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: Pyroxmangite HS325 DESCRIPT

DOCUMENTATION_FORMAT: MINERAL

SAMPLE_ID: HS325.3B

MINERAL_TYPE: Inosilicate

MINERAL: Pyroxmangite

FORMULA: MnSiO3

FORMULA_HTML: MnSiO₃

COLLECTION_LOCALITY: Colorado

ORIGINAL_DONOR: Hunt and Salisbury Collection

CURRENT_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory

ULTIMATE_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory

SAMPLE_DESCRIPTION:

This sample contains very small amounts of magnetite, pyrolusite and calcite. The visible spectrum is dominated by features typical of Mn²⁺ transitions, displaying bands at 0.35 µ, 0.37 µ, 0.42 µ, and 0.55 µ, resulting in the characteristic pink color of this mineral. The strong broad band near 1.04 µ and 1.9 µ features are typical of molecular water, probably in fluid inclusions.

Hunt and others (1973) mis-identified this sample as rhodonite. XRD analysis indicates it is pyroxmangite, a polymorph of rhodonite.

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, 7.3-9.5 keV
File: rhod325.mdi
References: Huebner's reference patterns; PDF2 #29-0985
Found: Pyroxmangite

Comments: Peaks are symmetric but not strong; alpha1-alpha2 are not resolved. The pattern has a high background caused by X-ray fluorescence (Mn- or Fe-rich composition is probable). HS-325 is very similar to Huebner's reference patterns for synthetic pyroxmangite of MnSiO3 composition (runs Hy-67 and run-130) and unlike that of rhodonite (run49; see Heubner, 1986). Profile based search-match returns pyroxmangite (PDF2 #29-0985) There are weak, very sharp reflections at 7.2 and 1.912 Angstroms but no mineral in the PDF2 database has two strong reflections at these positions.

Additional XRD analysis is consistent with pyroxmangite and not rhodonite. B. Benzel.

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_ # HS325.3B # 1= 0.2-3, 2= 1.5-6, 3= 6-25, 4= 20-150 microns