TITLE: Gypsum HS333 (Selenite) DESCRIPT

DOCUMENTATION_FORMAT: MINERAL

SAMPLE_ID: HS333

MINERAL_TYPE: Sulfosalt

MINERAL: Gypsum (Selenite)

FORMULA: CaSO4*2H20

FORMULA_HTML: CaSO4•2H20

COLLECTION_LOCALITY: Washington County, Utah

ORIGINAL_DONOR: Hunt and Salisbury Collection

CURRENT_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory

ULTIMATE_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory

SAMPLE_DESCRIPTION:

"This sample is colorless in hand specimen (colorless gypsum is called "selenite"), and is white when ground to fine particle size. It also appears to be quite pure, as its spectrum shows. As in the case of the previous sample, the near-infrared spectrum displays very prominent water bands beginning at 1µm and continuing out to 2.5µm."

Hunt, G.R., J.W. Salisbury, and C.J. Lenhoff, 1971, Visible and near-infrared spectra of minerals and rocks: IV. Sulphides and sulphates. Modern Geology, v. 3, p. 1-14.

END_SAMPLE_DESCRIPTION.

XRD_ANALYSIS:

Pure gypsum

Clark, R.N., King, T.V.V., Klejwa, M., Swayze, G.A., and Vergo, N., 1990, High spectral resolution reflectance spectroscopy of minerals: Journal of Geophysical Research, v. 95, no. 8B, p 12,653-12,680.

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:

Bimodal grain size distribution:
mode 1: 245 µm @ 98 vol%
mode 2: 30 µm @ 2 vol%

avg gr sz = 242 µm

Sample appears to be pure. Biaxial with good cleavages and low relief. Larger grains are 15% coated with smaller grains. All this is consistent wiht pure gypsum. G. Swayze.

END_MICROSCOPIC_EXAMINATION.

SPECTROSCOPIC_DISCUSSION:

END_SPECTROSCOPIC_DISCUSSION.

SPECTRAL_PURITY: 1_2_3_4_

LIB_SPECTRA_HED: where Wave Range Av_Rs_Pwr Comment

LIB_SPECTRA: splib04a r 1879 0.2-3.0µm 200 g.s.= 242 µm

LIB_SPECTRA: splib05a r ____ 0.2-3.0µm 200 g.s.=

LIB_SPECTRA: splib06a r ____ 1.5-25µm 250 g.s.=