DOCUMENTATION_FORMAT: MINERAL

SAMPLE_ID: HS338

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.

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: Sharp, strong pattern of orthopyroxene. Talc based on four basal compositional homogeneity. The carbonate lattice spacings are consistent with MnCO3-rich composition, probably in solid solution with hS136.3B Sphalerite magnesite and/or siderite.

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

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

END_XRD_ANALYSIS.

COMPOSITIONAL_ANALYSIS_TYPE: None # XRF, EM(WDS), ICP(Trace), WChem

COMPOSITION_TRACE:

COMPOSITION_DISCUSSION:

END_COMPOSITION_DISCUSSION.

MICROSCOPIC_EXAMINATION:

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 4176 0.2-3.0µm 200 g.s.=

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

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