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: Grossular WS483 Garnet DESCRIPT

DOCUMENTATION_FORMAT: MINERAL

SAMPLE_ID: WS483

MINERAL_TYPE: Nesosilicate

MINERAL: Grossular (Grossularite) (Garnet group)

FORMULA: Ca3Al2(SiO4)3

FORMULA_HTML: Ca₃Al₂(SiO₄)₃

COLLECTION_LOCALITY: Laguna de Jaco, Chihuahua, Mexico

ORIGINAL_DONOR: Wards Natural Science Inc.

CURRENT_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory

ULTIMATE_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory

SAMPLE_DESCRIPTION:

Forms series with Andradite, with Hydrogrossular, with Uvarovite.

END_SAMPLE_DESCRIPTION.

XRD_ANALYSIS:

40 kV - 30 mA, 6.5-9.5 keV
File: gros483.out, *.mdi (smear mount on quartz plate)
References: Borg and Smith (1969), JCPDS #39-368, DHZ, v. 1a (1982), Huebner's reference patterns
Found: Garnet

Comment: Moderately sharp reflections; some peaks appear to be closely-spaced doublets. This garnet is probably well crystallized with some compositional heterogeneity. The ao=11.85 angstroms, consistent with grossular. Only one cell dimension could be resolved, but the shape of some peaks suggests limited solid-solution toward andradite (or uvarovite).

J.S. Huebner, J. Pickrell, T. Schaefer, written communication 1994

END_XRD_ANALYSIS.

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

COMPOSITION_TRACE: None

COMPOSITION_DISCUSSION:

None.

END_COMPOSITION_DISCUSSION.

MICROSCOPIC_EXAMINATION:

mode:
98 vol% garnet
2 vol% diopside?

Bimodal grains size distribution:
mode 1: 180 µm @ 70 vol%
mode 2: 10 µm @ 30 vol%

average grain size= 150 µm

About 2 vol% grains have high interference colors and cleavage (diopside?) but these are limited to the smaller grains size population. Other grains are isotropic, with conchoidal fractures, and have refractive index > glycerin. All this is consistent with a slightly contaminated garnet sample. 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 1857	0.2-3.0µm	200	g.s.= 150 µm
LIB_SPECTRA:	splib05a r 2955	0.2-3.0µm	200	g.s.=

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