DOCUMENTATION_FORMAT: MINERAL

SAMPLE_ID: GDS83

MINERAL_TYPE: Sulfate

MINERAL: Alunite (Na63)(Alunite group)

FORMULA: (Na,K)Al3(SO4)2(OH)6 Na63

FORMULA_HTML: (Na,K)Al₃(SO₄)₂(OH)₆ (Na₆₃)

COLLECTION_LOCALITY: Komatsuga, Japan

ORIGINAL_DONOR: Roger Stoffregen, 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.

END_SAMPLE_DESCRIPTION.

XRD_ANALYSIS:

40 kV - 30 mA, 6.5-9.5 keV (n65alnt.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 angstroms / intensity): 2.81/100, 2.253/100, 2.002/2, 1.877/50, 1.575/10, 1.473/100. I 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.

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:

Standard used by Stoffregen et al.

Stoffregen, 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 gr sz = 35 µm

Uniaxial (+), low birefringence, length fast, basal cleavage, all consistent with alunite. Very little contamination. 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 215 0.2-3.0µm 200 g.s.= 35 µm

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

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