Sample Description USGS Spectral Library Version 7

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
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TITLE: Grossular WS485 Garnet DESCRIPT

DOCUMENTATION_FORMAT: MINERAL

SAMPLE_ID: WS485

MINERAL_TYPE: Nesosilicate

MINERAL: Grossular (Grossularite) (Garnet group)

FORMULA: Ca3Al2(SiO4)3

FORMULA_HTML: Ca₃Al₂(SiO₄)₃

COLLECTION_LOCALITY: Asbestos, Quebec, Canada

ORIGINAL_DONOR: Ward's Minerals

CURRENT_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory

ULTIMATE_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory

SAMPLE_DESCRIPTION:

Forms series with Andradite, with Hydrogrossular, with Uvarovite.

See additional spectra of grossular garnets in library for comparison. This sample has been washed in HCl acid to remove carbonate contaminants.

IMAGE_OF_SAMPLE:

END_SAMPLE_DESCRIPTION.

XRD_ANALYSIS:

40 kV - 30 mA, 6.5-9.5 keV
File: gros485.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: Extremely sharp, well-formed peaks indicate excellent crystallinity and suggest compositional homogeneity. ao=11.84, consistent with grossular-rich garnet.

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:

END_COMPOSITION_DISCUSSION.

MICROSCOPIC_EXAMINATION:

Bimodal grain size distribution:
mode1: 240 µm @ 50 vol%
mode2: 30 µm @ 50 vol%

avg. grain size = 171 µm

Sample looks clean with larger garnet grains 70% coated with finer grained garnet. Most grains are isotropic with parting surfaces. Trace contaminant could be feldspar because of low interference color and possible twinning. Optical properties are consistent with this sample being nearly pure garnet. G. Swayze.

END_MICROSCOPIC_EXAMINATION.

SPECTROSCOPIC_DISCUSSION:

END_SPECTROSCOPIC_DISCUSSION.

SPECTRAL_PURITY: 1b2b3b4_ # 1= 0.2-3, 2= 1.5-6, 3= 6-25, 4= 20-150 microns