jaspis

Jaspis is a term used for a group of opaque chalcedony varieties, a microcrystalline form of silica (SiO2). In the gemstone trade, jaspis is prized for its rich colors and dense patterns, though it is not a distinct mineral but a rock variety.

Jaspis forms when silica-rich fluids deposit microscopic quartz crystals within cavities and fractures in sedimentary rocks, producing nodules or layered masses rich in impurities. Its color and pattern are controlled by iron oxides, manganese oxides, and other trace elements.

Colors range from red, yellow, and brown to green and gray, often mottled or banded. Common varieties include red jaspis, bloodstone (green chalcedony with red inclusions), picture jaspis (landscape-like patterns), moss jaspis (green, mossy patterns), and ocean jaspis (Madagascar orbicular patterns).

Uses and care: Jaspis is widely used for cabochons, beads, and decorative carvings. It has a Mohs hardness of about 6.5 to 7 and a conchoidal fracture; it can be polished to a bright luster. Some jaspis pieces are dyed or stabilized to enhance color, and should be cleaned with warm soapy water.

Occurrence and history: Jaspis is found worldwide, with notable sources including India, Madagascar, Brazil, the United States, and Australia. It has been used in jewelry and ornamentation since ancient times and remains a common material in decorative stones.