Perhamite, a New Calcium Aluminum Silico-Phosphate Mineral, and a Re-Examination of Viséite

Pete J. Dunn and Daniel E. Appleman
Department of Mineral Sciences, Smithsonian Institution, Washington, D.C. 20560

Summary: A new calcium aluminum silico-phosphate mineral has been found at two locations on Newry Hill, Newry, Maine, U.S.A. Its composition closely approximates to 3CaO.3·5Al2O3.3SiO2.2P2O5.18H2O (Z = 1). Perhamite is uniaxial (+), c = 1577, ω = 1·564, density = 2·64 g/cm3. The mineral is hexagonal, probably P6/mmm, with a = 7·02 Å, c = 20·21 Å. The colour is light brown to white, the habit is as aggregates of discoidal hexagonal crystals. Cleavage is perfect {0001}, the lustre is vitreous, and the streak white. The mineral is named for a pegmatite miner and geologist, Frank C. Perham of West Paris, Maine, U.S.A.

The most similar species is viséite. A re-examination of viséite indicates that the composition previously given is incorrect. A new form of viséite, also from Visé, Liège, Belgium is also examined and found to differ in composition from the type material.

Mineralogical Magazine; December 1977 v. 41; no. 320; p. 437-442; DOI: 10.1180/minmag.1977.041.320.03
© 1977, The Mineralogical Society
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