U.S. Geological Survey home page


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: Hedenbergite HS10 DESCRIPT

DOCUMENTATION_FORMAT: MINERAL

SAMPLE_ID: HS10

MINERAL_TYPE: Inosilicate

MINERAL: Hedenbergite (Pyroxene group)

FORMULA: CaFe+2Si2O6

FORMULA_HTML: CaFe+2Si2O6

COLLECTION_LOCALITY: Silver Star, Montana

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 Diopside and with Johannsenite.

"S-17C. Pyroxene, variety Hedenbergite. Silver Star, Montana (10B). This sample has such strong ferric and ferrous ion bands on either side of 1µ that the reflectivity of the sample is reduced throughout the first half of the near-infrared range. Very weak water bands near 1.9 and 2.3 µ indicate the presence of some fluid inclusions. By contrast, a sample of artificially prepared hedenbergite displays a single strong ferrous ion band near 1.1 µ."

Sieve interval 74 - 250µm.

Hunt, G.R., J.W. Salisbury, 1970, Visible and near-infrared spectra of minerals and rocks: I. Silicate minerals. Modern Geology, v. 1, p. 283-300.

END_SAMPLE_DESCRIPTION.

XRD_ANALYSIS:

40 kV - 30 mA, 7.3-9.5 keV
File: hedbg10.mdi, *.out (smear mount on quartz plate)
References: JSPDS#41-1372; Huebner's reference patterns
Found: Clinopyroxene consistent with hedenbergite, minor quartz, unindexed weak to very weak reflections at 8.6, 3.16, 3.11 angstroms

Comment: Clinopyroxene pattern that is distinct from that of diopside (such as HS-15.3B). Pyroxene reflections are not sharp, suggesting poor crystallinity or compositional heterogeneity. Quartz identification originally based on four weak reflections, subsequently confirmed by optics (n=1.545). Optically, many grains are discolored by brown, heterogeneously distributed material; the actual pyroxene grains are colorless by comparison. Does the optical spectrum see the pyroxene?

END_XRD_ANALYSIS.

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

COMPOSITION_TRACE:

None

COMPOSITION_DISCUSSION:

None

END_COMPOSITION_DISCUSSION.

MICROSCOPIC_EXAMINATION:

mode:
45 vol% red stained pyroxene
42 vol% clinopyroxene
10 vol% Mica
3 vol% Calcite

Green gains are pleochroic green with prismatic cleavage ( slight < 90 degrees) and slightly inclined extinction. Biaxial (+), moderate 2V, all consistent with clinopyroxene. Sample has a considerable number of grains which fizz in HCl indicating significant carbonate contamination of sample. I suggest a cleaner sample be obtained. G. Swayze.

END_MICROSCOPIC_EXAMINATION.

SPECTROSCOPIC_DISCUSSION:

END_SPECTROSCOPIC_DISCUSSION.

SPECTRAL_PURITY: 1c2_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 2006 0.2-3.0µm 200 g.s.=
LIB_SPECTRA: splib05a r 3137 0.2-3.0µm 200 g.s.=


USA.gov logo  Take Pride in America button