A Mineralogical Study of Scapolite

Abstract

<p> Eight new scapolite analyses are presented. Determinations of refractive index, specific gravity, and lattice parameters are examined in conjunction with data available in five recent analyses. Particular reference is made to the regular variation of per cent Cl₂, CO₂ and SO₃ as a function of mole per cent meionite and the relation of these components to scapolite stability. End member formulae describing the composition of scapolite are developed. </p> <p> These scapolite samples are used in conjunction with synthetic plagioclase standards to obtain forty three electron microprobe analyses of scapolite-plagioclase pairs and twenty seven separate analyses of scapolite. The former analyses indicate that scapolite from amphibolite and granulite facies is generally more calcium-rich than the coexisting plagioclase. </p> <p> A petrographic study indicates that scapolite associated with the above grade of metamorphism is indicative of a volatile rich environment typified by the amphibolite facies by the assemblage sphene-pyroxene-scapolite. </p>