Pyroxmangite

Spectrum Details

Modality

NIR

Category

mineral

Material Type

Inosilicate

Sample ID

HS325.3B

Collection Locality

Colorado

Spectral Purity

1b2b3b4_ # HS325.3B # 1= 0.2-3, 2= 1.5-6, 3= 6-25, 4= 20-150 microns

Composition / XRD

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

Sample Description

This sample contains very small amounts of magnetite, pyrolusite and calcite. The visible spectrum is dominated by features typical of Mn^2+ 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:

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.

X Units

cm⁻¹

Y Units

Absorbance

Data Points

2,126