Sterling silver brooch with tourmaline "Fern"
Sterling silver, tournaline
Stone size: 11x7mm
Tourmalines are characterized by a hardness of 7-7.5
Tourmaline inclusions in rocks have a characteristic triangular cross-section —no other more common mineral has one. The surface of tourmaline crystals is characterized by vertical striations.
Like most hemimorph crystals, tourmaline crystals are excellent piezoelectrics, often pyroelectrics. When such a crystal is heated, one end of it becomes positively charged and the other — negatively. For this reason, tourmaline jewelry can attract dust in strong spotlights. It is these characteristics of tourmaline that made it a fashion gem in the early 18th century. Brightly colored Sri Lankan tourmalines were imported in large quantities to Europe and worked as jewelry, but very often found their way into laboratories and their electrical properties were demonstrated at high society events.
Tourmalines come in a variety of colors —black, blue, brown, yellow, green, red, pink, purple, etc. Very rarely tourmaline is colorless, at the same time multi-colored crystals are often found.
One popular type of tourmaline is watermelon tourmaline —green at one end and red at the other . Some types of tourmaline have pleochroisms—the color changes when looking at different directions of the crystal.