Properties
| Category | Cyclosilicate |
|---|---|
| Formula | (Ca,K,Na, ▢)(Al,Fe,Li,Mg,Mn)3(Al,Cr,Fe,V)6; (BO3)3(Si,Al,B)6O18(OH,F)4 |
| Crystal system | Trigonal |
| Color | Most commonly black, but can range from colorless to brown, red, orange, yellow, green, blue, violet, pink, or hues in-between. It can also be bi-colored, or even tri-colored. Rarely, it can be found as neon green or electric blue. |
| Crystal habit | Parallel and elongated; acicular prisms, sometimes radiating; massive; scattered grains (in granite) |
| Cleavage | Indistinct |
| Fracture | Uneven, small conchoidal |
| Tenacity | Brittle |
| Mohs scale hardness | 7.0–7.5 |
| Luster | Vitreous, sometimes resinous |
| Streak | White |
| Diaphaneity | Translucent to opaque |
| Specific gravity | 3.06+0.20–0.06 |
| Density | 2.82–3.32 |
From the Wikipedia article
Tourmaline is a crystalline silicate mineral group in which boron is compounded with elements such as aluminium, iron, magnesium, sodium, lithium, or potassium. This gemstone comes in a wide variety of colors.
Source
Source record: crystal-compendium/tourmaline/minerals.json. Fetched from English Wikipedia by the operator 2 October 2026.
https://en.wikipedia.org/wiki/Tourmaline — revision id 1371637733. Text and properties from Wikipedia, licensed CC BY-SA 4.0.