Referência: min-a41000-10
Tourmaline is a boro-silicate mineral with variable composition. It occurs in small quantities in acid igneous rock like granite, and is locally abundant or rock-forming. It also occur in small quantities in many metamorphic rocks; also in sedimentary placer depositos.
Schorl is an iron-rich black or blue variety.
Form: elongated prismatic crystals; also radiating, granular.
Transparente to opaque
- Chemical group: Boro-silicate
- Hardness: 7-7.5
- Specific gravity: 3-3.2