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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 WS478 Garnet DESCRIPT

DOCUMENTATION_FORMAT: MINERAL

SAMPLE_ID: WS478

MINERAL_TYPE: Nesosilicate

MINERAL: Almandine (Garnet group)

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

FORMULA_HTML: Fe+23Al2(SiO4)3

COLLECTION_LOCALITY: Wrangell, Alaska

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:alma478.out,*_mdi (smear mount on quartz plate)
References: Borg and Smith (1969), JCPDS #9-427, DHZ, v. 1a (1982), Huebner's reference patterns
Found: Garnet; weak reflection at 2.71 angstroms.

Comment: Very sharp reflections indicate good crystallinity and suggest compositional homogeneity. Garnet unit cell range is 11.47+/-3 angstroms indicating a pyrope-rich solid solution. The unidentified reflection is anomalously sharp (one grain?).

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

END_XRD_ANALYSIS.

COMPOSITIONAL_ANALYSIS_TYPE: EM # XRF, EM(WDS), ICP(Trace), WChem


COMPOSITION
KEYWORD
Oxide
ASCII
Amount Weight
Percent, %
Oxide
html
COMPOSITION: SiO2 39.09 wt% SiO2
COMPOSITION: TiO2 0.00 wt% TiO2
COMPOSITION: Al2O3 22.05 wt% Al2O3
COMPOSITION: Cr2O3 0.02 wt% Cr2O3
COMPOSITION: V2O3 0.01 wt% V2O3
COMPOSITION: FeO 33.10 wt% FeO
COMPOSITION: NiO 0.01 wt% NiO
COMPOSITION: MnO 1.73 wt% MnO
COMPOSITION: MgO 5.74 wt% MgO
COMPOSITION: CaO 0.57 wt% CaO
COMPOSITION: Total 101.32 wt%
COMPOSITION: O=Cl,F,S wt% #correction for Cl, F, S
COMPOSITION: New Total 101.32 wt%

COMPOSITION_TRACE: None

COMPOSITION_DISCUSSION:

None

END_COMPOSITION_DISCUSSION.

MICROSCOPIC_EXAMINATION:

avg. grain size = 125µm Range = 5-325µm

Smaller grains adhere to larger ones. Trace of limonite staining and individual limonite grains. Garnet has conchoidal fractured surfaces, and is mostly isotropic under cross-polarized light. G. Swayze

END_MICROSCOPIC_EXAMINATION.

SPECTROSCOPIC_DISCUSSION:

Fe-rich composition and spectrum are consistent with this sample being almandine and not pyrope.

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 183 0.2-3.0µm 200 g.s.= 125 µm
LIB_SPECTRA: splib05a r 246 0.2-3.0µm 200 g.s.=


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