The iron rich schorl is the most abundant tourmaline and is black and opaque. It is a common accessory mineral in igneous and metamorphic rocks and can form nice crystals. Although too opaque to be used as a gemstone, schorl is used as an ornamental stone when found as inclusions in quartz, a stone is called “tourmalinated quartz”. Usually when someone refers to tourmaline they are referring to either elbaite or schorl. 3/4″(med.) & 1″(lrg.) sizes