) the eucrites are denned as plagioclase-pigeonite achondrites and the howardites as plagioclasehypersthene achondrites (the two shergottites, Shergotty and Zagami are included with the eucrites).

Thus the distinction between eucrites and howardites was originally made on the basis of the nature of the pyroxene, the dominant pyroxene being

pigeonite in eucrites and orthopyroxene (hypersthene) in howardites. Mason (1962) noted that this

distinction could be correlated with the bulk chemistry of these meteorites, most clearly with the CaO

content and the FeO/(FeO + MgO) molecular percentage; he suggested that a dividing line could be

drawn at FeO/(FeO + MgO) = 50, eucrites showing

a higher ratio, howardites a lower one.

Lacroix (1926) felt there were insufficient grounds

for separating eucrites and howardites, but that if

such separation were desired, it would be better

made on structural grounds, howardites being

classed as brecciated eucrites. Wahl (1952) introduced the terms monomict and polymict breccias,

and classed the eucrites as unbrecciated or monomict, howardites as polymict pyroxene-plagioclase

27
28 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

achondrites. This distinction was adopted by Duke

and Silver (1967) and several other researchers.

Bunch (1975) provided a comprehensive account of

the large variety of rock and mineral clasts found

in the polymict pyroxene-plagioclase achondrites,

and clearly demonstrated the desirability of distinguishing these meteorites as howardites.

It is noteworthy that either the structural or the

mineralogical criterion is usually sufficient to classify unambiguously a pyroxene-plagioclase achondrite as a howardite or a eucrite, since meteorites

with dominant orthopyroxene are also polymict

breccias (except Binda), and most monomict breccias have pigeonite as the dominant pyroxene

(polymict breccias with dominant pigeonite are

Macibini, Bialystok and Nobleborough). In using

the terms howardite and eucrite, however, it is

desirable to state in what sense these terms are

used; in this paper we use them in the structural

sense. We also distinguish Shergotty and Zagami

from the eucrites on account of their distinctive

chemical and mineralogical composition.

In discussing the eucrites and howardites, frequent reference will be made to the diogenites (also

known as hypersthene achondrites). The diogenites,

although classed by Prior as calcium-poor achondrites, occupy one end of a spectrum of chemical

and mineralogical compositions extending through

howardites to eucrites. Prior did not specify a limiting value of CaO between the calcium-poor and

calcium-rich achondrites; currently the most calcium-rich diogenite is Garland with 2.60% CaO

(Fredriksson et al., 1976), and the most calcium-poor

howardite is Yamato-7307 (also known as Yamato(l)

with 3.83% CaO (Wanke et al., 1977). The amounts

of the other major components are equally close.

Nevertheless, these two meteorites are easily differentiated both macroscopically and microscopically, Garland being an aggregate of pale-green

orthopyroxene clasts with only trace amounts of

other minerals, whereas Yamato-7307, while containing a large amount of pyroxene similar in composition to that in Garland, also has a considerable

eucritic component (pigeonite + plagioclase). One

characteristic of howardites is that they frequently

contain clasts of diogenite composition. A close

relationship, therefore, exists between these two

classes, which will be further discussed later in this

paper.

Interest in the pyroxene-plagioclase achondrites

has increased greatly in recent years, largely because

they are the closest analogs to lunar rocks. Indeed,

Duke and Silver (1967) presented arguments suggesting that the eucrites, howardites, and mesosiderites were actually lunar rocks. The results of

the Apollo missions have negated this suggestion,

and therefore established that these meteorites

prove the previous existence of at least one other

body in the Solar System with analogous chemical

and mineralogical composition (and presumably

similar evolutionary history) to the moon. The nature and composition of this body ("eucrite parent

body") has been the subject of intensive research

(see, for example, Dreibus et al., 1977; Consolmagno

and Drake, 1977; Allegre et al., 1977; Stolper, 1977;

Anders, 1977).

In view of this great interest in the pyroxeneplagioclase achondrites, we have collected the published major-element analyses of these meteorites

and supplemented them with analyses of as many

previously unanalysed meteorites as possible. Where

published analyses are either incomplete or show

inconsistencies with the mineralogical composition

we have attempted to rectify this. Some of the new

analyses (by E. J.) are by classical wet-chemical

techniques; where only small samples were available the material was fused with lithium tetraborate

and the resulting glasses analysed with the electron

microprobe (by J. N.).

ACKNOWLEDGMENTS.—We are indebted to the

curators of the meteorite collections in the following institutions for providing material of meteorites

not represented in the Smithsonian Institution collection: Arizona State University; Australian Museum, Sydney; British Museum (Natural History);

Field Museum, Chicago; Geological Survey of

India; Museum d'Histoire Naturelle, Paris; Naturhistorisches Museum, Vienna.

Results

The analyses are presented in Table 1. In this

tabulation K2O and P2O5 are omitted (recent analyses show that K2O is consistently below 0.05% and

P2O5 is usually less than 0.1%); free nickel-iron is

also omitted, since it is a rare and erratically distributed accessory and is seldom determined; FeS,

if determined, is given in the table key.

The analyses are arranged in order of increasing FeO/(FeO + MgO) mole percentage. This is a
NUMBER 22 29

useful factor in distinguishing eucrites and howardites in the chemical sense (howardites have

FeO/(FeO + MgO) 30-45, eucrites 40-69, there

being a slight overlap). The ratio also correlates

positively with CaO and A12O3, and negatively with

MgO. Other parameters derived from the analytical

data are the composition and amount of normative

plagioclase, the composition and amount of normative pyroxene, and the amount of normative olivine

or silica. From a consideration of texture the meteorites are classified as unbrecciated, monomict breccias, and polymict breccias; if texture is used as the

discriminant factor between eucrites and howardites, then unbrecciated meteorites and monomict

breccias are eucrites, while polymict breccias are

howardites.

Notes on the individual meteorites (bearing the

analysis numbers used in Table 1) follow.

1. YAMATO-7307.—This meteorite, also known as

Yamato(l), was collected by the Japanese Antarctic

Expedition in 1973, and is of special interest since

it has the lowest FeO/(FeO + MgO) mole percentage

of any of these meteorites. As such, it is compositionally very similar to the diogenites. The diogenites, however, are essentially monomict breccias

(a small eucritic component has been recognized

in a few), with uniform pyroxene composition

(Fs 25-27). Sections of Yamato-7307 which we have

examined show that it is a polymict breccia, with

a wide range in pyroxene composition (Fs 19-49);

two grains of olivine were seen (Fa 17, 37), and a

diogenite enclave consisting essentially of pyroxene

with uniform composition (Fs 27).

2. MASSING.—The analysis shows that this meteorite is very similar in composition to Yamato-7307;

an incomplete analysis by Fukuoka et al. (1977) confirms this. It is a polymict breccia with a wide range

of pyroxene compositions (Fs 22—46); plagioclase

also shows a considerable range in composition

(Ab 4-21). It should be mentioned that specimens

of a chondrite mislabelled as Massing have been distributed (the specimens in the Museum d'Histoire

Naturelle, Paris, and Eidgenossische Technische

Hochschule, Zurich are such); the analytical data

on Massing A reported by Schmitt et al. (1972) are

probably of this mislabelled material.

3. CHAVES.—Thin sections of this meteorite show

that it is a typical polymict breccia. The groundmass consists largely of comminuted orthopyroxene

enclosing larger shocked clasts of the same mineral;

eucrite enclaves (unbrecciated, with ophitic texture)

are not uncommon, and one fragment of diogenite

was seen. Jeremine (1954) has provided a thorough

petrographic description of this meteorite; she noted

the presence of accessory tridymite and quartz,

which we have confirmed with the microprobe (note

the 0.5% of free SiO2 in the norm). Our microprobe

analyses show that the pyroxene consists largely of

orthopyroxene, with lesser amounts of pigeonite;

the Fs mole percent ranges from 20 to 51. Plagioclase also shows a range of composition, Ab 9-24.

4. FRANKFORT.—This meteorite has been described

by Mason and Wiik (1966a). It is a polymict breccia,

with pyroxene clasts (mainly orthopyroxene, some

pigeonite) in a comminuted groundmass; one small

eucrite enclave was observed. Our microprobe analyses show pyroxene compositions ranging from Fs 24

to Fs 39; similar results were reported by Takeda,

Miyamoto, Ishii, and Reid (1976).

5. ZMENJ.—Thin sections show a typical polymict

breccia, consisting largely of clasts of hypersthene

(major) and pigeonite (minor) in a comminuted

groundmass. Our microprobe analyses show pyroxene compositions ranging from Fs 23 to Fs 44, and

plagioclase ranging from Ab 4 to Ab 10 (normative

plagioclase is Ab 13, which suggests that the Na2O

in the analysis may be a little too high). Desnoyers

and Jerome (1973) analysed a number of grains of

olivine in Zmenj, and found compositions ranging

from Fa 15 to Fa 39.

6. BINDA.—This meteorite, originally classified as

a howardite because the pyroxene is largely hypersthene, was reclassified by Duke and Silver (1967) as

a eucrite because it is a monomict breccia. The

pyroxene in Binda has been described by Takeda

and Ishii (1975); they comment (page 500):

The bulk composition of low-Ca pigeonite

suggests the crystallization temperature is above 1110°C. The

temperature where augite blebs Ca44.7Mg42.4Fe12.9 developed

in the host orthopyroxene Ca2.4Mg64.4Fe33.2 is about 970°C.

The Binda howardite contains the most magnesian pigeonite

among the basaltic achondrites, and these pyroxenes are interpreted to be crystallized from magma and not the mechnical mixture of diogenite and eucrite pyroxenes. The Binda

meteorite may be classified as the most Mg-rich and Ca-poor

eucrite.

7. PAVLOVKA.—Thin sections show a polymict

breccia largely of mineral grains (hypersthene with

minor pigeonite and plagioclase), but small- to

medium-sized eucrite enclaves are not uncommon;

some plagioclase grains are unusually large, larger
30 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

than could be derived from common eucrites, suggesting a possible anorthositic parent. Our probe

analyses indicate an unusually wide range of

pyroxene compositions; orthopyroxene is dominant,

with Fs ranging 14-36, with lesser amounts of

pigeonite, Fs 36-55, and a few grains of ferrohedenbergite, averaging Wo38Fs47En15; a single grain,

Wo19Fs72En9, possibly pyroxferroite, was analyzed.

Plagioclase ranged Ab 7-13, average 9. Two grains

of olivine, Fa 33, 35 were analyzed. Desnoyers and

Jerome (1973) analyzed 15 grains of olivine in

Pavlovka, with Fa ranging 36-49.

An incomplete analysis by Fukuoka et al. (1977)

is very similar to that given in Table 1.

8. WASHOUGAL.—Jerome and Michel-LeVy (1972)

describe this meteorite as a very heterogeneous polymict breccia. From the refractive indices, they give

the range of composition of the pyroxenes as

Fs 20-47. They describe several kinds of lithic clasts,

among them eucritic fragments with an ophitic or

subophitic texture, and a cm-sized dunite xenolith

(olivine composition Fa 12.8).

9. BHOLGATI.—A thin section shows a breccia with

numerous clasts of orthopyroxene up to 1 mm

across, small less numerous clasts of pigeonite and

plagioclase, and rare grains of chromite, in a finegrained groundmass. Our microprobe analyses show

a range of Fs 23-62 in orthopyroxene and pigeonite

KEY TO TABLE 1

Identification of Analyses by Columns

9.

10.

11.

12.

13.

14.

15.

16.

17.

18.

19.

20.

21.

22.

23.

24.

25.

26.

Yamoto-7307, also known as Yamoto(l); Wanke

et al., 1977 (FeS = 0.30%).

Massing; J. Nelen, analyst.

Chaves; McCarthy et al., 1972.

Frankfort; Mason and Wiik, 1966b (FeS =

0.69%).

Zmenj; Wiik, 1969 (FeS = 0.48%).

Binda; McCarthy et al., 1973.

Pavlovka; J. Nelen, analyst.

Washougal; Jerome and Michel-Levy, 1972

(FeS = 0.99%).

Bholgati; E. Jarosewich, analyst.

Luotolax; Wiik, 1969 (FeS = 1.08%).

Yurtuk; J. Nelen, analyst.

Bununu; Mason, 1967a. (TiO2) revised, 0.51%).

Medanitos; Symes and Hutchison, 1970.

Le Teilleul; J. Nelen, analyst.

Molteno, non-magnetic fraction; Frost, 1971.

Moama; Lovering, 1975.

Jodzie; J. Nelen, analyst.

Serra de Mage; E. Jarosewich, analyst.

Kapoeta; Mason and Wiik, 1966a (FeS =

0.98%).

Malvern; McCarthy et al., 1972.

Pomozdino; Kvasha and Dyakonova, 1972 (FeS

= 2.79%).

Brient; Dyakonova and Kharitonova, 1961 (FeS

= 0.55%).

Petersburg; E. Jarosewich, analyst (FeS =

0.74%).

Nagaria; J. Nelen, analyst.

Moore County; Hess and Henderson, 1949

(FeS = 0.82%).

Shergotty; Duke, 1968.

27. Macibini; McCarthy et al., 1973.

28. Bialystok; E. Jarosewich, analyst (FeS =

0.55%).

29. Yamoto-74450; Wanke et al., 1977 (FeS =

0.65%).

30. Ibitira; Wanke et al., 1974.

31. Jonzac; J. Nelen, analyst.

32. Sioux County; Duke and Silver, 1967 (FeS =

0.45%).

33. Allan Hills No. 5; E. Jarosewich, analyst (FeS

= 0.27%).

34. Nobleborough; J. Nelen, analyst.

35. Chervony Kut; Zavaritskii and Kvasha, 1952

(FeS = 0.25%).

36. Cachari; McCarthy et al., 1973.

37. Kirbyville; J. Nelen, analyst.

38. Juvinas; Duke and Silver, 1967 (FeS = 0.53%).

39. Millbillillie; J. Nelen, analyst.

40. Mount Padbury enclave; J. Nelen, analyst.

42. Adalia; J. Nelen, analyst.

43. Palo Blanco Creek; J. Nelen, analyst.

44. Peramiho; Berwerth, 1903 (FeS = 0.80%).

45. Stannern; Von Engelhardt, 1963 (FeS =

0.72%).

46. Haraiya; E. Jarosewich, analyst (FeS =

0.27%).

47. Pasamonte; Duke and Silver, 1967 (FeS =

0.06%).

48. Bereba; McCarthy et al., 1973.

49. Emmaville; Mason, 1974.

50. Nuevo Laredo; Duke and Silver, 1967 {FeS =

0.21%).

51. Lakangaon; McCarthy et al., 1974, with Cr2O3

and Na2O by J. Nelen.
TABLE 1.—Analytical data on pyroxene-plagioclase achondrites (a = mole percent FeO/

(FeO + MgO); b = mole percent Ab in normative plagioclase; c = weight percent normative

plagioclase; d = mole percent Wo, Fs in normative pyroxene; e = weight percent normative

pyroxene; f = weight percent normative olivine (ol) or silica (q); g = texture (u = unbrecciated,

m = monomict breccia, p = polymict breccia); key to identification of analyses by columns on

facing page)

Constituent

SiO2

TiO2

A1203

Cr203

FeO

MnO

MgO

CaO

Na2O

a

b

c

d

e

f

g

Constituent

SiO2

TiO2

A12O3

Cr203

FeO

MnO

MgO

CaO

Na20

a

b

c

d

e

f

g

1

50.82

0.23

4.27

1.02

16.46

0.52

21.37

3.83

0.13

30.2

10

12

4,29

80

5.1 ol

P

11

49.0

0.54

9.1

0.78

16.5

0.45

14.8

7.26

0.22

38.4

8

26

7,36

69

2.0 ol

P

2

51.1

0.31

4.1

0.91

17.6

0.49

21.3

4.1

0.08

31.7

6

12

4,30

80

6.4 ol

P

12

48.67

0.11

8.87

0.56

16.04

0.53

14.20

6.77

0.34

38.8

12

26

6,36

69

0.5 ol

P

3

51.79

0.37

6.84

0.61

15.33

0.48

18.39

5.64

0.22

31.8

10

20

5,30

78

0.5 q

P

13

47.74

0.03

15.09

0.14

13.72

0.51

12.16

10.38

0.20

38.8

4

42

8,36

49

8.8 ol

m

4

49.48

0.46

5.10

1.34

17.39

0.53

20.50

4.02

0.17

32.2

10

15

3,31

73

8.9 ol

P

14

50.1

0.42

7.4

0.72

17.6

0.46

15.0

6.44

0.17

39.7

7

21

7,37

74

1.9 q

P

5

50.47

0.46

6.97

1.04

16.22

0.55

17.85

5.35

0.29

33.8

13

20

5,32

75

1.8 ol

P

15

47.54

0.41

8.83

0.53

15.94

0.41

13.15

6.65

0.29

40.5

10

25

6,38

66

1.1 q

P

6

50.41

0.23

6.95

0.75

16.83

0.54

17.75

5.82

0.20

34.8

9

20

5,33

76

3.8 ol

m

16

48.58

0.22

13.74

0.63

14.85

0.50

11.89

9.47

0.22

41.2

5

38

7,38

58

2.4 ol

u

7

49.9

0.29

6.0

0.86

18.1

0.52

17.8

5.3

0.17

36.3

9

17

5,35

76

4.6 ol

P

17

48.3

0.48

7.9

0.63

18.3

0.50

14.6

6.64

0.20

41.3

8

22

7,38

70

3.7 ol

P

8

50.22

0.32

6.70

0.83

17.34

0.47

16.95

5'. 60

0.18

36.5

8

19

5,35

77

0.5 ol

P

18

46.69

0.11

20.89

0.33

9.97

0.36

7.52

13.09

0.30

42.7

5

58

9,39

38

2.1 ol

u

9

49.35

0.41

8.30

0.71

16.27

0.53

15.56

6.14

0.27

37.1

10

24

5,35

72

0.2 ol

P

19

48.47

0.37

9.46

0.63

17.16

0.53

12.00

8.08

0.46

44.5

15

28

10,40

67

0.4 ol

P

10

50.42

0.64

9.03

0.87

16.09

0.52

14.97

6.83

0.37

37.6

13

26

6,35

71

0.6 q

P

20

49.15

0.49

9.96

0.56

18.03

0.53

12.40

8.06

0.42

44.9

13

29

9,41

67

2.3 ol

P
SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

TABLE 1.—Continued.

Constituent

SiO2

TiO2

A12O3

Cr2°3

FeO

MnO

MgO

CaO

Na20

a

b

c

d

e

f

g

Constituent

SiO2

TiO2

A12O3

Cr203

FeO

MnO

MgO

CaO

Na20

a

b

c

d

e

f

g

21

47.97

0.73

11.31

0.10

14.61

0.53

9.96

10.76

0.41

45.1

11

32

16,38

62

0.9 q

m

31

50.7

0.98

11.7

0.33

17.6

0.47

6.9

10.4

0.38

58.9

10

33

15,50

57

6.3 q

m

22

49.00

0.79

11.02

0.59

17.02

0.58

11.27

8.63

0.24

45.9

7

31

9,42

64

1.4 q

P

31

48.29

0.60

12.84

0.31

18.25

0.53

7.08

10.39

0.42

59.2

10

37

13,51

59

2.9 q

m

23

49.18

0.57

10.82

0.56

17.00

0.52

11.24

8.49

0.35

45.9

10

31

9,41

65

1.3 q

P

33

48.92

0.73

12.22

0.39

17.56

0.56

6.74

9.63

0.43

59.4

11

35

13,52

55

4.8 q

m?

24

47.4

0.38

15.7

0.51

15.0

0.40

8.97

11.0

0.40

48.4

8

44

10,44

50

3.8 ol

u

34

50.0

0.78

12.5

0.40

18.5

0.46

7.1

10.0

0.46

59.4

11

36

13,52

58

4.0 q

P

25

48.16

0.32

15.57

0.44

15.02

0.31

8.41

11.03

0.45

50.0

9

44

11,45

54

0.04 ol

u

35

48.80

0.71

13.44

0.21

18.47

0.63

6.98

11.48

0.52

59.8

12

39

16,50

61

0.3 q

u

26

50.10

0.92

6.68

0.18

18.66

0.50

9.40

10.03

1.28

52.7

48

23

21,42

72

0.2 ol

u

36

48.26

0.63

12.85

0.32

19.10

0.59

7.14

10.25

0.51

60.1

12

37

13,52

60

0.7 q

m

27

49.32

0.72

12.12

0.42

18.31

0.54

8.37

9.97

0.48

55.1

12

35

13,48

62

1.6 q

P

37

49.8

0.67

11.9

0.40

18.7

0.54

6.96

10.0

0.45

60.2

12

34

14,52

59

4.1 q

m

28

48.97

0.56

12.63

0.72

17.83

0.58

7.88

9.72

0.32

56.0

8

36

11,50

58

3.1 q

P

38

49.32

0.68

12.64

0.30

18.49

0.53

6.83

10.32

0.42

60.2

10

36

14,52

58

3.3 q

m

29

48.28

0.90

11.43

0.40

18.03

0.53

7.58

9.95

0.51

57.2

14

33

14,49

60

2.4 q

m ?

39

52.0

0.68

12.8

0.33

18.3

0.61

6.76

10.2

0.36

60.3

9

36

13,52

57

6.5 q

m

30

49.0

0.78

12.6

0.36

18.1

0.50

7.1

10.9

0.19

58.8

5

35

15,50

59

3.6 q

u

40

48.0

0.55

13.1

0.39

19.0

0.44

7.0

10.3

0.32

60.4

8

37

12,53

59

1.6 q

u
NUMBER 22 33

TABLE 1.—Continued.

Constituent

SiO2

TiO2

A12O3

Cr2O3

FeO

MnO

MgO

CaO

Na2O

a

b

c

d

e

f

g

41

49.5

0.67

12.8

0.32

18.3

0.57

6.70

10.4

0.36

60.6

9

36

14,52

58

3.9 q

m

42

50.1

0.78

11.8

0.39

19.0

0.51

6.91

10.3

0.41

60.7

11

34

15,52

60

4.2 q

u

43

48.7

0.36

12.4

0.28

20.4

0.63

7.41

9.44

0.31

60.8

8

35

10,55

62

1.5 q

m

44

49.32

0.42

11.24

19.99

7.15

10.84

0.40

61.0

11

32

16,51

64

2.2 q

m

45

49.33

0.96

12.34

0.28

17.92

0.50

6.36

10.58

0.60

61.3

15

39

16,51

54

3.8 q

m

46

48.30

0.57

11.92

0.33

19.95

0.43

6.96

9.67

0.37

61.7

9

34

12,54

61

2.3 q

m

47

48.59

0.65

12.70

0.33

19.58

0.56

6.77

10.25

0.45

61.8

11

36

13,54

60

1.6 q

m

48

49.13

0.70

12.75

0.32

19.83

0.55

6.80

10.48

0.47

62.C

11

37

14,54

61

1-.6 q

m

49

52.6

0.66

12.2

0.36

18.5

6.12

10.2

0.51

62.8

13

35

15,54

57

7.6 q •

m

50

49.46

0.95

11.78

0.29

20.10

0.56

5.46

10.40

0.57

67.4

15

34

16,57

59

4.0 q -

m

51

49.03

0.85

11.54

0.35

22.81

0.60

5.87

10.27

0.49

68.6

13

33

14,59

65

1-.6 q

m

compositions; plagioclase Ab 5-17, average 10; one

grain of augite, Wo44Fs26En30; one grain of olivine,

Fa 31; and one grain of a silica polymorph, probably tridymite.

10. LUOTOLAX.—Thin sections show a polymict

breccia mostly of individual mineral grains (hypersthene, pigeonite, plagioclase) but with occasional

eucrite clasts; one section had an anorthosite clast

(~90% plagioclase, 10% pyroxene). Microprobe

analyses showed pyroxene compositions ranging

Fs 33-52, plagioclase ranging Ab 4-19.

11. YURTUK.—Thin sections show a polymict breccia with large (up to 1 mm) orthopyroxene and

smaller pigeonite clasts; lithic fragments are also

present, both eucritic and diogenitic; rare grains of

olivine were seen. Microprobe analyses show pyroxene ranging in composition from Fs 31 to Fs 50.

12. BUNUNU.—This meteorite was described by

Mason (1967a), with an analysis by E. Jarosewich.

We have made microprobe analyses of the pyroxenes and the plagioclase. The range of plagioclase

composition is Ab 6-17, average 10. Orthopyroxene

and pigeonite range is Fs 24-63; one grain of augite,

Wo43Fs25En32, was analyzed.

13. MEDANITOS.—This meteorite was described by

Symes and Hutchison (1970), who classed it as a

howardite because of its high content of Ca-poor

pyroxene; however, Hutchison et al. (1977) reclassify

it as a eucrite, commenting (page 149): "Further

unpublished work . . . indicates that it is a eucrite,

mineralogically similar to Moore County and Serra

de Mage." The analysis is noteworthy for the very

low TiO2 and CraO3 and high A12O3.

14. LE TEILLEUL.—Thin sections show this meteorite is a polymict breccia; hypersthene clasts (some

with augite exsolution lamellae) predominate, with

minor amounts of pigeonite and rare eucrite enclaves; one enclave of coarse plagioclase, reminiscent

of an anorthosite, was seen. Microprobe analyses

show a range of Fs 24-41 in hypersthene and

pigeonite, and Ab 10-24 in plagioclase. Desnoyers

and Jerome (1973) analyzed 13 grains of olivine in

Le Teilleul, and found a composition range of

Fa 28-42.

15. MOLTENO.—This meteorite was described by

Frost (1971) as a howardite, with pyroxene ranging from Wo2Fs22En76 to Wo4Fs58En38 and then to

Wo41Fs26En33, with plagioclase (An 84), and with

small quantities of olivine (Fa 12), troilite, nickeliron, ilmenite and chromite. Desnoyers and Jerome
34 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

(1973) analyzed 9 grains of olivine in Molteno, and

record a composition range of Fa 11-56.

16. MOAMA.—The analysis of this meteorite shows

that it is very similar to Medanitos. Lovering (1975)

describes it as an unbrecciated adcumulate of pyroxene and plagioclase, with accessory amounts of

chromite, troilite, nickel-iron, and tridymite (the

presence of olivine in the norm and free silica as

tridymite in the mode is probably due to all Fe

being reported as FeO, whereas some is present

as troilite and nickel-iron). Lovering's microprobe

analyses show plagioclase of uniform composition (Ab 6); the major pyroxene is hypersthene

(Wo3 4Fs416En55 0) with exsolution lamellae of augite

(Wo44.9Fs18.4En36.7).

17. JODZIE.—Bunch et al. (1976) describe this meteorite as follows:

The Jodzie howardite is a polymict-regolith breccia similar

to other howardites with two unique exceptions: 1, large

cm size lithic clasts of cumulate ferrogabbros, and 2, fragments of C2 carbonaceous chondrites {8 vol. %). The cumulate

ferrogabbros contain large 1 to 5 mm ferrohypersthene or

ferropigeonite grains with exsolved ferroaugite lamellae, calcic

plagioclase (An 84-89), ilmenite, FeS, and rarely free silica

and phosphates. Bulk analyses of these clasts are similar to

lithic clast ferrobasalts in other howardites . . . The C2

fragments range in size from 1/t to 6 mm and are similar

in bulk composition and mineralogy to C2 inclusions in the

Abbott and Plainview chondrites and the Kapoeta and

Washougal howardites.

18. SERRA DE MAGE.—This meteorite has been described by Prinz et al. (1977) as follows:

The Serra de Mage meteorite is a medium to coarse grained

anorthositic norite cumulate (eucrite) with a mosaic texture.

. . . Phases present are plag (An95), opx (Enss 5), augite

(Wo45En39Fsi6), chromite (Cr2O3, 50-54%), SiO2, Ni-Fe (Ni,

0.3-1.5%; Co, 0.8-1.2%), troilite, and a trace of ilmenite;

zircon and phosphate are present but were not found in

section .. . It is highly equilibrated and the pyroxenes record

a complex subsolidus history.

Serra de Mage* is unique in having the highest

A12O3 content and hence the highest plagioclase

content of any meteorite. In its high plagioclase

content, and in other compositional and textural

features it is clearly related to Medanitos, Moama,

Nagaria, and Moore County.

19. KAPOETA.—The polymict character of this

meteorite was clearly established by Fredriksson and

Keil (1963), in one of the first applications of microprobe analysis to meteorite research; they analyzed

132 pyroxene grains from the light portion and

found Fe (weight percent) ranging from 8.3 to 28.4,

and 132 grains from the dark portion with an Fe

range of 7.5 to 26.3; they also analyzed five olivine

grains, with Fa ranging from 8.5 to 37.7 mole

percent. Their work has been greatly extended by

Dymek et al. (1976), who comment:

Kapoeta is a "regolith" meteorite, and mineral-chemical and

petrographic data were obtained for numerous other rock

and mineral fragments in order to characterize the surface

and near-surface materials on its parent body. Rock clasts

can be grouped into two broad lithologic types on the basis

of modal mineralogy—basaltic (pyroxene- and plagioclasebearing) and pyroxenitic (pyroxene-bearing). Variations in

the compositions of pyroxenes in rock and mineral clasts are

similar to those in terrestrial mafic plutons such as Skaergaard, and indicate the existence of a continuous range in

rock compositions from Mg-rich orthopyroxenites to very

iron-rich basalts. . . . We interpret these observations to

indicate that the Kapoeta meteorite represents the comminuted remains of differentiated igneous complexes together

with "primary" undifferentiated basaltic rocks. The presently

available isotopic data are compatible with the interpretation

that this magmatism is related to primary differentiation of

the Kapoeta parent body. In addition our observations preclude the interpretation that the Kapoeta meteorite is a

simple mixture of eucrites and diogenites.

20. MALVERN.—This meteorite is extremely similar to Kapoeta in chemical and mineralogical composition, and in texture, having the same prominent

contrasted light-dark areas. It has been described by

Simpson (1975) and Desnoyers and Jerome (1977),

who clearly established its nature as a polymict

breccia.

21. POMOZDINO.—Kvasha and Dyakonova (1972)

describe this meteorite as a eucrite. A section we

have examined shows that the meteorite is a monomict breccia, the breccia fragments consisting of a

subophitic intergrowth of plagioclase and pigeonite.

22. BRIENT.—This meteorite is described by

Zavaritskii and Kvasha (1952) as a howardite, and

their illustrations (page 230) show that it is a

polymict breccia. Thus in spite of the close similarity in chemical composition between Brient and

Pomozdino they are quite different structurally.

23. PETERSBURG.—Thin sections show that this

meteorite is a polymict breccia; the dominant clasts

are subequal amounts of orthopyroxene and pigeonite (up to 1 mm across); plagioclase clasts are also

present, and occasional olivine clasts (one olivine

clast 2 mm across); small ophitic eucrite enclaves

are not uncommon. Microprobe analyses show

orthopyroxene and pigeonite ranging in composi-
NUMBER 22 35

tion from Fs 22 to Fs 55; plagioclase ranges in composition from Ab 8 to Ab 14; two grains of olivine,

Fa 38 and Fa 42, were analyzed. Duke and Silver

(1967, fig. 15) have published a diagram showing

the compositional range of pyroxenes in Petersburg.

24. NAGARIA.—A thin section shows that this meteorite is unbrecciated with a cumulus texture, consisting of approximately equal amounts of plagioclase and pyroxene. It is very similar to Moore

County in chemical and mineralogical composition

and texture. The minerals are highly equilibrated.

Microprobe analyses show plagioclase of uniform

composition, Ab 8; the pyroxene evidently crystallized originally as pigeonite, but the individual

grains are now hypersthene (Wo1.3Fs5o.4En,48-.3) with

exsolved augite (Wo43.3Fs18.9En37.8).

25. MOORE COUNTY.—A comprehensive description of this meteorite was published by Hess

and Henderson (1949). Additional information on

the pyroxenes has been provided by Ishii and

Takeda (1974); they showed that the primary

pigeonite (Wo101Fs44.3En4g 6) has exsolved augite

(Wo415Fs217En36 8) and the host pyroxene now has

the composition Wo5 8Fs47 5En40 7. Plagioclase has

uniform composition, Ab 9.

26. SHERGOTTY.—Although it belongs mineralogically with the pyroxene-plagioclase achondrites,

Shergotty (and the closely-related Zagami) has several features distinguishing it from other meteorites

in this group. It contains much more Na2O than

the other meteorites, and as a result the plagioclase composition is that of labradorite instead of

bytownite-anorthite; the plagioclase has been shocktransformed into the isotropic form maskelynite. It

also contains magnetite, which indicates a much

higher oxygen fugacity in its place of crystallization than for the eucrites and howardites. Duke

(1968) has provided a comprehensive description

of Shergotty, with analyses of the bulk meteorite,

the maskelynite (Or:2Ab49An49), and the pyroxene

(Wo22Fs41En37); the pyroxene is strongly zoned, as

shown by Duke's microprobe analyses.

Binns (1967) has shown that Zagami is closely

similar to Shergotty both in texture and mineralogical composition; for an analysis of Zagami, see

Easton and Elliott (1977). We have compared thin

sections of the two meteorites, and find that Zagami

differs from Shergotty only in being somewhat finergrained (feldspar laths average twice as long in

Shergotty); it is certainly possible, if not probable,

that both had a common parent body. The chemical composition of Shergotty places it well away

from the main trend of the eucrites and howardites

(Figure 3). It is significant that Bunch (1975) found

no shergottite clasts in the howardites, although he

found numerous clasts of eucrites, and less numerous clasts of other meteorite types. All these facts

indicate that Shergotty (and Zagami) probably come

from a different parent body than the other

pyroxene-plagioclase achondrites.

27. MACIBINI.—This meteorite has been described

by Reid (1974), as follows:

The Macibini meteorite is a complex polymict breccia with

rock and mineral clasts that are extraordinarily diverse in

texture and composition ... . Pyroxenes encompass a range

from magnesian orthopyroxene through pigeonite and ferropigeonite to ferroaugite and to hedenbergite. The trend mimics, and extends the pyroxene trend shown by the basaltic

achondrite group of meteorites. The more magnesian pyroxenes are coarser grained and tend to occur as mineral

clasts; the more iron-rich pyroxenes are commonly present

within fine-grained eucritic lithic fragments that have subophitic textures. . . . From the coherence of the mineral

data, the parent materials are not a random set of unrelated

rocks but appear to be derived predominantly from a suite

of related samples, that may have differentiated from a

single source The sequence of mineral compositions appears

to be continuous and the basaltic achondrites appear to be

related by fractional crystallization, involving dominantly

pyroxene. There is evidence for the existence of achondrites

with compositions intermediate between the hypersthene

achondrites and the eucrites; howardites are not simply twocomponent mixtures.

We have examined sections of Macibini and agree

with Dr. Reid's comments. Our microprobe analyses

show orthopyroxene and pigeonite with a composition range Fs 19-61, together with occasional grains

of ferroaugite; plagioclase composition range is

Ab 7-21. Desnoyers and Jerome (1973) analyzed

11 grains of olivine in Macibini, with a composition

range Fa 56-83 (unusually iron-rich).

28. BIALYSTOK.—This meteorite resembles Macibini closely in composition and texture. It is a

polymict breccia, with mostly pyroxene clasts (pigeonite > orthopyroxene) in a fine-grained groundmass; small ophitic eucrite enclaves are present.

Microprobe analyses showed a range in composition

of Fs 25-62 for orthopyroxene and pigeonite, and

Ab 7-12 for plagioclase; three grains of olivine,

Fa 71-73, were analyzed, and rare grains of a silica

polymorph, probably tridymite, were seen.

29. YAMATO-74450.—This meteorite, collected by
36 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

the Japanese Antarctic Expedition in 1974, has been

analyzed by Wanke et al. (1977), who describe it as

a eucrite. We have been informed (H. Takeda, pers.

comm.) that Yamato-74450 is a monomict breccia,

with pyroxene compositions similar to those in

Pasamonte.

30. IBITIRA.—This meteorite has been described

by Wilkening and Anders (1975) and Steele and

Smith (1976). The latter authors describe it as

follows:

Ibitira meteorite is interpreted as a strongly metamorphosed,

unbrecciated, vesicular eucrite with a primary variolitic and

secondary hornfelsic texture dominated by 60% pyroxene

(bulk composition En37Fs48Woi5 exsolved into lamellae several micrometers wide of augite En32Fs27Wo4i and pigeonite

En40Fs56Wo4) and 30% plagioclase An94 (mosaic extinction

and variable structural state). Minor phases are 5% tridymite

plates one-quarter occupied by plagioclase (An94) inclusions;

several percent intergrowths of ilmenite and Ti-chromite

with trace kamacite Fe99Co05Nio.2 and narrow olivine (Fa8;i)

rims; one grain of low-Ti-chromite enclosed in tridymite;

trace troilite with kamacite FeggCox.oNio.g. Euhedral ilmenite,

Ti-chromite, plagioclase and merrillite in vesicles indicate

vapor deposition. These properties can be explained by a

series of processes including at least the following: (1) igneous

crystallization under pressure low enough to allow vesiculation, (2) prolonged metamorphism, perhaps associated with

vapor deposition and reduction, to produce the coarse exsolution of the pyroxene and the coarse ilmenite-chromite intergrowths, (3) strong shock which affected the plagioclase and

tridymite but not the pyroxene, (4) sufficient annealing to

allow recrystallization of the plagioclase and tridymite, and

partial conversion to the low structural state of the former.

31. JONZAC.—Thin sections show that this meteorite is strongly brecciated, only a few small areas

retaining the igneous subophitic texture of intergrown plagioclase and pyroxene. Our microprobe

analyses (Figure 1) show pyroxene ranging in composition from Wo2Fs65En34 to Wo47Fs24En29, the En

content remaining almost constant while the Wo

and Fs contents vary inversely; this pattern is

characteristic for most eucrites, as noted by Duke

and Silver (1967) for Sioux County, Juvinas, and

Nuevo Laredo. Plagioclase composition ranges from

Ab 7-17, with an average of Ab 11.

32. Sioux COUNTY.—Duke and Silver (1967) describe this meteorite as a monomict breccia made

up of coarse-grained lithic fragments with equigranular and ophitic textures. They show the range

in composition of the pyroxenes in the form of a

diagram (their fig. 15); the pyroxenes range continuously from pigeonite through subcalcic augite to

ferroaugite with relatively constant molecular percentage (~30) of MgSiO3.

33. ALLAN HILLS NO. 5.—This meteorite was collected in Antarctica in 1977 and described by Olsen

et al. (1978). They state: "Thus, in a strict sense,

Allan Hills #5 is polymict, however, the exceptional anorthosite clasts are so few, and the bulk

composition so close to the average for eucrites, we

classify this meteorite as a eucrite" (p. 223). This is

clearly a meteorite whose classification as a eucrite

or as a howardite depends on a subjective evaluation of the amount of foreign admixture.

34. NOBLEBOROUGH.—Thin sections show this

meteorite to be a polymict breccia, with clasts

dominantly of pyroxene (mostly pigeonite), minor

plagioclase (Ab 7-17, average 9), some tridymite

grains, and occasional lithic fragments of eucritic

composition and texture; one grain of unusually

iron-rich olivine (Fa 88) was found. The polymict

character is well illustrated by a plot of pyroxene

compositions determined by the microprobe (Figure 1); most of the pyroxene grains are pigeonite,

but compositions falling in the fields of hypersthene, augite, subcalcic ferroaugite, ferroaugite,

and ferrohedenbergite were recorded, and one grain

(Wo14Fs82En4) is almost certainly pyroxferroite. The

extreme contrast in pyroxene compositions between

Jonzac (a monomict breccia) and Nobleborough

(a polymict breccia), in spite of their almost identical bulk compositions, supports the division of the

pyroxene-plagioclase achondrites into eucrites and

howardites on the basis of structure rather than

composition. Of course, the mere existence in these

meteorites of pyroxenes with a wide range of composition is not necessarily evidence for a polymict

origin; a similar range of composition for a zoned

single crystal has been recorded for many pyroxenes

in lunar basalts (e.g., Mason et al., 1972). The wide

range of pyroxene compositions in Nobleborough,

however, has been recorded on discrete grains, not

zoned crystals. This indicates that at least some of

the rocks from which these grains were derived were

probably not cogenetic.

35. CHERVONY KUT.—This meteorite has been

described by Zavaritskii and Kvasha (1952). Their

illustration (fig. 252) shows an unbrecciated structure, with pigeonite and plagioclase in an equigranular to subophitic texture.

36. CACHARI.—Cachari is a monomict breccia,

extensively crushed, and veined with brown glass;
NUMBER 22 37

* *o°

FIGURE 1.—Pyroxene compositions (microprobe analyses) in the Nobleborough howardite and the

Jonzac eucrite, two pyroxene-plagioclase achondrites with very similar bulk compositions.

large areas, however, are unbrecciated, and show an

equigranular to subophitic association of pigeonite

and plagioclase. Cachari has been described by

Fredriksson and Kraut (1967) as a rather typical

brecciated eucrite, consisting of orthopyroxene

(Wo2Fs59En39) and clinopyroxene (Wo4l2Fs27En31),

plagioclase (An 88), with minor amounts of

chromite, ilmenite, and troilite.

37. KIRBYVILLE.—This meteorite has never been

described; a small portion was kindly made available to us by its owner, Mr. Oscar Monnig. It is a

monomict breccia; pyroxene compositions, determined by the microprobe, are similar to those in

Jonzac, ranging from Wo,Fs,66En32 to Wo40Fs29En31.

A silica polymorph, probably tridymite, was detected with the microprobe.

38. JUVINAS.—This meteorite has been extensively

described in the literature, most recently by Duke

and Silver (1967). They record it as a monomict

breccia, and provide a plot of pyroxene compositions, which show a continuous range from pigeonite through subcalcic ferroaugite to ferroaugite with

relatively constant MgSiO3 contents, similar to that

of Jonzac and other eucrites.

39. MILLBILLILLIE.—A sawn surface of this meteorite presents a brecciated appearance, with a

prominent light-dark structure. The brecciated appearance is not so marked in a thin section, but

can be seen as areas of coarser and finer grain.

Our microprobe analyses show pryoxene compositions similar to those in Jonzac, ranging from

Wo2Fs66En32 to Wo45Fs:26En,29; plagioclase composition range is Ab 9-18, average 12; a silica polymorph was observed.

40. MOUNT PADBURY.—This meteorite is a mesosiderite containing a varied range of achondrite

enclaves, which have been described by McCall

(1966). We have examined one of these, an unbrecciated hypidiomorphic-granular aggregate of

pyroxene and plagioclase. Its bulk composition is

essentially identical with many eucrites. Microprobe

analyses show pyroxene compositions ranging from

Wo2Fs64En34 to Wo20Fs49En32, i.e., pigeonite to subcalcic ferroaugite; plagioclase composition is very

uniform, Ab 8.

41. PADVARNINKAI.—This meteorite has been

classed as a shergottite, because it contains maskelynite; however, Binns (1967) showed that it differs significantly in chemistry and mineralogy from

Shergotty, and it still retains some untransformed

plagioclase, which has a bytownitic composition

quite different from the Shergotty maskelynite. The

chemical analysis shows that its composition is essentially identical with other eucrites. Our microprobe analyses show pyroxene compositions ranging

from Wo,2Fs,67En31 to Wo44Fs27En29, similar to those

in Millbillillie; the plagioclase composition range

isAb 10-23, average 11.

42. ADALIA.—This meteorite is unbrecciated, with

an ophitic texture. Our microprobe analyses show
SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

pyroxene ranging from WoaFs^Engg to Wo36Fs34

En30, closely similar to the preceding meteorites;

plagioclase ranges Ab 9-18, average 11; accessory

grains of a silica mineral were noted.

43. PALO BLANCO CREEK.—This meteorite is described by Lange and Keil (1976) as a monomict

pigeonite-plagioclase achondrite. Their plot of

pyroxene compositions show them closely clustered

in two areas, one pigeonite and one ferroaugite; our

microprobe analyses confirm this, with mean compositions Wo2Fs65En33 and Wo44Fs28En28; plagioclase is very uniform in composition, Ab 10.

44. PERAMIHO.—This meteorite was described by

Berwerth (1903); it is a typical monomict eucritic

breccia. Our microprobe analyses show pyroxene

compositions clustered around Wo2Fs63En35 and

Wo43Fs27En30, similar to those in Palo Blanco Creek;

feldspar composition range is Ab 9-14, average 11.

45. STANNERN.—This meteorite has been comprehensively described by von Engelhardt (1963). It

is a monomict breccia; some areas retain the original

ophitic texture of pigeonite and plagioclase, but

much of the meteorite is strongly crushed and brecciated. Our microprobe analyses show pyroxene

ranging in composition from Wo3Fs65En32 to

Wo26Fs46En28, and plagioclase from Ab 12 to Ab 20,

average 17.

46. HARAIYA.—This meteorite is a monomict

breccia, with areas of original ophitic texture separated by areas of crushed material; some of the

crushed material appears to have recrystallized into

a granular aggregate of pyroxene and plagioclase.

Our microprobe analyses show pyroxene compositions ranging from Wo2Fs67En31 to Wo43Fs29En2S;

plagioclase compositions range Ab 9-18, average 11.

47. PASAMONTE.—This meteorite is a breccia containing clasts dominantly of pigeonite with lesser

amounts of plagioclase, and lithic fragments with

ophitic texture. It has been classified as a monomict

breccia by Duke and Silver (1967) and by Takeda,

Miyamoto, and Duke (1976). Takeda et al. have

shown that Pasamonte is almost unique among the

monomict breccias in having strongly zoned pyroxenes with no visible exsolution lamellae. Our

microprobe analyses show pigeonite compositions

ranging from Wo6Fs33En61 to Wo6Fsr,5En29, with

some Ca-rich pyroxene ranging up to Wo33Fs39En28.

48. BEREBA.—The mineralogy and petrology of

this meteorite were comprehensively described by

Lacroix (1926). It is a monomict breccia; our microprobe analyses show pyroxene of composition

Wo3Fs61En36 with narrow exsolution lamellae of

ferroaugite (Wo36Fs35En29), and plagioclase with

composition Ab 8-10; a silica polymorph (quartz,

according to Lacroix) was detected.

49. EMMAVILLE.—This meteorite was briefly described by Mason (1974). It is a monomict breccia

with veinlets of brown glass. It is noteworthy for

being the finest-grained of all the eucrites, with a

hornfelsic hypidiomorphic-granular texture, the

pyroxene grains averaging 0.02-0.03 mm across and

set in a plagioclase matrix. Our microprobe analyses

show hypersthene (Wo2Fs66En32) coexisting with

augite (Wo47Fs25En28). Plagioclase compositions

range from Ab 9 to Ab 20, and average Ab 13. The

pyroxene compositions indicate that Emmaville

probably recrystallized and equilibrated at temperatures well below the liquidus.

50. NUEVO LAREDO.—This meteorite has been described by Duke and Silver (1967). It is a monomict

breccia in which the lithic clasts are rather fine

grained. Our microprobe analyses show pyroxene

compositions ranging from Wo5Fs68En27 to Wo41Fs34

En24, similar to those reported by Duke and Silver.

51. LAKANGAON.—There is very little published

information about this meteorite, except for the

analysis by McCarthy et al. (1974). It is a monomict

breccia, the individual lithic clasts being coarsegrained granular to subophitic intergrowths of

pyroxene and plagioclase. Pyroxene compositions

range from Wo5Fs60En27 to Wo43Fs33En24; plagioclase from Ab 10 to Ab 19, average Ab 15.

Neither analytical data nor a description are

available for Muckera, which is catalogued by

Hutchison et al. (1977) as a howardite. Melrose

(b), which we have not examined, was briefly described and identified as a howardite by Sibray et

al. (1976). We accept the identification by Tschermak (1872) of Constantinople as a mislabelled fragment of Stannern.

Chemical and Mineralogical Relationships

Examination of Table 1 reveals a number of regularities in the composition of the pyroxeneplagioclase achondrites. The SiO2 content is remarkably uniform at 50 ±3 percent (Serra de Mage",

with 46.69% SiO2, is exceptional because of its high

content of plagioclase). The FeO content is also

fairly uniform (Serra de Mag£ is again exceptional),
NUMBER 22 39

and the MgO content shows a fairly regular decrease with increasing FeO/(FeO + MgO) molecular percentage, whereas CaO and A12O3 show the

reverse effect. The Na2O content is low throughout, except in Shergotty (1.28%). Of the minor

components, MnO is rather constant (Dymek et al.

(1976) demonstrated that the FeO/MnO ratio in

Kapoeta pyroxenes is fairly uniform (~35) and

significantly lower than in lunar pyroxenes (~60),

and Marvin (1976) has confirmed this for other

pyroxene-plagioclase achondrites); Cr2O3 decreases

with increasing FeO/FeO+MgO) molecular percentage, whereas TiO2 increases.

A notable feature of Table 1 is the marked cluster

of analyses (analyses 29-49) with FeO/(FeO + MgO)

mole percentage of 60±3, i.e., almost half the analyses group together, with very limited internal variation. They are unbrecciated or monomict breccias,

except Nobleborough (34), and form what may be

called the main-group eucrites.

Additional correlations are revealed by the calculation of normative mineralogy (because the

actual minerals present are essentially identical with

those calculated in the norm, normative and modal

mineralogy are closely similar). Since practically

all the A12O3 is combined in plagioclase, A12O3 and

plagioclase contents are directly related; plagioclase

content increases with increase in FeO/(FeO + MgO)

mole percentage, from 12% in Yamato-7307 to

almost 40% in main-group eucrites. A few eucrites

(Medanitos, Serra de Mage, Nagaria, Moore County)

contains more than 40% plagioclase, and are believed to have a cumulate origin. Normative plagioclase composition is rather uniform at Ab 10±5,

except for Shergotty (Ab 48), reflecting the rather

uniform Na2O content; in individual meteorites

actual plagioclase composition may vary from grain

to grain and within grains but will average close to

the normative composition. Normative pyroxene increases in amount and becomes more calcic and ironrich with increase in FeO/(FeO + MgO) mole percentage. Actual pyroxene compositions vary widely

in the howardites, but generally show a limited and

systematic range in the eucrites (Figure 1).

70 -

60 -

Q 50 -

30 -

- •

o

©

-

Howarditat

Eucritos

Stwrgotty

1

a 9 *

7» •

06

• 5

• 3

I

17

* •

12 • • «

• to

23

I

O51

SOo

28 _

••2 7

© 3 6

O24

0 16

o13

1 1

8

CaO

10 12

FIGURE 2.—CaO (weight percent) plotted against FeO/(FeO + MgO) (mole percent) from analyses of the pyroxene-plagioclase achondrites (the ellipse encloses

values for 20 eucrites and one howardite; numbers are those of analyses in

Table 1).
40

SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

A significant feature that becomes evident from

the norm calculation is the close approach to silicasaturation in all the pyroxene-plagioclase achondrites, so close in many instances that a change of

less than 1% in SiO2 percentage would change an

analysis from olivine-normative to quartz-normative.

The eucrites, however, are consistently quartznormative (except Binda, Medanitos, Moama,

Nagaria, Moore County), whereas most howardites

are olivine-normative. Accessory olivine is present

in most howardites, but we have not found it in

any of the eucrites we have examined. Most eucrites

(even the olivine-normative Binda, Moama, and

Moore County) contain accessory free silica, usually

as tridymite, sometimes as quartz or cristobalite.

Additional relationships are clarified by composition diagrams. Figure 2 plots CaO weight percentage against FeO/(FeO + MgO) mole percentage. The

close groupings of analyses 29 through 49 is apparent; there are too many analyses to be shown

individually, but the one howardite within this

cluster is shown. Nuevo Laredo (50) and Lakangaon

(51), although identical to main-group eucrites in

CaO content, are clearly differentiated on FeO/

(FeO + MgO) mole percentage. Outside the maingroup eucrites are Binda (6) and six probable

cumulates: Medanitos (13), Moama (16), Serra de

Mage (18), Pomozdino (21), Nagaria (24), and Moore

County (25). Another intriguing feature is that

howardite compositions are fairly continuous in the

• 4

#3

.

7

 nl

10

.17 ' «

• 12

• «

• 1?

• Howardite

o Eucrites

0 Shvrgotty

.20

• 2 2

.27 O*8

• 26

to 12 20

AI2O,

FIGURE 3.—MgO (weight percent) plotted against A12O3 (weight percent) from analyses of the

pyroxene-plagioclase achondrites (the ellipse encloses the values for 20 eucrites and one howardite;

numbers are those of analyses in Table 1).
NUMBER 22 41

FIGURE 4.—Compositions of coexisting calcium-poor and calcium-rich pyroxenes in selected

eucrites (1 = Binda (Takeda, Miyamoto, Ishii and Reid, 1976); 2 = Moama (Takeda, Miyamoto,

Ishii, and Reid, 1976); 3 = Moore County (Ishii and Takeda, 1974); 4 = Ibitira (Steele and

Smith, 1976); 5 = Peramiho (this paper); 6 = Haraiya (this paper); 7 = Lakangaon (this paper)).

FeO/(FeO + MgO) range 30-46, but there is then a

hiatus to FeO/(FeO + MgO) = 55, with only three

beyond this—Macibini, Bialy stole, and Nobleborough.

The MgO-Al2O3 diagram (Figure 3) demonstrates many of the same relationships as Figure 2.

It shows even more clearly than Figure 2 the linear

relationship between the howardites and the maingroup eucrites, i.e., although the howardites are

polymict breccias, their bulk composition is dearly

constrained. The MgO-Al2O3 relationship can be

projected to include the diogenites, whose compositions cluster around 26% MgO, 1% A12O3; the

relationship between diogenites, howardites, and

eucrites will be discussed in a later section. Figure

3 shows how the Shergotty composition falls well

away from the eucrites and howardites, and justifies

placing it in a special category, as already indicated

by its mineralogy. Relative to the eucrites and

howardites, Shergotty is enriched in pyroxene and

depleted in plagioclase; its texture suggests a

pyroxene cumulate.

As demonstrated in Figure 1, howardites are distinguished from eucrites by their great range in

pyroxene composition; in eucrites pyroxene compositions may range in Wo content from pigeonite

to augite or ferroaugite, but the En content remains

practically constant. The extremes in pyroxene composition are plotted in Figure 4 for seven eucrites,

ranging from the most Mg-rich (Binda) to the most

iron-rich (Lakangaon). In most of these meteorites

all intermediate compositions between the extremes

may be found by microprobe analyses, because of

the presence of microscopic to submicroscopic exsolution lamellae of calcium-rich pyroxene in a calcium-poor host.

The Relationship between Diogenites, Howardites,

and Eucrites

The fact that the bulk compositions of diogenites, howardites, and eucrites form an almost

continuous sequence has long been known and

commented on. Mason (1962) suggested that these

three classes might be related as successive members of a fractional crystallization sequence from a

melt of approximately chondritic composition (the

pallasites being the initial member of the sequence).

Jerome and Goles (1971) pointed out that howardites are polymict breccias, and therefore are not

direct products of magmatic crystallization; from

that observation they proceeded to the postulate

that howardites are mechanical mixtures of diogenites and eucrites. This postulate has been sup

ported by McCarthy et al. (1972) and later researchers, most recently by Dreibus et al. (1977:211),
42 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

who state: "The hypothesis of Jerome and Goles

(1971) and McCarthy et al. (1972), according to

which howardites are thought to be mechanical

mixtures of eucrites and diogenites, is strongly confirmed by mixing computations."

The fatal flaw in this hypothesis is the remarkable uniformity of pyroxene compositions in diogenites (Fs 25-27), as has been demonstrated by

Mason (1963) and Fredriksson et al. (1976). Calcium-poor pyroxene compositions in eucrites (Figure 4) range from Fs 33 to Fs 68. Therefore, if

howardites are mixtures of diogenites and eucrites,

their pyroxenes should comprise a large component

with composition Fs 26±1 (the diogenite fraction)

and additional calcium-poor "pyroxenes possibly

ranging from Fs 33 to Fs 68 (the eucrite fraction).

That this is not the case was already evident in 1971

from the work of Fredriksson and Keil (1963) on

Kapoeta; figures 7 and 8 of their paper show

pyroxene compositions extending as low as Fs 14

and no large component at Fs 26. These results on

Kapoeta have been confirmed and extended by

Dymek et al. (1976). Similar evidence is available

from Macibini (Reid, 1974) and Malvern (Simpson, 1975); both Reid and Simpson conclude that

these meteorites could not have been produced by

the physical mixing of diogenite and eucrite (Desnoyers and Jerome (1977), however, disagree with

Simpson in the case of Malvern). Our data on the

howardites confirm and extend the conclusions of

Reid and Simpson. Not only do the howardites contain calcium-poor pyroxenes much more magnesian

than those in diogenites, but some of them (notably Pavlovka and Nobleborough) have pyroxenes

more iron-rich than have been found in any eucrite.

The presence of accessory olivine in many howardites, with a wide range of composition—Fa 11-83,

according to Desnoyers and Jerome (1973)—also

argues for a component not represented either in

the diogenites or the eucrites. We agree, nevertheless, with Reid's comment (1974:398) on Macibini:

"The parent materials [of the howardites] are not

a random set of unrelated rocks but appear to be

derived predominantly from a suite of related samples, that may have differentiated from a single

source."

The Eucrite Parent Body

Discussions of the eucrite parent body usually

imply the parent body of what we have called the

main-group eucrites, i.e., the compositional cluster

around FeO/(FeO + MgO) molecular percentage of

60. Within this group a wide variety of primary

(i.e., pre-brecciation) textures are seen, indicating a

considerable variety of crystallization conditions in

the parent body. Nevertheless, most, if not all,

crystallized under low pressure (the common occurrence of tridymite indicates a confining pressure

of 3 kbar or less).

Although the textures of the clasts in most of the

eucrites resemble those of the lunar basalts, the exsolution and inversion features show significant

differences. The pyroxenes in lunar basalts are

strongly zoned, and can range from orthopyroxene

through pigeonite to augite and hedenbergite in a

single crystal. In most eucrites the pyroxenes are

essentially unzoned, and consist of pigeonite of uniform composition with exsolution lamellae of

augite. Possibly the eucrites crystallized originally

like the lunar basalts, as thin surface flows, but later

were annealed (perhaps by burial under successive

flows), whereby originally zoned pyroxenes were

homogenized, and then exsolved augite on slow

cooling. If true, it is noteworthy that this equilibration occurred without textural change, except for

Ibitira and Emmaville, which have a hornfelsic

texture. Presumably the absence of water and other

volatiles inhibited textural alteration.

Some years ago one of us (Mason, 1967b) proposed that the eucrites were derived from a relatively thin surface crust of a differentiated asteroid

consisting of a pallasitic core and a diogenitic

mantle. The radius of the hypothetical asteroid was

set at 300 km, to be consistent with the measured

cooling rates of pallasite meteorites (Buseck and

Goldstein, 1967). It had a pallasitic core with radius

207 km, a diogenitic mantle 80 km thick, and a

eucritic crust 13 km thick. The overall mineralogical

composition of this asteroid was calculated to be

(weight percent): nickel-iron, 14; olivine, 25; hypersthene, 46; pigeonite, 9; plagioclase, 6. The bulk

composition of this asteroid was then calculated

from the average mineral compositions in these

meteorites, with the results as given in Table 2. It

is gratifying to see that recent deductions as to the

composition of the eucrite parent body, based on

sophisticated geochemical arguments (e.g., Morgan

et al., 1978) are in good agreement with the simple

petrological model. The composition derived by

Morgan et al. (Table 2, analysis 2) would give a
NUMBER 22 43

TABLE 2.—Composition of (1) an asteroid consisting of pallasite core, diogenite mantle, and eucrite crust (Mason, 1967b);

and (2) the eucrite parent body (Morgan et al., 1978)

Constituent

SiO2

A12O3

FeO

MgO

CaO

Na20

Fe

Ni

1

42.7

2.3

12.7

26.2

2.0

0.1

12.5

1.5

2

35.0

2.2

23.2

24.8

1.8

0.04

11.2

1.7

parent body with more olivine and less pyroxene

than that of Mason, i.e., one with a larger pallasite

core and smaller diogenite mantle.

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44 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

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NUMBER 22 45

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1952. Meteorites of the U.S.S.R. 245 pages. Moscow: Academy of Sciences of the U.S.S.R.
Fusion of Rock and Mineral Powders for Electron

Microprobe Analysis

Peter A. Jezek, John M. Sinton, Eugene Jarosewich, and Charles R. Obermeyer

ABSTRACT

Rock and mineral powders, finer than 100 mesh,

were fused in a molybdenum or tungsten boat in a

nitrogen atmosphere. The fusion times ranged from

5 to 30 sec at temperatures between 1650° C and

1750° C. The fusion bridge was powered by a

1.5 kVA welding transformer.

This fusion technique in combination with the

electron microprobe uses very small amounts of

sample and is suitable for very rapid analysis of

rock samples ranging in composition from 45 to

about 65 weight percent SiO2. In general, the glasses

are sufficiently homogeneous to be suitable for electron microprobe analysis. The electron microprobe

results, when compared to analyses obtained by classical chemical methods, have average accuracy better

than 5 percent (relative) for all major components

except TiO2, which is better than 13 percent (relative). A major part of the error in the TiO2 analyses

is probably due to the presence of minute residual

or quench Fe-Ti oxides in the glass.

The samples investigated suggest that if fusion

times of less than 20 sec are used, Na2O loss is prevented or greatly restricted and homogeneous glasses

still result.

Introduction

Brown (1977) summarized techniques used in

electron microprobe major elements analysis of

whole rock samples. He also described a new technique for fusing rock powders in molybdenum

boats in a pressurized (60 psi) argon atmosphere.

Peter A. Jezek, John M. Sinton, Eugene Jarosewich, and

Charles R. Obermeyer, Department of Mineral Sciences, National Museum of Natural History, Smithsonian Institution,

Washington, D.C. 20560.

We have investigated direct fusion of rock and

mineral powders in molybdenum and tungsten

boats in a nitrogen atmosphere (at atmospheric

pressure), using a strip furnace which is easily built

and inexpensive to operate. These experiments were

aimed at developing a rapid, simple, and inexpensive method of fusion of rock powders into

representative, homogeneous beads or shards suitable for analysis by electron microprobe, without

the need of an argon pressure chamber.

INSTRUMENTATION.—The fusion bridge (Figures

1, 2) is powered by a 1.5 kVA welding transformer.

The primary of the transformer is connected

through a Variac autotransformer to 115 VAC. The

secondary of the transformer, rated at 11.5 V, is

connected to a 100 A silicon diode bridge rectifier.

The DC output of the rectifier then powers the

fusion bridge (Figure 3). To reach a temperature

of 1670° C the strip receives 40 A at 4 VDC. Temperatures were measured by an optical pyrometer.

The particular welding transformer employed in

this instrument was used because of its availability;

two parallel-wired filament transformers, 25 A each,

could be used instead.

The Mo and W boats used in the fusion are inexpensive and readily available from most SEM suppliers. They are very practical for holding all

molten glasses, and are especially useful in restricting the how of low viscosity basaltic glasses. The

size best suited for routine sample fusion is a 1%

in. strip containing a boat 7/16 in. long, 3/16 in.

wide and 3/32 in. deep.

TECHNIQUE.—The melting boat, connected between two posts, is covered by a glass bell jar that is

continuously flushed by nitrogen (Figure 1). After

placing the powder, ground finer than 100 mesh,

46
NUMBER 22 47

FIGURE 1.—Front view of the fusion furnace: the fusion boat

is mounted between the two posts and the whole assembly is

covered by a glass bell jar that is continuously flushed by

nitrogen (for symbol explanation see Figure 3).

FIGURE 2.—Detail of the fusion bridge (P = positive and

negative terminals of the bridge; B = fusion boat; Q = outlet of the nitrogen quench line; O = outlets through which

the gas under the glass bell jar is forced out; S = vertical

shield behind which is located the outlet for the purge line

through which nitrogen enters the glass bell jar during the

flushing cycle (see Figure 3).

in the fusion boat and covering the fusion assembly

by the bell jar it takes about 1 min to establish an

atmosphere of almost pure nitrogen. This is documented by the lack of oxidation of a Mo strip

heated in this atmosphere at 1750° C for 25 min.

Two melting procedures were used. (1) Samples

were heated for about 10 sec at low temperature

(dark red glow of the strip) to drive off adsorbed

water and water of hydration if present. The temperature was then rapidly increased to approximately 1700° C. The powders usually melt in 3-5 sec

but total heating at the final temperature for about

10-30 sec promotes diffusion and thus formation of

more homogeneous glasses. (2) Rapid heating of the

cold powder to about 1700° C was also investigated.

When subjected to this technique the powders fuse

more rapidly probably due to the presence of water,

which is driven off when the first technique is used.

There is no apparent difference in the homogeneity

of the glasses produced by these two techniques.

Quenching of the melts is accomplished by simultaneously shutting off the power to the fusion

bridge and directing a stream of nitrogen onto the

bottom of the fusion boat. Cooling is sufficiently

fast to prevent crystallite formation in all but the

most mafic samples. Quench olivine is common in

the more mafic samples.

In order to avoid either strip-contaminated glass,

glass possibly depleted by elemental diffusion into

the strip (Brown, 1977), or elemental volatilization

into the nitrogen atmosphere, only glass in the interior of the bead or shard was analyzed.

The glasses were analyzed by a 9-spectrometer

computer-automated ARL-SEMQ electron microprobe. The spectrometers were equipped with the

following analyzing crystals. Si-EDDT, Al-EDDT,
48

F1 T1

QUENCH PURGE

SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

R1

T2

NITROGEN

FIGURE 3.—Wiring diagram of the fusion furnace (SI = DPDT

115-VAC 10 A switch; Fl = 10 A fuse; Tl - VARIAC autotransformer; T2 = welding transformer; BR1 = 100 A 50 PIV

silicon diode bridge rectifier; Rl = meter shunt, 150 A 50 mV;

Ml = 50 mV full scale meter calibrated to read 150 A at full

scale). Lower left: a diagram of the nitrogen system (the purge

line is located behind the vertical shield (S in Figure 2); the

quench line is located below the fusion boat (Q in Figure 2);

VI = 3 way valve, toggle actuated).

Fe-LiF, Mg-ADP, Ca-LiF, Na-RAP, K-LiF, P-ADP.

The data were corrected by an on-line computer using the method of Bence and Albee (1968). During

the analysis 15 kV accelerating potential and 0.02

fiA sample current were used. A defocused beam,

20-50 pjm in diameter, practically eliminates Na

volatilization during analysis and also helps to average local, small inhomogeneities which may exist

in the glass. It is recommended that 10 sec count

times be used and the analysis repeated at least ten

times to accumulate a statistically significant body

of data. The repeated measurements also help to

average possible larger scale inhomogeneities.

Results

Eleven rock powders and three mineral samples

were fused by the described technique. The rocks

were selected to cover as wide a compositional range

as possible. Analytical data for the eleven rock

samples are presented in Table 1. The electron

microprobe data show good agreement with the wet

chemical values, which were recalculated volatile

free in order to facilitate direct comparison with

the electron microprobe analyses. The CV values

(CV = standard deviation x 100/mean) reflect significantly the homogeneity of the glasses but also include a component of variation due to instrumental

instability. The standards used in the glass analyses

were analyzed by wet chemical techniques at the

Department of Mineral Sciences, Smithsonian Institution. Their compositions are given in Jarosewich, Nelen, and Norberg (this volume).

The average differences between the wet chemical

analyses and the electron microprobe analyses are

shown in Table 2. The average accuracy in weight

percent is better than 0.2 for all major components

except SiO2 which is accurate to better than 0.3. In
TABLE 1.—Analyses of 11 fused rock powder samples by wet chemical and electron microprobe

methods (A = wet chemical analysis (wt %); B = electron microprobe analysis (wt %), numbers

in parentheses are the numbers of point analyses averaged; CV (approximate measure of glass

homogeneity) = (SD x 100)/x; ND = no data; Std (standard or reference sample) 1 = VG-568

(glass), 2 = VG-A99 (glass), 3 = tektite glass (synthetic), 4 = VG-2 (glass), 5 = Kakanui hornblende; wet chemical analyses of W-1, BCR-1, and AGV-1 from Flanagan, 1973; remaining wet

chemical analyses by E. Jarosewich and J. Norberg, Department of Mineral Sciences, Smithsonian

Institution; all wet chemical analyses recalculated as volatile free to facilitate direct comparison

with microprobe analyses; standard analyses given in Table 1, Jarosewich, Nelen, and Norberg,

this volume)

Constituent

SiO2

TiO2

A12O3

FeO

MnO

MgO

CaO

Na2O

K2O

P2°5

Total

Temp. (°C)

Time (sec)

I

Constituent

sio2

TiO2

A12O3

FeO

MnO

MgO

CaO

Na2O

K2O

p2o5

Total

Temp. (aC)

Time (sec)

U3180/B159(b)

A

47.32

2.87

16.99

11.12

0.19

7.60

10.26

2.79

0.69

0.28

100.11

A

54.50

0.64

19.49

7.28

0.16

4.87

9.46

2.90

0.62

0.16

100.08

B(14)

47.41

2.67

16.85

10.97

ND

7.65

10.13

2.96

0.63

ND

99.27

1700

30

CV

1.07

3.19

1.99

1.43

2.40

1.55

2.42

10.17

113419

B(16)

54.51

0.60

19.75

7.04

0.17

4.84

9.30

3.17

0.60

ND

99.88

1670

30

CV

1.63

6.32

2.20

3.05

4.07

1.35

3.03

8.27

Std

4

5

4

4

5

4

3

3

Std

3

5

5

2

2

2

1

3

A

51.09

0.92

18.92

11.26

0.15

3.16

10.17

2.49

1.42

0.14

99.72

A

55.37

2.24

13.83

12.30

0.18

3.52

7.03

3.32

1.73

0.36

99.88

D-14-53

B(26)

51.19

0.98

19.14

11.11

0.14

3.34

10.11

2.30

1.30

ND

99.61

1750

30

CV

0.42

3.95

1.77

1.93

4.99

1.14

3.51

4.73

Std

3

5

5

2

2

2

1

3

FUSION

BCR-1

B(29)

55.21

2.09

13.79

12.26

ND

3.48

7.06

3.26

1.66

ND

98.81

1670

CV

0.78

4.06

2.42

2.35

4.33

1.79

2.25

2.75

Std

4

5

4

4

5

4

4

3

FUSION

10, 20

A

50.99

1.87

19.27

9.60

0.16

4.05

9.35

3.50

0.57

0.23

99.59

MI-8

B(46)

51.23

2.06

19.02

9.81

ND

4.01

9.33

3.58

0.57

ND

99.61

CONDITIONS

A

56.64

0.95

19.80

6.33

0.11

3.48

6.92

4.58

1.18

0.15

100.14

1650

20

CV

1.30

4.54

2.96

2.21

3.99

2.73

2.40

9.13

SH-384-2

B(25)

57.86

0.80

18.77

5.88

0.11

3.73

6.78

4.46

1.20

ND

99.59

CONDITIONS

1670

21

CV

1.99

9.29

3.65

3.81

3.84

1.34

2.92

6.75

Std

4

5

4

4

4

4

4

3

Std

3

5

5

2

2

2

1

3

A

53.00

1.08

15.10

10.05

0.17

6.67

11.04

2.16

0.65

0.14

100.06

A

60.14

1.06

17.58

6.23

0.10

1.56

4.99

4.34

2.95

0.50

99.45

W-1

B(29)

53.14

1.05

15.44

9.85

ND

6.51

11.15

2.14

0.62

ND

99.90

1670

15, 20

CV

1.29

5.33

1.90

2.56

2.51

1.46

2.92

7.77

AGV-1

B(22)

60.46

0.92

17.59

6.20

ND

1.55

5.09

4.05

2.84

ND

98.70

1670

15

CV

0.27

6.48

1.56

3.24

4.35

1.72

2.49

2.21

Std

4

5

4

4

5

4

4

3

Std

4

5

4

4

5

4

4

3
50 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

TABLE 1.—Continued.

Constituent

SiO2

TiO2

A12O3

FeO

MnO

MgO

CaO

Na20

K20

P

2°5

Total

Temp. (°C)

Time (sec)

A

63.76

0.66

17.69

4.48

0.08

1.91

5.12

4.85

1.40

0.13

100.08

SH-281

B(24)

63.67

0.60

17.78

4.33

0.08

1.87

5.05

4.95

1.33

ND

99.66

1670

10

CV

1.01

5.30

1.23

2.16

4.71

1.09

2.10

2.82

Std

3

2

5

3

3

3

1

1

A

64.01

0.32

12.95

6.79

0.13

5.47

7.51

1.83

0.95

0.06

99.96

111108

B(16)

63.37

0.36

13.06

6.65

0.13

5.84

7.34

2.01

0.86

ND

99.62

CV

1.65

7.99

2.72

2.35

2.73

1.92

3.16

7.04

Std

3

2

5

3

3

3

1

1

FUSION CONDITIONS

1700

15

A

76.70

0.12

12.42

1.23

0.03

<0.1

0.50

3.74

4.88

<0.01

99.73

VG-568

B(21)

76.48

0.18

12.33

1.24

ND

ND

0.54

3.71

4.89

ND

99.37

1750

10

CV

1.19

15.58

1.65

2.49

12.15

3.11

4.36

Std

1

1

1

1

1

1

1

TABLE 2.—Absolute differences and relative differences (percents of the amounts present) between

the wet chemical and electron microprobe analyses presented in Table 1

Constituent

sio2

TiO2

A12O3

FeO

MgO

CaO

Na2O

K20

Range of

Samples

47.32 -

0.12 -

12.42 -

1.23 -

<0.01 -

0.50 -

1.83 -

0.57 -

Analyzed

(wt %)

76.70

2.87

18.92

12.30

7.60

10.26

4.85

4.89

Average

Absolute

Difference

(wt %)

0.21

0.10

0.14

0.16

0.12

0.09

0.13

0.05

Range

Absolute

Difference

(wt %)

0.09 - 0.64

0.04 - 0.20

0.01 - 0.34

0.01 - 0.45

0.01 - 0.37

0.02 - 0.17

0.02 - 0.18

0.00 - 0.12

Average

Relative

Difference

a)

0.4

12.7

0.9

2.2

2.8

1.9

4 . 5

4 . 5

Range

Relative

Difference

(%)

0.1 - 1.0

2.8 - 50.0

0.1 - 2.3

0.3 - 7.1

0.6 - 7.2

0.2 - 8.0

0.8 - 9.8

0.0 - 9.5
NUMBER 22 51

relative percent the average accuracy is better than

5 for all major components except TiO2 which is

better than 13. The somewhat poorer accuracy in

measuring TiO2 is due in part to some very low

measured concentrations. In such cases a small error

(e.g., 0.06 wt % of TiO2 in sample VG-568) represents as much as 50% relative error. However, the

major part of the error is probably due to the presence of residual or quench Fe-Ti oxides observed in

the form of opaque spots in some glasses. Due to

their very small size a positive identification is

difficult.

Attempts to fuse granitic samples and MgO-rich,

low-silica samples to homogeneous glasses were unsuccessful. USGS samples G-2, GSP-1, and G-l produced very inhomogeneous glasses when less than

100 mesh powders were used. Subsequent testing

showed that if very fine powders are used more

homogeneous glasses result. The required preparation of very fine powders and the increased possibility of Na2O loss on fusion make routine fusion

of high-silica samples impractical. The MgO-rich,

low-silica samples could not be prevented from

growing skeletal olivine crystals during quenching.

Three mineral samples (Table 3) and a sample

of natural rhyolite glass (VG-568, Table 1) were

fused to evaluate: (1) Na^O loss, (2) the behavior

of hydrous minerals during fusion, and (3) the impact of rapid dehydration on the composition of the

resulting glass.

It is clear that prolonged fusion of the samples

results in Na2O loss. But fusion times ranging up to

20 sec produce good glasses with minimal Na^O loss.

The three fusion times used in the fusion of the

Lake County plagioclase sample (Table 3) did not

produce significantly large differences in the Na2O

TABLE 3.—Comparison of analyses of crystalline minerals with analyses of the same minerals

fused for various times (A = electron microprobe analyses of the unfused minerals; B = electron

microprobe analyses of fused minerals; numbers in parentheses are the numbers of point analyses

averaged; C = wet chemical analyses of crystalline mineral recalculated water free, based on

data in Table 1, Jarosewich, Nelen, and Norberg, this volume)

Constituent

SiO2

TiO2

Al2O.j

FeO

MgO

CaO

Na2O

K20

Total

Temp. (°C)

Time (sec)

Lake Co.

USNM

A

(13)

51.29

___

31.07

0.50

___

13.79

3.33

...

99.98

(17)

51.27

30.78

0.50

—

13.70

3.38

.—

99.63

1670

5

Plagioclase

115900

B

(13)

51.04

-__

30.78

0.50

--_

13.64

3.45

—

99.41

1670

(21)

51.30

31.01

0.49

___

13.77

3.30

—

99.87

1730

25

1

A

(14)

55.36

0.37

8.81

4.58

11.69

13.86

4.95

0.15

99.77

Omphacite

JSNM 110607

B

(18)

55.01

0.37

8.69

4.56

12.01

13.64

5.10

0.17

99.55

FUSION CONDITIONS

1700

10

(12)

55.48

0.37

8.60

4.63

12.03

13.67

4.20

0.15

99.13

1730

30

Arenal Hornblende

USNM 111356

C

42.36

1.44

15.81

11.72

14.55

11.80

1.95

0.21

99.84

B

(16)

42.18

1.22

15.56

11.79

14.97

11.63

2.12

0.21

99.68

1670

5
52

SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

concentration. However, the 25 sec fusion probably

records a small Na2O loss, and the 30 sec fusion of

omphacite has clearly resulted in a significant Na2O

loss.

Arenal hornblende frothed extensively during

fusion due to the escape of structural water (1.21 wt

% H2O). The composition of the resulting glass is

very close to the crystalline mineral composition

recalculated water free. Although it was anticipated

that Na2O may be volatilized more rapidly during

H2O release from hydrous minerals, no Na2O loss

was observed in three separate glasses, each produced by 5 sec fusion. The hornblende sample

was not fused longer than 5 sec because the water

present in the mineral facilitates rapid fusion.

No Na2O was lost during the 10 sec fusion of

VG-568. This sample is a natural glass and therefore

provides information only on Na2O stability during

fusion.

Summary and Conclusions

The described fusion technique uses very small

amounts of sample and is rapid. The furnace can

be built and operated inexpensively. When used in

conjunction with an electron microprobe, major

element concentrations can be measured rapidly

and quite accurately for rock samples ranging in

composition from basalts to high-silica andesites.

More mafic samples have a tendency to crystallize

olivine on cooling. Granites and other high-silica,

high-alkali samples produce glasses of high viscosity

preventing homogenization during the short fusion

times necessary to prevent Na2O loss. Fusion of extremely fine powders may decrease the inhomogeneity of the resulting glass and improve the resulting analysis.

In general the fused glasses are sufficiently homogeneous and the electron microprobe is suitably

accurate to allow routine use of the technique. The

average accuracy of better than 5% relative for all

major components except TiO2 (better than 13%)

is quite acceptable.

The rapidity and convenience with which the

samples can be prepared and analyzed allowed major element reconnaissance analyses of rock suites

previously not analyzed due to time and cost factors

involved. The rock powders and the three mineral

samples investigated suggest that if fusion times of

less than 20 sec are used Na2O loss is prevented or

greatly restricted and glasses result that are sufficiently homogeneous to be suitable for microprobe

analysis.

Literature Cited

Bence, A. E., and A. L. Albee

1968. Empirical Correction Factors for Electron Microanalysis of Silicates and Oxides. Journal of Geology,

76:382-403.

Brown, R. W.

1977. A Sample Fusion Technique for Whole Rock

Analysis with the Electron Microprobe. Geochimica

et Cosmochimica Ada, 41:435-438.

Flanagan, F. J.

1973. 1972 Values for International Geochemical Refererence Samples. Geochimica et Cosmochimica Ada,

37:1189-1200.
Microprobe Analyses of Four Natural Glasses and One Mineral:

An Interlaboratory Study of Precision and Accuracy

Eugene Jarosewich, Alan S. Parkes, and Lovell B. Wiggins

ABSTRACT

An interlaboratory study for precision and accuracy

of electron microprobe analyses of four natural

glasses and one mineral is reported in this compilation. The results obtained by the three participating

laboratories are in good agreement with chemical

analysis values (where available) for SiO2, A12O3,

FeO, CaO, and K^O (> 2 wt %). One laboratory shows a considerable bias for Na^O and a

slight bias for MgO. Some results for MnO, K2O

(/—0.2 wt %), and P2O5, considering their low concentrations, are in reasonably good agreement;

others show scatter. In general, considering that

different reference samples and operating parameters were used to obtain these analyses, the correlation of results is encouraging. On the basis of the

available data, however, it is evident that the precision and accuracy of these results cannot be improved much without more elaborate data acquisition techniques.

Introduction

The need for accurate microprobe analyses of

natural glasses is of great importance in the study of

volcanic and deep sea rocks. Melson et al. (1977)

briefly summarized this need, referring specifically

to the analyses of glasses from the Deep Sea Drilling

Project. Since a standardized method for analysis

of such glasses is not available, each laboratory has

developed its own techniques and has been using its

Eugene Jarosewich, Department of Mineral Sciences, National

Museum of Natural History, Smithsonian Institution, Washington, D.C. 20650. Alan S. Parkes, Department of Earth

and Planetary Sciences, Massachusetts Institute of Technology,

Cambridge, Massachusetts 02139. Lovell B. Wiggins, U.S. Geological Survey, Reston, Virginia 22092.

own preferred reference samples for these analyses.

It is rather remarkable that many of the results

obtained on the same or similar samples, using different techniques and reference samples, are generally in good agreement. Occasionally, however,

some of these results exceed accepted analytical

errors. Since more than one institution may participate in the study of volcanic or deep sea rocks and

the analytical data may be used interchangeably for

petrologic studies, it is of utmost importance that

the precision and accuracy of these analyses be determined. As a start in obtaining this type of data,

a set of the same samples has been analyzed by three

laboratories, each using its own standard operating

parameters; these results are compared for precision

and accuracy. The participating laboratories were:

Massachusetts Institute of Technology (MIT),

Smithsonian Institution (SI), and U.S. Geological

Survey (USGS).

The data presented in this paper are meant to

serve primarily as a general guide for the expected

accuracy and precision of microprobe analyses of

glasses; however, they can serve as a guide for such

analyses of minerals as well.

ACKNOWLEDGMENTS.—We would like to acknowledge Drs. W. G. Melson, G. R. Byerly and T. L.

Wright for their suggestions pertaining to this work

and Dr. J. S. Huebner for revising the data. We

would also like to express our appreciation to Ms. J.

Norberg of the Smithsonian Institution for compilation and arrangement of the data.

Experimental Procedure

One disc was prepared containing only one grain

of Kakanui hornblende and only one grain of each

53
54 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

of the following natural glasses:

VG-2 (USNM 111240-52), Basalt with a few rare microphenocrysts of olivine and plagioclase in section, less

than 1%. Chemical analysis, Table 4.

VG-A99 (USNM 113498-1). Basalt from Makaopuhi Lava

Lake, Hawaii (Wright and Okamura, 1977). Microphenocrysts of plagioclase in section, about 1% or less. Chemical analysis, Table 4.

VG-999 (USNM 113155-614). High-titanium ferro-basalt from

DeSteiguer dredge D6, Galapagos Spreading Center

(Byerly et al., 1976). Phenocrysts of plagioclase, augite,

and olivine. Microphenocrysts of plagioclase and augite,

about 10%—15% in section.

VG-D08 (USNM 113154-557). Basalt from DeSteiguer dredge

D5, Galapagos Spreading Center (Byerly et al., 1976).

Phenocrysts of olivine, plagioclase, and minor spinel.

No microphenocrysts in section.

This disc was carbon coated and sent to the three

laboratories for microprobe analysis.

These four glasses were selected because they

represent the approximate elemental ranges encountered in the study of natural basaltic glasses.

Classical chemical analyses are available for Kakanui

hornblende, VG-2, and VG-A99 for comparison with

the microprobe results (see Table 1, Jarosewich,

Nelen, and Norberg, this volume). Although no

chemical analyses are available for VG-999 and

VG-D08, these two samples were included in this

study to obtain additional data on the precision

among the microprobe analyses themselves. The

same grain was analyzed by each laboratory to eliminate the variable of possible inhomogeneities between different grains of the same sample.

Since the primary purpose of this work was to

obtain analytical values for the samples as they are

obtained under the laboratories' normal operating

conditions, the operating parameters (kv, /iA, beam

size, etc.) were not specified. The samples were

analyzed employing the standard operating parameters and reference samples used in each laboratory

(Tables 1, 2).

The precision was obtained by analyzing all samples using Kakanui hornblende as the reference

sample. In this manner discrepancies due to the use

of different reference samples were eliminated and

any deviations could be ascribed to the instrumental parameters. Since Kakanui hornblende is not an

ideal reference sample for obtaining accurate analyses of these glasses, the accuracy was determined by

analyzing these samples using each laboratory's preferred reference samples and comparing results with

the chemical analyses of these glasses. The analytical

results were compiled in the following manner. (1)

Each sample was analyzed several times using

Kakanui hornblende as the reference sample; the

number of individual analyses and the averages are

given in Tables 5-7. (2) The samples were analyzed

several times using each laboratory's preferred reference samples; the number of individual analyses,

the averages, and the type of reference samples used

in these analyses are also given in Table 5-7. (3)

The uncorrected averages obtained using Kakanui

hornblende as the reference sample are summarized

in Table 3 for comparisons of precision; these results indicate the variation of the data due only to

the instrumental variation. (4) Table 4 summarizes

the corrected results obtained using each laboratory's preferred reference samples; comparisons of

TABLE 1.—Instrumental parameters used by participating laboratories

Laboratory

MIT

SI

USGS

Instrument

ETEC MAC 5

ARL-SEMQ

9 spectrometers

ARL-EXM-SM

Accelerating

Potential

(kV)

15

15

15

Sample

Current

(yA)

0o03

0o05

0.05

Beam Size

(ym)

4

2, 30

20

Counting Time

30 sec or 60,000 counts

Seven 10 sec counts for

each analysis

20 sec or 20,000 counts

for each element
NUMBER 22 55

TABLE 2.—Analyses of reference samples used by participating laboratories

Reference sample

DJ35

P-140

AN-60

MAC AP

Orthoclase

Di2Ti

Mnllm

Coss

Kak hornblende

VG-2

Apatite

Fayalite

Rhodonite

Garnet-Pyrope

Orthoclase

Di2Ti

Diopside-Jadeite

SiO2

56.88

40.86

53.05

0.05

64.39

54.36

40.93

40.37

50.81

0.34

29.22

46.76

41.45

63.42

54.39

56.10

A 12°3

8.82

30.01

18.58

14.90

14.06

0.07

0.96

23.50

19.24

3.78

FeO

7.23

0.03

45.41

40.99

10.92

11.83

0.05

67.54

12.49

10.76

0.10

MgO

12.10

51.63

0.01

18.26

0.25

12.80

6.71

"0.42

18.80

18.26

15.84

CaO

MET

16.83

12.38

38.82

25.38

SI

10.30

11.12

54.02

USGS

5.62

5.09

0.08

25.38

22.02

Na2O

5.36

4.56

0.18

1.14

6.93

2.60

2.62

0.23

0.36

2.31

K

14

2

0

15

2°

.92

.05

.19

.34

TiO2

2.00

51.61

8.71

4.36

1.85

0.04

0.51

2.00

P

17

0

40

0

2°5

.86

.20

.78

.49

MnO

1.50

0.09

0.22

2.14

33.34

0.33

these results with the chemical values indicate the

accuracy of the microprobe results.

Discussion

Comparisons for precision of the results obtained

using Kakanui hornblende as the reference sample

(Table 3) indicate that careful microprobe analyses

for all major elements, titanium, and high potassium (>2 wt %) produce relatively precise results.

The results also indicate that minor elements and

sodium vary considerably and more careful work

must be done if the results for these elements are to

be used for exacting petrological work. There is no

pronounced bias in the results by any of the three

laboratories for the major elements except for a

slight bias in the magnesium results. There is a

bias in the results for sodium, low potassium

(~0.2 wt %), and phosphorus. The sodium and

phosphorus results analyzed by laboratory 1 run

consistently high. The potassium results by laboratory 2 run slightly high and by laboratory 3, low.

The discrepancy for these three elements is significant because all elements were determined using

the same reference sample, indicating that the techniques for acquiring the data should be examined.

Comparisons for precision of the results of microprobe analyses in which each laboratory's preferred

reference samples were used (Table 4) also check

favorably for the major elements, titanium, and

potassium (> 2 wt %); more important, these results are in excellent agreement with the values for

the three samples analyzed by classical chemical

methods, thus showing a high level of accuracy. The

results for sodium show a much larger discrepancy

than those given in Table 3; only the lowest values

of the microprobe analyses check well with the

chemically analyzed sodium values. Sodium frequently presents a problem in microprobe analysis

and to demonstrate this problem, laboratory 2 analyzed sodium using a 2 /im beam and a 30 /on beam;

the former gives somewhat lower values for some

samples (Table 6, results in brackets), the latter

gives acceptable values. Kakanui hornblende sodium results are not affected by the beam size. One

of the possible explanations for the higher results

of laboratory 1 and lower results of laboratory 2

with the small beam is the unique behavior of

sodium in the electron beam for both the reference

samples and the unknown samples. If for example

a reference sample in which sodium is easily "volatilized" (accepted description of decreasing inten-
56 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

TABLE 3.—Summary of uncorrected data from microprobe analyses of the 5 samples, using

Kakanui hornblende as the reference sample, for interlaboratory comparison of precision (figure

in parentheses indicates number of analyses averaged; each analysis represents up to 10 individual

point analyses; laboratory 1 = MIT, 2 = SI, 3 = USGS; data based on Tables 5-7)

Constituent

SiO2

A 1 2°3

FeO

MgO

CaO

Na2O

K20

TiO2

P

2°5

MnO

Lab

1

2

3

1

2

3

1

2

3

1

2

3

1

2

3

1

2

3

1

2

3

1

2

3

1

2

3

1

2

3

KH

40.45

40.58

40.31

14.88

14.97

14.98

10.85

10.91

10.81

12.83

12.67

12.92

10.20

10.39

10.24

2.74

2.59

2.67

2.02

2.05

1.96

4.36

4.38

4.27

0.09

0.06

0.08

0.07

0.09

0.19

(2)

(4)

(3)

(2)

(4)

(3)

(2)

(4)

(3)

(2)

(4)

(3)

(2)

(4)

(3)

(2)

(2)

(3)

(2)

(4)

(3)

(2)

(4)

(3)

(2)

(2)

(3)

(2)

(2)

(3)

VG-2

51.07

51.62

51.05

14.69

15.06

14.85

11.96

11.84

11.78

7.02

6.90

6.87

11.12

11.16

11.01

2.90

2.65

2.78

0.18

0.20

0.06

1.66

1.67

1.64

0.24

0.20

0.20

0.16

0.18

0.25

(2)

(4)

(4)

(2)

(4)

(4)

(2)

(4)

(4)

(2)

(4)

(4)

(2)

(4)

(4)

(2)

(2)

(4)

(2)

(4)

(4)

(2)

(4)

(4)

(2)

(2)

(4)

(2)

(2)

(4)

VG-A99

52.49

52.45

52.54

13.23

13.54

13.13

13.57

13.60

13.46

5.29

4.98

4.99

9.38

9.29

8.80

2.91

2.71

2.71

0.77

0.83

0.72

3.65

3.70

3.77

0.44

0.39

0.42

0.16

0.18

0.22

(1)

(4)

(2)

(1)

(4)

(2)

(1)

(4)

(2)

(1)

(4)

(2)

(1)

(4)

(2)

(1)

(2)

(2)

(1)

(4)

(2)

(1)

(4)

(2)

(1)

(2)

(2)

(1)

(2)

(2)

VG-999

52.27

52.21

51.88

13.61

14.12

14.41

13.79

13.71

13.66

5.98

5.81

5.57

10.39

10.40

10.26

2.89

2.60

2.66

0.14

0.17

0.03

1.72

1.74

1.66

0.22

0.19

0.17

0.17

0.20

0.13

(2)

(4)

(1)

(2)

(4)

(1)

(2)

(4)

(1)

(2)

(4)

(1)

(2)

(4)

(1)

(2)

(2)

(1)

(2)

(4)

(1)

(2)

(4)

(1)

(2)

(2)

(1)

(2)

(2)

(1)

VG-D08

50.17

50.56

50.36

16.60

17.27

16.71

9.00

8.97

8.88

9.36

8.71

8.70

12.48

12.39

12.13

2.77

2.38

2.40

0.06

0.08

0.00

0.98

1.01

0.92

0.16

0.12

0.12

0.16

0.14

0.16

(1)

(4)

(2)

(1)

(4)

(2)

(1)

(4)

(2)

(1)

(4)

(2)

(1)

(4)

(2)

(1)

(2)

(2)

(1)

(4)

(2)

(1)

(4)

(2)

(1)

(2)

(2)

(1)

(2)

(2)

slty) is used for standardization to analyze an

unknown sample which does not show this volatilization effect, the sodium results for the unknown

sample will be high. If on the other hand the sodium in the reference sample is "stable" and sodium

in the unknown sample is easily volatilized, low results will be obtained. The use of a larger beam size

may diminish this discrepancy.

Low potassium, manganese, and phosphorus results vary just as much as those in Table 3. It

should be noted that phosphorus corrects up by

15%-20% in most cases, giving much higher values

than those of the chemical analyses. These higher

phosphorus corrections are evident with both the

up-dated Bence-Albee (Albee and Ray, 1970) and

Magic IV correction procedures. Both correction

procedures performed by one of us (A. P.) give excellent agreement with each other for all elements

(Table 5).

Since for this study some grains were analyzed up
NUMBER 22 57

TABLE 4.—Summary of corrected data from microprobe analyses of the 5 samples using each

laboratory's preferred reference samples, along with chemical analyses of 3 of the samples, for

interlaboratory comparison of precision and accuracy (figures in parentheses indicates number of

analyses averaged; each analysis represents up to 10 individual point analyses; laboratory

1 = MIT, 2 = SI, 3 = USGS; Chem. = chemical analysis from Table 1, Jarosewich, Nelen, and

Norberg, this volume; microprobe data based on Tables 5-7)

Constituent Lab

SiO9

Z

Al90o

Z j

FeO

MgO

CaO

Nao0

z

K00

z

TiOo

z

P9 0

MnO

1

2

3

(Chem.)

1

2

3

(Chem.)

1

2

3

(Chem.)

1

2

3

(Chem.)

1

2

3

(Chem.)

1

2

3

(Chem.)

1

2

3

(Chem.)

1

2

3

(Chem.)

1

2

3

(Chem.)

1

2

3

(Chem.)

KH

40.65

40.72

40.42

40.37

14.61

14.95

14.76

14.90

10.45

10.93

10.54

10.92

12.95

12.70

13.03

12.80

9.99

10.47

10.12

10.30

2.80

2.60

2.72

2.60

2.10

2.06

1.94

2.05

4.87

4.40

4.65

4.36

0.14

0.07

0.04

0.00

0.10

0.11

0.06

0.09

(5)

(4)

(2)

(5)

(4)

(2)

(5)

(4)

(2)

(5)

(4)

(2)

(5)

(4)

(2)

(5)

(2)

(2)

(5)

(4)

(2)

(5)

(4)

(2)

(5)

(2)

(2)

(5)

(2)

(2)

VG-2

50.85

50.72

50.75

50.81

13.81

14.15

13.98

14.06

11.26

11.79

11.79

11.83

7.01

6.78

7.02

6.71

10.85

11.14

10.72

11.12

3.17

2.66

2.75

2.62

0.20

0.21

0.18

0.19

1.86

1.91

1.86

1.85

0.32

0.23

0.19

0.20

0.22

0.22

0.23

0.22

(1)

(4)

(1)

(1)

(4)

(1)

(1)

(4)

(1)

(1)

(4)

(1)

(1)

(4)

(1)

(1)

(2)

(1)

(1)

(4)

(1)

(1)

(4)

(1)

(1)

(2)

(1)

(1)

(2)

(1)

VG-A99

51.05

51.22

50.80

50.90

12.59

12.66

12.80

12.97

13.24

13.47

13.41

13.18

5.24

4.95

5.16

5.18

9.08

9.28

8.97

9.38

2.81

2.70

2.73

2.73

0.82

0.90

0.76

0.80

4.04

4.05

3.77

4.06

0.54

0.46

0.31

0.41

0.19

0.22

0.19

0.19

(4)

(4)

(1)

(4)

(4)

(1)

(4)

(4)

(1)

(4)

(4)

(1)

(4)

(4)

(1)

(4)

(2)

(1)

(4)

(4)

(1)

(4)

(4)

(1)

(4)

(2)

(1)

(4)

(2)

(1)

VG-999

51.16

51.41

50.70

13.06

13.36

13.54

12.94

13.68

13.30

5.99

5.77

6.13

10.12

10.36

10.18

3.06

2.61

2.57

0.14

0.19

0.04

1.93

1.96

1.80

0.29

0.22

0.15

0.29

0.25

0,20

(1)

(4)

(1)

(1)

(4)

(1)

(1)

(4)

(1)

(1)

(4)

(1)

(1)

(4)

(1)

(1)

(2)

(1)

(1)

(4)

(1)

(1)

(4)

(1)

(1)

(2)

(1)

(1)

(2)

(1)

VG-D08

50.29

50.18

49.77

15.80

16.17

15.44

8.67

8.96

8.78

8.88

8.46

8.78

12.23

12.41

12.05

2.79

2.25

2.39

0.07

0.09

0.09

1.09

1.14

1.03

0.23

0.15

0.08

0.18

0.17

0.13

(1)

(4)

(1)

(1)

(4)

(1)

(1)

(4)

(1)

(1)

(4)

(1)

(1)

(4)

(1)

(1)

(2)

(1)

(1)

(4)

(1)

(1)

(4)

(1)

(1)

(2)

(1)

(1)

(2)

(1)
58

SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

TABLE 5.—MIT laboratory individual analyses of Kakanui hornblende and 4 natural glasses

using Kakanui hornblende as reference sample and also the laboratory's preferred reference

samples

Run No.

1

2

4

5a

5b

6

8

1

Conditions

Standards

Uncorrected

B-A Corr.

Magic IV Corr.

a (5)

Uncorrected

B-A Corr.

Magic IV Corr.

a (6)

Standards

Uncorrected

B-A Corr.

Magic IV Corr.

o (10)

Uncorrected

B-A Corr.

Magic IV Corr.

o (5)

Uncorrected

B-A Corr.

Magic IV Corr.

a (5)

Standards

Uncorrected

B-A Corr.

Magic IV Corr.

a (10)

Standards

Uncorrected

B-A Corr.

Magic IV Corr.

a (10)

Standards

Uncorrected

B-A Corr.

Magic IV Corr.

a (10)

SiO2

KH

40.39

40.35

40.35

0.17

40,51

40.55

40.56

0.53

DJ35

38.21

40.29

40.36

0.34

38.92

40.97

41.07

0.21

38.71

40.75

40.85

0.32

DJ35

38.32

40.43

40.52

0.30

DJ35

38.71

40.82

40.92

0.19

KH

51.36

49.98

50.08

0.51

A12 O3

KH

14.69

14.68

14.68

0.11

15.07

15.07

15.08

0.08

AN-60

12.61

14.45

14.54

0.08

12.66

14.48

14.57

0.08

12.68

14.50

14.59

0.08

AN-60

12.83

14.71

14.80

0.09

AN-60

13.00

14.89

14.97

0.09

KH

14.51

14.03

14.03

0.13

FeO

KH

10.99

10.99

10.99

0.15

10.70

10.71

10.70

0.22

P-140

10.48

10.37

10.43

0.27

10.34

10.23

10.29

0.12

10.29

10.18

10.24

0.13

Coss.

10.26

10.68

10.60

0.12

Cost..

10.35

10.. 77

10.70

0.18

KH

12.15

12.15

12.15

0.14

MgO

Kakanui

KH

12.57

12.59

12.59

0.13

13.09

13.08

13.07

0.22

P-140

11.68

12.98

13.04

0.26

11.58

12.86

12.88

0.13

11.51

12.78

12.82

0.17

DJ35

12.38

13.10

13.18

0.10

DJ35

12.34

13.05

13.14

0.15

KH

6.83

6.89

6.88

0.08

CaO Na2O

hornblende

KH

10.13

10.13

10.13

0.15

10.27

10.28

10.28

0.07

DJ35

10.11

9.92

9.96

0.14

10.20

10.02

10.05

0.18

10.18

9.99

10.03

0.13

DJ35

10.18

9.98

10.02

0.07

DJ35

10.23

10.04

10.09

0.10

VG-2

KH

11.03

11.03

11.04

0.08

KH

2.71

2.71

2.71

0.12

2.77

2.76

2.75

0.12

DJ35

2.55

2.87

2.90

0.09

2.55

2.86

2.89

0.11

2.59

2.91

2.93

0.08

DJ35

2.49

2.80

2.83

0.11

DJ35

2.29

2.57

2.60

0.07

KH

2.82

2.84

2.84

0.11

K20

KH

2.03

2.03

2.04

0.02

2.00

2.00

2.00

0.04

Ortho

2.10

2.05

2.05

0.02

2.16

2.11

2.10

0.04

2.15

2.10

2.09

0.04

Ortho

2.16

2.11

2.10

0.05

Ortho

2.16

2.11

2.10

0.05

KH

0.19

0.20

0.19

0.00

TiO2

KH

4.34

4.34

4.35

0.03

4.37

4.38

4.37

0.03

Di2Ti

5.13

4.94

4.94

0.08

5.05

4.87

4.87

0.05

5.11

4.92

4.93

0.05

Di2Ti

5.03

4.84

4.85

0.05

Mnllm

4.20

4.79

4.73

0.05

KH

1.67

1.67

1.67

0.02

p2 o5

AP

0.10

0.12

0.12

0.00

0.08

0.10

0.12

0.00

MAC AP

0.10

0.12

0.12

0.00

0.11

0.13

0.15

0.00

0.11

0.15

0.15

0.00

MAC AP

0.11

0.15

0.15

0.02

MAC AP

0.13

0.16

0,15

0.00

AP

0.23

0.30

0.30

0.02

MnO

KH

0.04

0.04

0.05

0.01

0.10

0.10

0.10

0.03

Mnllm

0.10

0.11

0.11

0.03

0.12

0.13

0.12

0.01

0.11

0.12

0.12

0.03

Mnllm

0.04

0.04

0.04

0.04

Mnllm

0.11

0.11

0.11

0.03

KH

0.14

0.14

0.14

0.04
NUMBER 22

59

Table 5.—Continued

Run No.

2

5

2

4

5

6

8

Conditions

Uncorrected

B-A Corr.

Magic IV Corr.

a (10)

Standards

Uncorrected

B-A Corr.

Magic IV Corr.

o (6)

Standards

Uncorrected

B-A Corr.

Magic IV Corr.

a (10)

Standards

Uncorrected

B-A Corr.

Magic IV Corr.

a (10)

Uncorrected

B-A Corr.

Magic IV Corr.

o (10)

Standards

Uncorrected

B-A Corr.

Magic IV Corr.

o (5)

Standards

Uncorrected

B-A Corr.

Magic IV Corr.

a (10)

SiO2

50.77

49.52

49.61

0.41

DJ35

49.61

50.85

51.05

0.83

KH

52.49

50.68

50.84

0.43

DJ35

50.22

51.03

51.30

0.28

50.25

51.00

51.42

0.49

DJ35

50.32

51.17

51.43

0.32

DJ35

50.09

50.99

51.26

0.53

A12 O3

14.87

14.39

14.39

0.19

AN-60

12.49

13.81

13.88

0.13

KH

13.23

12.78

12.78

0.15

AN-60

11.18

12.36

12.44

0.09

11.20

12.34

12.44

0.08

AN-60

11.50

12.71

12.78

0.06

AN-60

11.73

12.95

13.03

0.11

FeO

11.76

11.77

11.76

0.18

P-140

11.39

11.26

11.33

0.14

KH

13.57

13.53

13.55

0.09

P-140

13.25

13.06

13.16

0.19

12.85

12.68

12.77

0.18

Coss.

13.11

13.61

13.53

0.19

Coss.

13.09

13.59

13.50

0.14

MgO

7.21

7.26

7.25

0.10

P-140

6.27

7.01

7.02

0.06

KH

5.29

5.42

5.41

0.08

P-140

4.61

5.24

5.26

0.10

4.54

5.16

5.17

0.07

DJ35

4.88

5.27

5.31

0.03

DJ35

4.88

5.27

5.30

0.10

CaO

11.20

11.20

11.21

0.07

DJ35

11.05

10.85

10.91

0.08

VG-A99

KH

9.38

9.36

9.37

0.10

DJ35

9.11

8.91

8.96

0.06

9.24

9.04

9.10

0.08

DJ35

9.29

9.08

9.14

0.01

DJ35

9.51

9.30

9.36

0.11

Na2O

2.97

2.99

2.99

0.12

DJ35

2.80

3.17

3.19

0.11

KH

2.91

2.99

2.99

0.08

DJ35

2.63

3.05

3.08

0.08

2.55

2.95

2.98

0.15

DJ35

2.24

2.61

2.63

0.11

DJ35

2.24

2.61

2.63

0.12

K20

0.17

0.17

0.17

0.01

Ortho

0.20

0.20

0.20

0.00

KH

0.77

0.77

0.77

0.02

Ortho

0.84

0.82

0.82

0.01

0.84

0.83

0.82

0.02

Ortho

0.83

0.81

0.81

0.02

Ortho

0.85

0.83

0.83

0.02

TiO2

1.65

1.66

1.65

0.03

Di2Ti

1.93

1.86

1.86

0.07

KH

3.65

3.64

3.64

0.03

Di2Ti

4.30

4.12

4.12

0.05

4.28

4.10

4.11

0.05

Di2Ti

4.27

4.08

4.09

0.05

Mnllm

3.41

3.87

3.83

0.07

P2°5

0.24

0.31

0.33

0.00

MAC AP

0.25

0.32

0.33

0.02

AP

0.44

0.56

0.56

0.02

MAC AP

0.42

0.54

0.53

0.02

0.41

0.53

0.53

0.02

MAC AP

0.43

0.55

0.56

0.00

MAC AP

0.42

0.54

0.53

0.02

MnO

0.18

0.18

0.18

0.04

Mnllm

0.20

0.22

0.22

0.03

KH

0.16

0.16

0.15

0.03

Mnllm

0.19

0.20

0.20

0.03

0.17

0.18

0.18

0.03

Mnllm

0.18

0.20

0.19

0.01

Mnllm

0.16

0.18

0.18

0.03
60 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

Table 5.—Continued

Run No.

1

2

5

2

5

Conditions

Standards

Uncorrected

B-A Corr.

Magic IV Corr.

a (5)

Uncorrected

B-A Corr.

Magic IV Corr.

o (10)

Standards

Uncorrected

B-A Corr.

Magic IV Corr.

o (10)

Standards

Uncorrected

B-A Corr.

Magic IV Corr.

a (10)

Standards

Uncorrected

B-A Corr.

Magic IV Corr.

o (10)

SiO2

KH

52.20

50.64

50.79

0.34

52.34

50.77

50.91

0.68

DJ35

50.07

51.16

51.42

0.45

KH

50.17

49.25

49.30

0.43

TXT35

48.68

50.29

50.43

0.60

A12 O3

KH

13.66

13.24

13.24

0.17

13.56

13.15

13.16

0.42

AN-60

11.80

13.06

13.16

0.08

KH

16.60

16.02

16.06

0.55

AN-60

14.35

15.80

15.86

0.06

FeO

KH

14.03

13.99

14.01

0.20

13.55

13.52

13.53

0.17

P-140

13.11

12.94

13.03

0.17

KH

9.00

9.04

9.04

0.09

P-140

8.73

8.67

8.72

0.10

MgO

KH

5.85

5.97

5.98

0.05

6.11

6.24

6.24

0.07

P-140

5.30

5.99

6.02

0.07

KH

9.36

9.20

9.20

0.18

P-140

8.13

8.88

8.88

0.12

CaO

VG-999

KH

10.23

10.21

10.24

0.07

10.54

10.52

10.54

0.08

DJ35

10.33

10.12

10.17

0.06

VG-D08

KH

12.48

12.53

12.54

0.08

DJ35

12.41

12.23

12.29

0.06

Na2O

KH

2.75

2.82

2.82

0.09

3.02

3.09

3.08

0.09

DJ35

2.66

3.06

3.09

0.20

KH

2.77

2.70

2.70

0.09

DJ35

2.55

2.79

2.81

0.12

K2°

KH

0.15

0.15

0.16

0.00

0.13

0.13

0.13

0.00

Ortho

0.14

0.14

0.14

0.01

KH

0.06

0.07

0.06

0.01

Ortho

0.07

0.07

0.07

0.00

TiO2

KH

1.70

1.69

1.70

0.03

1.73

1.73

1.73

0.03

Di2Ti

2.01

1.93

1.94

0.03

KH

0.98

0.99

0.99

0.03

Di2Ti

1.12

1.09

1.08

0.03

*2°5

AP

0.21

0.27

0.27

0.02

0.23

0.30

0.30

0.00

MAC AP

0.22

0.29

0.30

0.02

AP

0.16

0.21

0.21

0.00

MAC AP

0.18

0.23

0.24

0.02

MnO

KH

0.13

0.13

0.13

0.01

0.20

0.20

0.21

0.03

Mnllm

0.27

0.29

0.29

0.03

KH

0.16

0.16

0.17

0.03

Mnllm

0.17

0.18

0.18

0.03

to 40 times to obtain good precision, it is reasonable

to assume that, on the basis of the data in Table 3,

the precision of microprobe analyses of basaltic

glasses cannot be much improved without more

elaborate data acquisition techniques. The standard

deviations for various elements given in Tables 5-7

are of similar magnitudes for the three laboratories

and they realistically indicate the expected scatter

of analytical results. It is obvious that longer counts

would not improve the precision very much and,

indeed, extended counting times are impractical in

day-to-day operation.

The accuracy, on the other hand, can be in some

cases improved by the selection of suitable reference

samples for a given unknown sample. From the data

in Tables 5-7 it is evident that the microprobe results for some elements are in better agreement

with the chemical results when reference samples

other than Kakanui hornblende are used. The

standard deviation here again is similar to that of

the precision and thus could also be used as an

indication of the expected scatter of the results.

Analysis of elements below 0.1 wt % should be done

with extra care and accepted with caution.
NUMBER 22 61

TABLE 6.—SI laboratory individual analyses of Kakanui hornblende and 4 natural glasses using

Kakanui hornblende as reference sample and also the laboratory's preferred reference samples

Run No.

1

2

3

4

1

2

3

4

1

2

3

Conditions

Standards

Uncorrected

B-A Corr.

a (7)

Uncorrected

B-A Corr.

a (7)

Uncorrected

B-A Corr.

o (7)

Uncorrected

B-A Corr.

a (7)

Standards

Uncorrected

B-A Corr.

o (7)

Uncorrected

B-A Corr.

a (7)

Uncorrected

B-A Corr.

o (7)

Uncorrected

B-A Corr.

a (7)

Standards

Uncorrected

B-A Corr.

a (7)

Uncorrected

B-A Corr.

a (7)

Uncorrected

B-A Corr.

a (7)

SiO2

KH

41.09

41.09

0.49

40.45

40.46

0.28

40.03

40.13

0.38

40.76

40.76

0.23

KH

41.09

41.09

0.49

40.45

40.46

0.28

40.44

40.51

0.17

40.83

40.83

0.37

KH

52.04

51.18

0.42

51.32

50.49

0.73

50.89

50.19

0.48

A12O3

KH

15.05

15.02

0.23

14.83

14.82

0.24

14.95

14.98

0.21

15.06

15.02

0.28

KH

15.05

15.02

0.23

14.83

14.82

0.24

15.00

15.02

0.20

14.95

14.92

0.22

KH

15.10

14.55

0.18

14.90

14.38

0.16

15.12

14.64

0.19

FeO

KH

10.87

10.88

0.26

11.11

11.11

0.27

10.88

10.88

0.12

10.76

10.77

0.08

KH

10.87

10.88

0.26

11.11

11.11

0.27

10.95

10.96

0.14

10.76

10.76

0.07

KH

12.01

12.03

0.10

12.01

12.03

0.07

11.82

11.83

0.11

MgO

Kakanui

KH

12.78

12.75

0.43

12.60

12.60

0.38

12.79

12.83

0.26

12.51

12.49

0.21

KH

12.78

12.75

0.43

12.60

12.60

0.38

12.77

12.82

0.17

12.63

12.61

0.25

KH

6.85

6.87

0.19

7.00

7.03

0.09

6.91

6.98

0.21

CaO Na2O

hornblende

KH

10.70

10.72

0.26

10.22

10.24

0.04

10.22

10.23

0.07

10.40

10.42

0.14

KH

10.70

10.72

0.26

10.22

10.24

0.09

10.28

10.30

0.11

10.57

10.60

0.14

VG-2

KH

11.22

11.32

0.13

11.19

11.29

0.14

10.96

11.06

0.17

KH

T.51"

2.58

0.08

2.60

2.59

_0.0_7.

2.60

2.60

0.02

2.58

2.58

0.01

KH

T.58"

2.58

0.08

2.60

2.59

0_.0_7_

2.62

2.62

0.04

2.58

2.57

0.03

KH

F.53

2.53

0.11

2,53

2.53

.0.06

2.69

2.69

0.03

K20

KH

*1.98

1.98

0.08

2.13

2.13

0.07

2.04

2.04

0.05

2.05

2.05

0.06

KH

1.98

1.98

0.08

2.13

2.13

0.07

2.03

2.03

0.04

2.08

2.08

0.06

KH

0.19

0.19

0.02

0.20

0.20

0.02

0.21

0.21

0.02

TiO2

KH

4.33

4.34

0.12

4.45

4.45

0.11

4.43

4.43

0.04

4.29

4.30

0.07

KH

4.33

4.34

0.12

4.45

4.45

0.11

4.51

4.51

0.09

4.30

4.30

0.06

KH

L.67

1.68

0.07

1.71

1.72

0.01

1.69

1.70

0.03

P2°5

AP

0.05

0.07

0.02

0.06

0.07

0.02

AP

0.05

0.07

0.02

0.06

0.07

0.02

AP

i

0.20

0.25

0.03

0.19

0.24

0.03

MnO

KH

0.09

0.09

0.01

0.09

0.09

0.01

Fay

0.11

0.12

0.03

0.10

0.10

0.02

KH

0.17

0.17

0.02
62 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

Table 6.—Continued

Run No.

4

1

2

3

4

1

2

3

4

1

2

Conditions

Uncorrected

B-A Corr.

a (7)

Standards

Uncorrected

B-A Corr.

a (7)

Uncorrected

B-A Corr.

a (7)

Uncorrected

B-A Corr.

a (7)

Uncorrected

B-A Corr.

o (7)

Standards

Uncorrected

B-A Corr.

a (7)

Uncorrected

B-A Corr.

o (7)

Uncorrected

B-A Corr.

o (7)

Uncorrected

B-A Corr.

o (7)

Standards

Uncorrected

B-A Corr.

a (7)

Uncorrected

B-A Corr.

° (7)

SiO2

52.21

51.32

0.43

VG-2

50.56

50.57

0.48

50.69

50.71

0.51

50.93

50.99

0.59

50.52

50.60

0.61

KH

52.56

51.39

0.45

52.76

51.53

0.29

51.65

50.63

0.66

52.82

51.63

0.58

VG-2

51.08

50.78

0.75

51.71

51.38

0.28

A12O3

15.11

14.55

0.19

VG-2

14.14

14.13

0.25

14.08

14.08

0.26

14.15

14.16

0.19

14.21

14.23

0.24

KH

13.72

13.19

0.12

13.51

12.99

0.22

13.47

13.03

0.27

13.46

12.96

0.24

VG-2

12.68

12.65

0.23

12.65

12.62

0.20

FeO

11.53

11.55

0.09

VG-2

11.72

11.73

0.15

11.54

11.56

0.09

11.87

11.88

0.19

11.99

12.00

0.11

KH

13.90

13.88

0.08

13.59

13.57

0.06

13.62

13.59

0.12

13.30

13.29

0.17

VG-2

13.48

13.45

0.08

13.42

13.39

0.26

MgO

6.83

6.85

0.12

VG-2

6.57

6.57

0.11

7.01

6.99

0.15

6.69

6.70

0.11

6.83

6.84

0.08

KH

4.89

4.97

0.20

4.98

5.06

0.11

5.07

5.19

0.13

4.98

5.06

0.10

VG-2

4.78

4.83

0.06

4.95

5.00

0.44

CaO

11.28

11.39

0.14

VG-2

11.10

11.11

0.09

11.18

11.19

0.13

11.13

11.13

0.16

11.13

11.13

0.18

VG-A99

KH

9.30

9.36

0.08

9.34

9.38

0.18

9.07

9.10

0.17

9.46

9.50

0.08

VG-2

9.18

9.13

0.04

9.36

9.32

0.45

Na2O

2.60

2.59

0.03

VG-2

T.62

2.62

0.11

2.47

2.46

JD.21

2.64

2.65

0.06

2.66

2.66

0.05

KH

T.3T

2.37

0.10

2.22

2.26

2.72

2.75

0.03

2.70

2.75

0.03

VG-2

2~.4T

2.47

0.17

2.27

2.32

0.10

K20

0.20

0.20

0.03

VG-2

0.22

0.21

0.02

0.22

0.21

0.02

0.23

0.22

0.07

0.22

0.21

0.03

KH

0.84

0.84

0.12

0.82

0.83

0.04

0.80

0.81

0.02

0.84

0.85

0.02

VG-2

0.93

0.90

0.06

0.91

0.88

0.04

TiO2

1.62

1.63

0.05

VG-2

1.94

1.94

0.06

1.92

1.93

0.05

1.92

1.92

0.03

1.85

1.85

0.07

KH

3.66

3.66

0.06

3.68

3.68

0.03

3.81

3.81

0.10

3.65

3.66

0.06

VG-2

4.05

4.02

0.09

4.12

4.09

0.11

p2 o5

AP

0.19

0.24

0.02

0.18

0.22

0.03

AP

0.37

0.45

0.04

0.41

0.51

0.04

AP

0.38

0.47

0.04

0.37

0.45

0.01

MnO

0.18

0.18

0.02

Fay

0.20

0.22

0.02

0.19

0.22

0.02

KH

0.18

0.18

0.02

0.18

0.18

0.02

Fay
NUMBER 22

Table 6.—Continued

Run No.

3

4

1

2

3

4

1

2

3

4

Conditions

Uncorrected

B-A Corr.

CT (7)

Uncorrected

B-A Corr.

o (7)

Standards

Uncorrected

B-A Corr.

o (7)

Uncorrected

B-A Corr.

o (7)

Uncorrected

B-A Corr.

a (7)

Uncorrected

B-A Corr.

° (7)

Standards

Uncorrected

B-A Corr.

° (7)

Uncorrected

B-A Corr.

° (7)

Uncorrected

B-A Corr.

a (7)

Uncorrected

B-A Corr.

a (7)

SiO2

51.77

51.51

0.90

51.46

51.21

0.62

KH

52.46

51.47

0.70

52.17

51.20

0.77

51.89

51.02

0.61

52.31

51.35

0.44

VG-2

51.64

51.52

0.58

51.77

51.67

0.64

51.46

51.42

0.38

51.06

51.04

0.41

A12O3

12.74

12.72

0.22

12.64

12.65

0.13

KH

14.22

13.69

0.29

14.04

13.54

0.18

14.01

13.55

0.07

14.20

13.69

0.17

VG-2

13.32

13.30

0.13

13.35

13.34

0.22

13.37

13.37

0.10

13.39

13.42

0.03

FeO

13.39

13.36

0.11

13.73

13.69

0.14

MgO

4.83

4.89

0.11

5.00

5.07

0.14

VG-999

KH

13.91

13.89

0.11

13.76

13.75

0.13

13.59

13.58

0.03

13.56

13.55

0.13

VG-2

13.53

13.51

0.17

13.59

13.56

0.20

13.75

13.73

0.07

13.95

13.92

0.09

KH

5.71

5.77

0.11

5.96

6.03

0.06

5.83

5.93

0.15

5.72

5.80

0.11

VG-2

5.57

5.62

0.10

5.85

5.89

0.16

5.66

5.72

0.17

5.80

5.86

0.20

CaO

9.38

9.31

0.12

9.41

9.35

0.14

KH

10.59

10.66

0.19

10.43

10.50

0.03

10.10

10.17

0.13

10.47

10.54

0.07

VG-2

10.30

10.28

0.11

10.43

10.42

0.10

10.33

10.29

0.15

10.46

10.43

0.22

Na2O

2.64

2.70

0.03

2.63

2.69

0.06

KH

T.31

2.35

0.11

2.32

2.36

£.•92.

2.60

2.63

0.01

2.60

2.63

0.05

VG-2

rr.4ir

2.52

0.11

2.38

2.41

2.54

2.57

0.09

2.60

2.65

0.06

K20

0.94

0.91

0.04

0.92

0.89

0.04

KH

0.16

0.16

0.03

0.17

0.17

0.02

0.18

0.18

0.03

0.16

0.16

0.00

VG-2

0.21

0.20

0.02

0.16

0.16

0.02

0.20

0.20

0.03

0.18

0.18

0.03

TiO2

4.05

4.03

0.17

4.08

4.05

0.14

KH

1.71

1.71

0.06

1.75

1.75

0.08

1.75

1.76

0.07

1.73

1.73

0.03

VG-2

1.93

1.93

0.06

2.00

1.99

0.04

1.97

1.96

0.09

1.95

1.94

0.03

P2°5

AP

0.19

0.23

0.00

0.18

0.22

0.02

AP

0.18

0.22

0.03

0.18

0.22

0.03

MnO

0.19

0.21

0.02

0.20

0.22

0.01

KH

0.19

0.19

0.02

0.20

0.20

0.02

Fay

0.21

0.24

0.02

0.22

0.25

0.02

The data in Tables 5-7 contain a wealth of information for statistical evaluation that is beyond

the scope of this paper. One point, however, should

be emphasized: there is a general apprehension on

the part of the staff responsible for the microprobe

analyses regarding use of the observed standard deviation of a single day's analyses, based on one

standardization, as a measure of precision. Since

most microprobe users complete the analysis of a

particular mineral within one day, this is often the
64

SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

Table 6.—Continued

Run No.

1

2

3

4

1

2

3

4

Conditions

Standards

Uncorrected

B-A Corr.

a (7)

Uncorrected

B-A Corr.

a (7)

Uncorrected

B-A Corr.

a (7)

Uncorrected

B-A Corr.

a (7)

Standards

Uncorrected

B-A Corr.

a (7)

Uncorrected

B-A Corr.

a (7)

Uncorrected

B-A Corr.

o (7)

Uncorrected

B-A Corr.

o (7)

SiO2

KH

50.61

50.02

0.58

50.39

49.84

0.73

50.42

49.90

0.20

50.83

50.26

0.31

VG-2

49.37

49.63

0.46

50.22

50.49

0.37

50.08

50.37

0.56

49.93

50.22

0.24

A12 O3

KH

17.37

16.69

0.19

17.25

16.62

0.19

17.10

16.51

0.20

17.36

16.71

0.13

VG-2

16.09

16.06

0.13

16.05

16.04

0.20

16.30

16.25

0.21

16.33

16.31

0.12

FeO

KH

9.06

9.11

0.11

8.97

9.02

0.06

8.89

8.94

0.23

8.97

9.02

0.06

VG-2

8.85

8.89

0.12

8.89

8.93

0.26

8.91

8.96

0.20

9.01

9.05

0.05

MgO

KH

8.34

8.22

0.21

8.95

8.80

0.11

8.79

8.68

0.30

8.77

8.63

0.24

VG-2

8.36

8.20

0.12

8.99

8.81

0.44

8.45

8.28

0.11

8.73

8.56

0.25

CaO

VG-D08

KH

12.46

12.64

0.15

12.45

12.63

0.13

12.21

12.39

0.18

12.45

12.64

0.04

VG-2

12.25

12.33

0.05

12.24

12.33

0.45

12.39

12.46

0.17

12.44

12.51

0.16

Na2O

KH

T.3"4

2.28

0.06

2.31

2.24

0.03

2.32

2,. 25

0.09

2.44

2.37

0.06

VG-2

T.38

2.31

0.03

2.37

2.30

_0.16j

2.30

2.23

0.04

2.33

2.26

0.01

KH

0.07

0.07

0.02

0.09

0.09

0.02

0.08

0.08

0.07

0.07

0.07

0.02

VG-2

0.09

0.09

0.02

0.09

0.09

0.01

0.09

0.09

0.02

0.10

0.09

0.02

TiO2

KH

0.96

0.97

0.05

1.01

1.02

0.05

1.05

1.06

0.07

1.00

1.01

0.03

VG-2

1.13

1.14

0.06

1.11

1.12

0.02

1.14

1.15

0.05

1.12

1.13

0.06

P2°5

AP

0.11

0.14

0.02

0.12

0.15

0.02

AP

0.11

0.14

0.03

0.12

0.15

0.01

MnO

KH

0.13

0.14

0.02

0.15

0.15

0.03

Fay

0.16

0.18

0.01

0.14

0.16

0.01

2 results in brackets, obtained using a 2ym beam, are not included in compilations

of Tables 3 and 4. See explanation in text.

only measure of precision that can be observed. It is

clear, however, that the average values of analyses

made on two separate days, with separate standardizations, may occasionally be different. For example,

in the analysis of Kakanui hornblende, one of us

(A. P.) performed a Student's t-test for runs 1 and 2

(Table 5). Run 1 gives a mean for MgO of 12.57

with a standard deviation of 0.13 and run 2 gives

a mean of 13.09 with a standard deviation of 0.22.

The Student's Mest indicates that the difference between the two means (i.e., the error) is significant at

the 99% confidence level. Of course, this is to be

expected occasionally, given the limited stability of

the instruments and the vagaries of data acquisition

in general. For microprobe users, however, it is difficult to realize, and frequently even more difficult

to accept, the fact that their data might not be as

good as it appears. Concern about the precision and

accuracy of microprobe analyses is ever-present with

the discriminating worker. One way to monitor the
NUMBER 22 65

TABLE 7.—USGS laboratory individual analyses of Kakanui hornblende and 4 natural glasses

using Kakanui hornblende as reference sample and also the laboratory's preferred reference

samples

Run No.

1

2

3

4a

4b

1

2a

2b

3

Conditions

Standards

Uncorrected

B-A Corr.

a (10)

Uncorrected

B-A Corr.

a (10)

Uncorrected

B-A Corr.

a (10)

Standards

Uncorrected

B-A Corr.

a (5)

Uncorrected

B-A Corr.

a (10)

Standards

Uncorrected

B-A Corr.

a (10)

Uncorrected

B-A Corr.

o (4)

Uncorrected

B-A Corr.

a (10)

Uncorrected

B-A Corr.

a (5)

Standards

Uncorrected

B-A Corr.

a (10)

SiO2

KH

40.43

40.42

0.28

40.35

40.39

0.56

40.14

40.15

0.64

Di85

38.61

40.73

0.24

37.94

40.11

0.24

KH

50.63

49.58

0.68

51.38

50.25

0.77

51.00

49.91

0.48

51.18

50.05

0.28

Di85

49.19

50.75

0.42

Al2

KH

14.

14.

0.

15.

15.

0.

14.

14.

0.

°3

93

93

40

09

10

26

91

93

45

Ortho

12.

14.

0.

13.

15.

0.

71

48

43

21

04

42

KH

14

14

0

14

14

0

14

14

0

15

14

0

.87

.46

.21

.71

.30

.43

.75

.34

.40

.07

.61

.30

Grtho

12

13

0

.65

.98

.19

FeO

KH

10.

10.

0.

10.

10.

0.

11.

11.

0.

50

51

14

86

86

03

06

05

19

Garnet

10.

10.

0.

10.

10.

0.

53

50

44

59

57

19

KH

11

11

0

11

11

0

11

11

0

11

11

0

.94

.95

.26

.82

.83

.30

.77

.77

.19

.60

.61

.13

Garnet

11

11

0

.82

.79

.14

MgO

Kakanui

KH

13.

12.

0.

12.

12.

0.

12.

12.

0.

02

99

28

89

89

35

84

86

17

Di2Ti

12.

13.

0.

12.

12.

0.

34

13

58

15

93

17

KH

6

6

0

6

6

0

6

6

0

6

6

0

.93

.98

.10

.94

.98

.10

.88

.91

.18

.71

.73

.03

Di2Ti

6

7

0

.55

.02

.05

CaO Na2O

hornblende

KH KH

10.66

10.66

0.49

9.71

9.72

0.63

10.34

10.34

0.08

Di2Ti

10.57

10.20

0.32

10.40

10.04

0.11

VG-2

KH

10.90

10.91

0.20

10.97

10.98

0.28

10.94

10.95

0.21

11.22

11.24

0.08

Di2Ti

11.11

10.72

0.06

2.68

2.68

0.13

2.76

2.76

0.12

2.58

2.58

0.07

Di85

2.47

2.68

0.12

2.54

2.76

0.05

KH

2.77

2.79

0.11

2.75

..77

0.09

2.85

2.86

0.15

2.75

2.75

0.05

Di85

2.55

2.75

0.12

K20

KH

1.89

1.89

0.12

1.98

1.98

0.02

2.02

2.02

0.05

Ortho

1.95

1.91

0.04

2.01

1.97

0.02

KH

0.02

0.02

0.06

0.05

0.05

0.07

0.05

0.05

0.05

0.10

0.10

0»06

Ortho

0.19

0.18

0.06

TiO2

KH

4.31

4.32

0.18

4.30

4.30

0.08

4.20

4.20

0.13

Di2Ti

4.90

4.74

0.15

4.70

4.55

0.10

KH

1.63

1.63

0.03

1.65

1.66

0.08

1.66

1.66

0.07

1.63

1.63

0.03

Di2Ti

1.92

1.86

0.08

P2°5

AP

0.09

0.11

0.02

0.09

0.11

0.02

0.06

0.07

0.05

Ortho

0.02

0.02

0.07

0.05

0.05

0.05

AP

0.22

0.27

0.05

0.17

0.22

0.05

0.22

0.28

0.05

0.18

0.21

0.07

Ortho

0.20

0.19

0.05

MnO

KH

0.08

0.09

0.12

0.11

0.11

0.10

0.37

0.37

0.41

Rhod

0.07

0.07

0.04

0.04

0.04

0.01

KH

0.23

0.23

0.06

0.36

0.36

0.03

0.32

0.32

0.05

0.08

0.08

0.10

Rhod

0.21

0.23

0.05
66 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

Table 7.—Continued

Run No.

1

2

3•-I 3

Conditions

Standards

Uncorrected

B-A Corr.

° (10)

Uncorrected

B-A Corr.

o (6)

Standards

Uncorrected

B-A Corr.

° (10)

Standards

Uncorrected

B-A Corr.

a (10)

Standards

Uncorrected

B-A Corr.

° (10)

Standards

Uncorrected

B-A Corr.

° (10)

Uncorrected

B-A Corr.

0 (5)

Standards

Uncorrected

B-A Corr.

° (10)

SiO2

KH

52.39

50.80

0.51

52.69

50.69

0.28

Di85

49.58

50.80

0.60

KH

51.88

50.62

0.32

Di85

49.37

50.70

0.09

KH

50.30

49.47

0.73

50.41

49.60

0.66

Di85

47.97

49.77

0.24

A12O3

KH

13.25

12.84

0.30

13.00

12.62

0.08

Ortho

11.61

12.80

0.26

KH

14.41

13.98

0.40

Ortho

14.24

13.54

0.04

KH

16.38

15.86

0.47

17.04

16.46

0.34

Ortho

14.02

15.44

0.17

FeO

KH

13.39

13.36

0.15

13.53

13.50

0.27

Garnet

13.48

13.41

0.23

KH

13.66

13.63

0.36

Garnet

12.75

13.30

0.21

KH

8.75

8.79

0.22

9.01

9.05

0.19

Garnet

8.76

8.78

0.18

MgO

KH

4.89

.4.99

0.10

5.08

5.18

0.08

Di2Ti

4.76

5.16

0.10

KH

5.57

5.65

0.08

Di2Ti

5.67

6.13

0.10

KH

8.86

8.71

0.18

8.54

8.40

0.12

Di2Ti

8.36

8.78

0.07

CaO

VG-A99

KH

8.44

8.42

0.48

9.16

9.13

0.18

Di2Ti

9.33

8.97

0.17

VG-999

KH

10.26

10.25

0.14

Di2Ti

10.57

10.18

0.03

VG-D08

KH

12.03

12.10

0.66

12.22

12.29

0.15

Di2Ti

12.42

12.05

0.03

Na2O

KH

2.80

2.88

0.20

2.62

2.69

0.07

Di85

2.44

2.73

0.08

KH

2.66

2.72

0.11

Di85

2.30

2.57

0.03

KH

2.44

2.39

0.04

2.36

2.30

0.08

Di85

2.23

2.39

0.07

K20

KH

0.77

0.78

0.11

0.67

0.67

0.08

Ortho

0.77

0.76

0.07

KH

0.03

0.03

0.04

Ortho

0.04

0.04

0.00

KH

0.00

0.00

0.00

0.00

0.00

0.11

Ortho

0.09

0.09

0.06

TiO2

KH

3.81

3.79

0.10

3.73

3.71

0.10

Di2Ti

3.91

3.77

0.12

KH

1.66

1.66

0.08

Di2Ti

1.87

1.80

0.17

KH

0.88

0.89

0.03

0.96

0.97

0.07

Di2Ti

1.05

1.03

0.05

p2 o5

AP

0.40

0.49

0.04

0.44

0.54

0.02

Ortho

0.32

0.31

0.04

AP

0.17

0.21

0.01

Ortho

0.15

0.15

0.11

AP

Q.13

0.16

0.01

0.10

0.12

0.02

Ortho

0.08

0.08

0.02

MnO

KH

0.27

0.27

0.05

0.16

0.16

0.04

Rhod

0.18

0.19

0.06

KH

0.13

0.13

0.30

Rhod

0.20

0.20

0.04

KH

0.18

0.19

0.01

0.14

0.15

0.21

Rhod

0.12

0.13

0.01
NUMBER 22 67

precision and accuracy is to present data of samples

with known composition together with the microprobe analyses of the unknown samples. This suggestion has been made frequently and is followed

by many, but it would serve the scientific community much better if practiced even more extensively.

Literature Cited

Albee, A. L., and Lily Ray

1970. Correction Factors for Electron Probe Microanalysis

of Silicates, Oxides, Carbonates, Phosphates, and

Sulfates. Analytical Chemistry, 42(12): 1408-1414.

Byerly, G. R., W. G. Melson, and P. R. Vogt

1976. Rhyodacites, Andesites, Ferro-Basalts, and Ocean

Tholeiites from the Galapagos Spreading Center.

Earth and Planetary Science Letters, 30:215-221.

Melson, W. G., G. R. Byerly, J. A. Nelen, T O'Hearn, T.

L. Wright, and T. Vallier

1977. A Catalog of the Major Element Chemistry of

Abyssal Volcanic Glasses. Smithsonian Contributions

to the Earth Sciences, 19:31-60.

Wright, T. L., and R. T. Okamura

1977. Cooling and Crystallization of Tholeiitic Basalt,

1965 Makaopuhi Lava Lake, Hawaii. United States

Geological Survey Professional Paper, 1004:1-78.
Electron Microprobe Reference Samples for Mineral Analyses

Eugene Jarosewich, Joseph A. Nelen, and Julie A. Norberg

ABSTRACT

A table is presented containing compositional data

for 25 minerals, four natural glasses, and one synthetic glass prepared and analyzed for use as microprobe reference samples at the Smithsonian Institution. The table includes new chemical analyses of

minerals and some updated analyses of minerals

published previously.

Detailed descriptions of sample preparation and

evaluation of homogeneity are given.

Introduction

Microprobe analyses are an essential part of

present-day mineralogical and petrological studies.

It can be said that the application of the microprobe to mineral studies and material sciences in

general is one of the most significant advances since

the first use of the petrographic microscope in

the middle of the last century. The technique is

now well established, widely used, and capable of

high-quality analyses. As with all comparative instrumental techniques, however, it requires wellcharacterized reference samples. Prime prerequisites

for microprobe reference samples are homogeneity

at the micrometer level and availability in reasonable quantities for standard chemical analyses.

Either prerequisite is usually easily satisfied by itself

but together are difficult to achieve.

One of the problems with some minerals used as

microprobe reference samples is a lack of proper

documentation. Even if well-described minerals are

from the same locality and/or are obtained from

a reliable source, they may vary in chemical comEugene Jarosewich, Joseph A. Nelen, and Julie A. Norberg,

Department of Mineral Sciences, National Museum of Natural

History, Smithsonian Institution, Washington, D.C. 20560.

position. Therefore, a mineral sample intended as

a reference sample should be carefully selected and

used only when analytical data on this particular

specimen are available. Since natural materials fulfilling all the above requirements are not always

available, synthetic minerals and glasses have occasionally been prepared as substitutes. Again, homogeneity of these materials should be checked and

chemical analyses performed. The assumption that

the precalculated composition is correct is certainly

not always valid.

In general, the most reliable microprobe analyses

are obtained when a reference sample of composition and structure close to that of the unknown is

used because the matrix and possible wavelength

shift effects are minimized, and only small corrections are needed. It is generally accepted that,

regardless of the type of correction used, results

corrected by more than 10 percent should be viewed

with caution. Difficulties with correction procedures

in the Si-Al-Mg system have been pointed out by

Bence and Holzwarth (1977). Similar discrepancies

have been observed by other probe users.

All minerals and glasses described here, except

one, are of natural origin. Most have been obtained

from the Smithsonian collections and were selected

either in conjunction with specific projects or for

use in silicate analyses in general.

ACKNOWLEDGMENTS.—We wish to acknowledge

those curators and others listed in Table 1 who

provided us with samples for use as microprobe

reference samples. Brian Mason's careful examination and assistance in separation of minerals is also

greatly appreciated.

Preparation of Reference Samples

When a sufficient quantity (at least 2 g) of a mineral or glass is available for use as a microprobe

68
NUMBER 22 69

reference sample, a thin section is prepared for

microscopic examination. Next, a microprobe analysis for composition and homogeneity is performed.

If preliminary results are favorable, the material is

gently crushed, sized usually between 20 and 80

mesh, and further purified using either a heavy

liquid separation or a Franz magnetic separator or

both. In some instances cleaning with a suitable

acid is also useful. As a final step, the material is

examined under a low-powered microscope and

most remaining foreign grains are removed by

hand. The purified grains are again checked by

microprobe for homogeneity (sigma ratios) within

and among grains (Table 2). Finally, a chemical analysis using classical methods (Peck, 1964;

Hillebrand et al., 1953) is performed on the same

separate that is to be used as the reference sample.

Discussion

In Table 1 are presented the data for newly analyzed minerals, earlier published analyses, and updated analyses for several minerals that have been

in use for some time. Johnstown meteorite hypersthene and Springwater meteorite olivine have been

re-analyzed using what we believe to be much

cleaner separates. Kakanui hornblende has been

re-analyzed for TiO2.

Even after the most careful preparation of the

reference sample, a grain of accessory mineral or

matrix may remain in the sample, which, in the

course of preparation of the standard discs, could

be included with the reference sample. Occasional

grains of the standard itself will be "off composition," due to inhomogeneity. These problems can

never be totally eliminated. The user should be

aware of the possible presence of such "impurities"

and make a thorough check for them. For example,

occasional grains are found that are lower in sodium

and higher in potassium than usual in the reference

sample microcline, lower in manganese than usual

in Rockport fayalite, and lower in sodium than

usual in Lake County plagioclase. Infrequent inclusions in the glasses 72854, 111240/52, 113498/1, and

113716 are also found.

The overall homogeneity of each sample was determined using the criteria given by Boyd et al.

(1967) whereby the sample is considered to be homogeneous if the sigma ratio (homogeneity index) of

observed standard deviation (sigma) to the standard

deviation predicted from counting statistics alone

does not exceed 3. The sigma ratios were calculated

with reference to ten ten-second counts on each of

ten randomly selected grains. Table 2 gives sigma

ratios for the ten grains of each reference sample

for major and some minor elements. The values in

parentheses indicate the worst sigma ratio observed

for an element in a single grain. This does not,

however, imply a single worst grain, as different

grains may exhibit differing degrees of homogeneity

for each element present. When the criterion of

sigma ratios is used as a measure of homogeneity,

all the reference samples prove to be very homogeneous provided a reasonably large number of

counts are taken on a reasonably large number of

grains. In practice, however, fewer counts and grains

are normally used for standardization, and under

these circumstances a grain having a slightly different composition may influence the microprobe

results adversely. For this reason, grains showing

some discrepancy in composition should be avoided.

The percentages of these "impurities" in the whole

samples are minimal and the effects on the bulk

analyses of the samples are negligible.

These samples were prepared in only small quantities, but they can be judiciously made available to

microprobe users interested in the analysis of geologic materials. Potential users should remember

that the purified samples differ in bulk chemistry

from the specimens from which they were separated

and should be very specific in their requests—

i.e., the requests should be made for microprobe

standard USNM no. n rather than simply material

from specimen USNM no. n.

Literature Cited

Bence, A. E., and W. Holzwarth

1977. Non-Linearities of Electron Microprobe Matrix Corrections in the System MgO-Al2O3-SiO2. Proceedings

of the Eighth International Conference on X-Ray

Optics and Microanalysis and Twelfth Annual Conference of the Microbeam Analysis Society, page 38.

Boyd, F. R., L. W. Finger, and F. Chayes

1967. Computer Reduction of Electron-Probe Data. Carnegie Institution Year Books, 67:210-215.

Hillebrand, W. G., G.E.F. Lundell, H. A. Bright, and J. I.

Hoffman

1953. Applied Inorganic Analysis. 2nd edition, 1034 pages.

New York: John Wiley and Sons.

Peck, L. C.

1964. Systematic Analysis of Silicates. U.S. Geological Survey Bulletin, 1170:66.
70 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

KEY TO TABLE 1

Analysts, Sources,

Analysts:

1.

2.

3.

4.

5.

6.

7.

8.

9.

E. Jarosewich, Dept. of Mineral Sciences, Smithsonian Institution

J. Nelen, Dept. of Mineral Sciences, Smithsonian

Institution

J. Norberg, Dept. of Mineral Sciences, Smithsonian Institution

E. L. Munson, N. M. Conklin, J. N. Rosholt, and

I. C. Frost, U.S. Geological Survey

B. Wiik, Geological Survey, Finland

U.S. Geological Survey, Geochemistry and Petrology Branch

D. Mills, X-Ray Assay Laboratories, Ontario,

Canada; J. Nelen; J. Norberg

E. Kiss, Dept. of Geophysics and Geochemistry,

Australian National University

J. J. Fahey and L. C. Peck, U.S. Geological

Survey

Sources:

1.

2.

3.

4.

5.

6.

7.

P. Desautels, J. S. White, Jr., and P. J. Dunn,

Dept. of Mineral Sciences, Smithsonian Institution

B. Mason, Dept. of Mineral Sciences, Smithsonian Institution

G. Switzer, Dept. of Mineral Sciences, Smithsonian Institution

W. G. Melson, Dept. of Mineral Sciences, Smithsonian Institution

T. L. Wright, U.S. Geological Survey

H. Staudigel, Massachusetts Institute of Technology

R. S. Clarke, Jr., Dept. of Mineral Sciences,

8.

References

Smithsonian Institution

J. H. Berg, Northern Illinois University

References for previously published analyses:

1.

2.

3.

4.

5.

Stewart, D. B., G. W. Walker, T. L. Wright, and

J. J. Fahey

1966. Physical Properties of Calcic Labradorite

from Lake County, Oregon. American

Mineralogist, 51:177-197.

Young, E. J., A. T. Myers, E. L. Munson, and

N. M. Conklin

1969. Mineralogy and Geochemistry of Fluorapatite from Cerro de Mercado, Durango,

Mexico. U.S. Geological Survey Professional Paper, 650D:84-93.

Mason, B., and R. O. Allen

1973. Minor and Trace Elements in Augite,

Hornblende, and Pyrope Megacrysts

from Kakanui, New Zealand. New Zealand Journal of Geology and Geophysics,

16(4):935-947.

Jarosewich, E.

1972. Chemical Analysis of Five Minerals for

Microprobe Standards. In William G.

Melson, editor, Mineral Sciences Investigations, 1969-1971. Smithsonian Contributions to the Earth Sciences, 9:83-84.

Jarosewich, E.

1975. Chemical Analysis of Two Microprobe

Standards. In George S. Switzer, editor,

Mineral Sciences Investigations, 1972-

1973. Smithsonian Contributions to the

Earth Sciences, 14:85-86.
TABLE 1.—Chemical analyses of electron microprobe reference samples; analysts, sources, and

references identified in "Key to Table 1" on facing page; these purified samples all differ, to

greater or lesser degree, from the bulk chemistry of the USNM specimens from which they were

separated (see text).

Mineral

Ahorthite, Great Sitkin Island, AL

USNM 137041

Anorthoclase, Kakanui, New Zealand

USNM 133868

Apatite (Fluorapatite), Durango, Mexico1

USNM 104021

Augite, Kakanui, New Zealand

USNM 122142

Benitoite, San Benito County, CA2

USNM 86539

Chromite, Tiebaghi Mine, New Caledonia3

USNM 117075

Corundum, synthetic1*

USNM 657S

Diopside, Natural Bridge, NY

USNM 117733

Fayalite, Rockport, MA

USNM 85276

Garnet, Roberts Victor Mine, South Africa

USNM 87375

Garnet, Roberts Victor Mine, South Africa

USNM 110752

Glass, Basaltic, Juan de Fuca Ridge

USNM 111240/52 VG-2

Glass, Basaltic, Makaopuhi Lava Lake, HI

USNM 113498/1 VG-A99

Glass, Basaltic, Indian Ocean5

USNM 113716

Glass, Rhyolitic, Yellowstone Nat. Pk., WY6

USNM 72854 VG-568

Glass, Tektite, synthetic7

USNM 2213

Hornblende, Arenal Volcano, Costa Rica

USNM 111356

Hornblende, Kakanui, New Zealand8

USNM 143965

Hypersthene, Johnstown meteorite

USNM 746

Ilmenite, Ilmen Mtns., Miask, USSR9

USNM 96189

Magnetite, Minas Gerais, Brazil10

USNM 114887

Microcline, location unknown

USNM 143966

Olivine (F090). San Carlos, Gila Co., AZ11

USNM 111312/444

Olivine (F083), Springwater meteorite

USNM 2566

Omphacite, Roberts Victor Mine, So. Africa

USNM 110607

Osumilite, Nain, Labrador

USNM 143967

Plagioclase (Labradorite), Lake County, OR

USNM 115900

Pyrope, Kakanui, New Zealand

USNM 143968

Quartz, Hot Springs, AR12

USNM R177O1

Scapolite (Meionite), Brazil13

USNM R6600-1

SiO2

44.00

66.44

0.34

50.73

43.75

54.87

29.22

39.47

40.16

50.81

50.94

51.52

76.71

75.75

41.46

40.37

54.09

64.24

40.81

38.95

55.42

60.20

51.25

41.46

99.99

49.78

AI2O3

36.03

20.12

0.07

7.86

9.92

99.99

0.11

22.27

22.70

14.06

12.49

15.39

12.06

11.34

15.47

14.90

1.23

18.30

8.89

22.60

30.91

23.73

25.05

Fe2O3

0.06

3.69

1.32

2.77

2.17

2.23

1.87

1.12

0.48

0.64

5.60

3.30

11.6

67.5

0.00

1.35

0.34

FeO

0.62

0.20

0.00

3.45

13.04

0.24

66.36

13.76

9.36

9.83

11.62

8.12

0.80

4.32

6.43

7.95

15.22

36.1

30.2

0.04

9.55

16.62

3.41

6.38

0.15

10.68

0.17

MgO

<0.02

0.01

16.65

15.20

18.30

6.55

7.17

6.71

5.08

8.21

<0.1

1.51

14.24

12.80

26.79

0.31

0.03

49.42

43.58

11.57

5.83

0.14

18.51

CaO

19.09

0.87

54.02

15.82

0.12

25.63

14.39

18.12

11.12

9.30

11.31

0.50

2.66

11.55

10.30

1.52

0.02

<0.05

13.75

<0.03

13.64

5.17

13.58

Na2O

0.53

9.31

0.23

1.27

0.34

2.62

2.66

2.48

3.75

1.06

1.91

2.60

<0.05

1.30

5.00

0.39

3.45

5.20

K20

0.03

2.35

0.01

0.00

0.19

0.82

0.09

4.89

1.88

0.21

2.05

<0.05

15.14

0.15

4.00

0.18

0.94

TiO2

0.03

0.74

19.35

0.04

0.39

0.35

1.85

4.06

1.30

0.12

0.50

1.41

4.72

0.16

45.7

0.01

0.37

0.18

0.05

0.47

P2O5

40.78

0.20

0.38

0.12

<0.01

0.00

<0.01

0.00

0.00

MnO Cr2O3

O.Ox

0.13

0.11 60.5

0.04

2.14

0.59

0.19

0.22

0.15

0.17

0.03

0.11

0.15

0.09

0.49 0.75

4.77

0.04

0.14

0.30 0.02

0.10

0.01

0.28

H20

<0.05

0.01

0.04

0.1

<0.01

<0.01

0.02

0.02

0.18

0.12

0.10

1.21

0.94

0.00

<0.05

0.02

0.02

0.05

<0.01

0.21

Total

100.33

99.29

99.94

100.38

100.15

98.89

99.99

99.53

99.18

100.19

100.22

99.86

99.39

100.07

99.56

99.88

99.64

100.02

100.25

99.40

98.16

99.12

100.29

99.47

100.03

99.60

100.17

100.30

99.99

99.86

Analyst

1

3

4

5

2

2

1

2

2

1

1

1

3

3

3

6

1

1

3

7

3

8

1

3

1

1

9

1

1

2

Source

1

2

1

2

1

1

1

1

1

3

3

4

5

6

4

7

4

2

7

1

1

3

2

7

3

8

1

2

1

1

Reference j

2

3

4

4

5

5

4

4

1

4

1 SrO 0.07; RE2O3 1.43; ThO2 0.02; As2O3 0.09; V2Os 0.01; C02 0.05;

S03 0.37; F 3.53; Cl 0.41; sub-total: 101.52; 0 equivalent to Cl, F =

1.58; final total: 99.94.

2 BaO 37.05.

3 Total Fe reported as FeO.

"• Emission spectrometric analysis: Si 0.03; Fe 0.003; Mg 0.007;

Ca 0.003; Na 0.005; K 0.005.

5 S 0.12; sub-total: 100.13; 0 equivalent to S = 0.06; final total:

100.07.

6 Cl 0.13; sub-total: 99.59; 0 equivalent to Cl » 0.03; final total:

99.56.

7 C02 not determined (insufficient sample); Cl 0.00; F 0.01.

Synthetic glass prepared by Corning Glass Company.

8 New TiO2 value: 4.72.

9 Nb2O5 0.92.

10 Preliminary values: MgO 0.05; TiO2 0.16; MnO <0.01; Cr2O3 0.25.

11 NiO 0.37.

12 Emission spectrometric analysis: Al 0.0005; Fe 0.01; Mg 0.005;

Ca 0.001; Na 0.001; K 0.0003.

13 C02 2.5; S03 1.32; Cl 1.43; sub-total: 100.18; 0 equivalent to

Cl = 0.32; final total: 99.86.
72 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

TABLE 2.—Sigma ratios (homogeneity indices) for all analyzed grains of each reference sample

observed sigma for n grains

(sigma ratio for n grains = —; least homogeneous grain in

sigma predicted from counting statistics

parentheses; dashes = not evaluated)

Mineral

Anorthite

Anorthoclase

Apatite (Fluorapatite)

Augite

Dnn i f-r\1 t-Ck

DcIilLUJ-Lc

Chromite

Diopside

Fayalite

Garnet, 87375

Garnet, 110752

Glass, 111240/52 VG-2

Glass, 113498/1 VG-A99

Glass, 113716

Glass, 72854 VG-568

Glass, 2213

Hornblende, Arenal

Ho rnblende, Kakanui

Hypersthene

Ilmenite

Magnetite

Microcline

Olivine (Fogo), San Carlos

Olivine (F083), Springwater

Omphacite

Osumilite

Plagioclase (Labradorite)

Pyrope

Quartz

Scapolite (Meionite)

SiO2

0.96

(1.51)

1.09

(1.60)

0.99

(1.37)

1.07

(1.37)

0.95

(1.46)

0.89

(1.26)

0.88

(1.32)

0.94

(1.10)

0.94

(1.32)

1.12

(1.42)

0.97

(1.61)

1.05

(1.72)

1.07

(1.67)

1.01

(1.38)

1.07

(1.55)

0.94

(1.13)

0.81

(1.13)

0.96

(1.42)

0.89

(1.23)

0.96

(1.90)

1.09

(1.49)

1.08

(1.46)

0.99

(1.29)

A12 O3

0.81

(1.26)

0.79

(1.38)

0.97

(1.66)

1.00

(1.47)

1.01

(1.42)

0.94

(1.28)

0.89

(1.11)

1.10

(1.46)

1.00

(1.30)

1.00

(1.47)

0.87

(1.24)

0.97

(1.66)

1.00

(1.24)

1.04

(1.52)

0.95

(1.64)

1.27

(1.89)

0.95

(1.40)

0.95

(1.20)

0.95

(1.41)

FeO

0.84

(1.26)

1.01

(1.66)

1.14

(2.32)

1.06

(1.41)

0.90

(1.20)

0.86

(1.13)

1.07

(1.38)

0.94

(1.34)

1.01

(1.34)

1.12

(1.36)

1.30

(1.67)

1.10

(1.37)

1.72

(3.60)

0.84

(1.16)

0.90

(1.29)

1.06

(1.51)

0.96

(1.87)

1.20

(2.19)

1.09

(1.59)

MgO

0.94

(1.23)

1.11

(1.50)

0.97

(1.50)

1.01

(1.49)

1.00

(1.34)

0.96

(1.61)

0.92

(1.38)

1.01

(1.36)

1.11

(1.67)

1.16

(2.38)

0.93

(1.27)

1.00

(1.64)

0.99

(1.12)

0.91

(1.30)

1.00

(1.70)

0.98

(1.21)

CaO

0.92

(1.23)

1.02

(1.51)

1.00

(1.25)

0.95

(1.50)

0.86

(1.11)

0.87

(1.47)

1.00

(1.27)

0.93

(1.34)

0.83

(1.19)

1.05

(1.61)

1.01

(1.27)

1.10

(1.73)

1.02

(1.51)

1.04

(1.65)

0.97

(1.18)

0.91

(1.16)

Na2O

1.11

(1.57)

1.05

(1.31)

1.15

(2.10)

1.25

(2.59)

2.31

(3.45)

0.98

(1.32)

1.15

(2.15)

0.99

(1.31)

0.91

(1.33)

0.96

(1.41)

K20

0

(1

0

(1

1

(1

1

(1

.98

.36)

.90

.29)

.09

.59)

.13

.64)

TiO2

0.

(1.

1.

(1.

1.

(1.

97

44)

01

49)

34

98)

P2O5 MnO Cr2O3

0.97

(1.51)

1

(1

1

(1

1.12

(1.49)

.03

.58)

.21

.53)

observed sigma for all grains

Sigma ratio for 10 grains = sigm a pred icted from counting statistics

observed sigma for this particular grain

Sigma ratio for least homogeneous gra m = sigm a predicted from counting statistics

(in parentheses)
Smithsonian Contributions to the Earth Sciences

1. George Switzer and William G. Melson. "Partially Melted Kyanite Eclogite from the Roberts

Victor Mine, South Africa." 9 pages, 5 figures, 6 tables. 15 April 1969.

2. Paul A. Mohr. "Catalog of Chemical Analyses of Rocks from the Interaction of the African,

Gulf of Aden, and Red Sea Rift Systems." 1322 entries. 16 December 1970.

3. Brian Mason and A. L. Graham. "Minor and Trace Elements in Meteoritic Minerals." 17

pages, 1 figure, 17 tables. 17 September 1970.

4. William G. Melson, Eugene Jarosewich, and Charles A. Lundquist. "Volcanic Eruption at

Metis Shoal, Tonga, 1967-1968: Description and Petrology." 18 pages, 13 figures, 3 tables.

16 October 1970.

5. Roy S. Clarke, Jr., Eugene Jarosewich, Brian Mason, Joseph Nelen, Manuel Gomez, and

Jack R. Hyde. "The Allende, Mexico, Meteorite Shower." 53 pages, 36 figures, 6 tables.

17 February 1971.

6. Daniel J. Stanley and Noel P. James. "Distribution of Echinarachnius parma (Lamarck)

and Associated Fauna on Sable Island Bank, Southeast Canada." 24 pages, 8 figures, 6

plates, 1 table. 27 April 1971.

7. William G. Melson. "Geology of the Lincoln Area, Lewis and Clark County, Montana.'' 29

pages, 13 figures, 8 tables. 15 October 1971.

8. Daniel J. Stanley, Donald J. P. Swift, Norman Silverberg, Noel P. James, and Robert G.

Sutton. "Late Quaternary Progradation and Sand Spillover on the Outer Continental Margin

off Nova Scotia, Southeast Canada." 88 pages, 83 figures, 6 tables. 11 April 1972.

9. William G. Melson, editor. "Mineral Sciences Investigations, 1969-1971." 94 pages, 34 figures.

16 August 1972.

10. Louis H. Fuchs, Edward Olsen, and Kenneth J. Jensen. "Mineralogy, Mineral-Chemistry, and

Composition of the Murchison (C2) Meteorite." 39 pages, 19 figures, 9 tables. 14 August 1973.

11. Daniel J. Stanley and Peter Fenner. "Underwater Television Survey of the Atlantic Outer

Continental Margin near Wilmington Canyon." 54 pages, 18 figures, 2 August 1973.

12. Grant Heiken. "An Atlas of Volcanic Ash." 101 pages, 15 figures, 33 plates, 3 tables. 12

April 1974.

13. Nicolas A. Rupke and Daniel J. Stanley. "Distinctive Properties of Turbiditic and Hemipelagic Mud Layers in the Algero-Balearic Basin, Western Mediterranean Sea." 40 pages,

21 figures, 8 tables. 10 September 1974.

14. George S. Switzer, editor. "Mineral Sciences Investigations: 1972-1973." 88 pages, 29 figures.

2 July 1975.

15. Daniel J. Stanley, Gilbert Kelling, Juan-Antonio Vera, and Harrison Sheng. "Sands in the

Alboran Sea: A Model of Input in a Deep Marine Basin." 51 pages, 23 figures, 8 tables. 16

June 1975.

16. Andres Maldonado and Daniel Jean Stanley. "Late Quaternary Sedimentation and Straigraphy in the Strait of Sicily." 73 pages, 39 figures, 5 tables. 3 August 1976.

17. R. O. Chalmers, E. P. Henderson, and Brian Mason. "Occurrence, Distribution, and Age of

Australian Tektites." 46 pages, 17 figures, 10 tables. 9 September 1976.

18. Arthur Roe and John S. White, Jr. "A Catalog of the Type Specimens in the Mineral Collection, National Museum of Natural History." 43 pages. 22 November 1976.

19. Brian Mason, editor. "Mineral Sciences Investigations: 1974-1975." 125 pages, 48 figures, 37

tables. 9 March 1977.

20. Daniel J. Stanley. Henri Got, Neil H. Kenyon, Andre Monaco, and Yehezkiel Weiler. "Catalonian, Eastern Betic, and Balearic Margins: Structural Types and Geologically Recent

Foundering of the Western Mediterranean Basin." 67 pages, 33 figures. 20 September 1976.

21. Roy S. Clarke, Jr., and Joseph I. Goldstein. "Schreibersite Growth and Its Influence on the

Metallography of Coarse Structure Iron Meteorites." 80 pages, 28 figures, 20 tables. 14 April

1978.