Tourmaline
What is Tourmaline?
Tourmaline is a crystalline boron silicate mineral that comes in a variety of colors. It’s primarily found in Brazil, Sri Lanka, and parts of Africa. Tourmaline is often used as a gemstone and is a popular choice for jewelry due to its wide range of colors and spiritual significance.
Tourmaline is a colorful gemstone that comes in a variety of hues, including black, blue, green, pink, and multicolored. Its wide range of colors and lustrous appearance make it a popular choice for jewelry and decorative items. The stone is often used in rings, necklaces, and pendants, and is sometimes used to make beads.
| Chemical Classification | Inorganic - Silicate (Cyclosilicate) |
| Color | Comes in a wide range of colors, including black, brown, green, pink, blue, yellow, and even watermelon (green on the outside, pink on the inside). |
| Streak | White |
| Luster | Vitreous. |
| Transparency | Varies from transparent to opaque. |
| Occurrence | Brazil, Madagascar, Afghanistan. |
| Formation | Tourmaline is formed in pegmatites and metamorphic rocks, and sometimes in granites and volcanic rocks. |
| Diaphaneity | Transparent to translucent |
| Cleavage | Poor in two directions |
| Mohs Hardness | 7 to 7.5. |
| Specific Gravity | Approximately 3.06 to 3.10. |
| Diagnostic Properties | Prismatic crystals, often with striations, various colors. |
| Chemical Composition | (Ca,K,Na,[])(Al,Fe,Li,Mg,Mn)3(Al,Cr, Fe,V)6 (BO3)3(Si,Al,B)6O18(OH,F)4 |
| Pleochroism | Strong; different colors are visible from different angles. |
| Crystal System | Trigonal |
| Optical Properties | Uniaxial (-) |
| Refractive Index | 1.616 - 1.650 |
| Birefringence | 0.017 - 0.040 |
| 2V angle | Measured: 44° |
| Dispersion | 0.017. |