Black Tourmaline - Large Chunk (2-3 inch)

This large chunk of Black Tourmaline, 2-3 inches in diameter, is great for any mineral collection.

In its natural state, all Tourmalines are characterized by parallel ridges (striations) which run the length of the crystal. Tourmaline forms in igneous and metamorphic rocks and veins, and have a different shaped top than the bottom of the crystal. Another interesting characteristic is that this stone is a pyroelectric which means that when heated, a positive charge develops at one end and a negative charge at the other.

FOUND IN: TANZANIA, MADAGASCAR, BRAZIL, AUSTRALIA, SRI LANKA, RUSSIA & USA

Tourmaline’s name comes from the Sinhalese word “turmali,” which means “mixed.” Tourmaline, occurring in more colors and combinations of colors than any other gemstone variety, lives up to its name. Known for centuries, tourmaline first gained popularity when the Dutch began to import it in the early 17th century from Sri Lanka . Tourmaline is actually the name of a group of related mineral species. In gemological practice, individual species names are not used. Instead, all are simply termed tourmaline.

Color is the major characteristic for tourmaline. This stone is found in more hues, shades and nuances than any other gem.

Black Tourmaline Specifications:

• Moh’s hardness: 7 – 7½
• Specific gravity: 3.02 – 3.24
• Cleavage: None
• Fracture: Uneven, Small Conchoidal, Brittle
• Crystal system: Hexagonal (Trigonal)
• Chemical composition: SiO2 silicon dioxide (NaLica) (Fe11 Mg MN Al) Al ((OH) (BO) Si6 O18)
• Refractive index: 1.554 – 1.553
• Double refraction: -0.014 to -0.044
• Dispersion: 0.017