Sample Description USGS Spectral Library Version 7

USGS Spectral Library Version 7 Sample Description

Kokaly, R.F., Clark, R.N., Swayze, G.A., Livo, K.E., Hoefen, T.M., Pearson, N.C., Wise, R.A., Benzel, W.M., Lowers, H.A., Driscoll, R.L., and Klein, A.J., 2017, USGS Spectral Library Version 7: U.S. Geological Survey Data Series 1035, 61 p., https://doi.org/10.3133/ds1035
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TITLE: Alunite GDS83 Na63 DESCRIPT

DOCUMENTATION_FORMAT: MINERAL

SAMPLE_ID: GDS83

MINERAL_TYPE: Sulfate

MINERAL: Alunite (Alunite group)

FORMULA: (Na,K)Al3(SO4)2(OH)6

FORMULA_HTML: (Na,K)Al₃(SO₄)₂(OH)₆

COLLECTION_LOCALITY: Komatsuga, Japan

ORIGINAL_DONOR: Roger Stroffregen, SMU

CURRENT_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory

ULTIMATE_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory

SAMPLE_DESCRIPTION:

this alunite sample is from a high temperature, coarse vein deposit. Sample composition is 63 mole % Na from atomic absorption analysis Stroffregen, R.E., and C.N. Alpers, Observations on the unit-cell dimensions, H2O contents, and delD values of natural and synthetic alunite, American Mineralogist, 77, 1092-1098, 1992.

IMAGE_OF_SAMPLE:

END_SAMPLE_DESCRIPTION.

XRD_ANALYSIS:

GDS83 Na-(65) alunite 40 kV - 30 mA, 6.5-9.5 keV (n65aint.out) References: JCPDS #41-1467; Parker (1962) Found: alunite and a major unidentified phase Comment: The alunite closely matches natroalunite; its sharp reflections indicate good crystallinity and compositional homogeneity. The additional phase(s) has some strong lines (d in A / intensity): 2.81/100, 2.253/100, 2.002/2, 1.877/50, 1.575110, 1.4731100. 1 have been unable to identify this phase. Where not obscured by the alunite, peaks of this unidentified phase "tail off' toward larger d, suggesting compositional zoning.

see: Stroffregen, R.E., and C.N. Alpers, Observations on the unit-cell dimensions, H2O contents, and delD values of natural and synthetic alunite, American Mineralogist, 77, 1092-1098, 1992.

END_XRD_ANALYSIS.

COMPOSITIONAL_ANALYSIS_TYPE: NONE

COMPOSITION_TRACE: None

COMPOSITION_DISCUSSION:

Standard used by Stroffregen and others Stroffregen, R., and Alpers, C., 1992, Observations on the unit-cell dimensions, H2O contents and del D values of natural and synthetic alunite: American Mineralogist, v.77, p. 1092-1098.

END_COMPOSITION_DISCUSSION.

MICROSCOPIC_EXAMINATION:

avg. grain size = 35 microns, Uniaxial (+), low birefrigence, length fast, basal cleavage, all consistent with alunite. Very little contamination. G. Swayze.

END_MICROSCOPIC_EXAMINATION.

SPECTROSCOPIC_DISCUSSION:

Sample has relatively strong vibrational features between 1.4 - 1.5, 1.76, and 2.0 - 2.24, 2.33, and a complex centered at 2.5 microns.

END_SPECTROSCOPIC_DISCUSSION.

SPECTRAL_PURITY: 1b2b3b4_ # 1= 0.2-3, 2= 1.5-6, 3= 6-25, 4= 20-150 microns