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: Anhydrite GDS42 DESCRIPT

DOCUMENTATION_FORMAT: MINERAL

SAMPLE_ID: GDS42

MINERAL_TYPE: Sulfate

MINERAL: Anhydrite

FORMULA: CaSO4

FORMULA_HTML: CaSO4

COLLECTION_LOCALITY: New Mexico

ORIGINAL_DONOR: Gem Show purchase

CURRENT_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory

ULTIMATE_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory

SAMPLE_DESCRIPTION:

This sample was purchased at a Gem show. The sample is probably from New Mexico, but that is not 100% certain. The sample appears white with no contamination. The reflectance spectrum indicates virtually no contamination. There are very weak bands in the visible, possibly indicating some iron, but it is not apparent visually under a hand lens.

END_SAMPLE_DESCRIPTION.

XRD_ANALYSIS:

40 kV - 30 mA, 6.5-9.5 keV
Reference: JCPDS #6-226; Huebner's reference patterns
Found: Anhydrite
Sought but not found: gypsum

Comment: Extremely sharp reflections indicate good crystallinity. Excellent match up with the JCPDS card.

J.S. Huebner, J. Pickrell, and T. Schaefer, 1994, written communication.

END_XRD_ANALYSIS.

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

COMPOSITION_TRACE: None

COMPOSITION_DISCUSSION:

None

END_COMPOSITION_DISCUSSION.

MICROSCOPIC_EXAMINATION:

Bimodal grain size distribution:

population 1 170µm 82 vol%
population 2 10µm 18 vol%

avg. grain size of populations = 154µm

Prismatic grains, good cleavage, light blue color in hand specimen. Trace of opaques. High birefringence and biaxial (+). All these are consistent with andydrite. Twinning parallel to long dimension. Smaller grains adhere extensively to larger grains. G. Swayze

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 423 0.2-3.0µm 200 g.s.= 154 µm
LIB_SPECTRA: splib05a r 1049 0.2-3.0µm 200 g.s.=


USA.gov logo  Take Pride in America button