(Science: chemical) A mineral occurring usually in three-sided or six-sided prisms terminated by rhombohedral or scalenohedral planes. Black tourmaline (schorl) is the most common variety, but there are also other varieties, as the blue (indicolite), red (rubellite), also green, brown, and white. The red and green varieties when transparent are valued as jewels.
Alternative forms: turmaline.
Origin: F. Tourmaline, cf. It. Turmalina, tormalina, NL. Turmalina, turmalinus; all fr. Tournamal, a name given to this stone in Ceylon.