An Investigation of Two New Minerals: Rhodesite and Mountainite

J. A. Gard, H. F. W. Taylor and R. A. Chalmers
Department of Chemistry, University of Aberdeen

Summary: Rhodesite, from Kimberley, S. Africa, has been examined by electron-microscope, X-ray, and other methods. The acicular crystals are orthorhombic, with a 23·8, b 6·54, c 7·05 Å.; elongation c, cleavage (100); unit-cell contents approximately (Ca,Na2,K2)8Si16O40.11H2O; optical properties α 1·502, β 1·505, γ 1·515; α = b, β = α, γ = c. With it occurs a similar but distinct fibrous mineral, which appears to be a new species for which the name mountainite is proposed; it is monoclinic, with a 13·51, b 13·10, c 13·51 Å., β 104° elongation b, cleavage (001); unit-cell contents approximately (Ca,Na2,K2)16Si32O80.24H2O; optical properties α 1·504, β 1·510, γ 1·519; β = b (elongation). Both rhodesite and mountainite show close similarities to the fibrous zeolites, mountainite in particular resembling thomsonite. The possible structural basis of these similarities is discussed.

Mineralogical Magazine; December 1957 v. 31; no. 239; p. 611-623; DOI: 10.1180/minmag.1957.31.239.02
© 1957, The Mineralogical Society
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