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USGS Spectral Library Version 7 Sample Description

Kokaly, R.F., Clark, R.N., Swayze, G.A., Livo, K.E., Hoefen, T.M., Pearson, N.C., Wise, R.A., Benzel, W.M., Lowers, H.A., Driscoll, R.L., and Klein, A.J., 2017, USGS Spectral Library Version 7: U.S. Geological Survey Data Series 1035, 61 p., https://doi.org/10.3133/ds1035
For more information on the library, see: local link web link

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.

IMAGE_OF_SAMPLE:
Photo of sample

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, EPMA, 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: 1b2c3c4_ # 1= 0.2-3, 2= 1.5-6, 3= 6-25, 4= 20-150 microns