(For further information on spectrsocopy, see:
TITLE: Knebelite HS419 Olivine DESCRIPT
MINERAL: Knebelite (manganoan fayalite) Olivine group
ORIGINAL_DONOR: Hunt and Salisbury Collection
CURRENT_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory
ULTIMATE_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory
Forms series with Fayalite.
"N-5 Tephroite 419B--Japan: Ostensibly a manganese silicate, Mn2[SiO4], tephroite typically contains up to 10 percent iron. This sample is also contaminated with magnetite, which lowers its overall reflectivity. The manganese ion produces distinctive bands at 0.37, 0.415, 0.45, and 0.55 µ, which are subdued by the presence of the opaque magnetite, but are faintly discernible in the IV size range. The broad band near 1.0 µ, which continues out to near 1.7 µ, is due to the ferrous ion in substitution for Mn2+; (see rhodochrosite, Part II, p. 28, spectrum C-6 for typical manganese-iron, p. 28, spectrum C-6 for typical manganese-iron spectra). The combination of the manganese and iron absorptions results in a well-defined reflectivity maximum near 0.73 µ."
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.
40 kV - 30 mA, 7.3-9.5 keV
File: teph419.mdi (smear on quartz plate)
References: PDF2 #12-0220, 35-0748; Huebner's reference patterns
Sought but not found: alleghanyite, manganbabingdonite, nambulite, sonolite, pyroxmangite, rhodonite, santaclaraite, manganohumite, leucophenacite, hausmannite, marsturite, johannsenite
Comments: Weak pattern with moderately sharp peaks but poor resolution of alpha1-alpha2 components. Shoulders and broadening of peak tips suggest compositional zoning. Moderately high background is consistent with Mn X-ray fluorescence. Twenty five reflections were identified as tephroite; 19 were refined resulting in cell dimensions a=6.195(1), b=10.600(2), and c=4.868(1) angstroms. These dimensions are most consistent with ferroan or slightly mangesian tephroite. Subsequent profile-based search-match returned manganoan fayalite (12-0220). Additional reflections occur at 3.15, 3.12, 2.96, 2.92, 2.28, 2.12, and 1.613 angstroms. No single mineral (or simple combinations of minerals) explains these seven reflections.
COMPOSITIONAL_ANALYSIS_TYPE: None # XRF, EM(WDS), ICP(Trace), WChem
Hunt and Salisbury orignially thought this was a sample of tephroite but it has Fe and Mg in addition to Mn making it a knebelite.
SPECTRAL_PURITY: 1a2_3_4_ # 1= 0.2-3, 2= 1.5-6, 3= 6-25, 4= 20-150 microns
|LIB_SPECTRA:||splib04a r 4729||0.2-3.0µm||200||g.s.=|
|LIB_SPECTRA:||splib05a r 4052||0.2-3.0µm||200||g.s.=|
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