TITLE: Andradite WS487 Garnet DESCRIPT

DOCUMENTATION_FORMAT: MINERAL

SAMPLE_ID: WS487

MINERAL_TYPE: Nesosilicate

MINERAL: Andradite (Garnet group)

FORMULA: Ca3(Fe+3)2(SiO4)3

FORMULA_HTML: Ca3Fe+32(SiO4)3

COLLECTION_LOCALITY: Stanley Butte, Arizona

ORIGINAL_DONOR: Wards Scientific

CURRENT_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory

ULTIMATE_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory

SAMPLE_DESCRIPTION:

Forms series with Grossular and with Schorlomite.

Dry sieve to < 250 µm

Weak spectral features at 2.2 µm and 1.4 µm indicate presence of OH bearing mineral. Bands in the visible appear representative of andradite. Roger N. Clark

END_SAMPLE_DESCRIPTION.

XRD_ANALYSIS:

40 kV - 30 mA, 7.3-9.5 keV
File: andr487.out, *.mdi (smear mount on quartz plate)
References: Borg and Smith (1969), JCPDS #10-288, DHZ, v. 1a (1982), Huebner's reference patterns
Found: Garnet

Comment: Very sharp peaks indicate high degree of crystallinity and suggest compositional homogeneity. The garnet has ao=12.02 angstroms, consistent with andradite and uvarovite compositions; based on yellowish brown color,the garnet is andradite-rich.

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:

Optical examination gives the following mineral mode:

99.5 vol% andradite
0.5 vol% opaques

Mostly pure highly fractured andradite grains with opaques inclusions and single opaque grains. Uniform grain size distribution with an avg. grain size of 175µm. G. Swayze Grains mostly of tabular shape.

END_MICROSCOPIC_EXAMINATION.

SPECTROSCOPIC_DISCUSSION:

END_SPECTROSCOPIC_DISCUSSION.

SPECTRAL_PURITY: 1_2_3_4_

LIB_SPECTRA_HED: where Wave Range Av_Rs_Pwr Comment

LIB_SPECTRA: splib04a r 401 0.2-3.0µm 200 g.s.=175 µm

LIB_SPECTRA: splib05a r ____ 0.2-3.0µm 200 g.s.=

LIB_SPECTRA: splib06a r ____ 1.5-25µm 250 g.s.=