53.9 carats tourmaline crystals Origin. Afghanistan Quality. Good Suitable for facetation and cabochons Rare items Avg size 1.2 carat • Chemical Formula: Complex boron silicate with aluminum, iron, magnesium, lithium, and other elements. • Crystal System: Trigonal. • Hardness: 7–7.5 on the Mohs scale, making it suitable for everyday jewelry. • Color: Found in almost every color, including green, pink, red, blue, yellow, black, and bi-color or multi-color varieties. • Luster: Vitreous (glassy). • Transparency: Transparent to opaque, with transparent stones being the most valuable. • Refractive Index: Approximately 1.61–1.67, depending on the variety. • Specific Gravity: 3.00–3.26. • Cleavage: Indistinct or absent, making it less prone to splitting. • Fracture: Uneven to conchoidal. • Pleochroism: Strong, often showing different colors when viewed from different angles. • Inclusions: May contain liquid inclusions, hollow tubes, growth lines, and mineral crystals. • Durability: Good toughness and resistance to wear, suitable for rings, pendants, earrings, and bracelets. • Special Property: Pyroelectric and piezoelectric, meaning it can develop an electric charge when heated or subjected to pressure. • Major Sources: Brazil, Afghanistan, Pakistan, Mozambique, Nigeria, Madagascar, Namibia, Sri Lanka, and the United States.