SMITHSONIAN CONTRIBUTIONS TO THE

EARTH SCIENCES

NUMBER 9

wuiiam Q. Mehon Mineral Sciences

Investigations,

1969-1971

EDITOR

I S S11 E D

AUG .161972

SMITHSONIAN INSTITUTION PRESS

CITY OF WASHINGTON

1972
ABSTRACT

Melson, William G., editor. Mineral Sciences Investigations, 1969-1971. Smithsonian Contributions to the Earth Sciences, number 9, 94 pages, 34 figures, 1972.—

Seventeen short contributions from the Smithsonian's Department of Mineral Sciences from 1969 to 1971 are gathered together in this volume. The scientific and

technological subjects treated in these contributions include studies of lunar samples

from Apollo 12, meteorites, petrology and volcanology, and descriptive mineralogy,

as well as of the history and description of one of the Smithsonian Institution's most

important recent acquisitions—the Carl Bosch Collection of Minerals and Meteorites.

Official publication date is handstamped in a limited number of initial copies and is recorded

in the Institution's annual report, Smithsonian Year.

Library of Congress Cataloging in Publication Data

Melson, William G., 1938- comp.

Mineral sciences investigations, 1969-1971.

(Smithsonian contributions to the earth sciences, no. 9)

"Seventeen short contributions from the Smithsonian's Department of Mineral Sciences."

1. Mineralogy—Addresses, essays, lectures. 2. Petrology—Addresses, essays, lectures. I. National Museum of Natural History. Dept. of Mineral Sciences. II. Title. III. Series:

Smithsonian Institution. Smithsonian contributions to the earth sciences, no. 9.

QE1.S227 no. 9 [QE369] 55O'.8s [549'. 1] 72-355

For sale by the Superintendent of Documents, U.S. Government Printing Office

Washington, D.C. 20402 - Price $1.25 (paper cover)
Contents

Page

LUNAR STUDIES

Mineralogy and Petrography of Some Apollo 12 Samples, by Brian Mason,

William G. Melson, E. P. Henderson, Eugene Jarosewich, and Joseph

Nelen 1

Microhardness of a Lunar Iron Particle and High-Purity Iron Samples, by

E. P. Henderson, R. D. Buchheit, and J. L. McCall 5

PETROLOGY AND VOLGANOLOGY

Basaltic Nuees Ardentes of the 1970 Eruption of Ulawun Volcano, New

Britain, by William G. Melson, Eugene Jarosewich, George Switzerland

Geoffrey Thompson 15

Experimental Data Bearing on the Paragenesis of Two Hawaiian Basalts

from Kilauea Volcano, by R. F. Fudali 33

Iron-rich Saponite: Additional Data on Samples Dredged from the MidAtlantic Ridge, 22° N Latitude, by Harold H. Banks, Jr 39

Olivine Crystals from the Floor of the Mid-Atlantic Ridge near 22f'N Latitude, by George Switzer, William G. Melson, and Geoffrey Thompson ... . 43

Origin and Composition of Rock Fulgurite Glass, by George Switzer and

William G. Melson 47

METEORITES

The Estherville Meteorite, by Joseph Nelen and Brian Mason 55

Forest Vale Meteorite, by A. F. Noonan, Kurt A. Fredriksson, and Joseph

Nelen 57

Iron Meteorite Compositions, by Roy S. Clarke, Jr., and Eugene Jarosewich 65

The Nejo, Ethiopia, Meteorite by Roy S. Clarke, Jr., Eugene Jarosewich, and

Joseph Nelen 67

The Nakhon Pathom Meteorite, by Joseph A. Nelen and Kurt Fredriksson . . 69

MINERALOGY

Gorceixite in the Buffels River, Namaqualand, South Africa, by J. J. Gurney . 77

Tocornalite, by Brian Mason . - 79

STANDARDS FOR CHEMICAL ANALYSIS

Chemical Analysis of Five Minerals for Microprobe Standards, by Eugene

Jarosewich 83

T H E COLLECTIONS

Acquisition of the Carl Bosch Collection of Minerals and Meteorites, by Paul

E. Desautels 87

THIN-SECTION PREPARATION

Preparation of Doubly Polished Thin Sections, by Grover Moreland, Frank

Ingram, and Harold H. Banks, Jr. 93
LUNAR STUDIES
Brian Mason, William G. Melson,

E. P. Henderson, Eugene Jarosewich,

and Joseph Nelen

Mineralogy and

Petrography of Some

Apollo 12 Samples

ABSTRAC T

Samples of the Apollo 12 fines contain fragments of

crystalline rocks and breccias, mineral grains, and

glassy particles. The mineral grains are mainly pyroxene (pigeonite and augite) and olivine, with minor

amounts of plagioclase and ilmenite, and rare metal

grains. The compositions of the metal grains indicate

that some are of meteoritic origin and some are derived from lunar rocks. A single pyroxene crystal has

a pigeonite core, an augite mantle, and a rim of

ferrohedenbergite, with a narrow zone of pyroxferroite along a central fissure. One rock fragment from

a sample of coarse fines (12032) is a silica-rich hedenbergite granophyre, consisting of sanidine (50%),

quartz (30%), hedenbergite (10%), plagioclase

(7%), fayalite (3%), and accessory apatite, whitlockite, and zircon. A complete chemical analysis of

12001 fines has been made, and also a determination

of the water-soluble cations, a noteworthy feature

being the presence of 103 ppm water-soluble calcium.

The Smithsonian received the following samples from

the Apollo 12 collections:

Fines (-1 mm): 12001 (3.0 g); 12003 (0.5 g); 12033

(0.5 g); 12042 (0.5 g); 12057 (2.0 g);

12070 (2.0 g)

Coarse fines: (1 mm-1 cm): 12032 (0.5. g)

Rock sections: 12009, 12022, 12045, 12051

Each sample of the fines was sieved through 60-

mesh (0.250-mm opening) and 200-mesh (0.074-mm

opening) sieves. The grain-size distribution was similar in all, the weight proportions being: +60 mesh,

Brian Mason, William G. Melson, E. P. Henderson, Eugene

Jarosewich, and Joseph Nelen, Department of Mineral Sciences, Smithsonian Institution, Washington, D.C. 20560.

10-20%; 60-200 mesh, 20-30%; —200 mesh, 50-

60%. The fines contained fragments of crystalline

rocks and breccias, mineral grains, and glassy particles. The coarser fractions were density-separated,

using methylene iodide (D = 3.32). The fraction with

D>3.32 comprised about 30%, and consisted almost

entirely of grains of pyroxene (major), olivine (minor), and opaque minerals (small amount). The

fraction with D<3.32 (about 70%) consisted of rock

and breccia fragments, glass spherules and fragments,

and feldspar grains.

The —200-mesh fraction of 12,001 was further

separated with a 325-mesh sieve (0.044-mm opening), and a portion of the —325-mesh fraction analysed. The results are given in Table 1, along with

two analyses of Apollo 11 fines. The compositions of

the Apollo 12 and the Apollo 11 fines are rather

similar, except that the Apollo 12 fines contain about

half as much titanium as the Apollo 11 material;

this has already been noted in earlier reports (LSPET

1970). Our analyses also show distinctly higher potassium and chromium in Apollo 12 fines. Since

microscopic examination showed minute particles of

metallic iron in the glassy fraction of the fines, we

attempted to determine this in the Apollo 12 fines

(by dissolution in KCUCI3 solution). The figure

obtained, 0.33% Fe, is certainly a minimum value,

since the procedure would only dissolve those metal

particles exposed on the surface of the glass fragments, and not those totally enclosed. The high summation of the analysis of the Apollo 12 fines probably results from the reporting of some metallic iron

as FeO, and possibly some trivalent titanium as TiO2.

The calculated mineral compositions (norms) of

these analyses show about 40% feldspar of anorthitic

composition and about 45% pyroxene. The composi1
SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

TABLE 1.—Analyses and norms of Apollo 11 and Apollo 12 fines

(Eugene Jarosewich, analyst)

Constituent

SiOa

A12O3

TiO2

FeO

MgO

CaO

Na2O

K2O

P2O5

H2O -

MnO

Cr2O3

Ni

S

Femet

Sum

S = O

Sum

Analyses

12001

—325 mesh

45.83

13.45

2.99

15.78

10.28

10.63

0.47

0.25

0.22

0.00

0.21

0.45

0.03

0.17

0.33

101.09

0.09

101.00

(weight percent;

10084 10084

—525 mesh glass concentrate

42.02

14.61

6.38

15.59

7.92

12.39

0.45

0.15

0.27

0.00

0.15

0.17

0.03

100.13

43.28

14.83

5.43

14.91

7.63

12.56

0.48

0.19

0.17

0.00

0.18

0.10

0.03

0.13

99.92

0.07

99.85

Constituent

An

Ab

Or .

Di

Hy

Ol

11

Cr

Ap

Metal

FeS

Norms

12001

—325 mesh

33.9

4.0

1.5

14.4

33.0

7.0

5.7

0.7

0.5

0.3

0.5

(weight percent)

10084 10084

—325 mesh glass concentrate

37.4

3.8

0.9

18.4

20.4

6.2

12.1

0.3

0.6

37.8

4.1

1.1

19.4

22.5

4.1

10.3

0.2

0.4

0.4

tions are slightly undersaturated in SiOo, giving small

amounts of olivine. The Apollo 12 fines contain the

equivalent of about 5% ilmenite, compared to about

10% in the Apollo 11 material. After subtracting the

ilmenite, the FeO/FeO + MgO molecular percentage

is remarkably similar in all these analyses (42 for

the Apollo 12; 41 and 43 for the Apollo 11 analyses).

We also determined the water-extractable cations

in both Apollo 11 and Apollo 12 fines. A control experiment without sample yielded less than 1 ppm of

the cations determined. A sample of the Allende

meteorite was extracted for comparison. The results

are as follows (in ppm) :

Na K Mg Ca Fe Ni

12001 14 5 31 103 5 5

10084 21 5 16 325 5 5

Allende 238 5 25 20 5 5

The notable feature is the comparatively high amount

of extractable calcium, considerably less, however, in

12001 than in 10084. The extractable cations are not

present in the fines as halides, since Reed and Jovanovic (1970) report less than 2 ppm water-soluble

halogens in 10084. The high surface area and reactivity of the fresh lunar glass may be responsible. The

water-extractable calcium perhaps explains the reported stimulating effect of lunar dust on plant

growth.

Thirty grains of olivine in the Apollo 12 fines were

analysed with the microprobe. The range in composition, in mole percent Fe2SiO4 (Fa), is Faae-eoj with

no marked compositional preference; the mean is

Fa4i. Minor elements detected with the microprobe

were Ca (average 0.28%), Mn (0.24%), Cr (0.14%)

and Ti (0.08%). The contents of calcium are notably

high for olivine; in meteoritic olivines which we have

measured Ca is usually 0.01-0.02%, and Cr 0.02-

0.04%. This probably reflects a high temperature of

crystallization for the lunar olivine, and rapid chilling

preventing readjustment at lower temperatures.

Some sixty pyroxene grains in the Apollo 12 fines

were also analysed. They showed two compositional

clusters, one for pigeonite and the other for augitesubcalcic augite. The mean composition of the pigeonite cluster is \V011En55Fs33, of the augite-subcalcic augite cluster \V033En40Fs27. The principal minor elements are aluminum and titanium. The pigeonite grains average 1.4% A12O3 and 0.9% TiO2,

the augite and subcalcic augite 2.3% A12O3 and

1.3% TiOo.

The range of compositions shown by the isolated
NUMBER 9

pyroxene grains are essentially duplicated in a single

pyroxene crystal fragment picked from 12057. This

crystal fragment, 1.1 mm by 0.7 mm, has a central

core of pigeonite of rather uniform composition

(\V010En57Fs33) with a mantle of subcalcic augite

(\V037En37Fs26), and on one edge a narrow rim of

ferrohedenbergite (Wo3oEn7Fse3). A narrow rift in

the central core is lined with a thin zone of pyroxferroite. The individual minerals are clearly distinguished in crossed polars by the increase in birefrigence in passing from pyroxferroite to pigeonite to

augite to ferrohedenbergite. The compositional variation across this grain is given in Figure 1 in terms

of the pyroxene end members. A similar pyroxene

crystal from Apollo 12 material has been described

by Bence et al. (1970).

Plagioclase grains from the Apollo 12 fines show

a range of composition from Ans2 to Ange, with a

mean of An90. The plagioclase contains detectable

iron (average 0.4% FeO), potassium (average 0.1%

K2O), and titanium (average 0.08% TiO2 ).

Several metal-rich particles were extracted from

the Apollo 12 fines by means of a hand magnet. The

total amount in any sample is small, making up much

less than 1%. Two types of metal were distinguished;

one type is finely granular and shows deformation

structures, the other is coarse grained and undeformed. Microprobe analyses of the deformed grains

give figures for nickel and cobalt comparable with

those for meteoritic nickel-iron, suggesting that these

grains have been derived from meteorite impacts on

the lunar surface. The coarse-grained undeformed

metal usually has lower nickel concentrations than

meteoritic nickel-iron, and sometimes more cobalt

than nickel;' these fragments are presumably indigenous to the Moon, probably formed by localized

reduction of basaltic material. One such fragment is

essentially pure iron, with no detectable amounts of

other elements; it is extremely soft, comparable with

the purest strain-free iron we have been able to obtain. This metal fragment contains inclusions of olivine and ilmenite similar to these minerals in the

lunar basalts, from which it was presumably derived.

Our 0.5-g sample of coarse fines (12032, from the

rim of Bench Grater) was washed with acetone to

remove dust, and then density-fractionated in methylene iodide-acetone mixtures. The density fractions

were sorted by hand under a binocular microscope

into breccia fragments and crystalline rock fragments.

The results are set out in Table 2. The average

weight of individual fragments is 3.5 mg, and the

percentages of breccia and crystalline rocks are 82

and 18 respectively.

Several crystalline rock fragments were selected

for detailed examination. The most remarkable one

was a lone white fragment in the D<2.70 fraction,

which otherwise consisted of highly vesiculated black

breccia fragments. This crystalline fragment, 3-mm

long, proved to consist largely of sanidine, with minor

amounts of quartz, plagioclase, fayalite, and hedenEN

Dl

Ferrohedenbergite

FS

FIGURE 1.—Compositional zoning across a single pyroxene crystal from sample 12057, projected

in the system enstatite (En), ferrosilite (Fs), wollastonite (Wo); arrows indicate crystallization

sequence from core (pigeonite) through mantle (augite) to rim (ferrohedenbergite); a thin

zone of pyroxferroite occurs along the central fissure.
SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

bergite, and accessory zircon, apatite, and whitlockite.

The composition of the individual minerals, determined by the microprobe, is given in Table 3, along

with the calculated bulk composition.

The hedenbergite and fayalite are present as phenocrysts, up to 1-mm long, in a fine-grained groundmass of quartz and feldspar, much of it in microTABLE 2.—Fractionation of 0.5-g coarse fines from

the rim of Bench Crater (12032, 46)

Density

2.70

2.70-2.90

2.90-3.10

3.10-3.32

3.32

Totals

Weight percent

8

33

44

12

3

100

Number

Breccia

11

43

58

5

—

117

of fragments

Crystalline rocks

1

3

6

12

4

26

TABLE 3.—Analyses (microprobe) of minerals in hedenbergite granophyre (12032, 46—2)

Constituent

SiO2

TiO2

AI2O3 .

Gr2Os

FeO

MnO

MgO

CaO

Na2O

K2O

SrO

BaO

Microprobe Analyses

1*

65.4

18.6

0.82

n.d.

n.d.

0.31

2.96

11.6

n.d.

1.21

100.9

2*

57.0

26.8

1.10

n.d.

n.d.

8.74

6.85

0.15

n.d.

n.d.

100.6

3*

99.72$

0.28

n.d.

n.d.

n.d.

n.d.

n.d.

(100.0)

(weight percent)

4*

48.8

0.75

0.45

0.06

28.0

0.39

1.55

19.3

0.10

99.4

5*

29.8

0.21

0.04

0.13

67.8

0.95

1.22

0.67

n.d.

100.8

6*

72.0

01

11.1

5.3

0 1

0.2

?7

2.1

5.8

0 6

100.0

n.d. = not detected (<0.05%).

* Column 1: Sanidine (OrooAbasCn^ni); 50%.

Column 2: Plagioclase feldspar (AbssAnwOri); 7%.

Column 3: Quartz; 30%.

Column 4: Hedenbergite (Wo47En5Fsso); 10%.

Column 5: Fayalite (FaOT) ; 3%.

Column 6: Bulk composition (calculated).

J Calculated by difference.

graphic intergrowth. The percentages of sanidine and

quartz in this intergrowth are approximately 65:35,

a composition close to the temperature minimum on

the liquidus in the system KAlSiaOs—NaAlSiaOg—

S1O2. The rock is comparable to some terrestrial

granophyres, specifically the hedenbergite granophyres of the Skaergaard intrusion. One of these

(EG 3021) has essentially identical mineralogy, consisting of hedenbergite (Wo44En6Fs5o), fayalite

(Fa95), plagioclase (An40), potash feldspar, and

quartz and tridymite. Lindsley et al. (1969) estimate

temperatures of 950°—980° C and an oxygen fugacity

ranging from 10~13° to 10~13-

6

 atm for the crystallization of the Skaergaard rock, and these figures

should be equally applicable to the lunar granophyre.

The chemical, mineralogical, and textural features

of this rock strongly suggest that it represents the last

liquid differentiate from the fractional crystallization

of a large body of lunar basaltic magma (or possibly

an initial product of partial melting). Its composition

is similar to that of the high-silica glassy mesostasis of

many of the Apollo 11 igneous rocks, described by

Roedder and Weiblen (1970). It is also comparable

with the light-colored, silica-rich parts of the unique

rock 12013. Whether it was formed at or near the

locale of the Apollo 12 landing, or whether it is an

exotic fragment, possibly from a Copernicus ray, remains an open question.

This work has been supported by NASA Contract

9-8016.

Literature Cited

Bence, A. E., J. J. Papike, and C. T. Prewitt

1970. Apollo 12 Clinopyroxenes: Chemical Trends.

Earth and Planetary Science Letters, 8:393.

Lindsley, D. H., G. M. Brown, and I. D. Muir

1969. Conditions of the Ferrowollastonite-Ferrohedenbergite Inversion in the Skaergaard Intrusion, East

Greenland. Mineralogical Society of America

Special Paper 2:193.

LSPET (Lunar Sample Preliminary Examination Team)

1970. Preliminary Examination of Lunar Samples from

Apollo 12. Science, 1967:1325.

Reed, G. W., and S. Jovanovich

1970. Halogens, Mercury, Lithium and Osmium in

Apollo 11 Samples. Geochimica et Cosmochimica

Ada, Supplement 1:1487.

Roedder, E., and P. W. Weiblen

1970. Lunar Petrology of Silicate Melt Inclusions,

Apollo 11 Rocks. Geochimica et Cosmochimica

Acta, Supplement 1:801.
E. P. Henderson,

R. D. Buchheit,

and J. L. McCall

Microhardness of

a Lunar Iron

Particle and

High-Purity Iron

Samples

Introduction

Lunar soil recovered by the Apollo 11 and 12 missions is continually being subjected to critical analyses

and examinations by numerous scientists and engineers. A sample of the lunar soil, Sample 12032, 46-1

from the Apollo 12 mission which had been sieved

to a particle size of about 3 mm, was received for

studies by the Smithsonian Institution from the

Manned Space Flight Center. During the studies,

one particle of the lunar soil sample attracted attention because it was so strongly magnetic. Metallographic examinations showed the magnetic particle

to be metallic iron possessing an unusually low microhardness. A comparison of the microhardness of this

particle of metallic iron with the microhardness of

high-purity iron samples is reported herein.

Examinations of Lunar Iron Particle

The particle of lunar soil which exhibited a strong

magnetic attraction is shown in Figure 1 as a metallographic specimen etched in 1% Nital for about 20

seconds. Polishing was done using mechanical methods. The maximum diameter of the particle was about

2.3 mm. The microstructure of the particle consisted

of a coarse-grained mass of iron (kamacite) with

numerous nonmetallic inclusions concentrated in a

E. P. Henderson, Department of Mineral Sciences, Smithsonian Institution, Washington, D.C. 20560. R. D. Buchheit

and J. L. McCall, Battelle Memorial Institute, Columbus

Laboratories, Columbus, Ohio 43201.

peripheral zone. The dark inclusions are essentially

olivine but some ilmenite is associated with the

olivine.

The dark inclusion, left of center, Figure 1, which

is surrounded with a swathing zone, is shown at

higher magnification in Figure 2. The electron microprobe study of the inclusion showed that calcium and

phosphorus are present in about the proportions in

which they exist in apatite; since the surface of the

black material was chipped, a satisfactory probe

study was impossible.

A small metallic inclusion with a slightly different

reflectivity than the metal was found along the interface of the swathing metal around the apatite (?)

and the matrix. This grain was probed by Dr. K. F.

J. Heinrich and Mr. Charles Fiori of the National

Bureau of Standards who reported that although it

has essentially the composition of the surrounding

metal it probably contains a light element—carbon,

boron or nitrogen—in amounts too small to be measured. On this evidence, we suspect that this inclusion is a carbide.

The average diameter of the metal grains in the

lunar particle, determined by a lineal intercept

method, was found to be about 0.25 mm. We observed no work hardening or other physical damage

in the microstructure of this lunar iron.

MICROHARDNESS DETERMINATIONS

The microhardness values obtained on this Apollo 12

sample were lower than the values normally reported
SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

FIGURE 1.—Microstructure of lunar iron particle. Maximum dimension is 2.3 mm.

for commercially pure iron and much below the microhardness of kamacite in iron meteorites.

Recently E. P. Henderson found what is assumed

to be kamacite grains in stony meteorites which are

unusually soft. Some of these grains, when measured

with the Vickers diamond indenter, using a 25-gram

loan, gave a Vickers Hardness Number (V.H.N.)

between 120 and 130. The study of these soft Ni-Fe

grains in stony meteorite has not been completed.

The Vickers 136° diamond pyramid was chosen

for all these microhardness measurements because it

required a smaller area for a given load than the

Knoop indenter and it generally provides more precise data than ball-type indenters (Lea 1936). The

average value of the microhardness found with the

weight loads given below are:
NUMBER 9

. •A1ft9sf!

•./.mm

.-••••-*>V4t««SS

FIGURE 2.—The dark rough area at the left is tentatively identified as apatite. Along the interface of the apatite and metal there is some ilmenite. The metallic inclusion between the two

metallic areas may be a carbide. Width of field is about 0.1 mm.

Weight load

(grams)

25

50

100

V.H.N.

80.6

78.6

72.6

Indentations

3

8

8

Mr. T. B. Shives of the National Bureau of Standards measured the microhardness of the lunar particle

using a 100-gram load and reported an average value

of 69 V.H.N. Various loads were used for all these

and other microhardness measurements reported in

this paper because of the known variation in hardness

number when low-load microhardness testing is performed (Small 1960; Lysaght and DeBellis 1969;

Edmond 1958).

A recent study involving laboratory annealing of

kamacite with 7% nickel for long periods of time, at

temperatures of 300-700 °C, showed the lowest microhardness attained was 153 Knoop Hardness Number, which is equivalent to about 140 V.H.N. (Staub

and McCall, 1969).

It is widely accepted that the hardness of meteoritic iron (kamacite) is approximately proportional

to the nickel content suggesting that the low hardness

values obtained from the lunar iron particle could be

a result of high purity, essentially fully annealed, iron.

To check this out, electron microprobe analyses were

made on the lunar iron particle and the microhardness of the lunar iron was compared with the microhardness of three different high-purity iron samples.

ELECTRON MICROPROBE ANALYSES

Electron microprobe analyses of the particle of lunar

iron detected only iron and failed to detect the presence of Ni, Co, or P, elements generally found in

meteoritic iron. The detectability limits of the electron microprobe analyser used were 0.1% for Co and

0.05% for Ni. No other analytical techniques were

used on this particle because of its small size and the

desire to preserve as much of it as possible.
8 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

Impurity element

Carbon

Nitrogen, N2

Oxygen

Aluminum

Calcium

Chlorine

Cobalt

Chromium

Copper

Germanium

Potassium

Manganese

Sodium

Nitrogen, N

Phosphorus

Sulfur

Weight, ppm

l l a

7»

12b

0.2c

2.1c

12.7°

15.7°

8.4c

1.7c

5.2c

7.0c

1.0c

20.6c

15.8c

4.4c

0.6c

* Combustion analysis.

b

 Vacuum fusion analysis.

c

 Mass spectrographic analysis.

Microhardness Determinations of High-Purity Iron TABLE 1.—Impurity content of the Bain high-purity

Samples iron sample

A literature search for microhardness data for highpurity iron samples revealed a complete absence of

useful data. Therefore, an effort was made to procure

some samples of high-purity iron and to determine

their microhardness for comparison with the microhardness of the lunar iron particle. Three samples

of high-purity iron were obtained, one from the

Edger C. Bain Laboratory for Fundamental Research

of the U. S. Steel Corporation,1 one from the Columbus Laboratories of Battelle Memorial Institute,2

 and

the third sample from Lehigh University.3

BAIN HIGH-PURITY IRON SAMPLE

Details concerning the preparation of the Bain sample

of high-purity iron were not available; however, a

chemical analysis was reported and the impurity

elements and their contents in parts per million

(ppm) by weight are given in Table 1. The analyses

for all of the impurity elements except carbon, nitrogen, and oxygen were determined by mass spectroscopy. The analyses of carbon and nitrogen were made

by chemical determinations, and the analysis of oxygen was made by vacuum fusion. These analyses indicate the sample to be 99.985 + percent iron.

The Bain sample was mounted in Bakelite at a

pressure of 5000 psi and a temperature of about

130°C. The mounted sample was ground and polished metallographically and etched for 30 seconds in

1% Nital. Subsequently, microhardness tests were

made in several places on the polished and etched

surface.

All of the microhardness indentations were made

with a Vickers diamond microhardness tester attached to a Vickers metallograph. The microhardness

determinations were performed by one operator over

an interval of several days. Each day the balance pan

on the microhardness tester was reset. In order to

evaluate the uniformity of the microhardness values

and their reproductibility in the Bain high-purity iron

sample, four series of microhardness determinations

were made. The first series consisted of four identations equally spaced along a straight line and made

Courtesy of Dr. John Bromback.

Courtesy of American Iron and Steel Institute.

Courtesy of Dr. Joseph Goldstein.

with a load of 50 grams. The second series was made

near the first series and consisted of four rows of

four indentations in each row. The indentations in

the first and fourth rows were made with a 50-gram

load, and the indentations in the second and third

rows were made with a 25-gram load. The third

series consisted of two rows of four indentations in

each row made with a 100-gram load. The fourth

and last series of microhardness determinations consisted of three rows of five indentations in each row

made with a 25-gram load. The microhardness values

obtained from each of the four series of determinations in the Bain high-purity iron sample are given

in Table 2, and the average values are plotted versus

load in Figure 3. Included in Figure 3 is a plot of the

average Vickers microhardness values of the lunar

iron.

BATTELLE HIGH-PURITY IRON SAMPLE

The Battelle high-purity iron sample was floating

zone purified (Rengstorff 1968). The process of purification begins with commercially available iron, usually high-purity electrolytic iron. The starting material is electron-beam melted in a vacuum furnace and
NUMBER 9

TABLE 2.—Vickers Microhardness Numbers for three high-purity iron samples and the Apollo 12 lunar iron

particle and the total impurity content for the three high-purity iron samples

Total

Sample impurities,

ppm

Load grams

10 25 50 100 200 300 400 ^00

Battelle

Iron

Lunar Iron

Bain Iron ..

Lehigh

Iron

35-50 78.9 74.5 70.0 65.4 60.6 59.5 58.1 57.4

(70.5-83.8) (73.7-75.5) (69.0-71.2) (64.7-66.3) (58.5-62.4) (57.2-60.9) (56.3-61.3) (55.5-60.0)

unknown — 80.6 78.3 72.6 ____ _

(78-85) (74.2-82.5) (70.7-74.5)

124.4 — 81.9 78.3 77.9 — — — —

(77.2-85.7) (76.0-80.0) (75.7-79.8)

700.5 135.5 118.5 110.7 105.2 — — — —

(122-159) (109-131) (106-116) (100-112)

160r

140

120

A

W)

111

Z

§100

80

6 0

40

• LEHIGH HIGH-PURITY IRON

• BAIN

O APOLLO 12 '<

• BATTELLE "

25 50 100 200

LOAD IN GRAMS

300 400 500

FIGURE 3.—Vickers microhardness number versus load for three high-purity iron samples and

the Apollo 12 lunar iron particle.

cast into V/% -inch-diameter ingots. Four zone-melting

passes of the electron-beam-melted ingots complete

the purification process. No chemical analysis of the

elemental impurity content was obtained for the

particular sample made available, but the total impurity content was known to be 35—50 ppm by

weight. This means the sample was 99.9950+ percent iron.
10 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

The Battelle sample was mounted in a room-temperature setting epoxy resin, ground and polished

metallographically, and finally electropolished. Subsequently, microhardness determinations were made

on the electropolished surface.

All of the microhardness determinations were made

with a Vickers diamond indenter or an MO Tukon

Microhardness Tester using loads of 10, 25, 50, 100,

200, 300, 400, and 500 grams. The various loads

were used because of the previously shown variations

of hardness reading with load. The microhardness indentations were placed in 11 rows of 6 indentations in

each row. The spacing between rows and between

adjacent indentations was approximately 4 mils for

low load (50 grams and less) indentations and 8

mils for the heavier load indentations. Twelve microhardness determinations were made for each of the

10-, 25-, and 50-gram loads; six determinations were

made for each of the 100-, 200-, 300-, 400-, and 500-

gram loads. The microhardness indentations were

measured with a filar micrometer eyepiece in conjunction with a 50 X objective. The results of the

microhardness survey on the Battelle high-purity iron

sample are given in Table 2 and the average microhardness values versus load are plotted in Figure 3.

LEHIGH SAMPLE

The Lehigh sample, although regarded as high-purity

iron, differed from the Bain and Battelle samples in

that it consisted of a fine-grained microstructure containing many dark nonmetallic inclusions. The Lehigh iron was cast as a cylinder and then heat treated

at 1000°C for 12 hours. The reported analysis of the

Lehigh iron sample, shown in Table 3, indicates it

to be 99.9 + percent iron. The sample was mounted

in Bakelite and prepared metallographically for the

microhardness measurements.

The microhardness measurements were made using

loads of 10, 25, 50, and 100 grams by the same procedure described for the Battelle iron sample. The

microhardness values obtained are given in Table 2,

and the average values are plotted versus load in

Figure 3.

Discussion of Results

The comparison, shown in Figure 3, of the microhardness of the lunar iron particle with the microTABLE 3.—Impurity content of the Lehigh iron sample

Impurity element

Carbon

Oxygen

Nitrogen

Hydrogen

Tungsten

Nickel

Al, Ba, B, Ca, Zr

Co, Cu, Ge, Mn, Mo, V

Gr, Pb, Mg, Si, Sn, Ti, Zn

ppm

70»

200b

10b

<0.5b

<300c

<40c

<50c

<20c

<10c

a

 Combustion analysis.

b

 V&cuum fusion analysis.

c

 Emission spectrographic analysis.

hardness of three different high-purity iron samples

indicates that the lunar particle also is high-purity

iron. This indication is supported further by the

electron microprobe analyses made on the lunar particle which revealed no detectable elements other

than iron.

The hardness of a material usually is affected by

only three factors: the structure and grain orientation, the amount of strain (cold work), and the

composition. The structures of the three high-purity

iron samples, as well as the structure of the lunar

iron particle, consisted of single-phase alpha iron

(kamacite). The only difference among the structures

which might affect hardness (O'Neill 1967) was the

difference of grain sizes, but, since the grain sizes of

all the samples were large enough to entirely contain

a microhardness impression at all the loads used, this

effect is not believed to be significant. Another factor

known to affect hardness is the crystallographic orientation of the grains with respect to the plane on

which the microhardness measurements are made.

This effect is particularly significant for anisotropic

materials, but has been shown to be relatively minor

for isotropic materials such as alpha iron. Furthermore, the hardness measurements made on the samples in this study were found to be rather consistent

from reading to reading (grain to grain) within each

sample, indicating little or no orientation effect.

The amount of strain in a material very significantly affects hardness with the lowest hardness always being obtained for the condition of 0 percent

strain, i.e., fully annealed. The three high-purity iron
NUMBER 9 11

samples were intentionally prepared in this condition

and, in all cases, care was taken to metallographically

prepare their surfaces such that no strain was introduced (Vitovec and Binder 1955). The only indication that the lunar iron particle was strain free, other

than its low hardness, is its microstructure which revealed equiaxed grains with no "strain lines." Further

confirmation of this probably would require a destructive technique of examination, such as transmission

electron microscopy which was not permitted in this

study.

Finally, the hardness of materials are affected by

their compositions. This is well known for alloys and

probably is the most important reason for alloying

(strength is directly related to hardness (Lenhart

1955)). Less well kno\vn, however, is the effect of

small amounts of impurity elements on the hardness

of otherwise pure elements. Since the other contributing factors to hardness described above are believed

to provide only minor effects on the materials in

this study, it is believed that the present data (Figure

3) show only the effects of impurities on the hardness

of pure iron. The three high-purity iron samples were

found to have different impurity levels; the Battelle

iron had about 35—50 ppm of impurities, the Bain

sample had about 110 ppm of impurities, and the

Lehigh sample had about 700 ppm of impurities. The

microhardness data show that, for these samples, the

microhardness increases with increasing impurity

content.

Assuming that the microhardness of the three iron

samples and the lunar iron particle is affected primarily by the impurity content, as discussed above,

and that the effect is related only to the total impurity content and not to the content of selected impurities (perhaps a poor assumption since interstitial

elements generally have a more pronounced influence

on the hardness of iron than do substitutional elements), the close match between the microhardness

of the lunar iron particle and the Bain sample suggests the total impurity content of the lunar iron

sample is in the order of 100+ ppm. Unfortunately,

the small size of the particle and the requirement not

to destroy it prevented analyses for impurities to verify the correlation indicated between microhardness

and the total impurity content.

Acknowledgments

We are indebted to Dr. K. F. J. Heinrich and Mr.

Charles Fiori of the Bureau of Standards for the

electron microprobe studies made on the small metallic inclusion, and also to Messrs. Grover C. Moreland

and Harold Moore for mounting and preparing the

polished surface we studied.

Literature Cited

Edmond, L.

1958. Vickers-Knoop Hardness Conversion. Metals

Progress, 74(3):97.

Lea, F. G.

1936. Hardness of Metals. London: C. Griffin and Co.

Lenhart, R. E.

1955. The Relationship of Hardness Measurements to

the Tensile and Compression Flow Curves. Wright

Air Development Center Technical Report, 55:

114.

Lysaght, V. E., and A. DeBellis

1969. Hardness Testing Handbook. New York: American Chain and Cable Company.

O'Neill, H.

1967. Hardness Measurements of Metals and Alloys.

2nd edition. London: Chapman and Hall, 238

pages.

Rengstorff, G. W. P.

1968. Zone Purification and Analysis of Large Bars of

Iron. Memoires Scientifiques de la Revue de

Metallurgies LXV: 85-90.

Small, L.

1960. Hardness, Theory and Practice. Ferndale, Michigan: Service Diamond Tool Company.

Staub, R. E., and J. L. McCall

1969. Metallographic Studies of an Iron-Nickel Meteorite Following Long-Time Heat Treatments. Proceedings of the International Metallographic Society Second Annual Meeting, San Francisco,

California.

Vitovec, F. H., and H. F. Binder

1955. The Effect of Surface Preparation and Condition

on Microhardness. Wright Air Development Center Technical Report, 55:372.
PETROLOGY AND VOLCANOLOGY
William G. Melson, Basaltic

Eugene jarosewkh, Nu£e s Ardentes

George Switzer, 1O7 A

and Geoffrey Thompson OI th e lb>/ U

Eruption of

Ulawun Volcano,

New Britain

ABSTRACT

Ulawan volcano, New Britain, (5°02'40"S.,

151°2O'15"E.) erupted between January 9, 1970,

and February 10, 1970, producing a small nuee ardente about 0405 hours local time, January 22, 1970.

Ash eruptions of various intensities occurred throughout the episode, and a 5.6-kilometer-long lava flow

was produced during the final phases. The main nuee

ardente was essentially a hot avalanche of basaltic

scoria which could not have emitted large volumes of

gases during flow, but had the high mobility and

marginal hot "hurricane" winds which characterise

nuees ardentes. These features lend support to the

experimental evidence of McTaggart (1956) that

high temperatures alone can greatly increase the

mobility of avalanching materials.

The chemical composition of the eruptives which

produced the nuees ardentes and the lava flows are

identical. The nuees ardentes evidently occurred

when exteremely large volumes of scoria were disgorged at low ejection velocities, such that they fell

back as coherent fragmental flows on the upper slopes,

creating hot avalanches. The preferential direction of

the main avalanche, down the Northwest Valley reWilliam G. Melson, Eugene Jarosewich, and George Switzer,

Department of Mineral Sciences, National Museum of Natural History, Smithsonian Institution, Washington, D.C.

20560. Geoffrey Thompson, Woods Hole Oceanographic

Institution, Woods Hole, Massachusetts 02543. (Mr. Jarosewich made the chemical analyses; Dr. Switzer, the electron

probe analyses; and Dr. Thompson, the trace element

analyses.)

fleets the existence of a "notch," or low point in the

crater wall, at the head of this valley.

The ejecta of the 1970 eruption are plagioclase

phyric high-alumina basalts, which are compositionally like previous eruptive rocks. Three new analyses,

petrographic features, and electron probe analyses are

given. Of special interest are the compositions of glass

inclusions in phenocrysts, which give evidence for the

existence of high-alumina basaltic liquids, and may

indicate mixing of basaltic and dacitic magmas prior

to eruptions.

This eruption of Ulawun was a comparatively small

one. The combined volume of the nuee ardente deposits and lava flows probably are between 0.002 and

0.010 cubic kilometers. The area devastated by the

nuees ardentes is about 2 square kilometers—a small

area compared to most historic nuees ardentes.

Introduction

Ulawun volcano, New Britain, had an eruption early

in 1970. First reports to the Smithsonian Center for

Short-Lived Phenomena indicated that a well-developed nuee ardente (glowing-cloud eruption) had

been produced on January 22, 1970. This led to a

field study of the eruption as part of an ongoing project on the classification, properties, and origin of

nuees ardentes. Two other nuee-ardente-producing

eruptions were recently studied as part of this project

(1968 eruption of Mayon volcano, Phillippines, see

Moore and Melson 1969; 1968 eruption of Arenal

15
16 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

volcano, Costa Rica, see Melson and Saenz 1968).

This is an interim report dealing briefly with the results of the field observations at Ulawun volcano, and

of the laboratory studies of the samples from the

nuee ardente deposits and from an associated lava

flow.

Mr. R. Citron and the writer were at the volcano

from February 7 to 14, 1970. In addition to the

results reported here, extensive still photography and

16-mm cinematography were obtained by Mr. Citron.

We had hoped to use cinematography to get quantitative information on the velocity and other features

of nuees ardentes, but we arrived too late. Nonethless,

extensive photographic coverage was obtained of the

nuees ardentes deposits and the surrounding devastated zone. The still photographs (35-mm slides) and

motion pictures are now on deposit at the Smithsonian Institution.

We were accompanied throughout the field investigations by R. A. Davies, and part of the time by

G. A. M. Taylor and David Palfreyman, of the

Rabaul Volcanological Observatory, an organization

which is maintained by the Administration of the /

Territory of Papua, New Guinea, and draws its pro /

fessional staff from the Australian Bureau of Mineral

Resources, Geology, and Geophysics. We acknowledge^

the kind assistance and free exchange of information^

given by these gentlemen. R. A. Davies (192^0 and

1971) has discussed this eruption, and R. W. Johnson

(1970a) has described the volcano and its petrology

prior to the 1970 eruption. Further publications on

this eruption are contemplated by Davies, who

reached the scene of the eruption almost at its inception, and remained at hand until its termination.

Nuees Ardentes

Nuees ardentes ("glowing-cloud eruptions") have received much attention because of their incredible

destructive potential, as demonstrated by the obliteration of St. Pierre, Martinique, and its 30,000 inhabitants by a nuee ardente from Mount Pelee, an eruption described in the classic work on nuees ardentes

by A. Lacroix (1904). Since that time, numerous

other nuees ardentes have been described, and much

has been written about their mechanism of flow. One

of the most recent reviews is by McTaggart (1960).

Nuees ardentes are defined somewhat differently

by different authors, but perhaps the following definition is acceptable to most; it is the one used in

this report:

A nuee ardente is a type of volcanic eruption involving two components: (1) a hot, normally but not

always incandescent, highly mobile avalanche composed of either essential or accidental material or a

combination of the two, and (2) a hot envelope of

gases and ash, which is derived from the avalanche

but includes much heated air, which expands vertically in billowing, ash-laden clouds, and also travels

laterally, predominantly parallel and extending beyond the sides of the avalanche, and may extend very

far beyond the final terminus of the avalanche; these

lateral, ground-following ash and gas clouds can attain "hurricane" velocities, on the order of 100 mph,

and are responsible for most of the loss of life and

extensive damage associated with historic nuees

ardentes.

Ulawun Volcano: Background Information

The following summary is drawn largely from Johnson (1970a), who gives an account of the morphology, geology, and petrology of Ulawun prior to its

1970 eruption, and gives a schematic topographic

map. Johnson (1970b) also has reviewed the relationship between lava composition, volcano position,

and the Benioff zone beneath New Britain. Ulawun

(The Father) is a symmetrical stratovolcano on the

north coast of central New Britain which rises from

a base at sea level to 2,300 meters. It has a pronounced summit crater about 300 meters wide and up

to 130 meters deep, with notches which feed into the

major valleys, of which the Northwestern Valley

(Figure 1) was the course of the 1970 nuee ardente.

This Northwestern Valley is a pronounced "scar" on

the mainly smooth cone (Figure 1), and appears to

have been eroded by hot avalanches as well as by

normal erosive processes.

A pronounced older, deeply eroded, volcanic edific

trends roughly east-west along the south side of the

volcano (Figure 1), and is marked by a 160-meterhigh escarpment, which may be the remains of a

caldera or linear graben.

Eruptions of Ulawun appear to be characterized by

a mixture of strombolian and vulcanian eruptions.

Lava flows typically occur, and move as thin ribbons

down one or more valleys. These flows are interlayered with the volcanic fragmental debris, mainly
NUMBER 9 17

FIGURE 1.—Vertical aerial photograph of Ulawun volcano, New Britain, taken June 17, 1948.

scoria, and buttress the volcano with an interleaved

framework emanating from the summit. The relative proportion of fragmental deposits and coherent

flows is unknown, but they are perhaps on the order

of 1:1.

Observations of the 1970 eruption show that nuees

ardentes at Ulawun are of the avalanche type (St.

Vincent type, or d'explosion vulcanienne type of

Lacroix, 1904), and occur when the volcano disgorges

large quantities of fragmental debris at low ejection

velocities, such that large quantities fall immediately

back on the slopes, coalescing to form hot avalanches.

Table 1 summarizes some of the principal features

of Ulawun volcano.

Summary of the 1970 Eruption

The eruption was a brief one (about 32 days) and,

in terms of total volumes of ejecta, was not a major

eruption. Based on preliminary measurements, the

hot avalanche and associated marginal ash deposits
18 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

total about 0.005 cubic kilometers, and the main lava

flow, that in the Southwest Valley, totals about 0.003

cubic kilometers. The total area devastated by the

nuee ardente of January 22 is about 2 square kilometers. These estimates are calculated from the preliminary measurements of Davies (1970). No estimate can yet be made of the volume of airfall ash.

The area devastated by the nuee ardente is extremely small compared to the destruction caused

a major nuee ardente, such as that of January 21,

1951, at Mount Lamington, which ravaged over 200

square kilometers (Taylor 1958).

TABLE 1.—Summary of features of Ulawun volcano, mainly from Johnson (1970a)

and Fisher (1957)

SYNONYMS: Ulawon, Uluwun, The Father

TYPE: Stratovolcano

LOCATION: New Britain, Territory of New Guinea and Papua; opposite Lolobau Island (also

an active volcano), and 16 kilometers west of Bamus, an older dissected stratovolcano.

COORDINATES: 5°02'40"S., 151°20'15"E.

HEIGHT ABOVE SEA LEVEL: 2,300 meters, which slopes down to sea level; height above adjacent

sea floor 3,000 meters.

PREVIOUS ERUPTIONS: A number of mildly explosive events were recorded between 1915 and

1967, the most violent of these were in April 1915, and January 1967. No lava flows or

nuees ardentes were reported during these eruptions. The initial explosions seem to have

been most violent, and were followed by less violent eruptions for several months. Zones

of ash deposition are dependent on wind directions, which have ranged widely on the

different times of eruption.

PETROLOGY: Mainly porphyritic basic lavas, with plagioclase as dominant phenocryst, although

a few percent of pyroxene and olivine phenocrysts occur in most. Chemically, these lavas

are basalts, which are tholeiitic, i.e., they have low total alkalies. High alumina content

(17—19%) is a characteristic feature. Johnson (1970a) gives 4 chemical analyses, and 32

modal analyses of Ulawun rocks.

Davies (1970) has broken the eruption of Ulawun

into three overlapping phases:

1. January 9—14, 1970. Quiet vapor and ash

emission, white to grey vapor, occasional ejections of

ash, no audible activity.

2. January 15—27, 1970. Audible explosions; climactic explosion at 0405 local time, on January 22,

1970. Flows observed at 1650 the same day, moving

down Northwest Valley.

3. January 27-February 10, 1970. Quiet, effusive

phase, characterized by the major aa lava flow which

moved down the Southwest Valley. Activity slowly

declined, until February 10, 1970, when the main

flow ceased moving, and vapor-phase activity continued to decline.

A number of vents were active during the eruption,

all located circumferentially to the summit crater.

The elevation of Ulawun grew through cone building during the eruption, starting at about 2,250

meters high, and ending at about 2,340 meters high.

GEOPHYSICAL CHANGES ASSOCIATED

EMISSION OF THE NUEES ARDENTES

WITH THE

Davies (1970) also reports the changes in tilt and

seismicity associated with the major explosive activity of January 22, 1970. Tiltmeter readings of the

tangential component indicate a high in the inflation

of the volcano prior to this event, and a rapid deflation of 28 seconds of arc between February 5 and

8, 1970. Continuous harmonic tremor characterized

the seismicity. Impulsive tremors were not noted.

Ground motion increased steadily from January 16,

1970, when measurements began, and reached a

peak in excess of 25 microns during the night of

January 21-22, 1970, which coincided with the first

eruption of a nuee ardente. Ground motion decreased

after that, although significant peaks were recorded

on the afternoon of January 25 and the night of

January 27, 1970, the latter coinciding with the

production of three nuees ardentes, and the beginning

of the quiet effusive phase.
NUMBER 9 19

Account of the Major Nuee Ardente

Davies (1970), who was near the volcano, gives this

account of the event:

A "major" eruption from the northwest vent occurred at

0405 hours LT. The eruption, of Pelean type, was not preceded by any abnormal audible activity and explosive ejections of lava fragments and ash were observed prior to the

eruption. Dense ash-laden vapour clouds accumulated above

the summit, successive emissions gradually enveloping the

northwest vent. An eye witness described how some 40 seconds later, abundant spots of light could be seen on the

lower northwestern slopes. This can be ascribed to the avalanche (ash-flow) component of the nuee emerging from

the Northwest Valley. Incandescent blocks and igniting

vegetation marked the path of the nuee down into the

forested region. The dark ash cloud component, which had

blanketed the northwestern slopes, expanded rapidly to above

3,000 meters within 10 minutes. Between 0412 hours and

0432 hours an electric storm raged within the ash cloud and

at 0430 hours a light shower of accretionary lapilli (mud

pellets) and rain fell on the Mission.

Aerial inspection at 0700 hours (LT) revealed an area of

almost total devastation 2.4 kilometers long and 0.8 kilometers wide, extending down through the forested region on

the lower northwestern flanks of the volcano.

The northwest and .northeast vents were continually active

throughout the day, with little response from the southwest

vent. Ash-laden vapour emission was again voluminous, dense

clouds rising to over 5,000 meters. Cumulus cloud, together

with smoke haze rising from burning vegetation marginal to

the devastated area, rendered observation difficult. At 1650

hours (LT) a lava flow was seen descending the Northwest

Valley, formed by the merging of two streams from the

northeast and northwest vents, respectively. This flow was

probably initiated during the early morning and by 1800

hours it had reached an altitude of 1,000 meters above sea

level.

During the night all four vents were active, the lava

temperature on emission being estimated at 1000—1100° C

(by comparison with temperature-colour charts). Occasionally explosive ejections from two or more vents were synchronised, the more rhythmic ejections from the northeast

and northwest vents littering the upper slopes with great

volumes of incandescent blocks. Pulses of lava were frequently expelled from the north and northwest vents, the

incandescent fronts surging down into the Northwest Valley.

Audible explosions, which had persisted at irregular intervals

throughout the day, increased in intensity during the night.

OBSERVATIONS ON THE DEVASTATED ZONE AND HOT

AVALANCHE DEPOSITS

There was insufficient time during our field work to

prepare a detailed account of our observations on the

"%**

FIGURE 2.—Hot avalanche (light gray deposit in middle of photograph) filling lower portion

of Northwest Valley, February 7, 1970. Low altitude, oblique aerial photography.
FIGURE 3.—Hot avalanche deposits in Northwest Valley,

looking southeast toward Ulawun, at an elevation of about

500 meters. February 10, 1970.

devastated zone and hot avalanche deposits, or to

refine our initial observations. Some of these observations, recorded in a field journal immediately after

our first entry into the devastated zone, follow. Figures 2-12, all taken by Mr. R. Citron, illustrate

some features of the devastated zone and the hot

avalanche deposits.

We reached the devastated zone on February 7, 1970, some

16 days after the major nuee ardente had occurred. To

reach the zone, we travelled south from a point near the

airstrip, which is north of Ulawun and on the coast, through

heavy rain forest along a gradually rising stream course,

which, at an altitude of 450 meters, intersected the devastated zone. The first evidence of nearing the devastation was

the smell of smoldering wood and evidence of a clearing of

the rain forest ahead. The first damage we found was yellowed, nvithered vegetation. This withering became ubiquitous' within ten to a few tens of feet after these first,

irregularly distributed signs, and gave way to a totally devastated zone, where all trees had been either uprooted or

snapped off a short distance up their trunks. Uprooted trees

were aligned pointing down slope, that is, away from the

FIGURE 4.—Water vapor rising from the hot avalanche deposits after a rainstorm,

February 8, 1970.
NUMBER 9 21

volcano. These fallen trees included eucalyptus trees which

were up to 150 feet long. We noted very little ash in this

zone, although a thin veneer, less than a centimeter thick,

was present in places on the ground.

We traversed this zone of felled trees with difficulty, moving southwest so as to intersect the avalanche itself. After

about 300 to 400 meters, we reached a blackened, ashcovered zone, where trees were slightly charcoalized on the

side facing the volcano, and where some, those that had

been ignited at the time of the avalanche, were still smoldering. This zone was a few hundred feet wide, and was

confined to the margin of the channel down which the hot

avalanche had traveled.

Remarkably, a small number of tree trunks were still

standing near the margin but within the avalanche deposits, although their tops had been snapped off and carried

away. These trees were smoldering from the portion buried

in the avalanche deposits and, where their bases had been

burned through, had collapsed.

Smoke rose from buried,' smoldering wood in the ash flow,

and there were small, only weakly active fumeroles. The

avalanche here appeared to be several hundred feet wide,

and was composed largely of dark grey> to black, sometimes

red, scoriaceous basaltic bombs in a matrix of coarse ash,

mainly composed of seriate fragments derived from the

shattering and breaking up of the bombs during the avalanche. The bombs commonly had a knobby, "puffed-up"

appearance, and typically their interiors were more vesicular

than the oujter portions, as if the outer vesicles had been

flattened and compressed by pounding with other bombs

and blocks during the avalanche. The "puffed-out" appearance suggests that expansion and gas release continued during the avalanche, and that the bombs were in a thick,

pasty state during their ejection and subsequent avalanching.

The bombs ranged widely in size, from large, up to five feet

wide, on down to a few inches across.

Less abundant, but still conspicuous components, were

angular light-colored, apparently holocrystalline mediumgrained fragments, ranging up to large blocks, a few feet

across. These appear to be accidental inclusions, perhaps

from the plug and walls of the vent.

Subsequent field work gave a better overall view

of the avalanche deposits. From place to place, the

deposits range widely in the amount of coarse (e.g.,

greater than 6-inch maximum diameter) and the

amount of fine clasts. There is no evidence of sorting

in some places, whereas elsewhere there are areas,

FIGURE 5.—Hummucky topography of the avalanche near terminus. Direction of "flow" from

left to right, and about parallel to the direction indicated by the alignment of fallen trees in

the background. At an elevation of about 500 meters, February 8, 1970.
22 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

TABLE 2.—Analyses of some 1970 eruptives of Ulawun

volcano (Chemical analyses by E. Jarosewich; trace

element analyses by G. Thompson)

Constituent

SiO2

A12O3

Fe2O3

FeO

MgO

CaO

NasO

K2O

H2O+

H2OTiO2

P2O5

MnO

Totals

Q

OR

AB

AN

DI

HY

MT

IL

AP

Fe/Mg

B

Ba

Co

Gr

Gu

Ga

Li

Ni

Sr

V

Y

Zn

Zr

Chemical analyses (weight percent)

1* 2* 3*

52.77 52.62 51.51

18.00 18.31 18.96

2.99 3.23 2.72

7.14 6.81 7.50

4.98 4.94 4.92

10.48 10.45 11.14

2.29 2.40 2.24

0.37 0.40 0.32

<0.1 <0.1 <0.1

0.01 0.01 0.03

0.96 0.96 0.79

0.08 0.08 0.07

0.14 0.14 0.16

100.21 100.35 100.36

CIPW Norms

7.10 6.60 4.50

2.19 2.36 1.89

19.38 20.31 18.96

37.74 38.01 40.74

11.25 10.88 11.59

16.20 15.49 17.06

4.34 4.68 3.94

1.82 1.82 1.50

.19 0.19 .16

.36 .34 .40

Trace element analyses (parts per million)

30 28 15

100 110 75

40 40 38

30 35 35

160 110 90

20 18 18

10 8 7

21 23 22

350 300 280

300 300 300

25 '24 22

180 190 190

25 28 20

TABLE 3.—Comparison of the 1970 Ulawun e'jecta,

represented by the analysis of the scoria (Table 2)

in column 1, with an average oceanic deep-sea basalt

in column 2 (Melson et al. 1968), and overall average

basalt and andesite (Taylor and White 1966) in

columns 3, and 4 respectively

Constituent

SiO2

A12O3

Fe2O8

FeO

MgO .

CaO

Na2O

K2O

TiO2

P2OS

M nO . .

B

Ba

Co

Cr

Cu ...

Ga

Li

Ni

Sr

V

Y

Zn

Zr

Chemical analyses (weight percent)

1

52.77

18.00

2.99

7.14

4.98

10.48

2.29

0.37

0.96

0.08

0.14

2

49.21

15.81

2.21

7.19

8.53

11.14

2.71

0.26

1.39

Trace element analyses

30

100

40

30

160

20

10

21

350

300

25

180

25

7

12

32

296

87

18

8

123

123

289

43

122

100

5

48.9

15.7

10.7

8.70

10.8

2.32

1.02

1.82

4

59.5

17.2

6.10

3.42

7.03

3.68

1.60

.70

(parts per million)

5

250

48

200

100

12

10

150

465

250

25

110

10

270

24

56

54

16

10

18

385

175

21

110

* Column 1: Scoriaceous basalt bomb from 1,600 feet

level of main avalanche produced by nuee ardente of January 22, 1970. Sample number USNM 112480.

some almost dune-shaped with their long axis in

places perpendicular and in other places parallel to

the direction of flow, which appear to be well sorted,

consisting mainly of coarse—sand-sized fragments.

Typically, the deposits were estimated to be about

30 feet thick, although there was no way to accuColumn 2: Massive basalt from lava flow of 1970 eruption.

Collected from terminus of slowly moving flow on February

8, 1970, at elevation of 1,450 feet along the upper dry

course of the Matisibu River, the Southwest Valley of Ulawun volcano. Sample number USNM 112481.

Column 3: Light-gray holocrystalline basalt xenolith from

main avalanche deposit at 1,600 foot level of the Northwest

Valley. Sample number USNM 112482.
rately measure this thickness. The deposits do not

thin noticeably toward the terminus, but rather thin

abruptly, in a distance of a few hundred feet, ending

in a chaotic melange of large blocks, bombs, and

partly shattered and charcoalized tree trunks, with

perhaps about 60 to 70 percent of finer material. To

a first approximation, the deposits show no great

range in thickness from their point of first "heavy"

deposition, near the base of the northwest "shoot,"

to their terminus, another kilometer or so away.

The overlaying hot-ash "hurricane" proceeded beyond the terminus of the avalanche, withering vegetation up to 300 meters further down the "avalanche"

course. Beyond the avalanche terminus, the dry, flattish stream bed curved gently. The totally withered

zone gave way to zones where the withering alternates from one side, at one curve, to the other side,

at the next curve, as if the "blast" became narrow,

and ricocheted at each turn.

Composition of the Eruptives

Here, we search for significant chemical differences

between the melts which produced the nuee ardente

and those that produced the lava flow. We also selected a sample of a common variety of xenolith in

the main nuee ardente avalanche deposit, which, in

the field, appeared to be quite different from the

essential ejecta.

Table 2 shows that all these eruptives are chemically basalts (between 45 and 55 percent silica), that

they are slightly quartz normative (4.5 to 7.1 percent), and that they are remarkably similar to one

another, even in their trace element compositions.

The slightly higher ferric/ferrous iron ratio in the

flow compared to the bomb is an expected consequence of the longer high-temperature exposure of

the flow to the atmosphere. The very slightly lower

contents of B, Ba, Sr, and Zr in the xenolith comFIGURE 6.—Felled trees, uprooted, or snapped off, during nuee ardente of January 22, 1970.

Northeastern side of avalanche channel at about 400 meters elevation. Photograph taken

February 8, 1970. Vapor from steaming avalanche deposits in foreground.
24 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

TABLE 4.—Comparison of the 1970 eruptives (columns 1 and 2) with those of earlier

eruptions (columns 3-6) compiled by Johnson (1970a)

Constituent

SiOa

A12O3

Fe2O8

FeO

MgO

GaO

Na2O . . . .

KaO

HaO +

H2OTiO2

p2o«

MnO

/ •

52.77

18.00

2.99

7.14

4.98

10.48

2.29

0.37

0.1

0.01

0.96

0.08

0.14

100.21

Chemical

2

52.62

18.31

3.23

6.81

4.94

10.45

2.40

0.40

0.1

0.01

0.96

0.08

0.14

100.35

analyses (weight percent)

3

51.1

17.5

4.30

6.35

5.85

10.8

2.40

0.30

0.07

0.23

0.92

0.07

0.13

100.15

4

52.47

19.16

3.40

5.82

4.90

10.76

2.45

0.32

0.14

0.03

0.75

0.09

0.17

100.51

5

52.10

16.78

3.07

7.32

6.52

10.84

2.19

0.32

0.08

0.03

0.75

0.09

0.19

100.39

6

51.79

18.06

2.51

7.25

5.85

10.98

2.19

0.32

0.17

0.06

0.74

0.0$

0.17

100.26

•Column /: Basaltic bomb, from hot avalanche deposits, 1970 eruptions. E. Jarosewich,

analyst.

Column 2: Lava flow, sampled at terminus, 1970 eruption. E. Jarosewich, analyst.

Column 3: Ash, 1967 eruption, deposited on Lolobau Island (Jorgensen, analyst, in Johnson, 1970a).

Columns 4-6: A.J.R. White, analyst, in Johnson (1970a).

Columns 4 and 5: Prehistoric flows and a sill.

Column 6: Bomb from southwestern slope.

pared to the essential ejecta are also small but noteworthy features of the analyses.

The Ulawun rocks have high alumina contents

compared to most basalts. This is reflected modally by

the abundance of plagioclase. Other differences with

"average" basalts are brought out in Table 3, and

include higher boron, and lower nickel, chromium,

and zirconium.

The trace element abundances show both basaltic

and andesitic affinities (Table 3). The very low

nickel and chromium contents are close to the values

for andesites, and low compared to most basalts. On

the other hand, the cobalt and vanadium contents are

close to those of basalts. The zirconium is anomalously

low, and the copper, vanadium, boron, and zinc are

anomalously high compared to both average basalts

and average andesites. Gallium, yttrium, and lithium

show little differences between the Ulawun samples,

and the average basalts and andesite.

The Ulawun samples have low sodium contents

compared to deep-sea basalts and to most island and

continental basalts, and their potassium content, although higher than most deep-sea basalts, is lower

than most island and continental basalts. The iron/

magnesia ratio is higher, and the total iron is close

to and magnesia is less than the average basalts.

Table 3 indicates that the Ulawun basalts cannot

be related to either of the average basalts by a simple

near-surface (low pressure) fractionation scheme. If

we regard the average basalts as parents, we see that

separation of some olivine and chromite would account for the lower Mg, Ni, and Cr, and higher Si

of the Ulawun samples compared to these hypothetical

parents. However, the low Na and Zr content of the

Ulawun basalts is inconsistent with such near-surface

olivine fractionation of these hypothetical parents.

The recent and prehistoric eruptives of Ulawun are

of relatively uniform composition (Table 4). All are
NUMBER 9 25

TABLE 5.—Hand-specimen and petrographic description of the analyzed basalts from

the 1970 eruption of Ulawun Volcano. Mineral abundances in volume percent

Bomb Flow Xenolith

STRUCTURE (hand-specimen description)

Black, highly vesicular, nubby,

"puffed-out" outer portion;

more vesicular in interior than

on surface. Black to reddish

oxidized glass on surfaces.

Dense; black; scattered irregular cavities; porphyritic.

Light gray; porphyritic; lacks

significant pore space. Modal

analysis (volume %) : Plagioclase phenocrysts: 36.2; Plagioclase microlites: 21.4; Pyroxene (total) : 29.3; Olivine:

2.0; Oxides: 2.7; Silica (cristobalite): 1.5; Interstitial glass

and unresolvable material:

5.9; Pores: 1.0.

GROUNDMASS

Clear glass, plus microlites Brownish glass, with micro- Mainly crystalline, with about

and quench crystals of plagio- lites of plagioclase, pyroxene 40 percent pyroxene, 50 perclase and pyroxene. and opaque(s). cent plagioclase, and a few

percent oxide, and possibly

clear interstitial glass.

PHENOCRYSTS

Plagioclase (1-5 mm; about

35% volume percent); olivine

(mainly small, 1-2 mm across;

less than 5 volume percent),

rare rounded phenocrysts of

clinopyroxene, and still rarer

grains of hypersthene.

Plagioclase (1—5 mm across)

about 35 volume percent;

rounded olivine grains (mainly small, 1-2 mm, but some

up to 7 mm across; less than

5 %); rare rounded phenocrysts of clinopyroxene, and

still rarer grains of hypersthene.

Plagioclase (1-5 mm; about

35 volume percent); olivine

(small, 1-2 mm across; less

than 5 percent), pyroxene

(dark green clinopyroxene, a

few large and rounded, up to

8 mm long).

high-alumina, quartz-normative basalts, with relatively low total alkali contents, and K2O contents between 0.30 and 0.40 percent. Johnson (1970a) notes

that they are comparable in chemistry and mineralogy to alumina-rich rocks with abundant plagioclase

phenocrysts from various parts of Japan.

Mineralogy and Petrography

The three samples selected for chemical, electron

microprobe, and petrographic analyses are all basalts,

and all are porphyritic, with up to 40-volume-percent

phenocrysts (crystals greater than about 0.5 mm in

maximum dimension). The dominant phenocryst is

plagioclase, which composes about 35-volume percent. These have highly calcic cores (bytownite, An8s,

to anorthite, An90) with weak zoning to An80 at their

rims. In volume, there are less than 5 percent large,

normally rounded pyroxene and olivine grains, which

may be partially resorbed phenocrysts. Olivine occurs

in all the samples, and is around F074. No complete

analyses were made of the opaques, but they appear

to be mainly homogeneous titanmagnetite with about

17 percent TiC>2. Table 5 compares the hand speci-
26 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

TABLE 6.—Pyroxene analyses via electron microprobe. George Switzer, analyst. First

three pairs (1—2, 3-4, 5—6) are from the rims and cores of a single phenocryst in

each of the three analyzed samples in Table 2, the basaltic bomb, the flow, and

xenolith, respectively. The final analysis (Column 7), is of a pigeonite microlite in

the groundmass of the basaltic xenolith

Constituent

SiOa .

TiO2

AI2O3

Fe

M nO

MgO

GaO

Na2O

K2O

Fe

Mg

Ca

Bomb

1

51.5

0.4

2.3

7.4

0.2

17.2

20.6

0.2

0.05

14.4

46.1

39.5

Electron

2

51.4

0.4

2.5

8.4

0.2

17.3

19.3

0.2

0.05

16.3

46.5

37.2

microprobe

Flow

3

53.2

0.5

3.2

6.6

0.2

16.7

19.5

0.2

0.05

analyses

4

52.8

0.5

3.3

8.0

0.2

15.2

19.0

0.2

0.05

Molar ratios (mole

13.4

47.0

39.6

16.7

43.9

39.4

(weight

5

52.5

0.4

3.5

7.8

0.2

15.6

20.0

0.2

percent)

15.8

43.7

40.4

percent)

Xenolith

6

52.7

0.4

3.4

7.8

0.3

17.0

18.8

0.2

15.6

47.0

37.4

7

52.6

0.3

1.0

19.9

0.4

16.9

6.3

0.2

40.1

47.2

12.6

FIGURE 7.—Uprooted trunk of eucalyptus tree. Northeastern

margin of avalanche channel. Note abrasion of trunk. February 10, 1970.

men and petrographic features in the three analyzed

samples, and Figures 13 and 14 give comparisons of

petrographic features.

The pyroxene phenocrysts are typically augite in all

three samples (Table 6). Rarely, hypersthene phenocrysts occur, and intermediate pigeonite microlites

(analysis 7, Table 6) were found in the matrix granules of the only holocrystalline basalt examined—the

basaltic xenolith. Analyses of the rim and core of one

augite phenocryst was made in each of the three samples (Table 6, analyses 1—6). These show that there

is slight inverse zoning in the flow and bomb augites.

The cores are slightly higher in Fe and lower in Ca

than the rims.

The 1970 eruptives are petrographically similar to

those of earlier eruptions described by Johnson
NUMBER 9 27

FIGURE 8.—Felled and snapped-off tree trunks near terminus devastated zone. Avalanche deposits to right (note vapor); looking northwest (downslope). Unaffected trees in background.

February 8, 1970.

(1970a), except he reports that pigeonite phenocrysts

are commonly present, although in small amounts.

Johnson (1970a) gives more detailed descriptions of

reactions between phenocrysts and liquids than given

here, including oxidation and resorption of the olivine phenocrysts.

COMPOSITION OF GLASS INCLUSIONS IN PHENOCRYSTS: EVIDENCE FOR HIGH-ALUMINA BASALTIC

LIQUIDS AND OF MIXED MAGMAS

Some of the phenocrysts and large rounded grains

contain inclusions of clear to light brown glass (Figure 14). Electron probe analyses of some of these

glass inclusions are in Table 7. The glass (analysis 3,

Table 7) in a rounded olivine crystal in the analysed

basaltic bomb is quite close to the bulk composition

of the bomb, and suggests that this bulk analysis is in

fact representative of a liquid composition of a high

alumina basalt. In other words, the phenocrysts grew

from a high alumina basaltic liquid, and phenocrysts

have been neither added nor subtracted from this

parent during crystallization. The glass inclusions in

the plagioclase and augite phenocrysts are more difficult to understand, particularly the high silica

(65.4%) glass in the augite phenocryst from the lava

flow. This does not appear to be a residual glass, as

the alkalies are not noticeably higher than in the bulk

sample. One can explain this relationship by assuming

that the clinopyroxene crystal grew in a different

magma, e.g., a dacite, and that this magma was later

mixed with basaltic magma. Indeed, cases of eruptions of mixed magmas have been reported (e.g.,

MacDonald and Katsura, 1965). All analysed Ulawun lavas (Table 4) have remarkably similar bulk

composition, however, and thus if mixing of two
28 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

magmas is occurring, they must mix in the same

proportions in each eruption, and involve mixing of

basaltic magma with very small amounts of dacitic

magma.

Significance of Nuees Ardentes from Basaltic

Volcanoes

Normally, nuees ardentes are thought of as products

of explosive eruptions of acid to intermediate rocks.

Taylor (e.g., 1960) has pointed out that nuees ardentes are by no means restricted to such compositions, and reports of basaltic nuees ardentes of

Manam volcano, New Guinea. He also notes the

reports of nuees ardentes from basaltic eruptions

recorded by Lacroix (1904) and by Hantke (1951,

also at Manam volcano).

Gas emission during avalanching may be important

in giving the characteristic high mobility and billowing ash emission in nuees ardentes (see Taylor, 1958,

page 47, for a review of this mechanism). However,

McTaggart (1960) has demonstrated that high temperature alone without gas emission during flow can

account for the high mobility of nuees ardentes. He

experimented by pouring sand at various temperatures down an incline and recording its distance of

flow and geometry after deposition on a plane at the

TABLE 7.—Composition of glass inclusions in plagioclase (column 1), augite (column 2), olivine (column

3), compared to the bulk composition (column 4, analysis 1, Table 1). Analyses by electron microprobe by

G. Switzer. The glass inclusions are in the following

samples: columns 1 and 3 are in sample 1, Table 2;

column 2 is in sample 2, Table 2

Constituent

SiO2

AI2O3

TiO2

FeO*

MgO

CaO

NaaO

K2O

MnO

Q

OR

AB

AN

DI

HY

IL

Electron microprobe analyses

(weight percent)

1 2 3 4

55.1 65.4 51.1 52.8

13.3 18.5 17.9 18.0

1.6 1.0 1.1 1.0

15.8 5.0 10.3 10.8

4.2 2.5 4.7 5.0

7.1 5.9 10.7 10.5

2.0 2.1 n.d. 2.3

0.7 0.6 n.d. 0.4

0.2 0.1 n.d. 0.2

CIPW Norms

11.3 33.1 — —

0.4 0.4 — —

16.9 17.8 — —

27.1 29.3 — —

7.0 — — —

33.7 14.0 — —

3.0 1.9 — —

* All Fe recalculated as FeO.

n.d. = not determined.

FIGURE 9.—Splintered tree trunk in avalanche deposits near

terminus. This splintering occurred during transport of the

trunk in the avalanche. February 10, 1970.
- " ' » " '" * ' • ; * : - * ' , A i

• •« , ••• x $i/

FIGURE 10.—Surface of the avalanche deposits, showing abundance of lapilli-sized fragments.

February 10, 1970.

FIGURE 11.—Broken, scoriaceous bomb. Surface of avalanche deposits. February 10, 1970.
30 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

FIGURE 12.—Light-colored holocrystalline basalt xenoliths in the avalanche deposits.

base of the incline. The existence of basaltic nuees

ardentes mentioned above and of the 1970 eruption

of Ulawun volcano give strong support to McTaggart's idea. Basalts characteristically contain low contents of dissolved volatiles, and hence could not emit

large volumes of gases during avalanching. True, the

fragments in the avalanche deposits at Ulawun are

vesicular, but are scoriaceous rather than pumiceous,

and could not have emitted large quantities of volcanic gases. Gas emission from the avalanching material will enhance the mobility, but evidently is not

a prerequisite of fragmental materials which will produce nuees ardentes. Recently, nuees ardentes were

produced totally of nonessential, but hot material,

ejected during the explosive opening of a new vent

on the slopes of Arenal volcano, Costa Rica (Melson

and Saenz 1968). Here, as at Ulawun, gas emission

from the fragments in the avalanche had little to do

with the production of nuees ardentes. The mobility

at these volcanoes appears to have something to do

with the constant inclusion and heating of air, with

concomitant expansion. To my knowledge, an analysis of precisely how this mechanism works is not yet

available, and is an objective of our further studies.
NUMBER 9 31

FIGURE 13.—Comparison of textures in the three analyzed ejecta of the 1970 eruption of Ulawun volcano. Width of field equals 2 mm in each photomicrograph, A. Central, vesicular portion of the analyzed basaltic breadcrust bomb (analysis 1, Table 2). Colorless phenocrysts are

plagioclase; gray phenocrysts are augite. Matrix, crowded with microlites and minute oxide

grains, is opaque, B. Basalt, from lava flow, showing abundance of devitrified glass inclusions

in plagioclase phenocrysts and with clear overgrowths on margin. Plagioclase also abundant as

microlites in. matrix. Note scarcity of vesicles, c. Basalt, from lava flow, with large rounded

phenocryst of augite. Analyzed sample (analysis 2, Table 2). D. Basaltic xenolith. Holocrystalline, with comparatively large grains of opaques (magnetite). Inclusions in plagioclase are

holocrystalline, and mineralogically similar to the bulk sample (dominantly pagioclase and

augite).
FIGURE 14.—Basalt, with plagioclase phenocrysts rich in glass inclusions. Phenocryst is about

1 millimeter wide. Analysis 1 (Table 7) is of one of these glass inclusions.

Literature Cited

Davies, R. A.

1970. The 1970 Eruption of Mt. Ulawun, New Britain.

Smithsonian Institution Center for Short-lived

Phenomena Report, May 15, 1970: 14.

1971. The 1970 Eruption of Mt. Ulawun, New Britain.

Note on Investigation, 70501. 30 pages. Territory

of Papua of New Guinea, Geological and Volcanological Branch.

Fisher, N. H.

1957. Catalogue of the Active Volcanoes of the World

Including Solfatara Fields, Part 5, Melanesia. International Volcanological Association, Naples.

Hantke, G.

1951. Ubersicht uber die Vulkanische Tatigkeit 1941—

1947. Bulletin Volcanologique, Series II, 11.

Johnson, R. W.

1970a. Ulawun volcano, New Britain: Geology, Petrology,

and Eruptive History Between 1915 and 1967.

Australian Bureau of Mineral Resources, Geology

and Geophysics, Report 1970/21: 43.

1970b. Volcanoes of New Britain: a Summary of Preliminary Petrological Data. Australian Bureau of

Mineral Resources, Geology and Geophysics, Record 1970/72: 2-5.

Lacroix, A.

1904. La Montagne Pelee et Ses Eruptions. Paris: Masson et Cie. 626 pages.

MacDonald, G. A., and T. Katsura

1965. Eruption of Lassen Peak, Cascade Range, California, in 1915: Example of Mixed Magmas.

Geological Society of America Bulletin, 76:475-

482.

McTaggart, K. C.

1960. The Mobility of Nuees Ardentes. American

Journal of Science, 258:369-382.

Melson, W. G., and R. Saenz

1968. The 1968 Eruption of Volcano Arenal, Costa

Rica: Preliminary Summary of Field and Laboratory Studies. Smithsonian Center for ShortLived Phenomena, Report, November 7, 1968.

Melson, W. G., G. Thompson, and T. H. van Andel

1968. Volcanism and Metamorphism in the Mid-Atlantic

Ridge: 22°N. Journal of Geophysical Research,

73:5925-5941.

Moore, J. G., and W. G. Melson

1969. Nuees Ardentes of the 1968 Eruption of Mayon

Volcano, Philippines. Bulletin Volcanologique,

33(2):600-620.

Taylor, G. A.

1958. The 1951 Eruption of Mount Lamington, Papua.

Australian Bureau of Mineral Resources, Geology

and Geophysics, Bulletin, 38:117.

1960. An Experiment in Volcanic Prediction. Australian Bureau of Mineral Resources, Geology, and

Geophysics, Record, 74.

Taylor, S. R., and A. J. R. White

1966. Trace Element Abundance and Andesites. Bulletin Volcanologique, 24:177-194.
R. F. Fudali Experimental Data

Bearing on the

Paragenesis of

Two Hawaiian Basalts

from Kilaeua Volcano

Introduction

Mineral paragenesis (the order of formation of minerals in time succession) in igneous rocks is a matter

of much interest to petrologists concerned with compositional trends in the residual melts, and with the

genetic relations between different rock types which

are associated in time and place.

Paragenesis is, of course, largely a function of the

major element composition of the silicate melt but

can also be influenced by such variables as: (1) Total

confining pressure; (2) partial pressures (or fugacities) of H2O and O2; and (3) whether or not equilibrium between crystals and melt is maintained as

the crystallization proceeds.

In 1968, Dr. T. L. Wright of the United States

Geological Survey's Hawaiian Volcano Observatory

sent me specimens of two basalts which had issued

from the Summit of Kilauea Volcano in 19-19 and

1954, respectively. Although separated in time by 35

years the two lavas are virtually identical in their

major element content (Table 1).

However, these "isochemical" lavas apparently had

different paragenetic sequences, presumably due to

differences in one or more of the other variables

mentioned above. This conclusion was based on the

microscopic examination of samples from both rock

units which exhibited varying crystal/glass ratios.

R. F. Fudali, Department of Mineral Sciences, National

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

TABLE 1.—Chemical analyses of two Kilauean basalts

(weight percent)*

Constituent

SiO2

A12O3

TiO2

Fe2Oa

FeO

MgO

MnO

CaO

Na2O

K2O

H2O+ ....

H2OP2OS

CO2

Cl ...

F

Subtotal ..

Less 0

Total

1

50.20

14.04

2.74

1.83

9.50

7.03

0.17

11.49

2.25

0.57

0.1

0.02

0.27

0.02

—

100.14

1919

2

50.02

13.87

2.76

1.35

9.76

7.45

0.17

11.45

2.33

0.53

0.08

0.02

0.26

0.02

0.02

0.04

100.07

0.02

100.05

3

50.20

13.73

2.72

2.65

8.80

7.20

0.17

11.56

2.25

0.57

0.00

0.00

0.28

0.01

0.02

0.05

100.21

0.02

100.19

)54

4

50.09

13.79

2.68

1.80

9.59

7.31

0.17

11.51

2.28

0.53

0.08

0.02

0.26

0.01

0.01

0.05

100.18

0.02

100.16

* All analyses were performed at the U.S. Geoldgical Survey Rock Analysis Laboratory, Denver. Column 1: Analyst,

Lucille Tarrant. Column 2: Analyst, Ellen Danials. Column

3: Analyst, Lois Trumbull. Column 4: Analyst, Elaine

Munson.

33
34 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

The change in crystal/melt ratio in the different

specimens is normally a function of the temperature

that portion of the rock unit attained before it was

effectively quenched. Thus, by judicious selection of

samples one can examine, at least in a crude way, a

temperature and crystallization sequence for the rocks

in question. Dr. Wright (personal communication)

wrote:

The Halemaumau lava lake overflows [1919] show subequal amounts of pyroxene and plagioclase at crystallinities

varying from 5-20%. Evidently the two phases came out

simultaneously . . . and the two minerals crystallized at

nearly the same rate with falling temperature. By contrast,

in the current series of flows [1954] which come up quickly

from a depth of about 3 km* (,-^1000 bars total pressure)

clinopyroxene comes out distinctly earlier than plagioclase

(Cpx=8% by volume when plagioclase first appears) and

the rate of plagioclase crystallization does not equal that of

pyroxene until several tens of degrees lower temperature. I

would like to explain the contrast by saying that the overflows from Halemaumau lava lake were degassed and equilibrated at approximately 1 atm. total pressure whereas the

current flows retained a paragenesis on eruption characteristic of some PH o lower than 1000 bars but much greater

than 1 atm.

This theory was supported by the first chemical

analysis of the 1954 basalt (Table 1, column 3) which

reported a total iron content identical to that of the

1919 basalt but a substantially lower ferrous/ferric

iron ratio—i.e., the 1954 basalt was apparently oxidized relative to the 1919 basalt, a natural consequence of higher associated water (and oxygen)

fugacities.

However, subsequent chemical analyses and laboratory high-temperature, controlled atmosphere experiments performed here demonstrated this hypothesis to

be incorrect. Further, total pressure differences and

possible disequilibrium effects were also eliminated as

possible causes of the observed paragenetic differences. The inescapable conclusion is that an apparently trivial difference in A12O3 content (virtually

within the analytical error of the analyses) was responsible for stabilizing plagioclase at significantly

different temperatures in the two melts.

FeO and Total Iron Analyses

Divalent iron can be partially oxidized in sample

preparation and digestion so that correct FeO determinations are notoriously difficult. For this reason one

should always view reported FeO values with some

scepticism, especially if the reported FeO value is

lower than expected. One of the first things I did

upon receiving the rock samples was to reanalyze

them for FeO and total Fe as FeO.

The samples were very carefully ground to —80

mesh in an agate mortar, under alcohol. The analytical procedures used were standard wet chemical

methods previously described by Muan and Osborn

(1956) and myself (1965). Results of these analyses

are shown in Table 2. My results indicate an identical

ferrous/ferric iron ratio for the two rocks; a subsequent U.S. Geological Survey analysis (Table 1, column 4) supports this conclusion. The low ferrous iron

reported in analysis number 3 must be due either to

an analytical error or a nonrepresentative sample.

The identical ferrous/ferric ratios of the two rocks

eliminates the possibility of different associated fo/s,

since such a difference would be reflected in a large

difference between the two rocks in this ratio. The

possibility of differences in f|H2o is also eliminated

since, in the absence of significant amounts of other

gas species, H2O and O2 are inextricably related

through the dissociation of water equation (^O^*

H0 + 14O0). Different total confining pressures and/

or disequilibrium effects remained as possibilities.

TABLE 2.—Ferrous iron and total iron analyses of

1919 and 1954 basalts (weight percent)

Year and Iron Content

1919:

FeO

Total Fe as FeO

1954:

FeO

Total Fe as FeO

Fudali analysis

9.89

11.20

9.87

11.18

USGS analyses

9.50- 9.76

10.98-11.15

8.80- 9.59

11.18-11.21

* Determined from analyses of ground tilt.

Experimental Procedure

Representative samples of the two rocks were carefully crushed, under alcohol, to —80 mesh in an

agate mortar, as for the chemical analyses. One to

two hundred milligram charges of the homogenized

powders were dryed at 110°C and placed in 60%

Ag-40% Pd crucibles which, in turn, were placed in
NUMBER 9 35

vycor (silica glass) tubes, the ends of which had been

previously sealed. The open ends of the vycor tubes

were connected to a vacuum pump and, after the

system was evacuated, short lengths of tubing (containing the Ag-Pd crucibles) were necked off in the

flame of an oxy-hydrogen torch. The atmospheres inside the sealed vycor tubes were reduced to approximately

 l/2 mm Hg by this procedure. This prevented

the glass tubes from bursting at run temperatures.

More importantly, the amount of gas remaining in

the tube was so small, with respect to the weight of

the powdered charge, that this rock charge could

generate an equilibrium atmosphere at run temperature without a measurable change in its own

composition.

The charges, so prepared, were placed in a standard, platinum-wound, vertical quench furnace. Temperature control was maintained within d=l°C during the course of the run. After sufficient time for

the charge to equilibrate (in all but a few cases) at

run temperature—usually 24 to 48 hours—the charges

were quenched by plunging them in a beaker of cold

water and the quenched phases examined under the

petrographic microscope.

Temperatures were measured immediately before

and after each run with a Pt-Pt/lORh thermocouple,

previously calibrated against the melting points of

pure gold and diopside. Corrections were empirically

determined for the difference in thermal profile of

the reading thermocouple and the more massive vycor

tube et al. Absolute accuracy of the indicated temperatures, as measured by this method, may be no

better than ±2°G; however any error will be systematic rather than random. The indicated possible

temperature spreads shown in Table 3 do not reflect

such a systematic error. The indicated spread results

largely from the spread between the temperatures of

the two runs which most closely bracket the appearance or disappearance of given phase. One should

therefore recognize that, although the absolute temperature scales could be roughly 2° higher or lower

than those shown in Table 3, the relative temperature

differences shown will not change.

Both rocks were run in the same furnace, using

the same thermocouple, controller, and temperaturesensing instrument. Length of runs, quenching, and

examination techniques were identical.

The paragenetic sequences of the two rocks, determined by these methods, are shown in Table 3.

Discussion of Experimental Results

The experimental results represent crystallization sequences under conditions of constant total composition. The ratio of ferrous to ferric iron in the charge

does not change with falling temperature and the

TABLE 3.—Crystallization sequences of 1919 and 1954

Kilauean basalts—constant composition conditions

1919:

1182±2°

1174±2°

1162±3°

1105 + 5°

1078±5°

1050±5°

1954:

1179±3°

1163 + 2°

1161±2°

1100 + 3°

1078±5°

C olivine-liquidus

plagioclase

pyroxene

Fe oxide

Solidus 1

Solidus 2

C olivine-liquidus

pyroxene

plagioclase

Fe oxide

Solidus

associated gas phase has a composition which is a

function of the charge composition, rather than viceversa. Down to about the appearance of an oxide

phase the crystallization sequence is also an equilibrium sequence. With glassy starting charges it is an

equilibrium sequence to the solidus. With crystalline

starting materials crystallization at lower temperatures departs somewhat from equilibrium due to zoning effects in the crystals and the consequent inability

of the largely crystalline charge to equilibrate in the

experimental runs because of the low rate of solid

state diffusion at these temperatures.

The 1954 lava sample used in this work was largely

glass (^80%) and the determined sequence is

therefore an equilibrium sequence. Both completely

crystalline and glassy charges of the 1919 lava were

used. The only difference between the two is that,

with the crystalline charge, nonequilibrium effects as

discussed above result in the persistence of a small

amount of residual liquid to '—30° lower (solidus 2)

than is the case with glassy charges (solidus 1). The

sequence determined with crystalline starting charges

represents the actual sequence that the rock experienced in nature.

The modal analyses of samples of the two rocks

equilibrated at 1160°C are entirely consistent with the
36 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

modal observations reported by Dr. Wright (Table

4), and the experimental crystallization sequences do

indeed show a significant difference with respect to

the first appearance of plagioclase. However, the laboratory data does not support the interpretation based

upon the modal analyses of the natural rocks.

TABLE 4.—Modal analyses (volume percent)

Constituent

1919:

glass

pyroxene + olivine

plagioclase

1954:

glass

pyroxene + olivine

plagioclase

Experimental runs

equilibrated at

1160°C

*Original

rock modes

91.7

4.4

3.8

88.7

8.8

2.5

(Analysis #\,

Table 1)

89.2

5.1

5.7

(Analysis #4 ,

Table 1)

91.8

7.1

1.1

* Original rock modes supplied by Dr. T. L. Wright.

First, although plagioclase and pyroxene are present in subequal amounts in 1919 (at 8% total crystals) they did not begin to crystallize simultaneously.

Plagioclase has a crystallization interval of ^12 °

before pyroxene becomes stable. Pyroxene then crystallizes more rapidly over a short temperature interval

to approximately equal plagioclase in amount at

1160°C.

More importantly, since the observed differences in

crystallization histories have been duplicated experimentally under low-pressure, equilibrium conditions,

it is clear that neither confining pressure differences

nor nonequilibrium effects need be invoked to explain

the modal differences observed in the natural rock

specimens. Clearly the true explanation is simply that

the very slightly higher AI2O3 content of the 1919

lava stabilized plagioclase at a temperature approximately 13° higher than in the 1954 lava. Although

the determined sequences are not precise enough to

warrant further conclusions, the modal analyses at

1160° suggest that the temperature interval between

the appearance of pyroxene and plagioclase in the

1954 lava is larger than the nominal 2° indicated in

Table 4. Here again, very minor differences in major

element content (most likely slightly lower MgO and

slightly higher GaO as compared with the 1919 lava)

probably favored pyroxene over olivine in the 1954

lava in comparison with the 1919 lava.

Conclusions and Implications

An obvious conclusion of this study is that paragenetic

sequences are best determined in the laboratory,

rather than by examination of natural, quenched

rock samples supposed to represent different (but

unknown) temperatures.

Equally obvious is that, while gross differences in

paragenetic sequences may reflect significant differences in the governing parameters, modest differences

in paragenesis (e.g., a 13°C change in the appearance

of plagioclase out of a total crystallization range of

<~'100oC) may be caused by very small, indeed

perhaps virtually undetectable, major element differences. Clearly, not a great deal of significance should

normally be attached to such modest paragenetic

differences.

The experimental data gives a reasonably precise

estimate of the temperature of the 1954 magma prior

to its expulsion from the 3 km deep magma chamber.

The 1954 lava specimens contain abundant phenocrysts of olivine and pyroxene plus rare phenocrysts of

plagioclase embedded in a matrix consisting of glass

and thin plates and needles of plagioclase and pyroxene (obviously formed in the rapidly cooling lava

after extrusion). In the absence of water (less than

0.1% by wt.) the low confining pressure in the shallow magma chamber ('-'1000 bars) would not cause

a measurable change in the temperature of first appearance of the various mineral phases—with respect

to the temperatures determined in the laboratory.

Therefore, the temperature in the magma chamber

must have been lower than 1160° (for plagioclase to

be present) but no lower than 1155° (at which temperature plagioclase is approaching the abundance

of pyroxene).

The situation is not as clear-cut with the 1919 lava

since the crystallization which occurred at the surface

in a slowly cooling lava lake is not readily distinguishable from that which occurred at depth. Only

olivine phenocrysts can be identified with certainty

as being a product of crystallization at depth. So the

possible temperature spread for the 1919 lava prior

to extrusion is 1155-1175°C. Interestingly enough,
NUMBER 9 37

the flank eruption that began on May 24, 1969, and

is still continuing in the east rift zone of Kilauea, has

produced lavas throughout the eruption "whose closerange, optical pyrometer temperatures are normally

1160-1165 °C,"* in excellent agreement with the

experimentally deduced temperatures of the 1919 and

1954 eruptions.

The similarity in the major element composition of

the 1919 and 1954 lavas, and their deduced temperatures prior to eruption provide considerable information about the nature and location of the magma

source, given the reasonable assumption that both

magmas come from the same source.

The possibility that a constant composition silicate

melt existed from 1919 thru 1954 in a shallow magma

chamber and was thus able to erupt isochemical lavas

35 years apart is not tenable. At 1160° the magma

contains significant amounts of olivine and pyroxene.

Given these circumstances it would be remarkable

that separation of crystals and liquid did not occur,

yielding a more recent magma or magmas of substantially different composition(s) from the 1919

lava. Melt viscosity and density differences between

crystals and melt result in effective laboratory separations in a matter of days, with temperatures and

compositions similar to those indicated herein. Actually, volcanic activity during this period included

two additional summit eruptions (1934 and 1952)

and also periods of inflation and inferred injections

into the east rift zone (T. L. Wright, personal communication) .Neither the 1934 nor the 1952 lavas are

chemically identical with the 1919 and 1954 lavas.

No east rift lavas were actually erupted during this

period but two separate flows erupted in the east rift

zone in 1955 appear to be clearly derivative rocks,

presumably formed by removal of pyroxene and plagioclase from a summit basalt composition. Thus not

only should a shallow-seated magma differentiate,

but given the opportunity, some Kilauean magmas

have differentiated, to a recognizable extent, within

a period of time much shorter than 35 years.

Since all the Hawaiian lavas clearly originate by

partial melting in the upper mantle, a reasonable

explanation of the isochemical 1919 and 1954 lavas

is that they represent the primary melts of such a

* The Smithsonian Institution Center for Short-Lived

Phenomena, Event no. 14-17, card 1075, 12/22/70. Source:

Swanson and Peterson, U.S. Geological Survey, Hawaiian

Volcano Observatory.

process and were erupted before they had time to

differentiate.

The partial melting of mantle material most likely

occurs at, constant temperature, triggered by some

sort of pressure release mechanism. Since the lavas

carry phenocrysts rather than residual crystals they

must have been entirely liquid at one time, presumably when they originated. This necessitates an

absolute minimum source temperature of /~'1180°C

(liquidus temperature at 1 atm. pressure). A more

realistic source temperature*estimate is 1200— 1220°C

To keep basaltic material solid (prior to the melting

event) at such temperatures requires a depth of 60—

80 km for the source rock (Yoder and Tilley, 1962).

Such a depth is well within the earth's mantle and is

consistent with the frequent occurrence of ultramafic

xenoliths (considered by most geologists to be locally

derived mantle material) in some Hawaiian basalts.

As the magmas migrated upward from their mantle

source into the shallow chamber at 3 km depth they

cooled to ^1160°C, with some attendant crystallization. In most cases some differentiation took place

but the 1919 and 1954 lavas were erupted before the

melt-crystal mixture could separate appreciably.

A remarkable aspect of this volcanic complex is

demonstrated by the fact that two lavas, separated in

time by 35 years, could move 60-80 km upward

through the mantle and crust, from the same source,

to issue at the same surface vent. Either the conduit

system from the mantle source to the surface has

remained continuously open because it is filled with

magma, as suggested by T. L. Wright (personal communication) or the same conduit system has been

repeatedly opened, along a continual zone of weakness, by a periodic pressure release mechanism. In

any case it seems indisputable that the conduits have

been well-established, stable features from the surface to a depth of 60—80 km over at least the last

fifty years.

Acknowledgments

I thank Dr. T. L. Wright of the United States Geological Survey for supplying samples of the Hawaiian

basalts and making available to me their major element analyses prior to publication. His enlightening

discussions with me and his penetrating criticisms of

this manuscript are also greatly appreciated.
38 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

Literature Cited 1956. Phase Equilibra at Liquidus Temperatures in the

System MgO-FeO-F2O3-SiO». Journal of the

Fudali, R. F. American Ceramic Society, 39:121-140.

1965. Oxygen Fugacities of Basaltic and Andesitic Mag- Yoder, H. S., arid C. E. Tilley

mas. Geochimica et Cosmochimica Acta, 29: 1962. Origin of Basalt Magmas: an Experimental Study

1063-1075. of Natural and Synthetic Rock Systems. Journal

Muan, A., and E. F. Osborn of Petrology, 3(3):342-532.
Harold H. Banks, Jr. Iron-rich Saponite:

Additional Data on

Samples Dredged from

the Mid-Atlantic Ridge,

22° N Latitude

Banks and Melson (1966) reported the occurrence of

saponite in hydrothermally altered basalts and basaltic tuffs from the crest of the Mid-Atlantic Ridge

and in the median valley between 22° and 23° N

latitude. The present paper gives the results of a

chemical and X-ray study of that material as well as

of identical material tentatively identified as nontronite by Melson and van Andel (1966).

The 22° N latitude area was first examined in

detail during cruise 44 of R. V. Chain (SeptemberOctober 1964) of the Woods Hole Oceanographic

Institution and revisited in 1965 on cruise 1965-1 of

R. V. Thomas Washington (December 1965) of

Harold H. Banks, Jr., Department of Mineral Sciences, National Museum of Natural History, Smithsonian Institution,

Washington, D.C. 20560.

Scripps Institution of Oceanography. The geological and geophysical results were presented by van

Andel et al. (1965) and van Andel and Bowin

(1968). The petrology of the area has been discussed

by Melson and van Andel (1966) and Melson et al.

(1968). Siever and Kastner (1967) have described

the mineralogy of the sediments.

Saponite is a major constituent of massive basalts,

metabasalts, basaltic tuffs, and metatuffs dredged at

four stations in this area of the Mid-Atlantic Ridge

(Table 1).

In massive basalts, olivine phenocrysts are entirely

replaced, in some, by dark, gray-green saponite with

iron oxide, possibly goethite, localized at the crystalmatrix interface and in fractures in the pseudomorphs. The pseudomorphs are commonly connected

TABLE 1.—Location of dredge hauls on the Mid-Atlantic Ridge in the area between 22° and

23° N latitude containing abundant saponite-bearing rocks

Station

Thomas Washington, cruise 1965-1:

THV-4 (dredge 2)

THV-14 (dredge 17)

THV-18 (dredge 10)

Chain, cruise 44:

DR-2

Latitude and longitude

22°31.5'N, 45°W to 44°59.8'W

22°49.2'N, 45°8.8'W to

22°48.6'N, 45°10.1'W

22°10'N, 45°14.2'W to

22°11.4'N, 45°16.6'W

22°38.2'N, 44°58.6'W to 44°58'W

Depth (m)

1985-1735

3500-3000

3100-2600

2400-2100

39
40 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

by veinlets of optically identical material. Saponite

also occurs as thin films along cleavages and fractures

in subcalcic augite grains and along grain boundaries.

Plagioclase (ca. An65) often exhibits peripheral alteration to saponite, and any glass inclusions in the

plagioclase are entirely altered to saponite. Saponite

is also present as vesicle, interstitial, and vein filling.

Such relations may be seen in a single thin section.

Saponite occurs associated with albite (Ani—An4),

relict calcic plagioclase (as high as An75), ripidolitic

chlorite (MgO = 20%, FeO=19%, A12O3=18%),

actinolite (47-64% tremolite molecule), epidote (average composition about 75% clinozoisite molecule),

quartz, sphene, pyrite, and relict spinel in the metabasalts (Melson and van Andel 1966). It is commonly intergrown in vesicles and veins with material

which optically resembles chlorite. Veinlets and

shear planes in mylonitized and brecciated basalts

which have been only slightly altered in mineral

composition contain trace amounts of saponite associated with albite, actinolite, chlorite, epidote,

pumpellyite, and zeolites (probably mainly natrolite).

Marine tuffs dredged from the 22° N area show

considerable variation in texture and mineralogy, but

most show an abundance of saponite in the matrix,

absence of highly vesiculated fragments, and abundance of fragments of glassy, variolitic rinds as opposed to coarser-grained fragments.

The metatuffs are undeformed and consist of

lapilli of originally glass-rich basalt in a fine-grained

ashy matrix. The glass is completely replaced by ripidolitic cholorite which is commonly altered to saponite.

The matrix is composed of abundant saponite and

traces of actinolite.

Optically, the saponite is micaceous to fibrous in

habit, gray-green to yellow-brown in color, exhibits

moderate to high birefringence (ca. 0.02 ;NZ= 1.56)

and is weakly pleochroic. In hand-specimen, it is light

to dark gray-green with a greasy luster. Massive pieces

are extremely soft when wet but become harder and

brittle upon drying.

The saponite was identified using the identification

scheme of Warshaw and Roy (1961) for layer silicates. Samples were ground in a porcelain mortar,

and care was taken to prevent or at least minimize

the effects of fine grinding which can destroy the

ordered crystalline structure. The powders were then

mixed with a small amount of finely ground silicon

as an internal standard for X-ray study. Oriented

slides, glycolated and unglycolated (with ethylene

glycol) were analyzed on a diffractometer at 1°—

20/minute, with Cu radiation and a nickel filter.

Resolution of the (060) smectite* reflection (1.49—

1.52 A for dioctahedral smectite and 1.53-1.54 A for

trioctahedral smectite) was obtained by powder photographs using nickel filtered copper radiation in a

114.6 mm diameter camera. Powder data for two

massive samples of saponite (samples 2—17 and 10—

116) are given in Table 2.

TABLE 2.—X-ray powder data for saponite

dA

Indices1 Cahuenga Mid-Atlantic Ridge Mid-Atlantic Ridge

Pass, Station THV-4 Station THV-18

California1 (Sample 2-17) (Sample 10-116)

001

002

003

11 ,02

004

005

13,20

006

—

—

04,22

15,24

31

06,33

26,40

19,46

53

60,39

15.4

7.9

5.28

4.60

3.93

3.13

2.648

—

2.560

2.452

2.298

1.740

—

1.541

1.330

1.001

—

0.888

12.5382

4.605

2.640

2.520

2.311

1.739

1.536

(10) 8

(4)

(3)

(1)

(1)

(4)

12.5032

—

—

4.563

—

—

2.618

—

—

—

—

—

—

1.527

—

—

—

—

(10) 8

(4)

(3B)

(5)

1Data for griffithite, an iron-rich saponite (Faust 1955).

2

 X-ray pattern was made using the following instrumental

factors: GuKa radiation, \= 1.54178A; 38KV; 18MA;

silicon served as an internal standard. Peak shifted to 16.61 A

after treatment with ethylene glycol.

3

 Numbers in parentheses are estimated relative intensities.

B-broad.

* I use the term "smectite," proposed by British clay

mineralogists (Brown 1955), rather than "montmorillonitetype mineral," an approved, identical, but cumbersome

name.
NUMBER 9 41

Semiquantitative chemical analyses of saponite

(Table 3) from veins in a mylonitized olivine basalt

(sample 2—17) and from hydro thermally altered basaltic glass (sample 10—116) were performed by electron microprobe and X-ray fluorescence analysis,

respectively, of lithium tetraborate fusions, with analyzed oceanic basalt lithium tetraborate fusions serving as standards: the fusions were prepared following

the procedure outlined by Rose et al. (1963). For

sample 10-116, H2O was determined by the Penfield

method, Na2O and K2O by flame photometry: the

FeO and Fe2C»3 contents of both samples were determined by classical methods.

The chemical analyses of the samples were plotted

TABLE 3.—Semiquantitative chemical analyses of

iron-rich saponite, Thomas Washington 1965—1, Station THV-4, Sample 2-17*, and Station THV-18,

Sample 10-116f

Constituent

SiOa

AUO,

Fe2Os

FeO

MgO

CaO

Na2O

K2O

TiO2

H2O (total)

Chemical analyses (weight percent)

2-1T 10-1162

43.0

7.2

7.79

2.53

21.0

0.4

3.3

0.4

<0.05

18.9

41.6

5.0

11.32

0.78

18.3

0.6

2.2

•0.5

0.3

20.6

* Saponite from veins in mylonitized olivine basalt.

f Saponite derived by the hydrothermal alteration of

basaltic glass.

1

 Performed by electron microprobe analysis of lithium

tetraborate fusion using an enlarged electron microprobe

spot and classically analyzed oceanic basalt lithium tetraborate fusions as standards. FeO and Fe2O3 contents were

determined by classical methods.

2

 Performed by X-ray fluorescence, using the method of

Rose et al. (1963). H2O determined by Penfield method;

NassO and K2O by flame photometry; FeO and Fe2O3 by

classical methods.

on a FeO-Fe2O3-MgO ternary diagram (Figure 1)

which graphically distinguishes between the two smectites in which iron is an essential and major constituent: nontronite (dioctahedral; FeO = O-l%)

and iron-rich saponite (trioctahedral; FeO=l—8%).

Chemical analyses to delineate the smectite fields

shown in Figure 1 were selected from various sources:

saponites are from Ross and Hendricks (1945, analyses 77-79) and Deer et al. (1962, analysis 13);

nontronites are from Ross and Hendricks (1945,

analyses 55—67) ; iron-rich saponites are from Calliere and Henin (1951, analyses 4-5), Faust (1955),

and Sudo (1959).

The combined X-ray and chemical results indicate

that the clay is iron-rich saponite. The (001) reflection for the clay shifts from nearly 12.5A to 16.6A

upon treatment with ethylene glycol, and the critical

(060) reflection is greater than 1.52A which is indicative of trioctahedral smectite (see Table 3). In

addition, the semiquantitative chemical analyses of

the clay plot very nicely in the iron-rich saponite

region of the FeO-Fe2O3-MgO diagram (Figure 1).

I suspect that the high Fe2O3 content of sample 10—

116 (Table 3) is the direct result of the participation

of heated sea water with a high Eh in the formation

of the clay. The high Na2O content and the low GaO

content of both samples may very well be a primary

feature, but Na saturation may also result from cation exchange during weathering of a normal, Carich saponite in contact with sea water.

Textural relations of saponite in rocks from the

22°N area suggest several modes of origin for the

saponite: (1) hydrothermal alteration, by heated sea

water, of basaltic glass and silicates in the matrix of

basaltic tuffs during cooling and movement of the

tuffs; (2) low-grade metamorphism of basalts and

basaltic tuffs at a maximum temperature of 300 °G

(Melson and van Andel, 1966) and a pH2O of

about 500 bars; and (3) deuteric alteration of basaltic glass, olivine, plagioclase and augite in the

massive basalts.

I am indebted to Eugene Jarosewich, who provided

the semiquantitative chemical data for sample 10—116

and the total and ferrous iron analyses for sample 2—

17, and to Dr. Joel Arena who kindly assisted in the

preparation of samples for X-ray analysis. Special

thanks are due to Kenneth Towe and William G.

Melson for their helpful discussions of many of the

problems encountered during the course of this study.
42 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

FeO FeO

IRON-RICH SAPONITE

NONTRONITE

o ^aMgO Fe2O3

FIGURE 1.—Semiquantitative chemical analyses of saponite from the Mid-Atlantic Ridge (samples 2-17 and 10-116, open circles with solid centers) plotted on the ternary diagram FeOFe2O»-MgO. Open circles are nontronites selected from Ross and Hendricks (1945); open

squares are saponites selected from Ross and Hendricks (1945) and Deer et al. (1962); solid

triangles are iron-rich saponites selected from Calliere and Henin (1951), Faust (1955), and

Sudo (1959).

Literature Cited

Banks, H. H., Jr., and W. G. Melson

1966. Saponite from the Mid-Atlantic Ridge, 22° N

Latitude. 1966 Annual Meeting Geological Society of America, Abstracts: 9—10.

Brown, G.

1955. Report of the Clay Minerals Group Subcommittee

on Nomenclature of Clay Minerals. Clay Minerals Bulletin, 2:294-302.

Caillere, S., and S. Henin

1951. The Properties and Identification of Saponite

(Bowlingite). Clay Minerals Bulletin, 1:138-

144.

Deer, W. A., R. A. Howie, and J. Zussman

1962. Rock-Forming Minerals, 3:226-245. New York:

John Wiley & Sons.

Faust, G. T.

1955. Thermal Analysis and X-Ray Studies of Griffithite. Washington Academy of Science Journal,

45:66-70.

Melson, W. G., and Tj. H. van Andel

1966. Metamorphism in the Mid-Atlantic Ridge, 22° N

Latitude. Marine Geology, 4:165-186.

Melson W. G., G. Thompson, and Tj. H. van Andel

1968. Volcanism and Metamorphism in the Mid-Atlantic Ridge, 22° N Latitude. Journal of Geophysical Research, 73:5925-5941.

Rose, H. J., Jr., I. Adler, and F. Flanagan

1963. X-Ray Fluorescence Analysis of the Light Elements in Rocks and Minerals. Applied Spectroscopy, 17:81-85.

Ross, C. S., and S. B. Hendricks

1945. Minerals of the Montmorillonite Group. U.S.

Geological Survey Professional Paper, 205B:23-

77.

Siever, R., and M. Kastner

1967. Mineralogy and Petrology of some Mid-Atlantic

Ridge Sediments. Journal of Marine Research,

25:263-278.

Sudo, Toshio.

1959. Mineralogical Studies on Clays of Japan. Tokyo: Maruzen. Pages 227-268.

van Andel, Tj. H., and C. O. Bowin

1968. The Mid-Atlantic Ridge Between 22° and 23°

North Latitude and the Tectonics of Mid-Ocean

Rises. Journal of Geophysical Research, 73:

1279-1298.

van Andel, Tj. H., V. T. Bowen, P. L. Sachs, and R. Siever

1965. Morphology and Sediments of a Portion of the

Mid-Atlantic Ridge. Science, 148:1214-1216.

Warshaw, C. M., and R. Roy

1961. Classification and a Scheme for the Identification

of Layer Silicates. Geological Society of America Bulletin, 72:1455-1492.
George Switzer,

William G. Melson,

and Geoffrey Thompson

Olivine Crystals

from the Floor of

the Mid-Atlantic

Ridge near

22° N Latitude

Remarkably fresh, small, gemmy, single crystals of

olivine were found in the heavy mineral fraction of

foraminiferal sand dredged from the eastern flank of

the mid-Atlantic Ridge near 22°N. This occurrence

of euhedral, free olivine crystals in a marine sediment

is highly unusual in our experience. These olivine

crystals clearly grew in basaltic lava, and were then

freed by growth of vesicles, with gas exsolution commonly initiating at crystal-liquid boundaries. Ultimate

freeing of the crystals from the lava may entail more

than this. Conditions in a vesiculating, turbulent,

submarine lava fountain may be particularly favorable to the final freeing of these crystals.

Olivine phenocrysts, along with plagioclase phenocrysts, are the most common phenocrysts in deep-sea

basalts from the mid-ocean ridges. Thus, the occurrence of olivine in the central, volcanically active zone

of the mid-Atlantic Ridge is not surprising, but its

occurrence free of a basaltic matrix is.

The dredge which recovered the olivine crystals is

from the eastern slope of the median valley of the

mid-Atlantic, a zone of active sea-floor spreading,

characterized by frequent earthquakes and volcanic

eruptions. The rocks of the 22°N area are dominantly

fresh basalts and greenschist facies metabasalts (MelGeorge Switzer and William G. Melson, Department of

Mineral Sciences, National Museum of Natural History,

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

Thompson, Woods Hole Oceanographic Institution, Woods

Hole, Massachusetts 02543.

son and van Andel 1966, Melson et al. 1968). The

median valley here is essentially a rifted submarine

basalt field, where volcanism is manifested mainly

by fissure eruptions, some on the flanks, and others

along the floor of the median valley. The ridge from

which the olivine was obtained is a major bathymetric

feature, rising to within 1400 meters of the sea surface. This same ridge elsewhere produced pillow

lavas, massive basalts, and massive to schistose greenschist facies metabasalts. The bathymetry and geology

of this portion of the mid-Atlantic Ridge is also

described by van Andel and Bowin (1968). Details

of the recovery are as follows:

Cruise: R. V. Chain, cruise 44, of the Woods Hole

Oceanographic Institution.

Location: Dredge tract from 22°50.0'N, 45°05.6'W

at 3200 meters, to 22°50.6'N, to 45°04.2'W at 3400

meters.

Description: 450 grams of coarse foraminiferal

sand from a 4-inch pipe dredge, taken in dredge 8.

At Woods Hole, a portion of the sample was

leached with dilute hydrochloric acid and subjected

to grain size analysis and to density separations. The

grain size distribution was as follows: 27.35 gms

greater than 590 microns; 0.54 gms greater than 297

microns, but less than 590 microns; and 43.32 gms

less than 297 microns. Remarkably pure concentrates

of euhedral olivine crystals were produced in the size

fraction between 297 and 590 microns in the density

range of 2.9 to 3.3 gm/cc. These crystals compose

less than 1 percent of the total untreated sample.

43
44 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

The crystals occur with fresh fragments of basaltic

glass (n = 1.596). Olivine commonly occurs in this

glass as phenocrysts, which have in some places been

partially separated from their matrix by growth of

gas pockets (vesicles) along the crystal-lava contact.

It is thus quite clear that the free olivine crystals

originally crystallized from basaltic lava, but were

freed by growth of gas cavities around their surfaces,

evidently a favored site for gas exsolution during

vesiculation.

The olivine crystals are transparent, pale yellowish

green and range from about one-half to one milliFIGURE 1.—A-B, Complete individuals showing typical olivine morphology. XlOO. C-D, TWO

views of a crystal showing pitting and skeletal growth, (c X95, D X140). Scanning electron

microscope photographs by Walter Brown, Smithsonian Institution.
NUMBER 9 45

FIGURE 2.—A, Crystal showing pitting and skeletal growth, B, Crystal with attached glass

fragments X95. c, Crystal in cavity in vesiculated glass, X40. D, Spinel crystal in glass

matrix, X140. Scanning electron microscope photographs by Walter Brown, Smithsonian

Institution.

meter in maximum length. Their edges are remarkably sharp, and they have highly reflective faces.

There is no evidence whatsoever of abrasion. These

features, and the interesting skeletal forms shown by

some crystals are illustrated in the accompanying

scanning electron microscope photographs. The composition from microprobe analysis is Fo82. We did

not determine nickel and other minor and trace element contents. Small octahedra of a chromian spinel

are associated with the olivine.

The olivine crystals are similar in composition to

olivine phenocrysts (Fo85) described from pillow

lavas in this region (Melson et al. 1968, page 5929).

Acknowledgments

We wish to acknowledge the assistance of Dr. V. T.

Bowen, Chief Scientist, and the officers and crew of
46 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

the R. V. Chain, for their assistance in obtaining

these samples. Dr. Tj. H. van Andel has contributed

substantially, both in published accounts and in discussions, to our information on the 22°N area. Support for various aspects of this study aboard ship and

at Woods Hole came from the United States Atomic

Energy Commission, the Office of Naval Research,

and the National Science Foundation. The work at

the Smithsonian was supported partially by the

Smithsonian Research Foundation. This paper will

be contribution No. 2665 from the Woods Hole

Oceanographic Institution.

Literature Cited

Melson, W. G., and Tj. H. van Andel

1966. Metamorphism in the Mid-Atlantic Ridge, 22° N

Latitude. Marine Geology, 4:165-186.

Melson, W. G., G. Thompson, and Tj. H. van Andel

1968. Volcanism and Metamorphism in the Mid-Atlantic Ridge, 22° N. Latitude. Journal of Geophysical Research, 73:5925-5941.

van Andel, Tj. H., and C. O. Bowin

1968. The Mid-Atlantic Ridge Between 22° and 23°

North Latitude and the Tectonics of Mid-Ocean

Rises. Journal of Geophysical Research, 73:

1279-1298.
George Switzer Origin and

and William a Mdson Composition of

Rock Fulgurite

Glass

A great deal of attention has been given recently to

natural glasses, especially tektites, impact glasses, and

the glass phases of lunar rocks. However, fulgurites,

natural glasses formed as a result of fusion of rock

by lightning, have not been the subject of modern

study.

Fulgurites may be conveniently divided into two

types, those formed by fusion of loose sand, or sand

fulgurites, and those formed by fusion of solid rock,

usually referred to as rock fulgurites.

Sand fulgurites are normally of simple composition, from about 90 to 99 percent SiC>2 depending

on the purity of the sand. They are quite common

and have been described in detail by numerous investigators beginning^ the year 1711.

Rock fulgurites on the other hand appear to be

relatively uncommon, or at least have been observed

less frequently than sand fulgurites. Also, they are

petrologically more interesting since they may result

from fusion of any rock type. They have been described as formed from rocks ranging as widely as

andesite, granite, hornfels, glaucophane schist, and

serpentinite.

Investigation of rock fulgurite glass composition

by microprobe has revealed that these glasses are

extremely hetergeneous. As examples, we have looked

at the composition of glasses formed by fusion of

George Switzer and William G. Melson, Department of

Mineral Sciences, National Museum of Natural History,

Smithsonian Institution, Washington, D.C. 20560.

1

 Presented orally at the International Mineralogical Association Seventh General Meeting, Tokyo and Kyoto,

Japan, August 1970.

andesite from Little Ararat, Turkey; quartz diorite

porphyry from Crested Butte, Colorado; and hornfels from Castle Peak, Colorado.

Little Ararat

Little Ararat, in eastern Turkey, elevation 12,877

feet, has the most extensive development of fulgurites

reported anywhere in the world. The fulgurites are

in hypersthene diopside andesite.

Detailed chemical analyses were made of areas in

two thin sections of specimen USNM 52094. Figure

1A shows a partially melted plagioclase phenocryst.

A microprobe step scan, at five micron intervals, was

made along the line shown, and the results of the

analysis as given in Figure 1B. The plagioclase-glass

interface shows clearly in the photograph but is not

so clearly discernible from the chemistry. For some

distance beyond the interface the glass has plagioclase

composition. It then changes abruptly to a composition representing melted groundmass.

Figure 2A shows a partially melted diopside phenocryst. Two interfaces are clearly discernible, one between diopside and diopside glass, and the other between diopside glass and glass derived by melting of

groundmass. The same boundaries are reflected in

the chemistry, as shown in Figure 2B.

Crested Butte, Colorado

Crested Butte, elevation 12,172 feet, is a Tertiary

quartz diorite porphyry laccolith lying about 3 miles

northeast of the town of Crested Butte in west

central Colorado. The specimens used in this study

47
48 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

LITTLE ARARAT,TURKEY

- *? -Diopside- -»~-Diopside

Glass

LITTLE ARARAT, TURKEY

150 200 250 300

MICRON S

%NajO

0 50 100 150 200 250 300 350 400

Q Microns

FIGURE 1.—a, (Photo) Partially melted plagioclase phenocryst. Andesite, Little Ararat, Turkey, b, (Graph) Composition of glass along AB, Figure la.

FIGURE 2.—a, (Photo) Partially melted diopside phenocryst.

Andesite, Little Ararat, Turkey, b, (Graph) Composition

of glass along AB, Figure 2c.

(USNM 52981) were collected by Whitman Cross in

1885.

The extreme hetergeneity of rock fulgurite glass,

resulting from essentially no mixing while in the
NUMBER 9 49

molten state, is especially well exemplified by this

material. In thin section, shown in Figure 3A, the

plagioclase-glass interface is clearly seen, and heterogeneity of the glass is indicated by swirl marks, not

visible in the photograph.

A step scan was made along the line shown and

the results are shown in Figure 3B. There has been

so little mixing that areas of glass representing the

original phase can be recognized. Moving from left

to right the composition is first that of plagioclase,

then plagioclase glass. It then changes to quartz

glass (as shown by SiC>2 nearly 100 percent, all other

elements near zero), back to plagioclase glass, then

quartz glass, plagioclase glass once again, and finally

a glass high in Fe and Mg, probably representing

fused biotite. The areas cannot be detected optically,

but their dimensions correspond closely to the groundmass grain size of the rock.

FIGURE 3.—a, (Photo) Fusion crust on quartz

diorite, Crested Butte, Colorado, b, (Graph)

Composition of glass along AB, Figure 3a.

i „» ',y

CRESTED BUTTE.COLORADO

%SiO.

300 350 400 450

M I C R 0 N S

600 650 700
50 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

Castle Peak, Colorado

Castle Peak, elevation 14,265 feet, is in west central

Colorado and is the highest point in the Elk Mountains. The specimens studied (USNM 52980) were

collected by Whitman Cross in 1887. The rock is

an albite-quartz hornfels, with minor epidote, andradite, hornblende, calcite, and pyrite.

A photomicrograph of the glass analyzed, a bleb

attached to the wall of a tube, is shown in Figure 4A.

Because of the fine grain size, the glass appears optically homogeneous, and isochemical melting of individual grains cannot be seen. The results of a step

scan analysis along the line shown are given in Figure 4B. This analysis reflects the fine grain size of

the rock, but shows that even on this scale there

has been relatively little homogenization.

Discussion

A remarkable feature of some of the rock fulgurites

studied is the physical effect of the lightning strike.

For example, the hornfels from Castle Peak has a

nearly straight, glass-lined tube, 4 mm in diameter,

and extending entirely through 9 cm of rock. The

"entrance" of the tube is spalled and glass spattered,

and the "exit" has a raised glass lip.

m mm

FIGURE 4.—a, (Photo) Fusion crust on hornfels, Castle Peak, Colorado, b, (Graph) Composition of glass along AB, Figure 4a.

CASTLE PEAK, COLORADO

50 100 150 200 250 300 350 400 450 500 550

Microns
NUMBER 9 51

Specimens from other localities, such as Little

Ararat, show both broad surfaces covered by a thin

fusion crust, as well as irregular, sometimes branching,

glass-lined tubes.

The rock fulgurite glasses examined contain no

crystallites. This feature, combined with the observed

isochemical melting of individual mineral grains and

the extreme heterogeneity of the glasses, indicates

rapid melting and cooling. These features are predictable since the duration of a lightning strike is

of the order of one millisecond.

Measurements of lightning made by many investigators have shown that:

1. The potential difference between cloud base and

ground is of the order of 100,000,000 volts.

2. Peak current may be as high as 10,000 amperes,

and during most of the duration of the strike is of the

order of 1,000 amperes.

3. Air particles within a radius of 2 cm of the

channel are ionized at a temperature of about

30,000°K.

The tubes, such as the one described in hornfels,

if formed by lightning, must also have been formed

in a time interval of the order of millisecond. This

is a phenomenon difficult for us to comprehend even

knowing the vast amount of energy released by a

lightning stroke. Other explanations for the formation of these remarkable tubes must be considered,

particularly for the unusually straight tube in the

sample from Castle Peak, although as yet none more

plausible has occurred to us.

The extremely high temperatures conceivably

reached by fulgurites might lead to volatilization

of metallic oxides, particularly silica and those of

the alkalies. All the sand and rock fulgurites we

examined contain gas cavities, but these appear to

have formed mainly by boiling off of surface and

combined water; we have detected no loss of metallic

oxides.
METEORITES
Joseph Nelen

and Brian Mason

The Estherville

Meteorite

The Estherville meteorite fell near the town of the

same name in eastern Iowa on May 10, 1879. It belongs to the small class of mesosiderites, and is one

of only six that were observed falls. The material is

particularly suitable for research since it was collected

immediately after the fall and has not suffered from

the weathering that has seriously deteriorated most

other mesosiderites. No complete chemical analysis

has been published of the silicate material of this

meteorite, hence the present investigation.

Material was taken from specimen number 1722

in the meteorite collection of the United States National Museum of Natural History. The material was

crushed to pass through a 50-mesh sieve, and nickeliron particles were removed with a hand magnet.

This procedure evidently failed to remove all the

included metal, since 0.14% Ni was determined in

the analysed sample; using the figure of 8.57% Ni in

the metal phase of Estherville (Powell 1970), this

corresponds to 1.6% of nickel-iron. The analysed

sample also showed 1.05% S, equivalent to 2.88%

troilite. From the total iron determined by analysis

the appropriate amounts were allotted to nickel-iron

and troilite, and the remainder is reported as FeO.

The analysis is set out in Table 1, together with partial analyses of Estherville silicates by Powell (1970)

and Jerome (1970). Powell's data were obtained by

X-ray fluorescence analysis; Jerome's data by semimicro wet chemical analysis except for Cr2O3, obtained from instrumental neutron activation anlysis.

The normative mineralogical composition calculated from the analysis is (in weight percent) : pyroxene (En71Fs2-)Wo4), 72.6; plagioclase (An89), 18.4;

troilite, 2.9; nickel-iron, 1.6; tridymite, 1.6; chromite,

1.1; whitlockite, 0.7; ilmenite, 0.5. This is consistent

Joseph Nelen and Brian Mason, Department of Mineral

Sciences, National Museum of Natural History, Smithsonian

Institution, Washington, D.C. 20560.

with the observed mineralogical composition, except

that a little olivine (estimated 2%) is present; the

amount of modal pyroxene is therefore less than

normative pyroxene by about 2%, and the amount

of modal tridymite will be somewhat greater than the

1.6% in the norm. Modal chromite and ilmenite will

be somewhat less than the normative amount, because some chromium and titanium are combined in

the pyroxenes. Fuchs (1967) has shown that the

whitlockite in Estherville is accompanied by stanfieldite, Ca4Mg3Fe2(P04)o.

Estherville is a polymict breccia, and different samples of the silicate material are likely to give somewhat

different analyses. This certainly explains, at least

TABLE 1.—Analyses of silicate material of the

Estherville meteorite

Constituent

SiO2

TiO2

Al2Os

Cr2O3

FeO

MnO

MgO

CaO

Na2O

K2O

p2 o5

FeS

Fe

Ni

Total

FeO/FeO + MgO

(mole percent)

Chemical analyses

1*

50.03

0.29

6.24

0.76

12.27

0.51

18.88

5.18

0.22

0.02

0.31

2.88

1.46

0.14

99.19

26.8

(weight percent)

2*

55.42

0.43

8.44

11.80

0.47

14.16

5.62

0.74

31.9

3*

0.29

7.10

0.95

18.68

0.43

17.40

5.50

0.26

0.02

37.6

* Column 1: Analyst, Joseph Nelen.

Column 2: Powell (1970).

Column 3: Jerome (1970).

55
56 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

in part, the discrepancies between the different analyses in Table 1. The FeO/FeO + MgO molecular

percent given by Jerome's analysis is too high to be

consistent with the average composition of the pyroxenes; probably his sample contained some troilite

and nickel-iron whose iron was determined and reported as FeO. The SiO2 figure in Powell's analysis

appears to be somewhat too high; he gives a figure

of 10.1% for normative tridymite, which is considerably higher than the amounts we have observed.

Literature Cited

Fuchs, L. H.

1967. Stanfieldite, a New Phosphate Mineral from

Stony-Iron Meteorites. Science, 158:910-911.

Jerome, D. Y.

1970. Composition and Origin of Some Achondritic

Meteorites. Thesis, University of Oregon.

Powell, B. N.

1970. Petrology and Chemistry of Mesosiderites. I. Textures and Composition of Nickel-Iron. Geochimica et Cosmochimica Ada, 33:789-810.
A. F. Noonan, Forest Val e

Kurt A . Fredriksson,

and Joseph Nelen

ABSTRACT

The Forest Vale meteorite is a typical olivine-bronzite

chondrite. Chemical, mineralogical, and textural evidence indicates that all phases are genetically related,

crystallized at high temperature, and the later formed

agglomerate was lithified with no subsequent thermal

metamorphism.

Introduction

At about 3 p.m. on August 7, 1942, a shower of

meteorites fell near Forest Vale, New South Wales,

Australia. Forest Vale is about 12 miles (19.2 km)

northeast of Tullibigeal (Latitude 33°30'S; Longitude 146°48'E), which is on the Wyalong-Cargellico

railway line. The countryside has low relief with hills

of Devonian sedimentary rocks, granite, and Tertiary

lava flows.

Details are reported by Hodge-Smith (1942, 1943).

Five fragments were recovered which fitted together

to form an almost complete stone. Of these, three

have been preserved. The two smaller fragments have

been destroyed or lost since their discovery. It is estimated that the two lost specimens weighed nearly

4.5 kg, and the total weight of the stone was about

26 kg. In addition, another stone was discovered in

the immediate vicinity and its probable weight was

about 2 kg. Hodge-Smith (1943) wrote:

Both stones are chondritic. On the fractured surface the color

is bluish-grey and the texture is fine granular somewhat resembling a grey sandstone in appearance. The chondrules

A. F. Noonan, Kurt A. Fredriksson and Joseph Nelen, Department of Mineral Sciences, National Museum of Natural

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

vary in size from 1 mm. to 0.1 mm. in diameter. They are

very numerous, and many consist of olivine or enstatite, or

both. The groundmass consists mainly of the same two minerals. Nickel-iron is present in a very finely divided state,

fairly evenly distributed throughout the mass. It constitutes

roughly 20% by weight of the stone. Chemical analysis and

further optical studies have yet to be undertaken.

Mason (1963) determined the composition of the

olivine in the Forest Vale meteorite. The purpose of

this study is to expand the mineralogic and petrologic

data and, if possible, obtain some indications about

the conditions of formation of this meteorite and of

chondrites in general.

Chemical Composition

In addition to the wet chemical analysis by Jarosewich (1967), detailed phase analyses were made with

an ARL (Applied Research Laboratories) electron

probe microanalyzer. The instrument was operated

at 20 KV with a specimen current of about 0.03

microamps. All measurements were corrected for

deadtime, drift, background, and mass absorption.

In addition, secondary fluorescence corrections were

made for the metal phases. For details on the technique see Keil (1967). For the quantitative analyses,

pure metallic iron and nickel, Marjalahti olivine

(Fe = 8.7, Mg = 29.0 weight percent), and Johnstown

hypersthene (Ca = 0.99, Mg= 16.40 weight percent)

were used as standards.

WET CHEMICAL ANALYSIS

The chemical analysis in Table 1 was published by

Jarosewich (1967). However, the reported FeO

value (5.84%) is too low to be consistent with the

composition of the olivine and pyroxene as determined from microprobe analyses. This is probably due

57
58 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

to analytical error, since FeO was determined as the

difference between total iron and iron in metal and

sulfide. The analysis has been corrected by calculating

the amount of FeO (8.75%) required to make Fai7

from the acid-soluble MgO (23.95 weight percent).

Combined with the acid insoluble FeO, the total

FeO would then be 8.61%. This will in turn necessitate lowering the metallic iron to 17.24%, which is

much closer to the average of two recent analsyes for

metallic iron—17.57%—obtained by Jarosewich on

two other small pieces from this meteorite.

In Table 2 the data are also presented in the conventional form expressed as metal, troilite, and oxides;

in terms of the elements in weight percentages; and

in atom percentages after the elimination of O, C, H,

and S. The presentation in conventional form (column A) assumes that all S exists as FeS, that Fe in

excess of free metal and FeS is present in the ferrous

TABLE 1.—Analysis of the Forest Vale meteorite (Jarosewich 1967, with revised figures for Fe and FeO)

Constituent

Fe

Ni ..

Go

FeS

SiO2

TiO2

AUO,

Cr2O8 .

FeO

MnO

MgO

CaO

Na2O

KaO .

P2O8

H2O ( + )

H,O (- )

C

Total

Total Fe

Chemical analyses (weight percent)

1

Acid Soluble

56.59

24.00

0.03

0.14

8.75

23.95

0.58

43.48

2

Acid Insoluble

43.41

55.01

0.27

4.38

8.44

22.31

3.15

6.56

3

17.24

1.76

0.09

5.54

37.46

0.13

1.98

0.46

8.61

0.31

23.23

1.69

0.85

0.11

0.31

0.72

0.06

0.18

100.73.

27.45

state, and that all Ni and Co are present in the metal

phase. The second method of presentation (column

B) more closely reflects the results actually obtained

in analysis. The amounts of the different elements

are determined with the exception of O, which is

later added to make 100 percent. The expression of

the analysis in atom percentages after the elimination

of O, C, H, and S, was introduced by Wiik (1956).

This provides a method for comparing all stony meteorites regardless of the abundance or lack of volatiles. The normative mineral composition, calculated

from the chemical composition as recommended by

Wahl (1950), and expressed in weight percentages, is

given in Table 3 (A).

CARBON DISTRIBUTION

The carbon content as reported by Moore and Lewis

(1967) (0.18%—Table 1) appears somewhat higher

than normal. In an attempt to determine the distribution of carbon within this meteorite, a sample was

selectively drilled under a low-power microscope with

a dental drill (Fredriksson and Nelen 1969). The

collected material consisted of some finely powdered

matrix material and a few small chunks with adhering chondrules. After separating powder and chunks,

both fractions were analyzed for carbon content with

a Leco low-carbon analyzer. The powdered matrix

fraction contained 1.04% carbon, the chunks 0.19%

carbon.

In a second experiment, two small samples were

gently crushed in a mortar. The coarser pieces were

then manually picked out and the remaining material

separated in several size fractions by sieving. With

this technique the softer, fine-grained matrix material

tends to concentrate in the finer fractions, while the

harder chondrules and metal tend to remain with the

coarser material. Carbon content of the separates is

given in Table 4. Similar results have been obtained

for other normal (i.e., with constant olivine-pyroxene

composition) H and L group chondrites. Apparently

these chondrites have a carbonaceous matrix similar

to that in unequilibrated or carbonaceous chondrites,

although in smaller amounts. The presence of a

carbonaceous low-temperature fraction (Fredriksson

and Keil 1964; Anders 1964) would argue against a

high-temperature metamorphic event such as suggested by Dodd (1969) after the agglomeration of

the chondrites.
NUMBER 9 59

TABLE 2.—Chemical composition of the Forest Vale meteorite

A*

Constituent Weight percent Constituent Weight percent Constituent Atom percent

Fe 17.24

Ni 1.76

Co 0.09

FeS 5.54

SiO* 37.46

TiO2 0.13

A12O, 1.98

Cr2O, 0.46

FeO 8.61

MnO 0.31

MgO 23.23

GaO 1.69

Na2O 0.85

K2O 0.11

P2O« 0.31

H2O ( + ) 0.72

H2O (- ) 0.06

C 0.18

Total 100.73

Fe 27.45

Si 17.44

Mg 14.01

S 2.02

Ni 1.76

Ga 1.21

Al 1.05

Na 0.63

Cr 0.31

Mn 0.24'

G 0.18

P 0.14

Co 0.09

K 0.09

H 0.09

Ti 0.08

O 33.21

Total 100.00

Si 33.84

Mg 31.39

Fe 26.78

Al 2.11

Ca 1.65

Ni 1.63

Na 1.49

Cr 0.32

P 0.25

Mn 0.24

K 0.13

Ti 0.09

Co 0.08

Total 100.00

a

 Chemical analysis expressed as nickel-iron, troilite, and oxides (Jarosewich 1967, with revised figures for Fe and FeO).

b

 Chemical analysis expressed as elements, with oxygen added to make 100 percent.

c

 Chemical analysis expressed as atom percentages, with the elimination of O, C, H, and S.

TABLE 3.—Normative composition of the Forest Vale

meteorite

TABLE 4.—Carbon content of separates of the Forest

Vale meteorite

Constituent

Nickel-iron

Troilite

Bronzite

Olivine

Diopside

Albite

Anorthite

Orthoclase

Chromite

Apatite

Ilmenite

A

Bulk

19.1

5.5

31.6

28.5

4.0

7.2

1.3

0.7

0.7

0.7

0.2

B

Matrix

11.1

2.9

36.2

17.2

9.0

16.2

2.9

1.5

0.4

1.5

0.4

A. Normative composition calculated from chemical analysis according to Wahl (1950).

B. Matrix (44.6%)—Bulk normative minerals (column

A) minus modal amounts in weight percent of recognizable

mineral grains.

Size fraction

Sample 1

(% Carbon)

Coarse pieces

>80 Mesh

80-100 Mesh

< 100 Mesh

Sample 2

(% Carbon)

0.13

0.51

0.86

1.27

0.19

0.40

0.78

1.23

Mineralogy and Petrology

OLIVINE

In a crushed sample, olivine grains are abundant,

colorless, and frequently inclusion-filled. The fractures

are characteristically conchoidal.

The refractive indices are a =1.665 ±0.002, "Y =

1.702 ±0.002, indicating a content of 16 mole percent
60 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

of the Fe2SiO4 (Fa) component, according to the

determinative curve of Poldervaart (1950). The

(130) peak at 2.771A appears sharp and symmetrical

on the diffractograms indicating uniform composition.

According to the data of Yoder and Sahama (1957),

this peak shows the composition of olivine to be 16.5

mole percent Fe2SiO4.

Five or six points on each of about ten randomly

selected olivine grains, or a total of 55 points, were

analyzed with the microprobe. The olivine proved

Ni-poor (less than 0.02%) and with an essentially

homogeneous composition of Fal7.6.

In thin section, the crystal habit of olivine is variable. Subhedral grains are most common, although

euhedral crystals do exist. The well-developed crystals

are commonly elongated parallel to the C-axis, sixsided, and show (010) cleavage. Poikilitic inclusions

of small olivine grains in pyroxene are common. Grain

orientation is random, and crystals attain a maximum

length of 0.7 mm. Euhedral grains are length-slow

with parallel extinction.

PYROXENE

Pyroxene is also abundant and occurs as large prismatic crystals or fibrous aggregates. The grains are

colorless to opaque depending on the abundance of

inclusions, often part along cleavage planes, and frequently display both simple and polysynthetic twins.

The refractive indices are a =1.670 ±0.002, and

y= 1.684 ± 0.002, indicating a composition of 15 mole

percent of the FeSiO3 component, according to

Kuno's data (1954). This falls in the compositional

range of bronzite. The diffractograms indicate both

abundant bronzite and one or more clinopyroxenes.

These are probably clinobronzite with accessory

diopside.

Both orthorhombic and monoclinic pyroxene revealed a near constant composition of Fsis.g in both

twinned and untwinned crystals. A few anomalously

high Ga areas prompted the use of electron beam

scanning pictures taken of pyroxene grains and measured for Ca and Fe distribution, only one revealed

distinct Ca-rich rims (Figure 1). The enrichment ocFe Ca Al

FIGURE 1.—Photomicrograph of twinned and untwinned pyroxene viewed by polarized transmitted light at 450 X, upper left, the nearly correlative secondary electron emission photograph,

upper right, and electron probe elemental scans, lower three photographs, of iron, calcium, and

aluminum, moving from left to right.
NUMBER 9 61

curred on both twinned and untwinned crystals, and

the rims had a uniform composition of Wo34.9Fs10.6

En54.5. This Ca-armoring noted on only some rhombic and monoclinic pyroxene grains seems to eliminate

any significant equilibrating influence which might be

attributed to thermal metamorphism.

The pyroxene crystals range in external shape from

finely fibrous to the characteristic prismatic habit.

The (110) cleavage and (010) partings are present

on the numerous large distinct crystals. Orthopyroxene is most abundant, but half of the well-developed

grains, although of similar composition, are clinopyroxene and these display what appears to be polysynthetic twinning. The grains are randomly oriented

with the exception of the eccentrically radiating

chondrules made of fibrous crystals. The large crystals, which attain a maximum length of 0.8 mm, are

riddled with inclusions, and are length-slow with

parallel extinction.

OLIGOCLASE

Although oligoclase was not identified optically, the

X-ray diffractograms suggest it to be a minor constituent. The recalculated normative composition also

suggests that the dark matrix and devitrified glass in

barred chondrules is in part Na-rich plagioclase.

NICKEL-IRON

In reflected light, nickel-iron appears white, structureless, and in some grains bi-reflectant (possibly as

a result of deformation). The alloy appears grey and

nearly always isotropic under crossed nicols.

The maximum dimension of these irregularly

shaped masses, which occur most frequently between

the chondrules, is approximately 0.5 mm. The silicate

chondrules appear to control the shape and distribution of the large metal grains, but smaller, rounded,

nickel-iron particles are found in the matrix and are

included in chondrules. It is generally inclusion-free

and a limonitic alteration product usually exists

around the perimeters of the grains.

A very limited microprobe study of the Fe-Ni

phases was undertaken. Three tracks across two distinct grains were run at a speed of eight micron/

minute (Figure 2). The intensities for both Fe Ka

and Ni Ka were recorded while the pulses were simultaneously counted on the sealers at 10-second intervals. The taenite appeared Ni-deficient when compared to normal chondritic taenite, whereas the

kamacite was rather high in Ni. Also, there were no

low-Ni zones in the kamacite at the taenite-kamacite

interfaces. This suggests that equilibration of the NiFe was retained only through relatively high temperatures and that the metal was probably subject to

rapid cooling across the taenite-kamacite phase

boundary, thus restricting Ni diffusion.

TROILITE

Plane polarized light reveals this iron sulfide to be

distinctly yellow in color and slightly bi-reflectant.

Its anisotropism is distinct, with colors ranging from

silver-grey to brown revealing polycrystalline troilite

as the typical texture. This accessory mineral, which

usually occurs in close association with nickel-iron,

attains maximum dimensions of approximately 0.5

mm. Like nickel-iron, the borders are highly irregular, and its distribution seems to be controlled by

the surrounding silicate chondrules. Besides occurring

as large, distinct masses within the matrix, minute

grains are included in the chondrules and the larger

of the nickel-iron fragments.

CHROMITE

The accessory chromite grains, which are grey, isotropic, and structureless, occur most commonly as

extremely fine-grained aggregates within the matrix.

They do, however, attain a maximum dimension of

0.2 mm when included in chondrules.

MATRIX

The fine-grained, nearly isotropic matrix has very low

bi-refringence and occurs as interstitial aggregates

between chondrules. It does, however, merge with the

boundaries of some fine-grained chondrules. Although

the material could not be identified optically, the

recalculated norm suggests it is principally pyroxene,

plagioclase, and metallic iron.

GHONDRITIC TEXTURE

The Forest Vale meteorite is composed of olivine and

pyroxene chondrules uniformly distributed throughout

the stone and quite variable in their degree of crystallinity. They often range up to 1 mm in diameter,
62

SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

20- ,

~ 10:..,"

a.

U

L.

o

u

1

10 50

2

. 2 0 f •• :

10:..., V—.....

1

 • J '

10 40

2 0 - •

10--_-

10 30

Distance (u)

FIGURE 2.—Photomicrograph of nickel-iron observed at 190X and corresponding electron probe

compositional tracks. The low nickel content of the taenite and the lack of Ni depletion in the

kamacite at the taenite-kamacite interface is noteworthy.

retain their sphericity, and are set in a matrix of

fine-grained crystallites and opaque minerals (Figure

3).

MODAL ANALYSIS

A total of 5000 points were counted on two polished

thin sections. The mineralogical composition as calculated from the mode (in weight-percent) is: nickeliron 14.2; chromite 0.5; troilite 4.2; olivine 20.9;

pyroxene 15.6; and 44.6 percent fine-grained matrix

material which could not be identified. The abundance of pyroxene is higher in the norm than in this

mode, which suggests a large amount of the pyroxene

exists as fine-grained groundmass material, or as finegrained or glassy material within the chondrules, or
NUMBER 9 63

FIGURE 3.—Chondritic texture of the Forest Vale meteorite at 30 X using

polarized transmitted light.

both. Assuming that the insignificant amount of material was lost during polishing, and recalculating

the norm with the elimination of nickel-iron, troilite,

and silicates noted in the modal analysis, the finegrained matrix material is probably rich in pyroxene,

plagioclase, and metallic iron and poor in olivine

(Table 3, column B) . The gross similarity of the

norms, however, seems to suggest that matrix and

chrondules are cogenetic.

Classification

If the amount of nickel-iron and the ratio of MgO

to FeO in the silicates are considered, as suggested by

Prior (1920), the Forest Vale meteorite is an olivinebronzite chondrite. With regard to both the total iron

content and the oxidation state of the iron, it would

be placed in the high-iron (H) group of Urey and

Craig (1953), while the amount of reduced iron

would place it in Wiik's group (1956) of chondrites

with 15 percent to 19 percent metallic iron. The ratio

Fe/Fe + Mg) in both olivine and pyroxene, as suggested by Keil and Fredriksson (1964), would again

classify it as an H group chondrite. The Forest Vale

meteorite corresponds to that of the petrologic type 4

in the chemical-petrologic classification of Van

Schmus and Wood (1967). This group is characterized by well-developed chondrules, olivine and pyroxene of uniform or nearly uniform composition,

and an abundance of clinopyroxene.

Conclusions

1. If not attributable to shock, the high-temperature nickel-iron and devitrified glass in barred chondrules indicate a brief cooling history for the

chondrite.

2. Ca-rich coronas occurring on only some pyroxene grains indicate that the crystallization conditions

were not identical for all fragments.

3. The presence of metal particles in, and adjacent

to, chondrules, and the gross similarity in normative

mineralogy of both matrix and included fragments

suggest that although crystallization conditions were

not identical they may have been nearly the same.

4. The degree of chondrule integration, the hetero-
64 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

geneous pyroxene, the high C content in the matrix

and the high-temperature nickel-iron suggest accumulation and lithification of the genetically related fragments but with no subsequent metamorphism.

Acknowledgments

This manuscript is an extension of preliminary data

gathered and submitted in thesis form by A. F.

Noonan in partial fulfillment of the M.S. degree at

the University of Tennessee. This initial research was

carried out under a Smithsonian Research Foundation Grant. Additional costs for extended studies were

supported by NASA and United States Air Force

grants. We are indebted to the Department of Geology faculty at the University of Tennessee for an early

review of the paper, and to Dr. Brian Mason of the

Smithsonian Institution for many helpful suggestions

throughout the study.

Literature Cited

Anders, E.

1964. Origin, Age and Composition of Meteorites.

Space Science Reviews, 3:583-714.

Dodd, R. T.

1969. Metamorphism of the Ordinary Chondrites: A

Review. Geochimica et Cosmochimica Acta, 33:

161-203.

Fredriksson, K., and K. Keil

1964. The Iron, Magnesium, Calcium, and Nickel Distribution in the Murray Carbonaceous Chondrite.

Meteoritics, 2:201—217.

Fredriksson, K., and J. Nelen

1969. Carbon Distribution in Chondrites. Meteoritics,

4:271-272.

Hodge-Smith, T.

1942. A Fall of Meteorites at Forest Vale, New South

Wales. Australian Museum Magazine, 8:45—48.

1943. A Shower of Meteoritic Stones at Forest Vale,

New South Wales. Australian Journal of Science,

5:154-156.

Jarosewich, E.

1967. Analysis of Seven Stony Meteorites and One Iron

with Silicate Inclusions. Geochimica et Cosmochimica Ada, 31:1103-1105.

Keil, K.

1967. The Electron Microprobe X-Ray Analyzer and

its Application in Mineralogy. Fortschritte der

Mineralogie, 44:4-66.

Keil, K., and K. Fredriksson

1964. The Fe, Mg, and Ca Distribution in Coexisting

Olivines and Rhombic Pyroxenes in Chondrites.

Journal of Geophysical Research, 69:3487-3515.

Kuno, H.

1954. Study of Orthopyroxene from Volcanic Rocks.

American Mineralogist, 39:30-46.

Mason, B.

1963. Olivine Composition in Ghondrites. Geochimica

et Cosmochimica Ada, 27:1011-1023.

Moore, C. B., and C. F. Lewis

1967. Total Carbon Content of Ordinary Chondrites.

Journal of Geophysical Research, 72:6289-6292.

Poldervaart, A.

1950. Correlation of Physical Properties and Chemical

Composition in the Plagioclase, Olivine, and Orthopyroxene Series. American Mineralogist, 35:

1067-1079.

Prior, G. T.

1920. The Classification of Meteorites. Mineralogical

Magazine, 19:51-63.

Urey, H. C, and H. Craig

1953. The Classification of the Stone Meteorites and

the Origin of the Meteorites. Geochimica et

Cosmochimica Acta, 4:36—82.

Van Schmus, W. R., and J. A. Wood

1967. A Chemical and Petrologic Classification for the

Chondritic Meteorites. Geochimica et Cosmochimica Acta, 31:747-765.

Wahl, W.

1950. The Statement of Chemical Analysis of Stony Meteorites and the Interpretation of the Analysis in

Terms of Minerals. Mineralogical Magazine, 29:

416-426.

Wiik, H. B.

1956. The Chemical Composition of Some Stony Meteorites. Geochimica et Cosmochimica Acta, 9:279—

289.

Yoder, H. S., and T. G. Sahama

1957. Olivine X-Ray Determinative Curve. American

Mineralogist, 42:475-491.
Roy s. Clarke, Jr. Iron Meteorite

and Eugene Jarosewich Compositions

During the past several years chemical analyses for the

elements nickel, cobalt, and phosphorus have been

performed on twelve meteorite specimens from the

Smithsonian collection. Classification or curatorial

considerations have normally prompted individual

investigations. The data are summarized in the accompanying table in order to make them available

to others.

Recent analyses of four of these same meteorites

Roy S. Clarke, Jr. and Eugene Jarosewich, Department of

Mineral Sciences, Division of Meteorites, National Museum

of Natural History, Smithsonian Institution, Washington,

D.C. 20560.

have been given by Moore et al. (1969), and their

paper includes a general discussion of the problems of

iron meteorite analysis. Our results on these four

meteorites are in excellent agreement with their

results. Nickel analyses have also been performed on

all twelve of these meteorites by Wasson as part of

his comprehensive study of chemical groupings among

iron meteorites (John T. Wasson, personal communication, 1970). Agreement is again good, but it was

noted that our nickel values are normally 0.1 to 0.2

percent higher than Wasson's. Older analyses of these

meteorites and references to descriptive papers are

cited by Hey (1966).

TABLE 1.—Chemical analyses for nickel, cobalt, and phosphorous on twelve meteorite

specimens from the Smithsonian collections

Name

NMNH

cat. no.

Structure

class* Ni

Weight percent

Co Notes

Angelica, Wisconsin

Arlington, Minnesota

Bodaibo, Siberia

Cacaria, Mexico

Cruz del Aire, Mexico

Cumpas, Mexico

Elbogen, Bohemia

El Capitan, New Mexico

Monahans, Texas

New Westville, Ohio

Obernkirchen, Germany ...

St. Genevieve County,

Missouri

2177

627

2149

1480

1441

1591

309

2754

1303

1412

1611

454

Om

Om

Of

Om

Of

Om

Om

Om

D

Of

Of

Of

7.50

8.55

8.05

7.74

9.19

8.14

10.25

8.80

10.79

9.38

7.67

7.96

0.50

0.41

0.36

0.46

0.50

0.47

0.64

0.48

0.52

0.34

0.36

0.36

0.11

0.02

0.04

0.11

0.30

0.18

0.22

0.43

0.09

0.18

0.02

0.24

(1)

(0(4)

(1)

(2)(5)

•Buchwald and Munck (1965).

(1) Recent analysis reported by Moore et al. (1969).

(2) Recent analyses' reported by Wasson (1967).

(3) A doubtful analysis for Ni in Monahans was reported by Cobb (1967).

(4) Analysis reported by Dyakonova and Kharytonova (1963).

(5) Recent analyses reported by Lewis and Moore (1971).

65
66 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

All of the meteorites in this group are finds and

have, therefore, been subjected to varying degrees of

terrestrial weathering. In each case material was

carefully selected to be free of oxidation and obvious

inclusions. Samples were in the size range of 1.2 to

3.0 g, large enough to be representative of the metallic phases. They were dissolved in an HCI-HNO3

mixture, and then evaporated to dryness several times

with HC1. Residues were taken up with 5 ml of concentrated HG1, diluted with H2O and filtered into

a 100 ml volumetric flask. Appropriate aliquots were

taken for the determination of nickel, cobalt, and

phosphorus. Nickel was precipitated with dimethylglyoxene and determined gravimetrically, cobalt spectrophotometrically with nirosto-R salt, and phosphorus spectrophotometrically using the molybedenum

blue method (Moss et al., 1961).

Literature Cited

Buchwald, V. F., and Sole Munck

1965. Catalogue of Meteorites. Analecta Geologica, 1:

1-81.

Cobb, James C.

1967. A Trace-Element Study of Iron Meteorites. Journal of Geophysical Research, 72:1329-1341.

Dyakonova, M. Y., and V. Y. Kharytonova

1963. Composition of Nickel-Iron in Some Iron and

Stony-Iron Meteorites of Various Types. Meteoritika, 23:42-44.

Hey, Max H.

1966. Catalogue of Meteorites, lxviii+637 pages. The

British Museum (Natural History).

Lewis, Charles F.3 and Carleton B. Moore

1971. Chemical Analyses of Twenty-eight Iron Meteorites. Meteoritics, 6:195-205.

Moore, Carleton B., Charles F. Lewis, and David Nava

1969. Superior Analyses of Iron Meteorites, in Meteorite Research. P. M. Millman, editor. Pages 738-

748. Dordrecht, Netherlands: D. Reidel Publishing Company.

Moss,, A. A., M. H. Hey, and D. I. Bothwell

1961. Methods for the Chemical Analysis of Meteorites:

I. Siderites. Mineralogical Magazine, 32:802-

816.

Wasson, John T.

1967. The Chemical Classification of Iron Meteorites: I.

A Study of Iron Meteorites with Low Concentrations of Gallium and Germanium. Geochbnica

et Cosmochimica Ada, 31:161-180.
Roy S. Clarke, Jr.,

Eugene Jarosewich,

and Joseph Nelen

The Nejo,

Ethiopia,

Meteorite

A stony meteorite fell 16 km due west of Nejo, near

the village of Jarso, Wollega Province, Ethiopia, at

11:30 a.m. local time on May 11, 1970. The coordinates of the fall site are 9°30'N, 35°20/E. The

fall was observed by local residents and reported to

Professor Pierre Gouin, Director, Geophysical Observatory, Haile Selassie I University, Addis Ababa, Ethiopia. Professor Gouin visited the site and reported

obtaining three pieces weighing a total of 2.4 kg that

had been recovered1, apparently from an individual

stone. The stone had made a small hole in hard

ground, and he estimated that its impact weight

was 4-4.5 kg.

Professor Gouin's reports on the meteorite fall and

visit to the site were circulated by the Smithsonian

Institution Center for Short-Lived Phenomena on

July 23, 1970, and August 4, 1970. On July 21, 1970,

Professor Gouin sent the Smithsonian Institution a

287 g specimen (NMNH 5420) of the Nejo meteorite

to be made available for time-dependent research.

Material was distributed for this purpose to Edward

Fireman, Smithsonian Astrophysical Observatory,

Cambridge, Massachusetts 02138, Louis A. Rancitelli,

Battelle Memorial Institute, Richland, Washington

99352, and G. D. O'Kelley, Oak Ridge' National

Laboratory, Oak Ridge, Tennessee 37830. Reports on

these investigations will appear elsewhere. We have

undertaken a brief mineralogical and chemical characterization that will be summarized here. A detailed

Roy S. Clarke, Jr., Eugene Jarosewich, and Joseph Nelen,

Department of Mineral Sciences, National Museum of Natural History, Smithsonian Institution, Washington, D.C.

20560.

petrographic investigation is being undertaken by

Dr. Bill Moreton, Geology Department, Haile Selassie

I University, Addis Ababa.

Mineralogy and Chemistry

The Nejo meteorite is a hypersthene chondrite, an

L6 meteorite in the classification of Van Schmus

and Wood (1967). It is coarsely crystalline with a recrystallized matrix, and no distinct chondrules were

observed. The olivine and pyroxene were examined

by the electron microprobe and found to be equilibrated. The olivine compositions clustered closely

around 25 mole percent fayalite (Fa2s) and the pyroxene around 20 mole percent ferrosilite (Fs2o)-

Plagioclase, chlorapatite, and chromite were identified by the microprobe and the troilite was observed

to be essentially free of nickel. The presence of both

kamacite and taenite was observed microscopically

on etched polished sections and confirmed by the

microprobe. Kamacite and taenite occur as individual grains, in association with one another, and

in association with troilite. Troilite grains are comparatively large and monocrystalline or coarsely crystalline. The larger kamacite grains frequently contain

slightly distorted Neumann bands. Evidence of strong

shock appears to be lacking.

Our specimen contained a small area of welldeveloped fusion crust. The vesicular glass crust

ranged up to 0.3 mm thick and was seen in polished

section to contain precipitated magnetite. It is underlain by a zone injected with sulfide veins penetrating

as far as 1 mm below the surface (Ramdohr 1967).

Within this zone, particularly near the surface, are

67
68 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

TABLE 1.—Chemical composition of the Nejo, Ethiopia, meteorite, NMNH 5420 (Eugene Jarosewich,

analyst)

Constituent

Fe

Ni

Co

FeS

SiO3

TiOa

AlaO,

Gr2O3

FeO

MnO

MgO

GaO

NaaO

K2O

PaO,

H2O( + )

ftO(-)

G

Total

Total Fe

D(g/cm8)

Percent

7.10

1.27

0.06

6.47

39.98

0.12

2.27

0.56

14.22

0.32

24.83

1.82

0.92

0.10

0.24

<0.1

0.03

0.01

100.32

22.26

3.59

eutectic structures resulting from the melting of

metallic phases and troilite. Kamacite grains throughout this zone have been transformed to alpha-2

structure, indicative of heating to temperatures

around 500°C.

The bulk chemical analysis of the Nejo meteorite,

typical of hypersthene chondrites, is given in the accompanying Table 1. The analytical procedures employed are outlined in an earlier paper (Jarosewich

1966).

Literature Cited

Jarosewich, Eugene

1966. Chemical Analyses of Ten Stony Meteorites. Geochimica et Cosmochimica Ada, 30:1261-1265.

Ramdohr, Paul

1967. Die Schmelzkruste der Meteoriten. Earth and

Planetary Science Letters, 2:197-209.

Van Schmus, W. R., and J. A. Wood

1967. A Chemical-Petrologic Classification for the Chondritic Meteorites. Geochimica et Cosmochimica

Acta, 31:747-765.
Joseph A. Nekn Th e Nakhon

and Kurt Fredriksson

Meteorite

ABSTRACT

The Nakhon Pathom meteorite from Thailand has

been chemically analyzed and found to be an olivinehypersthene chondrite, belonging to the L-group, with

24 mole percent Fe2SiO4 in olivine and 21 mole percent FeSiOg in orthopyroxene. It shows dark-light

structure of light gray areas surrounded by dark gray

bands, probably caused by hypervelocity shock. The

chemical composition of both parts is similar.

Introduction

The meteorite fell on December 21, 1923, at about

2100 hours. It was found in the province of Nakhon

Pathom, Thailand, probably shortly after the fall,

since it is fresh and unaltered. The place (13°44'N,

100°05'E) is a swampy area in the Don Yai Nom

subdistrict about 10 kilometers south-south-east of

the town of Nakhon Pathom. Two stones were placed

in a case of curios in the National Museum in Bangkok, because of their unusual properities. When Dr.

and Mrs. Edward P. Henderson were visiting Thailand in 1960, Mrs. Henderson saw the stones and

suspected them to be of meteoritic origin. The picture

showing both stones (Figure 1) was taken at that

time by Dr. Henderson. Eventually, the smaller stone

was loaned to the United States National Museum

for study. Mason (1967) has described the meteorite

briefly, giving full data and olivine composition. It is

not otherwise reported in the literature. The main

Joseph A. Nelen and Kurt Fredriksson, Department of Mineral Sciences, National Museum of Natural History, Smithsonian Institution, Washington, D.C. 20560.

mass is in the National Museum in Bangkok, Thailand. The United States National Museum has 413

grams of the smaller piece in its collection (NMNH

3192).

The total weight of the two pieces was 32.2 kilograms. The meteorite shows light-dark structure, the

density of the lighter part being 3.56 gm/cc of the

darker part, 3.51 gm/cc. The average density of a

piece containing 41% dark material and 59% light

is 3.53. Stones with a light-dark structure were first

described by Reichenback (1865). Similar meteorites

include Walters (Roy et al. 1962), Stalldalen (Fredriksson et al. 1963), and Lanzenkirchen (Kurat and

Kurzweil 1965).

Description

The meteorite Nakhon Pathom broke in two pieces.

The smaller piece, weighing 9.6 kilograms, is covered

on two sides with a dark brown fusion crust 2 millimeters thick. The side oriented toward the front

during the fall shows well-formed "thumbprints,"

covered by a smooth dull crust (Figure 2). The back

side is flat and is covered with a rougher crust, traversed by cracks.

A cross-section (Figure 3) shows a brecciated structure of light gray material surrounded by areas of

darker gray. In the darker parts many smaller round

to angular light gray bodies can be observed. The

lighter parts are broken pieces of a well-crystallized

chondrite. They contain only a few recognizable

chondrules or parts of chondrules, strongly intergrown

with the coarsely crystalline matrix (Figure 4). The

chondrules and crystals show strong mechanical deformation. The cracks are frequently filled with

droplets or angular particles of troilite and nickel69
70 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

FIGURE 1.—The two pieces of the Nakhon Pathom meteorite in the National Museum, Bangkok,

Thailand (smaller stone 210 X 160 mm).

iron. The black veins penetrating the lighter mass

consist mostly of comminuted silicates and opaque

minerals.

Mineralogy

The minerals identified in a polished thin section of

the meteorite are olivine, orthopyroxene, clinopyroxene, plagioclase, whitlockite, chromite, kamacite, and

taenite.

Olivine is mostly xenomorphic, has a wavy extinction, and is often, especially in the dark part, mixed

with nickel-iron and troilite. The composition in both

dark and light parts as determined by electron

microprobe analysis is given in Table 1.

The average fayalite content, Fa24, is the same as

that given by Mason (1967) who obtained his figure

by X-ray diffraction. Orthopyroxene is also mostly

xenomorphic, shows strong wavy extinction, and is

mixed with nickel-iron and troilite in the same manner as olivine. The composition is given in Table 2;

it averages 21 mole percent FeSiOa.

Most of the clinopyroxene exhibits similar properties. A little calcium-rich clinopyroxene was also observed. Plagioclase with wavy extinction occurs occasionally as interstitial grains, both in chondrules
NUMBER 9 71

FIGURE 2.—The smaller piece of the Nakhon Pathom meteorite, showing comparatively thick

fusion crust and prominent regmaglypts (210 X 160 mm).

and in the groundmass. Whitlockite is common as

interstitial crystals or aggregates of fairly large size,

especially in the light gray areas. Chromite occurs

together with nickel-iron and troilite, as well as

intergrown with silicates; it is fairly large and almost

xenomorphic. Troilite is mixed with nickel-iron in

the larger aggregates. Separately it occurs as small

droplets and irregular-shaped aggregates in the interstices of the silicates. Kamacite and taenite occur

separately from each other and could not be distinFIGURE 3.—Polished surface on the main mass of the

Nakhom Pathom meteorite, showing prominent light-dark

structure, together with veining and brecciation (130 X

90 mm).
72 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

FIGURE 4.—Photomicrograph of thin section of the Nakhon

Pathom meteorite in .ordinary light. The dark part, upper

half, has barely recognizable chondrules and a brecciated

texture. In the light, lower part chondrules and matrix are

almost entirely intergrown. The black areas consist of nickeliron and troilite. The length of the section is 9 mm.

TABLE 1.—Olivine composition of the Nakhon

Pathom meteorite in light and dark portions

Area

Light

Dark

FeO weight percent

Range

21.9-22.5

21.9-23.4

Average*

22.2

22.5

FeO

FeO+MgO

Mole percent Fa

24.0

24.3

* The averages represent ten to fifteen grains with about

three to four measurements in each grain.

TABLE 2.—Orthopyroxene composition of the Nakhon

Pathom meteorite in light and dark portions

Area

Light

Dark

FeO weight percent

Range

13.8-14.7

13.9-14.8

Average*

14.2

14.2

FeO

FeO+MgO+CaO

Mole percent Fs

21.1

21.2

guished microscopically, but were identified with the

electron microprobe.

Chemistry

The sample selected for chemical analyses had a total

weight of 18.8 grams. The light and dark material

was carefully separated and each portion reweighed.

Total recovery was about 18.6 grams of which 41.1%

was dark and 58.9% light.

Each portion was analyzed separately by techniques

previously described by Jarosewich (1966, 1967). The

results are expressed as oxides, troilite, and metal in

Table 3. The elemental composition with oxygen by

difference and the elements calculated on a volatilefree basis are given in Table 4 under A and B. The

normative mineral content, expressed as weight percentages in Table 5, was calculated as suggested by

Wahl (1950). It agrees well with the observed mineral abundances. The phosphorus was calculated as

apatite. Microscopic observation and semiquantitative

microprobe measurements indicate that the phosphorus mineral is whitlockite. The titanium is probably associated with the silicate phases, since ilmenite

was not found.

TABLE 3.—Chemical composition of the Nakhon

Pathom meteorite (weight percent) (Joseph Nelen,

analyst)

Constituent

•Th e averages represent ten to fifteen grains with one

to three analyses in each grain.

Fe

Ni

Go

FeS

SiO2

TiO2

A12O,

Cr2O8

FeO

MnO

MgO

GaO

Na2O

KaO

P3O«

H2O+

HjOG

Total

Fe (Total)

Dark portion 41.06% Light portion 58.94%

7.08

1.17

.05

6.46

39.98

0.17

1.81

0.60

13.52

0.31

24.71

1.84

0.98

0.10

0.26

0.58

0.07

0.08

99.77

21.69

8.15

1.22

.06

5.84

40.00

0.17

1.79

0.51

13.26

0.31

24.45

1.83

0.97

0.10

0.24

0.66

0.04

0.14

99.74

22.17
NUMBER 9 73

TABLE 4.—Elemental composition of the Nakhon

Pathom meteorite

Constituent

H

C

O

Na

Mg

Al

Si

P

S

K

Ca

Ti

Gr

Mn

Fe

Go

Ni

Total

Dark portion

A B

0.07

0.08

37.04

0.73 1.21

14.90 24.70

0.96 1.59

18.69 30.98

0.11

2.36

0.08 0.13

1.32 2.19

0.10 0.16

0.41 0.67

0.24 0.40

21.69 35.95

0.05 0.08

1.17 1.94

100.00 100.00

Light portion

A B

0.08

0.14

36.90

0.72 1.19

14.75 24.32

0.95 1.57

18.70 30.83

0.10

2.13

0.08 0.13

1.31 2.16

0.10 0.16

0.35 0.58

0.24 0.40

22.17 36.55

0.06 0.10

1.22 2.01

100.00 100.00

A. Chemical analysis in weight percent of the elements,

with oxygen to bring the sum to 100.

B. Atomic percent of the elements on a volatile (C,H,O,

S)-free basis.

TABLE 5.—Normative minerals of the Nakhon

Pathom meteorite (weight percent)

Constituent

Nickel-iron

Troilite

Olivine (Fa 24) . .

Hypersthene (Fs 21)

Diopside

Orthoclase

Albite

Anorthite

Apatite ...

Ghromite

Ilmenite

Dark portion

8.30

6.46

41.14

26.07

5.81

0.61

8.20

0.22

0.60

0.95

0.32

Light portion

9.43

5.84

39.40

27.38

5.83

0.61

8.17

0.22

0.57

0.83

0.32

Summary

The chemical and mineralogical composition of the

Nakhon Pathom meteorite shows that it is an olivinehypersthene chondrite in Prior's classification (1920).

The total iron content, about 22 percent, places it

in the low-iron (L) group of Urey and Craig (1953).

The olivine composition, Fa24, determined by microprobe analysis, also confirms that this meteorite is

an L-group chondrite (Keil and Fredriksson 1964).

The minerals present are the same in the light and

dark parts both according to microscopic observations

and chemical composition. The microprobe analyses

appear to show a slightly higher iron content and

more variability for olivines in the dark portion. The

difference, however, is practically within the limits

of analytical error and is not considered significant.

The bulk chemical composition, Table 3, is also similar in both parts and the meteorite may therefore be

classified as a monomict breccia (Wahl 1952).

The meteorite was severely shocked. The dark and

light structure and the black veins, containing small

troilite bodies, are similar to the black veins and

the darkening produced in the gray chondrite Stalldalen by artificial shock as described by Fredriksson

etal. (1963).

It should also be noted that the carbon content

is lower in the dark part than in the light (Table 3),

and consequently the dark color is not caused by

carbon as suggested by Wlotzka (1963) for the

Pantar meteorite. The carbon values are averages of

five analyses of each part, of which two of each were

carried out by Dr. Gharleton Moore, Arizona State

University. All analyses agreed with ±0.03%C.

Acknowledgments

We wish to thank Dr. Louis Walter and Dr. Brian

Mason for their critical review of the paper.

Part of the expenses of this paper have been met

by grants from the National Aeronautics and Space

Administration (Grant NsG—688) and the United

States Air Force (Contract AF19(628)-5552).

Literature Cited

Fredriksson, K., P. S. De Carli, and A. Aaramae

1963. Shock-Induced Veins in Chondrites. Space Research 111:974-983. North Holland Publishing

Company, Amsterdam.

Jarosewich, E.

1966. Chemical Analyses of Teh Stony Meteorites. Geochimica et Cosmochimica Ada, 30:1261—1265.

1967. Chemical Analyses of Seven Stony Meteorites and

One Iron with Silicate Inclusions. Geochimica et

Cosmochimica Ada, 31:1103-1106.
74 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

Keil, K., and K. Fredriksson

1964. The Iron, Magnesium and Calcium Distribution

in Coexisting Olivines and Rhombic Pyroxenes of

Chondrites. Journal of Geophysical Research,

69:3487-3515.

Kurat, G., and H. Kurzweil

1965. Der Meteorit von Lanzenkirchen. Annalen des

Naturhistorischen Museums in Wien, 68:9—24.

Mason, B.

1965. The Chemical Composition of Olivine-Bronzite

and Olivine-Hypersthene Chondrites. American

Museum Novitates, 2223:38.

1967. Olivine Composition in Chondrites—A Supplement. Geochimica et Cosmochimica Acta, 31:

1100-1103.

Prior, G. T.

1920. The Classification of Meteorites. Mineralogical

Magazine, 19:51-63.

Reichenbach, C. V.

1865. Die schwarzen Linien und Ablosungen in den

Meteoriten. Poggendorff's Annales der Physik

und Chemie, 125:308-325, 420-441, 600-618.

Roy, S. K., J. J. Glass, and E. P. Henderson

1962. The Walters Meteorite. Chicago National History

Museum Fieldiana. Geology, 10:539-550.

Urey, H. C, and H. Craig

1953. The Composition of the Stone Meteorites and the

Origin of the Meteorites. Geochimica et Cosmochimica Acta, 4:36-82.

Wahl, W.

1950. The Statement of Chemical Analyses of Stony

Meteorites and the Interpretation of the Analyses

in Terms of Minerals. Mineralogical Magazine,

29:416-426.

1952. The Brecciated Stony Meteorites and Meteorites

Containing Foreign Fragments. Geochimica et

Cosmochimica Acta, 2:91-117.

Wlotzka, F.

1963. Uber die Hell-Dunkel-Structur der urgashaltigen

Chondrite Breitscheid and Pantar. Geochimica

et Cosmochimica Acta, 27:419-429.
MINERALOGY
j . J. Gumey Gorceixite in the

Buffels River,

Namaqualand,

South Africa

Gorceixite is a hydrated basic phosphate of barium

and aluminium of uncertain formula but approximating to [BaAl3(PO4)2(OH)5H2O] (Hussak 1906).

The mineral has been reported to be present in

carbonatites such as Mrima Hill, Kenya, (Binge and

Joubert 1966), but is better documented as a "Fava"

or pebble in the diamantiferous gravels of Brazil,

British Guiana, West Africa, Rhodesia, and now

South Africa. Gorceixite is of no economic value in

itself but is generally thought to be a good indicator

of the presence of diamonds (Beard 1941).

In Brazil the mineral has been reported to occur

as pebbles in the diamantiferous gravels of the rivers

Abiete Bagagem and Douradinhos in the Minas

Geraes, the Paranhijba and Verissimo in Goyaz, and

the Patrocinio de Sapucahy and the Canoas in Sao

Paulo. Gorceixite has also been reported to be associated with diamonds at Issineru, British Guiana;

Bonsa River, Gold Coast; Oiyi District, Sierra Leone;

and at Somabula, Rhodesia (Palache, Berman, and

Frondel 1951). More recently it has been discovered

in the Bongou River in French Equatorial Africa

(Miller 1959).

Pebbles of gorceixite contain some impurities, usually of silica, iron, and titanium. Calcium and the

rare earth elements may substitute for barium and a

strontium analogue of the mineral (goyazite) has

been reported from the same gravel deposits.

The pebbles found in the Buffels River were obtained from the heavy mineral concentrate of the

/. /. Gumey, Department of Mineral Sciences, National

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

diamond mining operations of the Buffelsbank Diamante Edms. Bpk. This company is recovering diamonds from a quaternary drainage channel of the

Buffels River in the Spektakel Valley, west of Springbok, Namaqualand.

The pebbles range from greyish white to light

brown to dark brown and are up to 2 cm across. An

analysis of a light brown pebble is given in Table 1.

This pebble had a porcelaneous fracture, hardness of

about 6, specific gravity of 3.14, and vitreous lustre.

An X-ray diffractogram confirmed that the mineral

was gorceixite.

In the analysis reported, some calcium, strontium,

and rare earth substitution of barium is apparent.

Neither the ideal formula, nor that suggested as an

alternative by Palache, Berman, and Frondel (1951)

are identical to the analytical result seen after the

obvious impurities are ignored (see Table 1).

The source of the gorceixite in the Buffels River

is unknown and there is no reported association between gorceixite and diamond except in river gravels.

It seems probable that similarity in specific gravity

was the chief agent in bringing the two minerals into

close association in this environment. Possibly gorceixite is more common than might be supposed from

its sparsely reported occurrences. It is unimpressive in

appearance and can easily be overlooked.

Acknowledgments

The author would like to thank Mssrs F. Hoffman

and F. Mostert, Managing Director and Mine Manager of the Buffelsbank Diamante Edms. Bpk, for

77
78 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

TABLE 1.—Analysis of gorceixite from the Buff els

River, Cape Province, South Africa

Constituent

BaO

CaO

Total

R. E. ..

SrO

AUO,

PaO8

HSO+ .

SiOa

TiO,

F e sO, ....

N a 2O

KaO

HsO -

Total ...

Chemical anlaysis

1*

Ba Ah(POi)i

(OH)sHsO

29.98

29.96

27.75

12.31

100.00

2*

Gorceixite

Buffels

River

23.38

0.92

1.71

1.50

27.64

19.76

16.11

2.63 '

0.95

2.49

0.29

0.15

0.32

97.85

(weight percent)

3* 4*

Recalcu- Ba AL(POi)i

lated less (OH)sHzO

impurities

25.12 26.02

1.00

1.86

1.62

29.70 34.59

21.23 24.10

17.11 15.29

> Impurities

97.64 100.00

* Column /: Theoritical composition.

Column 2: New analysis, J. J. Gurney.

Column 3: Recalculation after subtraction of probable

impurities (SiO2, T1O2, FesOj, NasO, K2O, H2O-).

Column 4: Ideal composition.

submitting the samples investigated for examination.

Permission to publish the results was kindly granted

by the Board of Directors of the operating company

and the X-ray diffraction work was carried out by

P. Hofmeyr.

Literature Cited

Beard, E. H.

1941. Recent Discoveries of Gorceixite. Bulletin of

Imperial Institute, 39(2): 160-164.

Binge, J, and P. Joubert

1966. The Mrima Hill Niobium Deposit, Coast Province

Kenya. Information Circular No. 2 Republic of

Kenya Geological Survey.

Hussak, E.

1906. Uber die Sogenannten 'Phosphat—Favas' der Diamantfuhrenden Sande Brasiliens. Mineralogische

und Petrographische Mittheilungen, 25:336.

Miller, M.

1959. Sample Submitted to Smithsonian Institution 3/

2/59. Locality Bongou River, French Equatorial

Africa.

Palache, C, H. Berman, and C. Frondel

1951. Dana's System of Mineralogy, 7th edition, 2:833.

New York: John Wiley and Sons.
Brian Mason ToCOmallte

In 1968 I received from Sir Maurice Mawby (Melbourne, Australia) a mineral specimen from Broken

Hill, New South Wales, for identification. The mineral for identification filled a small cavity in a coralloid mass of embolite; it was soft, mealy, bright yellow

in color but extremely photosensitive, rapidly turning

gray-green and then black on exposure to bright

light. Sir Maurice had obtained it in 1922 from the

underground manager of the Block 14 mine at Broken

Hill (the Block 14 mine is now part of the North

Broken Hill property).

The association with embolite and the photosensitivity immediately suggested a silver halide. However,

an X-ray powder photograph gave a distinctive pattern (Table 1) which could not be matched with any

of the silver halides in the ASTM index. On checking against the silver halide minerals in the literature,

my attention focused on the obscure mineral tocornalite, as described in Palache et al. (1951) :

A name given to a supposed iodide of silver and mercury

found with other ill-defined chloride-iodides of silver and

mercury at Chanarcillo, Chile. Granular massive. Color pale

yellow, becoming darker on exposure. Streak yellow. An

analysis of impure material gave Ag 33.80, Hg 3.90, I 41.77,

siliceous residue 16.65, total 96.12; the loss is due to some

water belonging in the residue, and probably some iodine.

A mineral referred to tocornalite was found at the Proprietary Mine, Broken Hill, New South Wales, as a deep yellow

powder, blackening in sunlight, associated with iodyrite and

cinnabar.

In the mineral collection of this department was one

small specimen (No. C906) labeled "Tocornalite,

Chanarcillo, Chile"; material from this specimen

gave an X-ray powder photograph identical with that

from the Broken Hill specimen.

The published identification of tocornalite at

Broken Hill was the work of Mr., George Smith

(1926), who was associated with the mines for many

Brian Mason, Department of Mineral Sciences, National

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

TABLE 1.—X-ray powder photograph of tocornalite,

Broken Hill, Australia (Cu Ka radiation, intensities

visually estimated)

Line Intensity d-spacings

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

7

2

2

9

9

1

4

4

3

4

10

1

2

7

3

5

4

2

2

3

4

3

6.37

4.67

4.51

3.76

3.61

3.39

3.29

3.19

2.998

2.894

2.644

2.468

2.309

2.254

2.127

2.036

1.877

1.834

1.743

1.695

1.634

1.583

years from 1888 onward, first as an ore buyer and

assayer, then as a mine manager, and subsequently

as Inspector of Mines for twenty-one years. It is

eloquent testimony to his discerning eye and his mineralogical knowledge that he was able to recognize

tocornalite in the Broken Hill material from the description of the Chilean mineral published many years

earlier. The Proprietary Mine, from which his material came, was contiguous with the Block 14 Mine.

Tocornalite was described by Ignacio Domeyko in

1867. I have attempted to find type material of this

mineral, both in Chilean and in European collections,

without success. However, the Chanarcillo specimen

in our collection does correspond well with the origi79
80 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

nal description. Unfortunately, neither in this specimen nor in the Broken Hill material is there sufficient

tocornalite for a quantitative chemical analysis to

check the composition arrived at by Domeyko. Experiments at synthesizing this mineral have so far been

unsuccessful; a variety of products has been obtained

by precipitating mixed silver and mercury solutions

with potassium iodide, but none of the precipitates

has given an X-ray powder photograph agreeing with

that of tocornalite. Attempts at indexing the powder

photograph of tocornalite and thereby determining its

crystal system, cell dimensions, and ultimately its structure have also been unsuccessful.

Tocornalite is evidently a valid species, occurring at

both Chanarcillo and Broken Hill, but additional

work on better material is needed to characterize it

completely.

I am indebted to John S. White, Jr., for the preparation of numerous X-ray powder photographs.

Literature Cited

Domeyko, Ignacio

1867. Mineralojia de Chile, Appendix 11:41.

Palache, C, H. Berman, and C. Frondel

1951. Dana's System of Mineralogy, 7 th edition, 2:1124.

New York: John Wiley and Sons.

Smith, George

1926. A Contribution to the Mineralogy of New South

Wales. New South Wales Mines Department,

Mineral Resources, 34: 145.
STANDARDS FOR CHEMICAL ANALYSIS
Eugene Jarosewich Chemical Analysis

of Five Minerals

for Microprobe

Standards

There is a growing need for the availability of reliable

microprobe standards for chemical analysis of various

materials, in our particular case for the analysis of

minerals.

Unfortunately, there are a very limited number of

acceptable standards. Perhaps one of the main reasons for this is lack of homogeneous materials, an

essential property of microprobe standards. Homogeneity should be the micron level, and the material

should be stable under the electron beam. Also, there

Eugene Jarosewich, Department of Mineral Sciences, National Museum of Natural History, Smithsonian Institution,

Washington, D.C. 20560.

should be sufficient material for a chemical analysis.

We have analyzed five minerals which have been

successfully used as microprobe standards. These

standards served very well in plotting the calibration

curves with standards from other sources, and excellent results were obtained. Nevertheless, we still are

contemplating a more thorough study of homogeneity.

These standards were obtained by crushing hand

specimens of a rock or mineral and then selecting a

fraction between 80 and 60 mesh for heavy liquid and

Franz magnetic separations. Each sample was visually

inspected for impurities. In this manner between 0.8 g

to 1.5 g of sample was obtained. Approximately 20

grains of each sample were mounted on a one-inch

TABLE 1.—Chemical analyses of minerals for use as microprobe standards (weight

percent)

Constituent

Kakanui Kakanui Omphacite Garnet Garnet

Hornblende Pyrope (USNM110607) (USNM 87375) (USNM110752)

SiO,

A1*O,

Fe»Os

FeO

MgO

CaO

Na3O

K,O

H*O +

H^OTiO,

P«O.

MnO

Total

40.37

14.90

3.30

7.95

12.80

10.30

2.60

2.05

0.90

0.04

4.38

0.00

0.09

99.66

41.46

23.73

N.D.

10.68

18.51

5.17

N.D.

N.D.

N.D.

<0.01

0.47

N.D.

0.28

100.30

55.42

8.89

1.35

3.41

11.57

13.75

5.00

0.15

N.D.

0.02

0.37

ND.

0.10

100.03

39.47

22.27

2.77

13.76

6.55

14.39

N.D.

N.D.

N.D.

<0.01

0.39

0.59

100.19

40.16

22.70

2.17

9.36

7.17

18.12

N.D.

N.D.

N.D.

<0.01

0.35

0.19

100.22

83
84

glass and checked for major elements homogeneity on

the microprobe. The chemical analyses were performed employing classical methods (Hillebrand 1953

and Peck 1964). Sodium and potassium were determined by flame photometry.

Omphacite USNM 110607 was separated from eclogite, garnet USNM 87375 and garnet USNM 110752

were separated from kyanite eclogite, all from Robert

Victor Mine, South Africa. Kakanui hornblende and

pyrope were prepared from nodules described by

Brian Mason (1966).

SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

Literature Cited

Hillebrand, W. F., G. E. F. Lundell, H. A. Bright, and J. I.

Hoffman

1953. Applied Inorganic Analysis. 2nd edition, 1034

pages. New York: Wylie and Sons.

Mason, B.

1966. Pyrope, Augite and Hornblende from Kakanui,

New Zealand. New Zealand Journal of Geologv

and Geophysics, 9.

Peck, L.

1964. Systematic Analysis of Silicates. Geological Survey Bulletin, 1170.
THE COLLECTIONS
Paul K Desautds Acquisition of the

Carl Bosch Collection

of Minerals

and Meteorites

A five-year effort by the Division of Mineralogy to

acquire ownership of the Carl Bosch Collection of

minerals and meteorites was brought to a successful

conclusion in 1970. This collection, once belonging

to the late Nobel Prize winner, Professor Dr. Carl

Bosch (Figure 1), is a very large and important collection of about 25,000 specimens including almost

600 meteorites. It is especially strong in specimens

from old, exhausted, Central European localities. The

representative suites of older species in a wide range

of variation from many now-extinct mines are unmatched in any other private collection. These and

many other specimens in it are of materials that are

most difficult or impossible to acquire today. The

meteorite segment of the collection is a major collection in its own right, consisting largely of falls which

are unavailable now. Considering the difficulty and

expense of acquiring any new meteoritic material

this is an incredible accumulation. As is true with

most large collections, the Bosch Collection contains

several pre-existing collections. Among the best of

these is the well-known Seligmann Collection which

contains a large number of specimens that have been

described in the mineralogical literature of the past.

Assembled and enjoyed by Dr. Carl Bosch, the

collection was transported, for safekeeping, to the

United States from Germany in 1951. Arrangements

were made for its deposition at Yale University on a

fifteen-year loan. By 1966, with the loan period expiring and Yale University having made no move to

acquire the collection, the heirs of Dr. Bosch decided

Paul E. Desautels, Department of Mineral Sciences, National

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

to dispose of the collection through sale. Although

little used by Yale in the fifteen-year period, the collection had been kept intact and in relatively good

condition. Its original catalog was in rather good

agreement with the contents of the collection.

For several reasons it was considered imperative to

acquire and place the collection in the Smithsonian

Institution for conversion to maximum use as part of

the National Collection of minerals and meteorites.

Firstly, the collection was of major size with its 25,000

specimens including the nearly 600 meteorites. Collections of such size rarely become available for wholesale reinforcement of constantly changing specimen

needs of the National Collection. In numbers, though

not in quality or species representation, it would be

the largest single collection of minerals ever acquired

by the National Museum of Natural History. Also,

the collection contained extensive suites of rare reference specimens unobtainable through normal channels. Even those specimens duplicating others already

in the Museum were considered usable for supplying

additional material to meet ever-increasing research

and exchange demands. Several hundred pieces were

thought to be of public exhibit quality. The strong

representation of old Central European mineral occurrences was specially significant because of the new

support which would be available for the weakest part

of our Museum collection. Being an older collection,

much of the specimen material was of a type totally

unavailable today through normal sources. Of course,

the presence of the included Seligmann Collection

with its many described specimens increased the number of scientifically significant pieces generally unavailable at any price. The meteorite materials had

87
88 SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

FIGURE 1.—Dr. Carl Bosch—late Nobel Prize winner—who assembled the Bosch Collection of

minerals and other natural history collections in the early 1900s. Photograph supplied by Dr.

Henning Borchers.

unusually high, current, scientific importance and

needed to be carefully conserved. Our meteorite collections were already under such careful control that

conservation-research procedures were already set up.

Finally, the excellent state of preservation and organization of the collection would make it possible to convert it to maximum use in minimum time (Figure 2).

The Bosch Collection had already been openly

offered for sale by the time the decision had been

made to attempt acquisition. When it appeared that

there was a distinct possibility the collection would be

sold outside the United States, negotiations were accelerated. There was no established price but our own

appraisal and independent appraisals were arranged

and a reasonable price of $250,000 was agreed upon.

In retrospect, faced with a continuing rapid rise in
NUMBER 9 89

FIGURE 2.—Cafarsite—a newly (1966) described mineral species. This very fine specimen was

found in the Bosch Collection where it had been labeled as an "unknown." Thus, Dr. Bosch had

discovered the species long before its "official" discovery.

the market price of mineral specimens, this was a very

fair agreement. By this time, Dr. Carl Bosch, Jr., had

concluded that the Smithsonian was the logical repository for his father's collection. When it became

obvious that there was little hope of our raising the

total payment, he was willing to help as much as

possible. Accordingly, Dr. Bosch agreed to donate

$70,000 of the value with the remaining $180,000 to

be paid over a period of five years. With the aid of

a $47,000 grant from the National Science Foundation and $13,000 in available private funds, an initial

payment was made in the spring of 1966. Necessary

packing and moving arrangements were made and

the collection was transferred promptly to Washington

in two large vans. The problems of packing and moving such a large collection containing much fragile

material were anticipated in advance and the moving company was so cooperative that there were no

mishaps of any account during the transfer. Most of

the actual handling of specimens was, of necessity,

done by our own staff.

Without waiting for complete ownership, the sorting, relabeling, cataloging and integration of the collection into our existing operation were begun. To

date, about 14,500 specimens have been processed.

Since the original collection's cataloging and labeling

are not up to our present standards, the task is difficult. German script of names and localities—often

abbreviated—must be translated and related to modern speciation and geography. These difficulties, together with the necessary physical handling and the

shortage of trained personnel, have made cataloging

the collection slow work but completion of the project is expected in 1971. The size and nature of this

collection as a unit suggested the possibility of using

it for a pilot program in computerization of the

mineral collection. Accordingly, cataloging has been

arranged in such a way as to make the necessary

information available eventually for the computer.

Meanwhile, this important collection has already

been pressed into service for our normal research,

educational, and exhibits programs.
THIN-SECTION PREPARATION
Grover Moreland,

Frank Ingram,

and Harold H. Banks, Jr.

Preparation of

Doubly Polished

Thin Sections

A technique for preparing polished thin sections

which show greater textural and mineralogical detail

has been developed for stony meteorites, rocks, and

minerals.

The preparation of polished thin sections—sections

which can be examined in both reflected and transmitted light and used for electron microprobe

studies—has been discussed at length by Moreland

(1968). This procedure, in summary, is to cement

an optically flat surface of a specimen, which has been

sized for a petrographic section or for a circular

microprobe section, to a glass slide and then to handgrind the specimen to a thickness of 30 microns. Next,

the opaques are given a rough polish, then the nonopaques are polished, and lastly the section is subjected to a final polish.

In the course of preparing polished thin sections

of deep-sea basalts, volcanic ejecta, and Apollo 11

and 12 samples, it was observed that the polishing of

both sides of a sample enhanced the optics by

yielding sharper images, particularly of groundmass

minerals in fine-grained rocks and of inclusions in

minerals.

The first step in the preparation of a doubly polished thin section is to cut a wafer of the specimen,

approximately 7/8 inch square and 3/16 inch thick

with smooth parallel surfaces, using a 5-inch by 0.015-

inch diamond saw blade. The wafer is then ground

on one face to an optically flat surface, using a water

slurry of 600 aluminum oxide on an 850 rpm, 12-inch

cast-iron lap.

Grover Moreland and Harold H. Banks, Jr., Department of

Mineral Sciences, National Museum of Natural History,

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

Ingram, Ingram Laboratories, Griffin, Georgia 30223.

After washing the wafer with water and drying it

for approximately 30 minutes at 200 °F, it is immersed, under vacuum, in a mixture composed of

equal portions of Araldite AY105 and Hardner 935F

(Moreland 1968:2071) dissolved in three parts of

toluene. The vacuum occasionally is broken and restored to help force the impregnating solution into the

pores and cavities of the sample. The wafer is removed from the vacuum and the impregnating solution, after two to three hours, and placed on a hot

plate or in a drying oven to allow the impregnating

medium to cure, which takes about one hour at

200°F and 15 minutes at 300°F. The wafer is reground to expose the sample and the impregnation

procedure is repeated.

The next step is polishing the ground face of the

wafer. For this, a double thickness of kraft, heavyduty, wrapping paper is used instead of a lap cloth.

The paper is cut to the size of the lap and evenly

smeared with a one-half-inch length of 3-micron

diamond abrasive and a small amount of polishing oil,

until it appears moist. Unlike a lap cloth, the kraft

paper minimizes plucking and subsequent scratching

of the sample and ultimately gives a much better

polish; in addition, it is inexpensive. The polishing

technique is described by Moreland (1968:2073).

However, it must be noted that the lap should turn

at 200 rpm. After the final polish, the wafer is

mounted with the polished face down on a glass slide,

using Araldite AY105 and Hardner 935 (Moreland

1968:2071).

An Ingram Model 103 thin section cut-off saw is

used to reduce the wafer to a thickness of 0.020 inches*

and an Ingram Model 303 thin section grinder with

a diamond wheel is utilized to still further reduce the

thickness. Additional grinding is done by hand, using

93
94

a slurry of 600 aluminum oxide and water on a 850

rpm horizontal lap, until the desired thickness is

reached. A standard thickness of 30 microns is obtained using a glass plate with a slurry of 1500 aluminum oxide and water.

Final step in the preparation of the doubly polished

thin section is polishing of the wafer, which is described by Moreland (1968).

Doubly polished thin sections of grain mounts are

prepared in essentially the same manner. Grains between 177 and 105 microns (80 to 150 mesh) are

sprinkled one layer thick onto a glass slide, which

has been smeared with a mounting medium of equal

portions of Araldite AY 105 and Hardner 935F and

heated to 200 °F on a hot plate.

After curing, an Ingram thin section grinder is

used to expose the individual grains which are then

SMITHSONIAN CONTRIBUTIONS TO THE EARTH SCIENCES

ground to an optically flat surface and polished in the

same manner as a doubly polished thin section. A

0.015-inch diamond saw blade is used to remove all

outer regions of the glass slide devoid of grains; the

slide is then mounted, polished face down, on another

glass slide. Once the mounting medium has cured,

the sample is placed in an Ingram thin section cut-off

saw and the thickness of the slide containing the

unpolished surface of the grains is reduced so that the

grains are just barely exposed. The section is then

ground and polished to a standard thickness of 30

microns.

Literature Cited

Moreland, G.

1968. Preparation of Polished Thin Sections.

Mineralogist, 53:2070-2074.

American

U.S. GOVERNMENT PRINTING OFFICE: 1972 -484- 316/1B