Black Tourmaline has a Trigonal crystal system and is in the mineral class of ring silicate plus oxide. While it comes in many colors and in various combinations, the black variety is many times called ‘shorl’.
Tourmaline, which is formed magmatically, consists of varying mineral forming substances but always displays the same crystal structure within its seven basic varieties. The black variety can be very brittle if formed quickly. When embedded in rock they have a higher silicate content, and nicely formed crystals are found, but these can still be fractured apart with much less effort than the colored varieties.