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: Spessartine HS112 Garnet DESCRIPT

DOCUMENTATION_FORMAT: MINERAL

SAMPLE_ID: HS112.3B

MINERAL_TYPE: Nesosilicate

MINERAL: Spessartine (Garnet group)

FORMULA: Mn3Al2(SiO4)3

FORMULA_HTML: Mn₃Al₂(SiO₄)₃

COLLECTION_LOCALITY: Haddon, Connecticut

ORIGINAL_DONOR: Hunt and Salisbury Collection

CURRENT_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory

ULTIMATE_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory

SAMPLE_DESCRIPTION:

Forms series with Almandine.

"Spessartite 112B--Haddon, Conn. Mn₃Al₂(SiO₄)₃: Spessartite is less common than many garnets, occurring primarily in metamorphic rocks and granite pegmatites. The dominant features in the spectrum are the intense bands at 1.275 and 1.7 µ due to the presence of ferrous iron in eight-fold coordination, as discussed above. The visible spectrum falls off sharply to the blue producing a maximum near 0.8 µ. In the larger particle sizes this feature shows a shoulder near 0.9 µ, indicating the presence of Fe³⁺. While the visible spectrum displays the very sharp feature at 0.41 µ characteristic of Mn²⁺ absorption, the rest of its usually distinctive spectrum is degraded by the presence of absorptions by both Fe³⁺ and Fe²⁺. Together these 3 ions can account for the bands at 0.37, 0.43 µ, the broad general absorption centered near 0.55 µ, and the fall off to the blue."

Hunt, G.R., J.W. Salisbury, and C.J. Lenhoff, 1973, Visible and near-infrared spectra of minerals and rocks: VI. Additional silicates. Modern Geology, v. 4, p. 85-106.

IMAGE_OF_SAMPLE:

END_SAMPLE_DESCRIPTION.

XRD_ANALYSIS:

40 kV - 30 mA, 6.7-9.5 keV
File: spes112.mdi
References: Huebner's reference patterns
Found: Garnet, minor quartz

Comments: Garnet peaks are moderately sharp. Resolution of the alpha1-alpha2 components is not as good as might be expected from the sharpness, and slight shoulders extend toward larger d-spacings, suggesting that slight compositional zoning may be present. The cell dimension of the garnet is 11.65 Angstroms, consistent with a spessartine-rich garnet.

END_XRD_ANALYSIS.

COMPOSITIONAL_ANALYSIS_TYPE: None # XRF, EPMA, ICP(Trace), WChem

COMPOSITION_TRACE:

COMPOSITION_DISCUSSION:

END_COMPOSITION_DISCUSSION.

MICROSCOPIC_EXAMINATION:

END_MICROSCOPIC_EXAMINATION.

SPECTROSCOPIC_DISCUSSION:

END_SPECTROSCOPIC_DISCUSSION.

SPECTRAL_PURITY: 1b2c3c4_ # HS112.3B # 1= 0.2-3, 2= 1.5-6, 3= 6-25, 4= 20-150 microns