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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
For more information on the library, see: local link web link

TITLE: Lepidolite HS167 DESCRIPT


SAMPLE_ID: HS167.1B, HS167.2B, HS167.3B, HS167.4B, HS167.6

MINERAL_TYPE: Phyllosilicate

MINERAL: Lepidolite (Mica group)

FORMULA: K(Li,Al)3(Si,Al)4O10(F,OH)2

FORMULA_HTML: K(Li,Al)3(Si,Al)4O10(F,OH)2


ORIGINAL_DONOR: Hunt and Salisbury Collection

CURRENT_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory

ULTIMATE_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory


Original Spectrum published in: 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.

With the note:"In addition to the substitutions given in the general formula for lepidolite, considerable amounts of sodium, rubidium and cesium may substitute for potassium; and iron, manganese and magnesium may substitute for aluminum. It is the substituted ferric iron and manganese that give rise to the bands at 0.8µ, 0.55 µ, and 0.45µ, together with the drop off to the extreme blue. The band near 1.4µ is due to the overtone of the OH stretching fundamental, and the very weak band at 1.9µ indicates that a small amount of included water is present. The bands near 2.2µ, 2.35µ, and 2.45µ are also due to combination bands involving the OH stretch and possibly the Al-O-H bending mode (at 2.2µ) as discussed above, and the very weak bands at 1.28µ, 1.33µ, 2.03µ and 2.14µ are OH combined with lattice modes."

Grain size fractions are indicated by the extension after the sample number:
.1B = <5 µm
.2B = <74 µm
.3B = 74-250 µm
.4B = 250-1200 µm
.6 = cut slab

Photo of sample



40 kV - 30 mA, 6.5-9.5 keV
File: lpd1673B.mdi (thick smear on quartz plate)
References: Huebner's reference patterns; JCPDS patterns for micas; Deer, Howie, and Zussman (1962); Bailey (1984a,b); PDF2 #33-1161, 42-1399, 41-1480, 15-0062, 09-0466
Found: Quartz, a lepidolite-group mica, minor albite

Comment: The pattern is dominated by strong, sharp quartz reflections. Mica reflections are sharp but not sufficiently intense to show clear separation of alpha1-alpha2 components, even at high 2 theta. The mica phase was compared to Huebner's reference patterns and the JCPDS mica indexes. Both 2M1 and 2M2 lepidolites and muscovites yield good matches. Search-match based on eight strong lines returns quartz, zinnwaldite, and calcian albite; little of the intensity of a reflection at 4.96 Angstroms was explained by zinnwaldite (002). Profile based search-match returned quartz, ordered albite, zinnwaldite, lepidolite-12O as likely hits. The reflection at 4.96 Angstroms is explained by lepidolite superlattice reflection (00.12); zinnwaldite contributes little to the interpretation of the pattern. Examination of the original sample shows a distinctive lavender-violet color implying that a member of the lepidolite mica group is present.










SPECTRAL_PURITY: 1b2_3_4_ # HS167.1B # 1= 0.2-3, 2= 1.5-6, 3= 6-25, 4= 20-150 microns
SPECTRAL_PURITY: 1b2_3_4_ # HS167.2B # 1= 0.2-3, 2= 1.5-6, 3= 6-25, 4= 20-150 microns
SPECTRAL_PURITY: 1b2c3c4c # HS167.3B # 1= 0.2-3, 2= 1.5-6, 3= 6-25, 4= 20-150 microns
SPECTRAL_PURITY: 1b2_3_4_ # HS167.4B # 1= 0.2-3, 2= 1.5-6, 3= 6-25, 4= 20-150 microns
SPECTRAL_PURITY: 1b2_3_4_ # HS167.6 # 1= 0.2-3, 2= 1.5-6, 3= 6-25, 4= 20-150 microns