Nephrite

An exceptionally tough, compact, fine-grained greenish or bluish mixture of actinolite and tremolite; it is a calcium magnesium silicate with traces of chromium and nickel, which produces its color. With jadeite, it is one of two minerals commonly called "jade." Nephrite has an oily, lustrous appearance when polished and is sometimes variegated in color that can incorporate white, yellow, brown, gray, and black. Nephrite has been used since Neolithic times for small utensils, decorative carvings and jewelry. When heated to about 1025 C, nephrite changes mineral forms to diopside.