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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: Uvarovite NMNH106661 Garnet DESCRIPT

DOCUMENTATION_FORMAT: MINERAL

SAMPLE_ID: NMNH106661

MINERAL_TYPE: Nesosilicate

MINERAL: Uvarovite (Garnet group)

FORMULA: Ca3Cr(+3)2(SiO4)3

FORMULA_HTML: Ca3Cr+32(SiO4)3

COLLECTION_LOCALITY: Unknown

ORIGINAL_DONOR: National Museum of Natural History

CURRENT_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory

ULTIMATE_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory

SAMPLE_DESCRIPTION:

Forms series with Grossular.

The garnet group includes a series of isostructural subspecies with space group Ia3d; the crystallize in the hexoctahedral class of the isometric system and are similar in crystal habit. Garnet compositions can be expressed by the general structural formula A3B2(SiO4) where the A site houses Ca, Mg, Fe+2 or Mn+2 and the B site incorporates Al, Fe+3, and Cr+3.

IMAGE_OF_SAMPLE:
Photo of sample

END_SAMPLE_DESCRIPTION.

XRD_ANALYSIS:

40 kV - 30 mA, 6.5-9.5 keV
File: uvarv106.out, *.mdi (smear mount on quartz plate)
References: JCPDS #11-696, Huebner's reference patterns
Found: garnet, talc, minor additional phase

Comment: Talc based on three strong basal reflections. There were three unindexed reflections at 2.940, 2.510, and 1.495 Angstroms. The garnet has a=11.90 Angstroms, between that of uvarovite (12.00 Angstroms) or andradite (Angstroms) and grossular (11.85 Angstroms) or other garnet components with smaller cell dimensions. Based on the intense green color, this garnet contains significant uvarovite component, but the identity and proportions of other components is not known.

END_XRD_ANALYSIS.

COMPOSITIONAL_ANALYSIS_TYPE: EPMA # XRF, EPMA, ICP(Trace), WChem

COMPOSITION
KEYWORD		 Oxide
ASCII		 Amount Weight
Percent, %		 Oxide
html
COMPOSITION: SiO2 35.9700 wt% SiO2
COMPOSITION: TiO2 0.0744 wt% TiO2
COMPOSITION: Al2O3 5.7720 wt% Al2O3
COMPOSITION: Cr2O3 19.9300 wt% Cr2O3
COMPOSITION: V2O3 0.2657 wt% V2O3
COMPOSITION: FeO 1.0750 wt% FeO
COMPOSITION: NiO 0.0099 wt% NiO
COMPOSITION: MnO 0.7153 wt% MnO
COMPOSITION: MgO 0.4420 wt% MgO
COMPOSITION: CaO 32.5200 wt% CaO
COMPOSITION: Total 96.7743 wt%

COMPOSITION_TRACE:

COMPOSITION_DISCUSSION:

Microprobe by G. Swayze, average of several points

END_COMPOSITION_DISCUSSION.

MICROSCOPIC_EXAMINATION:

END_MICROSCOPIC_EXAMINATION.

SPECTROSCOPIC_DISCUSSION:

Strong sharp OH absorption near 2.73 microns may be from a hydroxyl component in the garnet -- it does not match the wavelength position of talc. However, weak absorptions at 1.4 and 2.3 microns do match the wavelength position of talc. G.Swayze.

END_SPECTROSCOPIC_DISCUSSION.

SPECTRAL_PURITY: 1c2c3c4_ # NMNH106661 # 1= 0.2-3, 2= 1.5-6, 3= 6-25, 4= 20-150 microns