TITLE: Holmquistite HS291 Amphibole DESCRIPT
MINERAL: Holmquistite (Amphibole group)
ORIGINAL_DONOR: Hunt and Salisbury Collection
CURRENT_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory
ULTIMATE_SAMPLE_LOCATION: USGS Denver Spectroscopy Laboratory
Forms series with Ferroholmquistite and Magnesioholmquistite.
Dimorphous with Clinoholmquistite.
"I-20 Holmquistite 291B--Quebec, Li2(Mg,Fe2+)3(Al,
Fe3+)2(Si8O22)(OH,F)2): Holmquistite is a rare
amphibole, the main occurrences of which are located at or close to the
contact between lithium-rich pegmatites and country rocks. There are
broad general absorption bands in the spectrum of this sample centered
near 0.7 and 1.0µ due to Fe3+ and Fe2+. The weak OH feature
near 1.4µ is accompanied by a considerably stronger OH band at
2.35µ. As in the cases of the tremolite and riebecite above, the
additional strength and slight longward shift of the 2.35µ band is due to a small contribution from a carbonate contaminant. The low reflectivity and poorly defined bands are a result of the presence of opaque magnetite and pyrite as impurities."
Sieve interval 74 - 250µm.
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.
40 kV- 30 mA, 7.0-9.5 keV
File: holmq291.out, -.mdi
References: Huebner's reference patterns
Found: K-mica, orthoamphibole, minor chlorite and K-feldspar, trace quartz
Comment: Peaks are sharp; the constituent minerals appear well-crystallized and compositionally homogenous. The amphibole has lattice spacings consistent with the characteristic cell dimensions of holmquistite. Not all peaks were indexed; a fifth phase may be present.
COMPOSITIONAL_ANALYSIS_TYPE: None # XRF, EM(WDS), ICP(Trace), WChem
Sample is very contaminated with:
40 vol% Anthophyllite ? biaxial (-), parallel extinction
40 vol% Plagioclase (altered to sericite?)
17 vol% quartz (uniaxial +)
3 vol% Holmquistite (light blue color in plane light)
If Holmquistite is the light blue amphibole with parallel extinction and amphibole cleavage (biaxial -), then this mineral only forms 3 vol% of the contents of this bottle. I suggest sample be X-rayed to see if green amphibole is the Holmquistite or anthophyllite. If the green amphibole turns out to be Holmquistite, then it may be separated using heavy liquids or Franz separator. If blue mineral is Holmquistite then these separation procedures will probably not give enough Holmquistite to make the effort worthwhile.
LIB_SPECTRA_HED: where Wave Range Av_Rs_Pwr Comment
LIB_SPECTRA: splib04a r 2164 0.2-3.0µm 200 g.s.=
LIB_SPECTRA: splib05a r ____ 0.2-3.0µm 200 g.s.=
LIB_SPECTRA: splib06a r ____ 1.5-25µm 250 g.s.=