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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: Rhodochrosite HS338 DESCRIPT

DOCUMENTATION_FORMAT: MINERAL

SAMPLE_ID: HS338.3B, HS338.6

MINERAL_TYPE: Carbonate

MINERAL: Rhodochrosite

FORMULA: MnCO3

FORMULA_HTML: MnCO3

COLLECTION_LOCALITY: Montana

ORIGINAL_DONOR: Hunt and Salisbury Collection

CURRENT_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory

ULTIMATE_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory

SAMPLE_DESCRIPTION:

Rhodochrosite, MnCO3, is a comparatively rare carbonate mineral, usually occurring in hydrothermal veins with ores of silver, lead and copper, and with other manganese minerals. Divalent iron and calcium substitute for manganese, and a complete solid solution series appears to extend to siderite and calcite.

Hunt, G.R., J.W. Salisbury, 1971, Visible and near-infrared spectra of minerals and rocks: II. Carbonates. Modern Geology, v. 2, p. 23-30.

Grain size fractions are indicated by the extension after the sample number:
.3B = 74-250 µm
.6 = cut slab

IMAGE_OF_SAMPLE:
Photo of sample

END_SAMPLE_DESCRIPTION.

XRD_ANALYSIS:

40 kV - 30 mA, 7.3-9.5 keV
File: rhdch338.out, -.mdi
References: Huebner's reference patterns
Found: Rhombohedral carbonate, minor quartz, unidentified reflections at 2.88 Angstroms (moderately strong), 2.61i Angstroms (moderately weak), and 1.406 Angstroms (weak)
Sought but not found: pyrolusite, manganite, Mn-silicates

Comment: The carbonate lattice spacing's are consistent with MnCO3-rich composition. Sharp, well-formed peaks suggest good degree of crystallization and compositional homogeneity. The carbonate lattice spacing's are consistent with MnCO3-rich composition, probably in solid solution with magnesite and/or siderite.

J.S.Huebner, J. Pickrell, T. Schaefer, written communication(USGS 1994)

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: 1b2b3b4_ # HS338.3B # 1= 0.2-3, 2= 1.5-6, 3= 6-25, 4= 20-150 microns
SPECTRAL_PURITY: 1b2_3_4_ # HS338.6 # 1= 0.2-3, 2= 1.5-6, 3= 6-25, 4= 20-150 microns