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i

NASA/TM—2014–217502

Beneficiation of Stillwater Complex Rock

for the Production of Lunar Simulants

D.L. Rickman

Marshall Space Flight Center, Huntsville, Alabama

C. Young

Metallurgical and Materials Engineering, Montana Tech, Butte, Montana

D. Stoeser

USGS, Denver, Colorado

J. Edmunson

Jacobs ESSSA Group, Huntsville, Alabama

March 2014

National Aeronautics and

Space Administration

Marshall Space Flight Center • Huntsville, Alabama 35812
ii

Available from:

NASA STI Information Desk

Mail Stop 148

NASA Langley Research Center

Hampton, VA 23681–2199, USA

757–864–9658

This report is also available in electronic form at

<http://www.sti.nasa.gov>

Acknowledgments

Special thanks goes to the Stillwater Mining Company and to so many of their employees. Without their extremely 

generous contributions of access, labor, and expertise the work reported here could not possibly have been done. The 

Mouat family freely permitted access to the Mountain View mine and the Mouat mining claims, which was crucial to 

the success of our work.
iii

TABLE OF CONTENTS

1. INTRODUCTION ............................................................................................................. 1

2. STILLWATER COMPLEX ................................................................................................ 2

2.1 Waste Dumps ................................................................................................................ 4

2.2 Outcrops ....................................................................................................................... 4

2.3 Tailings ......................................................................................................................... 9

2.4 Petrographic Textures ................................................................................................... 12

2.5 Analysis ........................................................................................................................ 16

3. SEPARATIONS ................................................................................................................. 19

3.1 Background .................................................................................................................. 19

3.2 Road Norite .................................................................................................................. 21

3.3 Mill Tailings .................................................................................................................. 24

3.4 Flowsheet Design .......................................................................................................... 25

4. CONCLUSIONS ................................................................................................................ 27

REFERENCES ....................................................................................................................... 28
iv

LIST OF FIGURES

 1. Composite stratigraphic section from Boudreau showing zones 

and modal mineral stratigraphy (cumulus minerals only): S denotes sulfideenriched zones, A–K denotes the major chromites, P denotes podiform 

concentrations of sulfide of limited lateral extent, and J-M Reef marks 

the platinoid-rich zone being mined .......................................................................... 3

 2. Surface sample locations of material used in simulant development: 

A–anorthosite, B–road norite, C–harzburgite, and D–othropyroxinite. 

Chromite ore was collected from bulk sample piles adjacent to point C 

(image © 2013 Google and USDA Farm Service Agency) ........................................ 5

 3. Hand sample of the road norite in a lightly weathered surface. The light-colored 

material composing ~60% of the rocks is plagioclase with a composition 

of ~An85. The medium brown crystals are orthopyroxenes; the rich green masses 

are clinopyroxene. Rickman et al. listed typical compositions of the pyroxenes ........ 6

 4. Road cut in the anorthosite I zone from above the Stillwater Mine. This was 

used as a feedstock for LHT-1M and -2M. Dark rock to the left of the contact 

is troctolite and further to the left, the more blocky rock, is a zone of norite. 

Note the reddish material in the anorthosite is one of many alteration mineral 

assemblages (localized along fractures) in the anorthosite ........................................ 7

 5. Detail of anorthosite in road exposure. Dark green in the lower center 

is clinopyroxene, which has grown around euhedral plagioclase crystals. 

The yellow arrow points along a fracture line on which there is alteration. 

In this photo there are at least five such fracture lines, which are almost parallel ...... 8

 6. Alteration zones in anorthosite. Two subparallel zones of intense hydrothermal 

alteration, 30–40 cm wide, can be seen running from lower left to middle right ........ 9

 7. Stillwater mill sand. The material is susceptible to sorting by particle size, 

which is evident along the left edge of the image ...................................................... 10

 8. SEM backscatter image of mill sand (P–plagioclase, A–albite, M–mixed 

plagioclase, and alteration products, Z–zoisite, O–orthopyroxene, 

X–clinopyroxene, L–olivine ± Fe-oxide, Cr–chromite, Cl–chlorite, 

E–epidote, H–hornblende?, and C–calcite (white bar = 500 μm)) ............................. 11
v

LIST OF FIGURES (Continued)

 9. Relatively unaltered rock from Stillwater. This sample shows textures typical 

of Stillwater rock. See text for discussion. Section id: STW3 ..................................... 13

10. Locally complete replacement of plagioclase by alteration minerals without 

significant alteration of the remaining plagioclase. See text for discussion. 

Section id: STW12 .................................................................................................... 14

11. Alteration localized along fractures and at crystal boundaries. See text 

for discussion. Section id: STW11 ............................................................................. 15

12. Disseminated chloritic alteration. See text for discussion. Section id: ST21B ............ 16

13. MLA micrograph of the nonmagnetic product made by dry processing outcrop 

material with the RE Magnetic Belt Separator .......................................................... 21

14. SEM micrograph illustrating a locked particle in the nonmagnetic product made 

by dry processing outcrop material with the RE Magnetic Belt Separator. 

Region 1 contains Fe and is considered magnetic whereas region 2 does not 

and is considered nonmagnetic ................................................................................. 22

15. MLA micrograph of a product produced by dry processing outcrop material 

with a RE Magnetic Belt Separator ........................................................................... 23

16. Potential flowsheet that was developed for processing road norite outcrop 

material .................................................................................................................... 25

17. Potential flowsheet that was developed for processing the wet mill tailings 

material produced at the Nye Concentrator .............................................................. 26
vi
vii

LIST OF TABLES

1. Mineralogy of the road norite from hand-picked samples ......................................... 6

2. Grain size analysis of Stillwater mill waste by dry sieving ......................................... 10

3. Chemical composition and normative mineral calculation for mill waste 

feedstock used for LHT-1M; average of 12 analyses .................................................. 11

4. Reconnaissance SEM-based modal mineralogy of the mill sand based 

on 172 grain EDS x-ray spectrum mineral identifications .......................................... 12

5. Secondary minerals reported in the Stillwater Complex. Abundance of the

minerals decreases from group 1 to group 2 to group 3. The sulfides are primary

and locally secondary minerals. As these are strongly associated with the precious 

metal content being mined, they do not commonly show in either the waste pile 

or the milling tailings ................................................................................................. 17

6. Characteristic wt.% abundance of major minerals in lunar regolith compared 

to road norite outcrop and mill tailings from SMC’s Nye operations ........................ 19

7. Properties of minerals in the road norite and tailings materials ................................. 19

8. Recovery of road norite outcrop material at various size fractions by RE 

Magnetic Belt Separation .......................................................................................... 23
viii
ix

LIST OF ACRONYMS AND SYMBOLS

Al aluminum

Ca calcium

CMC carboxymethyl cellulose 

Fe iron

H2O water

Mg magnesium

MLA mineral liberation analysis

Na sodium

O oxygen

OH hydroxyl ion or radical

RE Rare-Earth (magnetic belt)

SEM scanning electron microscopy

SMC Stillwater Mining Company

TM Technical Memorandum

USGS United States Geological Survey

WHIMS Wet, High-Intensity Magnetic Separator

XRD x-ray diffraction

XRF x-ray fluoresence
x
1

TECHNICAL MEMORANDUM

BENEFICIATION OF STILLWATER COMPLEX ROCK FOR THE PRODUCTION 

OF LUNAR SIMULANTS

1. INTRODUCTION

Simulation of the lunar regolith is technically problematic once the utility of milling a single 

terrestrial source is exceeded. In addition to particle textures, there are several compositional reasons for this. For example, high calcium plagioclase, which is common on the Moon, is rare in bulk 

terrestrial rocks. The ratios of specific minerals and their exact compositions, as found in the lunar 

regolith, are not found in terrestrial sources. Most terrestrial rocks contain significant amounts of 

associated hydroxyl or water bearing mineral phases, whereas these are absent or rare on the Moon. 

Minerals, such as quartz, clays, albite, zeolites, and amphiboles, are common in terrestrial sources, 

but these minerals and their associated fabrics are not useful and may be significantly detrimental 

in emulating lunar prototypes. 

One way to address such problems in the creation of a simulant is to separate terrestrial 

source rocks into constituent mineral fractions. This is a technology that has been developed for 

many centuries1 and is essential for the mining industry. For simulant production, this would 

permit extraction of desired mineral phases from different source rocks into mineral separates 

while removing undesired minerals. Each mineral separate would be a feedstock to subsequent 

production of a needed simulant. The result would be easier manufacturing of higher fidelity 

simulant.

The separation of a rock into its constituent minerals is a complex scientific and engineering 

problem. It combines economic factors, details of chemistry, applications of physics, and the 

specifics of the rock being processed. Therefore, for every mineral one wishes to extract from 

a specific rock, it becomes necessary to test possible separation techniques. This Technical 

Memorandum (TM) addresses a series of separation tests using source rocks from the property of 

the Stillwater Mining Company (SMC), specifically their operations near Nye, Montana. Other 

tests using dry magnetic separation are reported in Rickman et al.2
2

2. STILLWATER COMPLEX

A good general overview of the Stillwater Complex is by McCallum.3 The Complex is 

a classic example of a layered mafic intrusive and formed by processes similar in many respects 

to those that formed the lunar crust.4,5 For this reason, a large body of literature exists that compares various aspects of Stillwater petrology, mineralogy, and geochemistry to that of primary 

lunar crustal rocks (e.g. Raedeke and McCallum6 and Salpas et al.7). In its well defined layers, the 

Stillwater Complex contains many rock types similar to the lunar upper crust (see fig. 1) which 

makes them a good resource for feedstock in the manufacture of lunar regolith simulants. Many of 

the Stillwater rock types are exposed as outcrops, but only a few are accessible from roads. Other 

types come from the activities of the SMC at their Nye and East Boulder mines as they excavate 

the J-M Reef material. The J-M Reef is a narrow zone (<3 m wide) located in the lower banded 

series in which extremely fine-grained, platinum group minerals are present in sulfides. This sulfide 

zone is the ore that is mined and processed for economic gain. Millions of tons of ore are processed 

annually. First, the rock is ground such that most of the particles are smaller than 75 mm, a very 

fine sand. Then mineral separation is achieved using froth flotation. The valuable, platinum-bearing, sulfide minerals report to the floated fraction and are thus concentrated. The gangue minerals, 

the nonfloating fraction, are disposed of as waste in the mine or to the tailings. In addition, waste 

rock must also be removed by mining in order to access the ore. This rock is discarded into piles 

referred to as waste dumps. The bulk of both the tailings and the waste dumps is a plagioclase-rich, 

noritic gabbro.

Lunar regolith simulant can be produced from not only the outcrops that are accessible 

from nearby roads, but also from the mill tailings and waste dumps produced by SMC. Each of 

these resources are discussed in the ensuing sections.
3

6,000

Zones

Upper Banded Series Middle Banded Series Lower Banded Series

Ultramatic Series

NORITE I GN I OB I BZ GN II NORTE II

Banded Series

0 50 100

5,000

4,000

3,000

2,000

1,000

0

Gabbronorite III

(GN III) Pigeonite

Augite

Plagioclase

Plagioclase

Plagioclase

Plagioclase

Orthopyroxene

Orthopyroxene

Massive and

disseminated

sulfides

Sulfide Rare and Pegmatoids Locally Common

Throughout Peridotite and Orthopyroxenite Zones

Olivine

Olivine-bearing V

(OBV)

Olivine-bearing IV

(OB IV)

Olivine-bearing III

(OB III)

Olivine

Augite

Augite

Olivine-bearing II

(OB II)

Gabbronorite II

(GN II)

Norite II (NII)

Olivine-bearing I

(OB I)

Gabbronorite I (GN I)

Norite I (NI)

Anorthsite I

(AN I)

Bronzitite Zone

(BZ)

Peridotite Zone

(PZ)

Basal Series

Anorthosite II

(AN II)

Mineral Mode (%)

P

S

P

S

S

S

S

S

K

J

I

G

CBA

E

H

P

P

P

Picket Pin

Pt/Pd

Deposit

AS

TS

S

Op

J-M REEF

Meters

Figure 1. Composite stratigraphic section from Boudreau8 showing zones and modal mineral 

stratigraphy (cumulus minerals only): S denotes sulfide-enriched zones, A–K denotes 

the major chromites, P denotes podiform concentrations of sulfide of limited lateral 

extent, and J-M Reef marks the platinoid-rich zone being mined. 
4

2.1 Waste Dumps

Rock in the waste dumps is predominantly norite, but also contains gabbronorite, clinopyroxene gabbro, altered troctolite, anorthosite, and orthopyroxenite. The abundance of each rock 

type varies almost hourly, depending on the development of the mine. The dump material varies from very fresh to very altered. Polovina et al.9 note that, in their sample of seven drill cores, 

hydrothermal alteration near the J-M Reef varied from 10% to 90%. Alteration minerals identified by D. Stoeser and S. Wilson of the USGS in waste dump rock consisted mainly of hydrated 

silicates including chlorite, albite, epidote, zoisite, talc, sericite, amphibole, serpentine, magnetite, 

stilbite, and calcite. As hydrothermal alteration in the J-M Reef rock is spatially associated with 

and probably related genetically to sulfide deposition, it has received some attention in the geological literature. McCallum gave brief statements on alteration in various parts of the Complex.3 Any 

bulk use of dump materials will unavoidably include a significant amount of low-grade altered 

rock. A study has been initiated to characterize the variability of the waste dumps, but this has not 

yet been completed. Only modest amounts of high-quality material can be hand-picked off the 

dumps; doing so is difficult due to a thick layer of rock dust covering the surfaces of all stones.

2.2 Outcrops

Useful outcrop sources for feedstock are primarily restricted to exposures in road cuts and 

float below outcrops. A comparatively good road, shown in figure 2, provides access to the Mountain View chromite mine, which is owned by the Mouat family. The road crosses the anorthosites 

of the Middle Banded Series, the Lower Banded Series, and provides access to the Bronzitite and 

Peridotite Zones of the Ultramafic Series. Cuts along this road have been repeatedly used for two 

simulant feedstocks, a norite and an anorthosite. Rock available at and above the Mountain View 

main portal have also been used for simulant development. These include harzburgite, orthopyroxenite, and chromite ore. 
5

Figure 2. Surface sample locations of material used in simulant development: 

A–anorthosite, B–road norite, C–harzburgite, and D–othropyroxinite. 

Chromite ore was collected from bulk sample piles adjacent to point C 

(image © 2013 Google and USDA Farm Service Agency).

The material informally termed ‘road norite’ was obtained in a road cut below the Mountain View Mine, at 45.390208°, –109.893324°. Road norite is relatively unaltered by hydrothermal 

processes (see fig. 3). However, the amount of alteration and the ratios of the major minerals 

varies within the road cut. Careful selection of individual rocks from this site by senior geologists 

involved in the simulant development project provided the single largest constituent in the 

NU-LHT series of simulant prototypes.
6

Figure 3. Hand sample of the road norite in a lightly weathered surface. The light-colored 

material composing ~60% of the rocks is plagioclase with a composition of ~An85. 

The medium brown crystals are orthopyroxenes; the rich green masses are clinopyroxene. Rickman et al. listed typical compositions of the pyroxenes.2

Table 1 gives an analysis of road norite from hand-picked samples.2 The ratio of the two 

pyroxene minerals (opx/(opx+cpx)) is 87.3. The minerals quartz, albite, calcite, biotite, epidote, 

and a potassium feldspar were found in an analysis of the simulant NU-LHT-2M;10 although not 

reported in table 1, their likely source is the road norite. These six minerals, as well as the chlorite 

and talc, are loosely considered to have originated by hydrothermal alteration and their abundance 

varies noticeably within the road cut.

Table 1. Mineralogy of the road norite from hand-picked samples (after Rickman et al.2).

Mineral

Family Specific Mineral Fitted Composition Wt.%

Plagioclase Bytownite (Ca0.86Na0.14)(Al1.86Si0.14)Si2O8 75.0

Orthopyroxene Enstatite Mg(Ca0.054Mg0.946)(Si2O6) 18.4

Clinopyroxene Diopside (Augite) CaMgSi2O6 2.7

Chlorite Clinochlore IIb Mg4.54Al0.97Fe0.46Mn0.03(Si2.85Al1.15O10)(OH) 1.2

Talc 2M Mg3(OH)2(Si4O10) 1.9

Hornblende Na0.9K0.4Ca1.6Mg2.8Fe1.4Ti0.5Al1.4(AlSi6O23(OH)) 0.8
7

The locations used for the harzburgite, orthopyroxenite, chromite ore, and anorthosite are 

also shown in figure 2. The harzburgite came from 45.383269°, –109.907372°. The orthopyroxenite 

came from 45.388833°, –109.905966°. The anorthosite came from 45.398638°, –109.885209°. The 

harzburgite was used in NU-LHT-1M, providing olivine, pyroxene, and chromite. For NU-LHT2M, commercially available olivine was used, as it was essentially pure olivine instead of the harzburgite.11 The orthopyroxenite was not used after NU-LHT-1M, as the norite provided sufficient 

pyroxenes for the target simulant composition and the commercial olivine contains lower amounts 

of alteration minerals. Further, the ratio of clinopyroxene to orthopyroxene in the orthopyroxenite 

is even further from the targeted ratio than the ratio that exists in the norites. Because additional 

chromite was not needed in the simulants, the chromite collected from the bulk sampling dumps 

was not used.

Stillwater anorthosites were used in all of the NU-LHT series simulants. Much of it came 

from one road cut, indicated in figure 2 as anorthosite and shown in figure 4. The anorthosite consists of approximately 90%–95% plagioclase with the remainder of the primary (meaning original) 

minerals in the rock being poikolitic clinopyroxene (augite) up to 5 or 6 cm in diameter (see fig. 5). 

Where present, the clinopyroxenes enclose earlier cumulate plagioclase crystals. The plagioclase 

was quite homogeneous in composition with an An content of ~78. Locally within this site, there 

are planes of intense alteration (see fig. 6). All samples larger than ~10 cm on a side have at least 

some hydrothermal alteration. But careful hand selection yields a feedstock that is estimated to be 

better than 95% pure primary minerals.

Figure 4. Road cut in the anorthosite I zone from above the Stillwater Mine. This was used as 

a feedstock for LHT-1M and -2M. Dark rock to the left of the contact is troctolite 

and further to the left, the more blocky rock, is a zone of norite. Note the reddish 

material in the anorthosite is one of many alteration mineral assemblages (localized 

along fractures) in the anorthosite.
8

Figure 5. Detail of anorthosite in road exposure. Dark green in the lower center is clinopyroxene, which has grown around euhedral plagioclase crystals. The yellow arrow points 

along a fracture line on which there is alteration. In this photo there are at least five 

such fracture lines, which are almost parallel.
9

Figure 6. Alteration zones in anorthosite. Two subparallel zones of intense hydrothermal 

alteration, 30–40 cm wide, can be seen running from lower left to middle right.

2.3 Tailings

The Stillwater tailings from the mill is a waste material commonly called mill sand. It is the 

lithic residuum left over from processing the Stillwater ore after the valuable minerals are extracted. 

The tailings piles of SMC contain several million tons of mill sand. The mill sand is a homogeneous, fine-grained sandy material as illustrated in figure 7 and shown in table 2. Because of the 

nature of the ore deposit and the mixing inherent in the mining and milling processes, the mill sand 

is relatively consistent in its composition and size distribution, which is surprising for a geologic 

material. As shown in table 3, the mill waste has the composition of a feldspathic, leuco-gabbroic 

norite that contains more normative magnesium (Mg)-iron (Fe) silicate minerals than typical lunar 

highlands (65% normative plagioclase compared to an average of 75% for the highlands at the 

Apollo 16 site). Because its parent rock is from the ore zone, it contains more alteration minerals 

than typical of the lower norite zone as a whole (see fig. 8 and table 4). As the mill sand is similar 

to lunar highlands in chemical composition and mineralogy, it has been used as the feedstock for 

making the pseudo-agglutinate and glassy components of the LHT simulants.
10

Figure 7. Stillwater mill sand. The material is susceptible to sorting by particle size, which 

is evident along the left edge of the image.

Table 2. Grain size analysis of Stillwater mill waste by dry sieving.

Mesh

Size

Interval

(μm)

Cumulative

% Total

24 >701 –

30 701–595 –

80 595–180 4.04

100 180–150 7.70

120 150–125 13.15

200 125–75 61.39

325 75–44 82.37

325 <44 100.00

– – –
11

Table 3. Chemical composition and normative mineral calculation for 

mill waste feedstock used for LHT-1M; average of 12 analyses.

Major Element

Chemistry

CIPW

Normative Mineralogy

Oxide Wt.% Mineral Cation% Wt.%

SiO2 48.19 or 0.72 0.73

TiO2 0.12 ab 8.81 8.43

Al2O3 22.29 an 55.05 55.87

Fe2O3 – Total plag 64.58 65.03

MnO 0.09 en 86.2 86.9

MgO 9.82 di 6.46 6.51

CaO 13.03 hy 23.71 22.71

Na2O 1.00 Total px 30.17 29.22

K2O 0.12 opx:cpx 77.23 78.22

P2O5 0.07 ol 3.22 2.93

FeOt 5.26 mt 1.72 2.42

Total 100.18 il 0.16 0.23

ap 0.15 0.17

Figure 8. SEM backscatter image of mill sand (P–plagioclase, A–albite, M–mixed plagioclase, and alteration products, Z–zoisite, O–orthopyroxene, X–clinopyroxene, 

L–olivine ± Fe-oxide, Cr–chromite, Cl–chlorite, E–epidote, H–hornblende?, 

and C–calcite (white bar = 500 μm)).
12

Table 4. Reconnaissance SEM-based modal mineralogy 

of the mill sand based on 172 grain EDS x-ray 

spectrum mineral identifications.

Material Count %

Primary minerals:

 Plagioclase 108 63

 Orthopyroxene 20 12

 Clinopyroxene 14 8

 Olivine (± Fe-oxide blebs) 11 6

 Chromite 3 2

Total primary 156 91

Secondary minerals:

 Albite 4 2

 Mixed plagioclase and 

 alteration minerals

2 1

 Zoisite 1 0.6

 Fe-epidote 1 0.6

 Chlorite 6 4

 Amphibole 1 0.6

 Calcite 1 0.6

Total secondary 16 9.4

Total 172 100

Although the Stillwater Complex is a virtual smorgasbord of potential simulant materials, 

rock that can be accounted as simulant feedstock reserves is limited. (Reserves are geologic material that is legal, economical, and technically feasible to extract.) For example, the Complex above 

the anorthosite I zone is not accessible by road. Feedstock material can only be obtained by handpicking float blocks, inactive mine waste piles, and from road cuts. The road norite location has 

been estimated to hold no more than 30 tons of high-quality material that is safe to remove by 

hand. None of the feedstock resources are greater than ~50 tons without heavy equipment and 

appropriate engineering. (Resources are geologic material that might become economically valuable to extract.) The exceptions to the above are the SMC’s mine dump and mill waste piles, which 

are private property. 

2.4 Petrographic Textures

While the abundance of alteration minerals is important, the distribution of the minerals 

and the interfaces between the minerals are equally important when attempting to extract specific 

minerals from rocks. In many cases, features within individual crystals, such as fractures, are also 

important. Collectively, these and related features are referred to as textures. Although at least one 

nanoscopic texture is known to exist in Stillwater rock, specifically the presence of nanoscopic needles of primary magnetite in primary plagioclase,12 optical examination of planar sections through 
13

whole rock is the standard way to evaluate textures. For Stillwater rocks, the appropriate technique 

is to make petrographic thin sections, which are slices of rock approximately 27 mm × 45 mm ×

30 μm thick mounted on glass slides. When prepared to this thickness, light is readily transmitted 

through the sample and important textural features can easily be seen.

Figures 9–12 are thin sections chosen to illustrate textural features common in the Stillwater 

rocks. Of specific emphasis are the textures of the alteration minerals. In these images, plagioclase 

is nearly colorless, clinopyroxene is a green, and orthopyroxene varies, having shades of brown 

with grey or pink tones. The ratios between plagioclase, clinopyroxene, and orthopyroxene are not 

significant for this TM. The exact identity of the alteration minerals seen in figures 10–12 has not 

been established by qualitative methods. It is common for geologists to assign an identity based 

on judgment, pending positive identification, should it be necessary.

Figure 9 is typical of essentially unaltered rock. The individual crystals are approximately 

equant and the interfaces are relatively simple. The bulk of the mass of each mineral is in crystals 

with a limited size range, approximately to 2–3 mm. Also note the lack of opaque material, which 

would appear black in these images. In detail, other primary textures can be observed in Stillwater rock, but to the nonigneous petrologist the different textures share the characteristics of being 

dominated by relatively equant crystals having a limited range in crystal size and simple crystal to 

crystal boundaries.

Figure 9. Relatively unaltered rock from Stillwater. This sample shows textures typical 

of Stillwater rock. See text for discussion. Section id: STW3.
14

In figure 10, a patch of alteration at A has completely replaced the plagioclase. Minerals 

typical in such alteration include sericite, albite, calcite, epidote, and chlorite. Note the lack of 

alteration in the remaining plagioclase. Alteration of the pyroxenes is extensive. The perimeters 

of the crystals are extensively replaced and the bodies of several are deeply corroded by alteration. 

Opaque minerals, probably magnetite, have precipitated in crystallographically-controlled patches 

inside the original pyroxenes. A secondary crystal of biotite has developed at B.

Figure 10. Locally complete replacement of plagioclase by alteration minerals without 

significant alteration of the remaining plagioclase. See text for discussion. 

Section id: STW12.
15

In figure 11, much of the alteration is clearly associated with fractures. At A, magnetite has 

formed and other magnetite deposition can be seen in patches. Magnetite is localized by the crystallography of the host pyroxene in the upper right of the image. Contacts between crystals are 

common foci for the diffusion of hydrothermal alteration. This is apparent at and around B. At C, 

two parallel fractures through the plagioclase contain what may be epidote. 

Figure 11. Alteration localized along fractures and at crystal boundaries. See text

for discussion. Section id: STW11.
16

Pervasive chloritic alteration is seen in figure 12. At A, the chlorite is extensively replacing 

the orthopyroxene and magnetite has precipitated along crystallographic boundaries of the host 

pyroxene. Other patches of magnetite, which is black in this section, can be seen along boundaries of the plagioclase crystals, especially at triple junctions. Patches of chlorite are seen throughout 

the plagioclase, for example at B, not just at crystal boundaries. The plagioclase in this rock has an 

approximate formula of (Ca0.85,Na0.15)(Al1.85Si2.15)O8. Chlorite is a family of minerals, which are 

generally not discriminated in thin section. A common and likely chlorite has an approximate formula (Mg5Al)(AlSi3)O10(OH)8. As the host plagioclase does not contain magnesium, that element 

has been transported through the plagioclase by the hydrothermal fluids. 

Figure 12. Disseminated chloritic alteration. See text for discussion. Section id: ST21B.

2.5 Analysis

The lunar regolith is dominated by high calcium plagioclase, clinopyroxenes, orthopyroxenes, olivine, and glasses made dominantly from these minerals. Suitable olivine can be purchased 

commercially. Plagioclase can be purchased, but its calcium content is not as high as that of the 

best material from the Stillwater Complex. For simulants, the calcium content of the plagioclase is 

important in many cases, as it affects the melting point of the simulant and changes the chemistry 

of the resulting melt. There are no commercial sources for the pyroxenes.

All of the Stillwater material contains some alteration minerals, often to excessive levels. 

However, by hand selection, it is possible to get rock with <5% total secondary minerals. But 

the selection process requires some skill, training, and experience. The tonnage available by this 

approach, without heavy equipment, proper engineering, and permits, is in the tens of tons.
17

The waste dumps and the mill tailings of SMC’s Nye, Montana, operations contain millions 

of tons of material. This material, which is dominantly high calcium plagioclase, orthopyroxene, 

and clinopyroxene, has variable amounts of hydrothermal alteration minerals as secondary minerals. Almost all of these secondary minerals are objectionable in simulants of lunar regolith for several reasons. A partial list of secondary minerals observed in the Complex is given in table 5. The 

list in table 5 is not exhaustive and the relative abundances indicated are estimates. Different zones 

of the Complex definitely have different secondary minerals and the abundances of the secondary 

minerals will also vary substantially. 

Table 5. Secondary minerals reported in the Stillwater Complex. Abundance of the 

minerals decreases from group 1 to group 2 to group 3. The sulfides are primary 

and locally secondary minerals. As these are strongly associated with the precious metal content being mined, they do not commonly show in either the waste 

pile or the milling tailings.

Group 1 Group 2 Group 3 Sulfides

Chlorite Calcite Apatite Phrenite Chalcopyrite

Albite Epidote Biotite Serpentine Pentlandite

Talc Hornblende ‘Clay’/sericite Sphene Pyrrhotite

Magnetite Ferropargasite Stilbite Pyrite

Quartz FeOx TiO2 species

(Clino-) Zoisite K-feldspar Tremolite

Phlogopite

Experimentation is required to establish whether or not the plagioclase, clinopyroxenes, 

and orthopyroxenes can practically be recovered from the waste dumps or mill sands. Using either 

resource, is it practical to separate the plagioclase, orthopyroxene, and clinopyroxene from each 

other and to simultaneously remove any or all of the secondary minerals? If the separations are 

possible, what are the purities, retention versus loss ratios, and the costs per ton of processing?

Of particular note is the realization that successful separation techniques developed for the 

various Stillwater materials can almost certainly be adopted for use with other feedstocks. This 

could be very useful. For example, the clinopyroxene to orthopyroxene ratio in the Stillwater materials generally is significantly <1; in other words, enstatite is much more common than augite in the 

Stillwater rocks. Much of the lunar regolith, especially the mare, has values >1.13 If the pyroxene 

ratio is important to the performance of the simulant, to reproduce a desired lunar ratio using Stillwater rock would likely require processing to remove and dispose of orthopyroxene from the Stillwater feedstock. Further, the Stillwater pyroxenes tend to have at least some secondary minerals.

There are alternative sources. One could make pyroxene separates from two different sources 

such that, when the separates are combined, they yield the equivalent of lunar regolith. Specifically, 

the Bushveld Complex of South Africa has a much better clinopyroxene to orthopyroxene ratio for 
18

simulant production. Much of the Bushveld rock is also free of any alteration mineralogy. Bushveld rock with a desirable pyroxene ratio is commonly imported into this country under several 

trade names, including Impala Black, Nero Impala, Rustenburg Granite, and Rustenburg Gabbro. 

This means the source rock is readily accessed by heavy equipment and inexpensively shipped internationally. However, the plagioclase in the Bushveld rock has significantly less calcium compared to 

both lunar and Stillwater modes, which is known to be important in many uses of simulants. Similarly, techniques developed for segregating plagioclase from the pyroxene in any of the Stillwater 

feedstocks would permit using Bushveld pyroxenes with Stillwater plagioclase, for example.
19

3. SEPARATIONS

3.1 Background

In order to make separations, the constituents being sought or to be removed must first be 

identified. The goal is to then identify differences in the physical and chemical properties of those 

constituents. Separations can only be made if differences exist, and separation becomes easier as 

the differences increase. In this regard, tables 6 and 7 were developed. Table 6 compares the major 

minerals in lunar regolith to the mineralogy of the road norite outcrop and mill tailings. Because 

neither resource contains significant, unaltered olivine, an olivine separate cannot be made. As 

mentioned previously, an olivine separate can also be obtained simply by purchasing a commercially available commodity, as long as it meets the necessary chemical and mineralogical specifications. Table 7 lists the various properties of the minerals and differences show that, for example, 

a plagioclase separate could be made first by magnetic separation and then the two pyroxenes 

separated by electrostatic separation to make clinopyroxene and orthopyroxene separates. In addition, based on differences in density, gravity separation could also be used to make a plagioclase 

separate; however, experience suggests that magnetic separation should work better. This does not 

mean that gravity separation will not be considered but rather does not have as high of a priority 

for testing. 

Table 6. Characteristic wt.% abundance of major minerals in lunar regolith compared 

to road norite outcrop and mill tailings from SMC’s Nye operations.

Mineral Formula Outcrop Tailings Regolith

Plagioclase (Na,Ca)(Si,Al)4O8 75 63 75

Orthopyroxene (Mg,Fe,Ca)(Mg,Fe,Al)Si2O6 18.4 12 10

Clinopyroxene (Ca,Na)(Mg,Fe)(Si,Al)2O6 2.7 8 5

Olivine (Mg,Fe)2SiO4 – 6 10

Table 7. Properties of minerals in the road norite and tailings materials.

Mineral

Family Specific Density Conductor Magnetic Hydrophobic

Plagioclase Anorthite 2.8 N N (Dia) N

Orthopyroxene Enstatite 3.2 N Y (Para) N

Clinopyroxene Augite 3.2 Y Y (Para) N

Olivine Forsterite 3.3 N Y (Para) N

Talc 2.8 N N (Non) Y
20

Finally, although not present on the Moon, talc is included in table 7 because it is present 

in the two SMC resources and is functionally significant in mineral separation. Talc is naturally 

hydrophobic and can be separated from other silicate minerals by flotation. The processing of the 

ore by SMC is designed to float the platinum-bearing sulfide minerals; thus, if talc also floats, it 

would significantly dilute the concentrate. To force the talc to report to the tailings, SMC adds 

carboxymethyl cellulose (CMC) to their flotation circuit. This chemical is a talc depressant which 

thereby prevents it from floating.

A major advantage of using mill tailings is that material preparation by additional comminution is minimal, if at all. However, because the mill tailings are already slurried, only wet 

processing technologies can be considered, thus avoiding expensive dewatering processes to enable 

dry processing. In addition, it is important to consider process reagents, like CMC, that might be 

present in the mill tailings as a result of SMC’s milling process for extracting the valuable precious 

metal bearing sulfide minerals. By comparison, the road norite outcrop requires comminution. 

However, because this material is dry, both wet and dry separations can be considered.

The effectiveness of typical separations is normally measured by grade and recovery where 

grade refers to the purity of separates and recovery refers to the amount of separate being produced. Both quantities can be measured with a variety of analytical and characterization tools 

which, in this case, included x-ray fluoresence (XRF), x-ray diffraction (XRD), and scanning electron microscopy (SEM)/mineral liberation analysis (MLA), depending on the separate being examined. These tools are commonly used in mineral analysis with SEM/MLA being a recent innovation 

that has revolutionalized the mineral processing industry. SEM/MLA is a state-of-the-art technology that uses the greyscale, back-scattered images from the SEM and correlates them to their 

energy dispersive x-ray spectra to determine what minerals they contain, then gives each mineral 

a representative or ‘false’ color, and quantifies them accordingly to produce an MLA micrograph.

For this study, the various separators that were used were all located at Montana Tech and 

included a (dry) Electrostatic Separator, (dry) Rare-Earth (RE) 25,000 Gauss Magnetic Belt, (dry) 

Multi-Element 2500-8000 Gauss Magnetic Drum, (wet) Electromagnetic 15,000 Gauss Drum, Wet 

High-Intensity Magnetic Separator (WHIMS) 20,000 Gauss Magnetic Carousel, and a 2-L batch 

flotation cell. The flotation cell is from Wemco and all other separators were from Eriez.

Outcrop materials for the work reported here were hand selected from the outcrop by 

D. Stoeser and D. Rickman as part of a larger collection effort. The rock was then broken as 

needed with a sledge hammer to 100% passing 4 inches, then dry crushed to 100% passing 1⁄2 inch 

with a 5-inch laboratory jaw crusher, and then to 100% passing approximately 1⁄10 inch with a 

6-inch laboratory double-roll crusher. It was then either wet or dry ground with 6 inch ×10 inch 

laboratory batch ball mills to 80%, passing either 600 μ (Tyler 28 Mesh) or 45 μ (Tyler 325 Mesh). 

Due to equipment constraints, feed to the WHIMS had to be <45 μ. Flotation tests were conducted 

on both size fractions. In some cases, experiments were conducted on fractions sized by sieving. 

Tests were conducted on as-received wet mill tailings. Size measurements via sieve analysis showed 

the materials to be 80% passing 45 μ (Tyler 325 Mesh), which concurs with the results presented 

in table 1.
21

3.2 Road Norite

Figure 13 shows the MLA micrograph of the nonmagnetic fraction produced from the outcrop material using the dry RE Magnetic Belt Separator. Results indicate that a plagioclase product 

results with an assay of 97.74% plagioclase and 1.29% pyroxene. These results are comparable with 

the results reported in Rickman et al.2 When this fraction was size separated, XRF analysis of the 

coarse fractions were found to assay 27.1% Si, 20.0% Al, 15.0% Ca, 1.1% Na, and 0.8% Fe with the 

balance being 36.00% O, whereas the fine fractions assayed 19.2% Si, 16.6% Al, 12.4% Ca with no 

Na and Fe present, and the balance being 51.8% O. The differences are attributed to the separation 

being dependent on particle size as well as liberation. Figure 14 confirms that incomplete liberation 

likely caused the grade of the plagioclase product to not be pure. In this case, region 1 of the locked 

particle contains Fe and is presumed to be paramagnetic in spite of reporting to the nonmagnetic 

fraction. By comparison, region 2 does not contain Fe. Finally, XRD analysis of this product suggests the plagioclase is bytownite.

200 μm

Figure 13. MLA micrograph of the nonmagnetic product made by dry processing 

outcrop material with the RE Magnetic Belt Separator. 
22

100 μm

Figure 14. SEM micrograph illustrating a locked particle in the nonmagnetic product 

made by dry processing outcrop material with the RE Magnetic Belt Separator. Region 1 contains Fe and is considered magnetic whereas region 2 

does not and is considered nonmagnetic. 
23

By comparison, figure 15 shows the MLA micrograph of the magnetic fraction produced 

with the dry RE Magnetic Belt. In this case, the grade was 34.94% plagioclase and 64.83% pyroxene. This product clearly needs upgrading. Figure 15 demonstrates locking occurs as indicated by 

the boxed-in particle; however, reducing the particle size further by additional grinding did not 

improve the separation with the dry RE Magnetic Belt such that even the nonmagnetic fraction 

was not improved. Comparing figures 14 and 15 suggests that locking affects the magnetic fraction more and that the dry RE Magnetic Belt Separator does not process fine materials as well as 

coarse materials. When the feed was sized, results showed that the weight fraction reporting to the 

magnetic product was consistently between 63%–68% in agreement with an independent study; 

however, when the feed size was <150 μ, recovery fell to 50%, and when the feed size was <75 μ, 

separation was poor (see table 8).

200 μm

Figure 15. MLA micrograph of a product produced by dry processing outcrop 

material with a RE Magnetic Belt Separator.

Table 8. Recovery of road norite outcrop material at various size fractions by

RE Magnetic Belt Separation.

Size

(μm)

Feed

(g)

Mag Con

(g)

Weight Recovery

(%)

–1,000 / 600 564.0 380.0 67.4

–600 / 300 665.1 453.3 68.2

–300 / 150 429.9 274.8 63.9

–150 / 75 240.3 117.4 48.9

–75 Too Fine
24

Electrostatic separations were performed to process outcrop material as well as both the 

magnetic and nonmagnetic products from the dry RE Magnetic Belt Separator. Results were 

negative in all cases. Therefore, further electrostatic separations were not performed in subsequent 

experiments. 

A dry RE Magnetic Belt Separation was repeated and the resulting nonmagnetic product 

was wet ground to 80% passing 45 μ and prepared for flotation. The slurry was adjusted to pH 9 

with lime and floated in three stages each for 5 minutes with stage 1 employing only Dow Froth to 

separate talc, and with stages 2 and 3 employing both Dow Froth and Cytec Aero 704 Fatty Acid 

Promotor to separate any remaining talc and other hydrated silicates. In this reverse flotation strategy, the unfloated fraction is the plagioclase concentrate which was found to measure effectively 

100% anorthite.

The magnetic product from the dry RE Belt separation was also wet ground for liberation 

purposes and then processed with the wet High Intensity Magnetic Carousel. The nonmagnetic 

fraction from this WHIMS separation step was then subjected to the same flotation procedure as 

just described. In this case, a plagioclase concentrate was found to have a grade of 89% anorthite. 

Combining the two products will yield an overall plagioclase concentrate near 94% anorthite which 

will be more than acceptable as a separate.

With most of the talc and plagioclase removed, the magnetic fraction from the WHIMS 

separation step should be predominantly pyroxene. Table 7 suggests it will contain orthopyroxene 

and clinopyroxene in a 3:1 ratio along with various secondary mafic minerals. All that needs to 

be done is purify the product and either remove some orthopyroxene or add clinopyroxene from 

another separate to obtain the 2:1 ratio in lunar soil. Work continues in this regard as well as to 

determine an analytical method for precisely measuring the pyroxene content. This work is being 

done by Frank Asirifi, MS candidate in Metallurgical and Materials Engineering, Montana Tech.

3.3 Mill Tailings

Mill tailings from the SMC’s Nye Concentrator in Montana were also examined. Because 

the material was already 80% passing 45 μ, it was first processed with the wet Electromagnetic 

Drum Separator to remove any ferromagnetic material that may be in the material including mill 

scale. This protects the WHIMS which is used next to process the nonferromagnetic product from 

the Electromagnetic Drum Separator. The WHIMS magnetic fraction should contain predominantly pyroxene but XRD and SEM/MLA analyses were not reliable. As noted above, a precise 

analytical method is being developed. However, table 7 suggests the product will contain orthopyroxene and clinopyroxene in a 0.5:1 ratio. It is conceivable that this product could be combined 

with that produced from the road norite outcrop material such that the 2:1 ratio in lunar soil is 

obtained. Work also continues in this regard as well as to try and separate the pyroxene minerals.

The WHIMS nonmagnetic fraction was then treated by flotation in order to remove talc. 

However, for this to work, it was first going to be necessary to destroy the CMC used at the Nye 

Concentrator as a talc depressant. The slurry was found to be at pH 8.5 and was left as is. Flotation was conducted in five stages, each for 5 minutes. Stages 1–4 used only Dow Froth; stage 5 
25

used Cytec Aero 704 Fatty Acid Promotor and Dow Froth. However, prior to stages 2, 3, 4, and 5, 

hydrogen peroxide was added and allowed to react for 5, 20, 40, and 3,000 minutes, respectively. The 

resulting plagioclase concentrate was also found to be free of talc and other hydrated silicates and 

also measured 100% anorthite. 

3.4 Flowsheet Design

Based on the information gathered, the flowsheets shown in figures 16 and 17 would be used 

to process the road norite outcrop and mill tailings, respectively. The road norite material is dry 

comminuted and beneficiated with a RE Magnetic Belt Separator. Resulting nonmagnetic materials 

are then wet ground and processed by flotation to remove naturally hydrophobic, hydrated minerals such as talc. A second stage of flotation is conducted to remove any remaining talc but requires 

the use of a collector. Removing talc in two stages in this manner minimizes reagent consumption which helps minimize overall expenses. Likewise, concentrator material was first separated 

with a Wet Drum Separator to remove the strong magnetic fractions. The remaining material was 

processed with WHIMS and cleaned by flotation albeit CMC in the mill tailings had to first be 

destroyed. It is important to point out that figure 17 is incorporated into figure 16; consequently, 

they could be operated together.

Road Norite

Crush and Grind (Dry)

Rare Earth Magnetic

Belt Separator

Wet Grind 80%

Passing 45 μm

Wet Grind 80%

Passing 45 μm

Flotation

(No Collector)

Flotation

(Collector)

Nonmagnetic

Materials

Hydrated Silicates

Hydrated Silicates

Paramagnetic Materials Nonmagnetic Materials

Paramagnetic Materials

Pyroxene Concentrate

Plagioclase Concentrate

WHIMS

Figure 16. Potential flowsheet that was developed for processing road norite

outcrop material.
26

Electromagnetic Wet

Drum Separator

Stillwater Mill Slurry

80% Passing 45 μm

Paramagnetic/Nonmagnetic

Materials

Nonmagnetic Materials

(Plagioclase)

Magnetic Materials

Pyroxene Concentrate

Paramagnetic Materials

Hydrated Silicates

Plagioclase Concentrate

Flotation

WHIMS

Figure 17. Potential flowsheet that was developed for processing the wet mill 

tailings material produced at the Nye Concentrator. 
27

4. CONCLUSIONS

It has been previously established that a high purity plagioclase product could be obtained 

from the road norite.2 Work reported here shows the same. Work here shows this can also be 

achieved using mill tailings. More than 6 tons of high calcium plagioclase concentrate could, in 

principle, be obtained from every 10 tons of feedstock. The availability of such pure, high calcium 

plagioclase would be a significant asset in any attempt to manufactured high-quality lunar simulants. By demonstrating successful plagioclase recovery from mill tailings, the need to have Ph.D. 

senior geologists hand pick rocks from a limited outcrop is obviated. Further, the reserve of road 

norite is clearly limited unless heavy equipment is brought in. 

This study is an attempt at using mineral processing technologies to make simulant reserves 

from two Earth resources, namely the road norite outcrop and mill tailings from SMC’s Nye Concentrator in Montana. These resources contain three of the four silicate minerals that lunar soil 

contains in both high and pure amounts. Based on promising results obtained from a series of tests, 

flowsheets were developed showing how these resources could be processed and made into ‘separates’ of (1) high calcium plagioclase and (2) orthopyroxene/clinopyroxene with the thought that 

they would be combined later to make simulant. Although both of these Earth resources also contain olivine, it was not present in significant amounts to produce a separate. Therefore, a different 

resource will be needed to do that and will also be the subject of a future study.
28

REFERENCES

 1. Agricola, G.: De Re Metallica, the 1st Latin ed. of 1556, H.C. Hoover and L.H. Hoover (trans. 

and eds.), Dover, New York, 393 pp., 1950. 

 2. Rickman, D.L.; Stoeser, D.B.; Benzel, W.M.; et al.: “Notes on Lithology, Mineralogy, 

and Production for Lunar Simulants,” NASA/TM—2011–216454, Marshall Space Flight 

Center, AL, p. 64, January 2011. 

 3. McCallum, I.S.: “The Stillwater Complex: A Review of the Geology,” in Proc. Stillwater Complex, Geology and Guide, 9th International Platinum Symposium, Billings, MT, July 21–25, 

2002, pp. 1–25, 2002. 

 4. Hess, H.H.; and Smith, J.R.: Stillwater igneous complex, Montana: A quantitative mineralogical 

study, (The Geological Society of America. Memoir), Memoir No. 80, 230 pp., 1960. 

 5. McCallum, I.S.; Raedeke, L.D.; and Mathez, E.A.: “Investigations of the Stillwater Complex, 

Montana, Part I: Stratigraphy and Structure of the Banded Zone,” American Journal of Science, Vol. 280A, pp. 59–87, 1980.

 6. Raedeke, L.D.; and McCallum, I.S.: “A Comparison of Fractionation Trends in the Lunar 

Crust and the Stillwater Complex,” in Proc. Lunar Highlands Crust, J.J. Papike and R.B. 

Merrill (eds.), Houston, TX, November 14–16, 1979, Pergamon Press, New York and Oxford, 

pp. 133–153, 1980. 

 7. Salpas, P.A.; Haskin, L.A.; and McCallum, I.S.: “Stillwater anorthosites-A Lunar Analog?, 

Proc. 14th Lunar and Planetary Science Conference, Houston, TX, March 14–18, 1983, Journal 

of Geophysical Research (Supplement), Vol. 88, pp. B27–B39, 1983. 

 8. Boudreau, A.: “Fluid Fluxing of Cumulates: The JM Reef and Associated Rocks of the Stillwater Complex, Montana,” Journal of Petrology, Vol. 40, No. 5, p. 755, 1999. 

 9. Polovina, J.S.; Hudson, D.M.; and Jones, R.E.: “Petrographic and Geochemical Characteristics of Postmagmatic Hydrothermal Alteration and Mineralization in J-M Reef, Stillwater 

Complex, Montana,” The Canadian Mineralogist, Vol. 42, No. 2, pp. 261–277, doi:10.2113/

gscanmin.42.2.261, April 1, 2004.

10. Rickman, D.L.; and Lowers, H.A.: “Particle Shape and Composition of NU-LHT-2M,” 

NASA/TM—2012–217458, Marshall Space Flight Center, AL, p. 136, June 2012. 
29

11. Rickman, D.L.; Wilson, S.A.; Weinstein, M.A.; and Edmunson, J.E.: “Manufacture of Lunar 

Regolith Simulants,” NASA/TM—2013–217491, Marshall Space Flight Center, AL, p. 74, 

October 2013. 

12. Xu, W.; Geissman, J.W.; Van der Voo, R.; and Peacor, D.R.: “Electron Microscopy of Iron 

Oxides and Implications for the Origin of Magnetizations and Rock Magnetic Properties of 

Banded Series Rocks of the Stillwater Complex, Montana,” Journal of Geophysical Research, 

Vol. 102, No. B6, p. 12,139, doi:10.1029/97JB00303, 1997. 

13. Papike, J.J.; Taylor, L.A.; and Simon, S.B.: “Lunar Minerals,” in Lunar Sourcebook: A User’s 

Guide to the Moon, G. Heiken, D. Vaniman, and B.M. French (eds.), pp. 121–182, Cambridge 

University Press, 1991.
30

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Beneficiation of Stillwater Complex Rock for the Production

of Lunar Simulants

D.L. Rickman, C. Young,* D. Stoeser,** and J. Edmunson***

George C. Marshall Space Flight Center

Huntsville, AL 35812

National Aeronautics and Space Administration

Washington, DC 20546–0001

Unclassified-Unlimited

Subject Category 91

Availability: NASA STI Information Desk (757–864–9658)

Prepared by the Science & Research Office, Science & Technology Office

*Metallurgical and Materials Engineering, Montana, Tech, Butte, MT, **USGS, Denver, CO, 

***Jacobs ESSSA Group, Huntsville, AL

M–1378

Technical Memorandum

NASA/TM—2014–217502

beneficiation, regolith simulant, lunar, Stillwater, simulant manufacture

01–03–2014

UU 44

NASA

U U U

The availability of pure, high calcium plagioclase would be a significant asset in any attempt to manufacture highquality lunar simulants. A suitable plagioclase product can be obtained from materials obtained from the Stillwater 

Complex of Montana. The access, geology, petrology, and mineralogy of the relevant rocks and the mill tailings are 

described here. This study demonstrates successful plagioclase recovery from mill tailings produced by the Stillwater 

Mine Company. Hydrogen peroxide was used to remove carboxymethyl cellulose from the tailing. The characteristics 

of the plagioclase products are shown and locked grains are identified as a limit to achievable purity. Based on the 

experimental results, flowsheets were developed showing how these resources could be processed and made into 

‘separates’ of (1) high calcium plagioclase and (2) orthopyroxene/clinopyroxene with the thought that they would 

be combined later to make simulant. 

STI Help Desk at email: help@sti.nasa.gov

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