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Tourmaline is a group of minerals that are known for their vibrant colors and hardness. It's a borosilicate mineral that forms in long, prismatic crystals with a triangular cross-section.

Physical properties

Hardness: 7–7.5 on the Mohs scale, making it hard enough to be used as a gemstone

Crystal structure: Trigonal, with a six-member ring cyclosilicate structure

Shape: Long, prismatic crystals with a triangular cross-section

Cleavage: Indistinct

Fracture: Conchoidal, sometimes forming spherical lumps

Specific gravity: 3.0–3.12, varying with color

Pleochroism: Strong, visible to the naked eye, and varies with color

Color

Tourmaline can be found in many colors, including black, blue, green, yellow, pink, red, orange, purple, and brown

Some tourmalines have a cat's-eye effect called chatoyancy

Some tourmalines are zoned with a combination of colors

Uses Tourmaline is often cut into gemstones and Tourmaline can be used for carving.

Examples of tourmaline

Elbaite: A variety of tourmaline that is often transparent and colorful

Schorl: An iron tourmaline that is black in color

Dravite: A magnesium tourmaline that is brown in color

Rubellite: A pink alkali tourmaline

Brazilian emerald: A green alkali tourmaline

Achroite: A colorless alkali tourmaline