Gem Grade Black Tourmaline from Afghanistan (complete piece) 

Weight:  24.5 gram (122.5 carat)

Dimension:    29x22x20 mm

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Tourmaline

Color: Colorless, pink, brown, red, yellow, green, blue, black, violet, multi-colored

Moh's Harness: 7-71/2

Specific Gravity: 2.82-3.32

Refractive Index: 1.614-1.666

Double Refraction: -0.014 to -0.032

Fluorescence: Weak or none

Cleavage: Indistinct

Fracture: Uneven, small conchoidal, brittle

Crystal System: Trigonal. Long crystals with triangular cross section and round sides.

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. The many different colors or Tourmaline mean that this stone can easily be mistaken for just about any other gemstone.

One of the most versatile of gemstones, tourmaline is available in every color, from colorless to black. You can find every tone from pastel to dark, and even with one or more colors appearing in the same stone. It truly is a wondrous and fascinating stone!

Known for centuries, tourmaline first gained popularity when the Dutch began to import it in the early 17th century from Sri Lanka .

Color is the major characteristic for tourmaline. This stone is found in more hues, shades and nuances than any other gem. Here are some of the most common varieties that are recognized in the gem trade.

Tourmaline has strong pleochroism , which means you can see different colors or depths of color when viewed at different angles, such as when you rotate the stone in the light.