MINERAL: K_Alunite (Alunite Group)
ORIGINAL_DONOR: Roger Stroffregen
CURRENT_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory
ULTIMATE_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory
Synthetically prepared pure K-endmember sample made at 150C. Sample is 100% mole fraction K.
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.
For sample (GDS97B) heated to 400C: 40 kV - 30 mA, 6.5-9.5 keV (kalunt.out) References: JCPDS #14-136, 23-767, 7-17 Found: alunite, KAI(SO4)21 trace K-alum, and four unidentified weak reflections Comment: The K-alum identification is based on 5 weak to very very weak reflections. The unidentified phase(s) has (d/l, as above) 4.60/20, 3.139/100, 3.095/80, 1.550/20. All reflections are sharp, indicating good crystallinity and compositional homogeneity.
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.
COMPOSITIONAL_ANALYSIS_TYPE: NONE #XRF, EPMA, ICP(Trace),WChem
Sample has relatively weak vibrational features between 1.4 - 1.5, 1.76, and 2.17, and 2.32 microns. Other pure K-endmember alunites prepared at higher temperatures have much stronger vibrational features.
SPECTRAL_PURITY: 1_2a3_4_ # 1= 0.2-3, 2= 1.5-6, 3= 6-25, 4= 20-150 microns