Schorl mineral. Schorl is an alternative name for the black opaque variety of tourmaline, a complex aluminium-boron silicate mineral occurring in igneous and metamorphic rocks worldwide. Schorl is the most widespread variety in the tourmaline group. This sample shows a fragment of quartz interspersed within the glossy black tourmaline prisms. Actual width of sample is 120 millimetres. Sample from Minas Gerais, Brazil.