A proposal for the definition, nomenclature, and classification of soapstones

Currently, the term soapstone often refers to both talc-bearing ultramafic metamorphic rocks and other rocks having a wide range of variation in mineral composition. As a result, the name provides little information on the major mineral constituents in the rock. This proposal for the classification and nomenclature of soapstones is based on the absolute and relative modal mineral compositions. It does not consider textural attributes. According to the International Union of Geological Sciences, Subcommission on the Systematic of Metamorphic Rocks (IUGS-SCMR), rock names should be understood uniquely and without ambiguity. Therefore, we recommend: (1) soapstone has to contain 35-75% talc, (2) soapstone cannot contain more than 35% hard silicates. Further division is made based on the ratios of oxide, chlorite, and carbonate. Finally, the name of the additional hard silicate is considered as a prefix, if its content exceeds 5%.