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DOCUMENTATION_FORMAT: MINERAL
SAMPLE_ID: HS419.1B, HS419.2B, HS419.3B, HS419.4B, HS419.6
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.
Grain size fractions are indicated by the extension after the sample number:
.1B = <5 µm
.2B = <74 µm
.3B = 74-250 µm
.4B = 250-1200 µm
.6 = cut slab
IMAGE_OF_SAMPLE:
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.
Samples HS419.3B and HS419.4B have carbonate contamination but samples HS419.1B and HS419.2B do not have detectable carbonate contamination. G. Swayze.
END_XRD_ANALYSIS.
COMPOSITIONAL_ANALYSIS_TYPE: None # XRF, EPMA, ICP(Trace), WChem
COMPOSITION_TRACE:
COMPOSITION_DISCUSSION:
Hunt and Salisbury originally 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: 1b2_3_4_ # HS419.1B # 1= 0.2-3, 2= 1.5-6, 3= 6-25, 4= 20-150 microns
SPECTRAL_PURITY: 1b2_3_4_ # HS419.2B # 1= 0.2-3, 2= 1.5-6, 3= 6-25, 4= 20-150 microns
SPECTRAL_PURITY: 1c2c3b4b # HS419.3B # 1= 0.2-3, 2= 1.5-6, 3= 6-25, 4= 20-150 microns
SPECTRAL_PURITY: 1c2_3_4_ # HS419.4B # 1= 0.2-3, 2= 1.5-6, 3= 6-25, 4= 20-150 microns
SPECTRAL_PURITY: 1c2_3_4_ # HS419.6 # 1= 0.2-3, 2= 1.5-6, 3= 6-25, 4= 20-150 microns