Kunzite

Kunzite forms in granite pegmatites. It is found in Afghanistan, Brazil (Minas Gerais), Madagascar and the US state of California, where the Pala district of San Diego County produces fine gem crystals; Myanmar also yields gem-quality spodumene. Crystals are often large: the Smithsonian Institution holds a faceted heart-shaped kunzite of 880 carats.

Kunzite is identified by its pink to violet color with strong pleochroism (colorless along one direction, pink or violet along another), refractive index 1.653 to 1.682, two perfect cleavages and, often, hollow growth tubes. It fluoresces pink to orange under long-wave ultraviolet light. Much kunzite on the market has been irradiated and heated to deepen its color; both treated and natural colors can fade with heat and bright light, and some irradiated stones turn an unstable blue-green.

Kunzite's color can fade with exposure to heat and bright light, so store it away from strong light and heat. Its two perfect cleavages make it fragile: a small knock can split a stone, and prongs must be tightened carefully because a cleavage direction lies along the girdle.

In 1902, specimens of an unidentified pink crystal from San Diego County, California, were sent to George Frederick Kunz, mineralogist of Tiffany & Co. He confirmed that they were spodumene in a previously unrecognized color and described the lilac spodumene from Pala in 1903. That same year, the chemist Charles Baskerville named the new variety kunzite in Kunz's honor.