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Clark et. al. 2003 USGS Open File Report 03-395
Spectral Library splib05a Sample Description

(For further information on spectrsocopy, see: http://speclab.cr.usgs.gov)

TITLE: Almandine WS477 Garnet DESCRIPT

DOCUMENTATION_FORMAT: MINERAL

SAMPLE_ID: WS477

MINERAL_TYPE: Nesosilicate

MINERAL: Almandine (Garnet group)

FORMULA: (Fe+2)3Al2(SiO4)3

FORMULA_HTML: Fe+23Al2(SiO4)3

COLLECTION_LOCALITY: Roxbury, Connecticut

ORIGINAL_DONOR: Ward Science Collection

CURRENT_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory

ULTIMATE_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory

SAMPLE_DESCRIPTION:

Forms series with Pyrope and with Spessartine.

END_SAMPLE_DESCRIPTION.

XRD_ANALYSIS:

40 kV - 30 mA, 7.3-9.5 keV
File: alma477.out, alma477b.out, *_mdi
References: Borg and Smith (1969), JCPDS #9-427, DHZ, v. 1a(1982), Huebner's reference patterns
Found: Garnet; very weak un indexed reflection at 3.32 angstroms

Comment: The garnet reflections are very sharp, indicating excellent crystallinity and suggesting compositional heterogeneity. The garnet ao=11.51+/-3 angstroms, consistent with (but not proving) almandine-rich composition.

END_XRD_ANALYSIS.

COMPOSITIONAL_ANALYSIS_TYPE: None # XRF, EM(WDS), ICP(Trace), WChem

COMPOSITION_TRACE: None

COMPOSITION_DISCUSSION:

None.

END_COMPOSITION_DISCUSSION.

MICROSCOPIC_EXAMINATION:

Mineral mode:

85 vol% Almandine
15 vol% limonite stained almandine grains

avg. grain size = 50µm Range = 5 - 200µm

Trace amphibole? All other grains isotropic under cross-polarized light. Conchoidal fracture in almandine. Limonite staining and limonite grains embedded in almandine grains. G. Swayze

END_MICROSCOPIC_EXAMINATION.

SPECTROSCOPIC_DISCUSSION:

END_SPECTROSCOPIC_DISCUSSION.

SPECTRAL_PURITY: 1b2_3_4_ # 1= 0.2-3, 2= 1.5-6, 3= 6-25, 4= 20-150 microns

LIB_SPECTRA_HED: where Wave Range Av_Rs_Pwr Comment
LIB_SPECTRA: splib04a r 172 0.2-3.0µm 200 g.s.= 50 µm
LIB_SPECTRA: splib05a r 233 0.2-3.0µm 200 g.s.=


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