Mineral group · Tourmaline group
Tourmaline
XY3Z6(T6O18)(BO3)3V3W (group)
Tourmaline is a group of boron cyclosilicates whose members elbaite (gem colours), schorl (black) and dravite (brown) are the ones collectors meet; the rounded-triangular cross-section and striated prisms identify all of them. Pegmatites in Brazil, Afghanistan, California (Himalaya and Stewart mines), Maine and Madagascar supply crystals. 'Tourmaline' on a label should be qualified with the species where known.
| Formula | XY3Z6(T6O18)(BO3)3V3W (group) |
|---|---|
| IMA status | group |
| Crystal system | Trigonal |
| Mohs hardness | 7–7.5 |
| Group | Tourmaline group |
| Type locality | None |
| Streak | White |
| Specific gravity | 3.0–3.2 |
Elsewhere
Cite this article
Stratum Strata. "Tourmaline" (Mineral). Stratum Strata pack 2026.09, as of 2026-09-21. https://stratum.black/strata/minerals/tourmaline. Accessed 2026-09-21.
@misc{stratum-tourmaline,
title = {Tourmaline},
author = {{Stratum Strata}},
howpublished = {\url{https://stratum.black/strata/minerals/tourmaline}},
year = {2026},
note = {Mineral article, Stratum Strata pack 2026.09, as of 2026-09-21; sources: stratum, wikidata, commons. Accessed 2026-09-21.}
} Citations carry the pack version and the article's as-of date so they resolve to the same text later. The facts themselves belong to the sources listed below; cite those for the science.