DOCUMENTATION_FORMAT: MINERAL

SAMPLE_ID: HS200

MINERAL_TYPE: Tectosilicate

MINERAL: Celsian (Feldspar group)

FORMULA: BaAl2Si2O8

FORMULA_HTML: BaAl₂Si₂O₈

COLLECTION_LOCALITY: Australia

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 Orthoclase. Dimorphous with Paracelsian.

"This barium feldspar contains garnet and tourmaline as impurity. Its spectrum displays a very well defined and intense 1.9µ water feature with accompanying 1.4µ, 2.2µ, and 2.36µ features which are surprisingly weak."

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.

Sieve interval 74 - 250µm.

The impurities cause the large 2.0 band, and the weak features at 1.4 µm and in the 2.2-2.4 µm region. Celsian has no diagnostic spectral features in this spectral region. Roger N. Clark

END_SAMPLE_DESCRIPTION.

XRD_ANALYSIS:

Quartz - major component
Feldspar - major component (max microcline is best match)
Trioctahedral mica - more than a trace (phlogopite?)
Minor amounts of other minerals possible

Konnert, Judith and Marta Flohr, 1992, unpublished data, USGS Reston, VA.

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:
98-99 vol% celsian feldspar
1-2 vol% tourmaline (pleochroic, conchoidal fracture)
tr other (garnet?, deep green)

Twins, two cleavages at 90 degrees, biaxial (-), low order interference color, 2-3 vol% fluid inclusions, some alteration (about 5 vol%). All consistent with celsian. Smaller (10-20 µm) grains coat larger grains up to 20-30% surface of larger grains. 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 873 0.2-3.0µm 200 g.s.= 253 µm

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

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