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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: Barite HS79 DESCRIPT

DOCUMENTATION_FORMAT: MINERAL

SAMPLE_ID: HS79

MINERAL_TYPE: Sulfate

MINERAL: Barite (Barite group)

FORMULA: BaSO4

FORMULA_HTML: BaSO4

COLLECTION_LOCALITY: Custer County, Colorado

ORIGINAL_DONOR: Hunt and Salisbury Collection

CURRENT_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory

ULTIMATE_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory

SAMPLE_DESCRIPTION:

Theoretical percentages of the oxides in the formula are BaO 65.7%, SO3 34.3%. Sr substitutes for Ba and a complete solid solution series extends to celestite, but most material is near one end or the other of the series. A small amount of Pb may also substitute for Ba.

Sieve interval 74-250µm.

END_SAMPLE_DESCRIPTION.

XRD_ANALYSIS:

40 Kv - 30 mA, 6.5-9.5 keV
File: barit79_mdi, *.out (smear mount on quartz plate)
References: JCPDS #24-1035
Found: Barite

Comment: Observed all listed reflections but the weak reflection at 2.735 angstroms. Lattice spacing's consistent with BaSO4 composition. Observed one un indexed very weak reflection at 4.22 angstroms. Moderately sharp reflections (the alpha1-alpha2 splitting is not distinct at 40-50 degrees 2 theta) indicate moderate crystallinity.

END_XRD_ANALYSIS.

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

COMPOSITION_TRACE: None

COMPOSITION_DISCUSSION:

No compositional analyses.

END_COMPOSITION_DISCUSSION.

MICROSCOPIC_EXAMINATION:

Optical examination gives the following mineral mode:

80 vol% barite
20 vol% pink Fe-stained barite

avg. grain size = 200µm

Rectangular grains some with bundles of limonite? imbedded. Others stained by limonite. Heavy sample, biaxial (+), low 2v, all consistent with barite. G. Swayze

END_MICROSCOPIC_EXAMINATION.

SPECTROSCOPIC_DISCUSSION:

END_SPECTROSCOPIC_DISCUSSION.

SPECTRAL_PURITY: 1b2_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 646 0.2-3.0µm 200 g.s.= 200 µm
LIB_SPECTRA: splib05a r 1297 0.2-3.0µm 200 g.s.=


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