Tourmaline

Tourmaline is one of the world's most versatile gemstones, occurring in more colors than any other mineral species. Known as the 'Rainbow Gemstone', it can exhibit multiple colors in a single crystal (like Watermelon Tourmaline). Its name comes from the Sinhalese word 'turmali', meaning 'mixed gems'. It is technologically unique because it is both piezoelectric and pyroelectric.

Formation & Geology

Tourmaline typically forms in granite pegmatites and in metamorphic rocks like schist and marble. It grows in long, slender, striated crystals that are often prismatic. The wide range of colors is due to various metal ions (iron, magnesium, manganese, lithium, etc.) substituting into its incredibly complex crystal lattice. The most rare and valuable variety is the 'Paraiba' tourmaline, which owes its neon blue color to copper.

Physical & Technical Characteristics

Tourmaline has a hardness of 7 to 7.5 and no cleavage, making it very durable. It is famous for its strong pleochroism—viewed from different angles, the crystal can show different shades or even different colors. Its most remarkable scientific property is its ability to generate an electric charge when heated (pyroelectricity) or when put under pressure (piezoelectricity).

Historical Significance

Because of its variety, tourmaline was often mistaken for other gems like rubies or emeralds. The 'Caesar's Ruby' in the Russian crown jewels was actually a red tourmaline (rubellite). It was recently added as a birthstone for October, often shared with opal. Legend says that tourmaline traveled along a rainbow and gathered all its colors.

The "Electric" Stone

Tourmaline has a fascinating physical property called pyroelectricity. When the crystal is heated, it generates a static electric charge, with one end becoming positive and the other negative. This causes it to attract dust and ash. In the 18th century, Dutch traders used long tourmaline crystals to pull ash out of their tobacco pipes, earning it the nickname "Aschentrekker" (ash puller).