Synonyms:
tourmaline
Meaning: a mineral that is a complex borosilicate and hydroxide of aluminum containing iron and magnesium and calcium and lithium and sodium; it is usually black but occurs in transparent colored forms that are used as gemstones
Usage examples
Most of the broad summit is comparatively level and thick sown with crystals, quartz, mica, hornblende, feldspar, granite, zircon, tourmaline, etc., weathered out and strewn closely and loosely as if they had been sown broadcast.