tourmalines
Sign in to savethumb|upright=1.3|Main tourmaline producing countries
AI overview
I cannot write the overview you requested because the provided context only contains a caption about tourmaline-producing countries without any substantive information about what tourmalines are or why they matter. To accurately answer your question, I would need context that includes actual details about the mineral itself.
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Key facts
- Mineral.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.
- Mineral.habit
- Parallel and elongated; acicular prisms, sometimes radiating; massive; scattered grains (in granite)
- Mineral.cleavage
- Indistinct
- Mineral.fracture
- Uneven, small conchoidal
- Mineral.tenacity
- Brittle
- Mineral.mohs
- 7.0–7.5
- Mineral.luster
- Vitreous, sometimes resinous
- Mineral.polish
- Vitreous
- Mineral.refractive
- n = 1.635–1.675n = 1.610–1.650
- Mineral.opticalprop
- Double-refractive, uniaxial negative
- Mineral.birefringence
- −0.018 to −0.040; typically about −0.020 but in dark stones it may reach −0.040
Article
24 sectionsContents
- History
- Species and varieties
- Schorl
- Dravite
- Elbaite
- Chemical composition
- Physical properties
- Crystal structure
- Color
- Magnetism
- Treatments
- Geology
- Localities
- United States
- Maine
- California
- Brazil
- Africa
- See also
- References
- Citations
- General and cited sources
- Further reading
- External links
thumb|upright=1.3|Main tourmaline producing countries
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.