Tourmaline is the chameleon gemstone, found in the widest range of colors, including black, white and everything in between. It is believed to come from the Sinhalese word turmali, which means “mixed.”
Magnificent tourmaline crystals can contain luminescent bands of several colors, from red to green to blue. It is often mistaken for other gems, as it comes in shades of blue that mimic sapphires and can also appear as green as emeralds. The rarest of all these being Paraiba, a neon blueish-green through to greenish-blue. Tourmaline is also found in ‘bi-color, with two colors forming in one crystal.
Due to its formation, tourmaline is usually highly included and scarcely comes inclusion free in larger sizes.
With a Moh’s scale hardness of 7-7.5, the beauty of tourmaline has won a following among cutting-edge jewelry designers in the U.S. and Europe who have been inspired by the vivid colors and beautiful crystal shapes of the gem.
All gems in the tourmaline family are mixed crystals of aluminium boron silicate that also contain elements such as iron, manganese, sodium, lithium, or potassium.
Most tourmaline deposits are found in veins that run through rocks, which were created by molten magma from volcanoes. As the magma cools, large cracks form and fill with a solution of water and minerals such as iron, lithium or manganese. It is these trace elements that give tourmalines their vivid colors, ranging from red, green and blue to yellow and orange.
As the crystal grows, it uses the elements that fit most easily within the structure. As these elements in the solution are depleted, other elements are substituted and the color of the crystal changes.
The bi-colored and multi-colored zoning that we see in watermelon tourmaline gems happens when the trace elements change in concentration during a crystal’s growth. In watermelon tourmaline, pink and green Elbaite crystals are found in the same stone, and these color zones provide a visual record of its formation process, a pink watermelon center through a pale zone and green rind.
Photo credit gemstonist.com