zoisite

Zoisite is a calcium aluminum silicate mineral in the epidote group. It typically forms monoclinic crystals and occurs in metamorphic rocks such as schists and marbles, often alongside minerals like epidote, quartz, calcite, garnet, and chlorite. The mineral was named after the Slovenian naturalist Sigmund Zois.

Chemically, zoisite is part of the sorosilicate family and can occur with varying amounts of iron and other trace elements, which influence its color. The common range includes greens, browns, and yellows, with more prized specimens displaying vivid blue to violet hues in certain varieties. Color in zoisite is often enhanced by processing or by the presence of trace elements such as manganese in pink varieties.

Zoisite occurs worldwide, with notable gemstone forms. Tanzanite is the blue to violet variety of zoisite found in Tanzania; it is widely known for its strong pleochroism and is typically heat-treated to intensify color. Thulite is a pink variety, caused by manganese. In jewelry, zoisite is valued for its range of colors and relatively good hardness, but it is less durable in daily wear than some other gemstones and should be protected from sharp blows and scratches. Ruby-zoisite, a mosaic stone combining zoisite with ruby crystals, is also marketed as a decorative gemstone.