From Longman Dictionary of Contemporary Englishsoapstonesoap‧stone /ˈsəʊpstəʊn $ ˈsoʊpstoʊn/ noun [uncountable] DHCHEa soft stone that feels like soap
Examples from the Corpus
soapstone• They were focussed greeny-yellow eyes, like lumps of soapstone.• Once at sea level, smooth soapstone slabs had to be traversed for some distance to reach the cliff. 