Krasnoite, the fluorophosphate analogue of perhamite, from the Huber open pit, Czech Republic and the Silver Coin mine, Nevada, USA

Krasnoite is a new mineral (IMA2011-040) from the Huber open pit, Krasno ore district, Czech Republic and the Silver Coin mine, Nevada, USA. Krasnoite is the fluorophosphate analogue of perhamite. Krasnoite occurs as compact to finely crystalline aggregates, balls and rosette-like clusters up to 1 mm across. Individual crystals are platy, show a hexagonal outline and can reach 0.1 mm on edge at Krasno and 0.4 mm at Silver Coin. At both localities, krasnoite occurs very late in phosphaterich paragenetic sequences. Krasnoite crystals are partly transparent with a typically pearly lustre, but can also appear greasy (Krasno) or dull (Silver Coin). The streak is white and the hardness is 5 on the Mohs scale. Crystals are brittle, have an irregular fracture, one imperfect cleavage on {001} and are not fluorescent under SW and LW ultraviolet light. Penetration twinning ⊥ {001} is common. The density for both Krasno and Silver Coin material is 2.48(4) g cm −3 , measured by the sink–float method in an aqueous solution of sodium polytungstate. The calculated density is 2.476 g cm −3 (Krasno). Krasnoite crystals are uniaxial (+), with ω = 1.548(2) and ϵ = 1.549(2) (Krasno) and ω = 1.541(1) and ϵ = 1.543(1) (Silver Coin). The simplified formula of krasnoite is: Ca 3 Al 7.7 Si 3 P 4 O 23.5 (OH) 12.1 F 2 ·8H 2 O. Krasnoite is trigonal, space group P 3I m 1, with a = 6.9956(4), c = 20.200(2) A, V = 856.09(9) A 3 and Z = 3. Raman and infrared spectroscopy, coupled with magic-angle spinning nuclear magnetic resonance (MAS–NMR) spectrometry, confirmed the presence of PO 3 F, PO 4 , SiO 4 , H 2 O and OH in the crystal structure of krasnoite.