Abstract

Veatchite is a hydrated strontium borate originally described by Switzer (1938). In the present study x-ray precession patterns have been correlated with crystal habit and indices of refraction to yield the following data: monoclinic, space group A2/aC2h6 (or less likely, Aa–C84), a = 20.81±0.04, b = 11.74±0.03, c = 6.637±0.02 Å, β = 92°02′±05′, V = 1620 Å3; dominant forms {100}, {111}, {h11} with h = 2, 3, 4; cleavage perfect parallel to (100) and (011); optical orientation Z = b, X = c, Y∧a = –2°. Previous chemical analyses considered together with the present crystallographic data show that the correct formula is SrO·3B2O3·2H2O, one of two possibilities proposed by Switzer and Brannock (1950). For eight [SrO·3B2O3·2H2O] per cell, the calculated density is 2.86 g.cm.–3; an observed density of 2.78±0.03 g.cm.–3 was obtained on the Berman balance for a 2.4 mg. sample of excellent single crystals. X-ray powder pattern data are given with calculated interplanar spacings for d≥2.300 Å.

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