Abstract

Yedlinite is a new hydrated oxychloride of lead and chromium found associated with diaboleite, quartz, wulfenite, dioptase, phosgenite, and wherryite on specimens from the Mammoth Mine, Tiger, Arizona. Yedlinite occurs as prismatic crystals up to one millimeter long which are red-violet, transparent to translucent and somewhat sectile, with white streak, Mohs' hardness of about 2 1/2, and observed density of 5.85 g/cc. Crystals show rhombohedral symmetry with forms {1120}, {1101}, {0001}, {1010} and {2021} in order of decreasing prominence. Crystals are occasionally doubly terminated and exhibit distinct {1120} cleavage. The morphological axial ratio is c/a – 0.763(2). Yedlinite is optically uniaxial negative and dichroic with ω – 2.125 (pale cobalt blue) and ɛ = 2.059 (lavender): X-ray diffraction shows space group R3 or R3 (R3 is indicated by morphology and confirmed by structure determination), a – 12.868(2) Å, c = 9.821(2) (hexagonal axes), c/a – 0.7632(3). The most intense powder diffraction lines in order d (I) (hexagonal hkil) are: 2.952 100 3141, 2.622 68 3142 and 1342, 4.506 65 0112, 6.44 32 1120 and 2.47327 3251 and 0333. Electron probe analysis combined with structural information yields the chemical formula Pb6Cl6Cr6X6Y2 with X = O or (OH) and Y = H2O or (O,OH). The hexagonal unit cell content, Z=3, and the calculated density is 5.80 g/cc. The name honors Mr. Neal Yedlin.

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