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Clark et. al. 2003 USGS Open File Report 03-395
Spectral Library splib05a Sample Description

(For further information on spectrsocopy, see: http://speclab.cr.usgs.gov)

TITLE: Knebelite HS419 Olivine DESCRIPT

DOCUMENTATION_FORMAT: MINERAL

SAMPLE_ID: HS419

MINERAL_TYPE: Nesosilicate

MINERAL: Knebelite (manganoan fayalite) Olivine group

FORMULA: (Fe2+,Mg,Mn)2SiO4

FORMULA_HTML: (Fe2+,Mg,Mn)2SiO4

COLLECTION_LOCALITY: Japan

ORIGINAL_DONOR: Hunt and Salisbury Collection

CURRENT_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory

ULTIMATE_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory

SAMPLE_DESCRIPTION:

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.

END_SAMPLE_DESCRIPTION.

XRD_ANALYSIS:

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
Found: Knebelite
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.

END_XRD_ANALYSIS.

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

COMPOSITION_TRACE:

COMPOSITION_DISCUSSION:

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.

END_COMPOSITION_DISCUSSION.

MICROSCOPIC_EXAMINATION:

END_MICROSCOPIC_EXAMINATION.

SPECTROSCOPIC_DISCUSSION:

END_SPECTROSCOPIC_DISCUSSION.

SPECTRAL_PURITY: 1a2_3_4_ # 1= 0.2-3, 2= 1.5-6, 3= 6-25, 4= 20-150 microns

LIB_SPECTRA_HED: where Wave Range Av_Rs_Pwr Comment
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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