tourmalines

Also known as tourmaline supergroup, tourmaline

thumb|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.

AI-generated from the Wikipedia summary — may contain errors.

In the Vinony graph

Vinony's link graph records 652 inbound references to tourmalines, and connects out to lithium, silicate mineral and tantalite.

It is catalogued under topics including Aluminium minerals, Cyclosilicates and Gemstones.

Vinony links it to 63 Wikipedia language editions.

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
Mineral.dispersion: 0.017
Mineral.fluorescence: Pink stones; inert to very weak red to violet in long and short wave
Mineral.absorption: Strong narrow band at 498 nm, and almost complete absorption of red down to 640 nm in blue and green stones; red and pink stones show lines at 458 and 451 nm, as well as a broad band in the green spectrum
Mineral.streak: White
Mineral.gravity: 3.06+0.20–0.06
Mineral.density: 2.82–3.32
Mineral.diaphaneity: Translucent to opaque

via Wikipedia infobox

Wikidata facts

Image: TourmalineUSGOV.jpg

Show 3 more facts

Commons gallery: Tourmaline
Commons category: Tourmaline
IMA Mineral Symbol: Tur

Sources (3)

via Wikidata · CC0

~20 min read

Encyclopedic overview

24 sections

Contents

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.

Excerpted from Wikipedia’s “tourmalines” article, available under the CC BY-SA 4.0 licence.