Chrysoprase

Hardness: 6.5-7 on the Mohs scale. Color: Translucent to opaque, typically deep green, but can be apple green. Luster: Waxy to vitreous. Crystal Structure: Trigonal (cryptocrystalline quartz). Cleavage: None (conchoidal fracture). Specific Gravity: 2.58-2.64.

Chrysoprase is a cryptocrystalline form of silica, meaning it is composed of very fine intergrowths of quartz and moganite. Its distinctive apple-green color is attributed to the presence of small amounts of nickel inclusions (specifically, finely dispersed particles of a nickel-bearing silicate mineral like garnierite or pimelite), not chromium or vanadium, as is the case with emerald. It forms in nickel-rich serpentinites or other ultramafic rock deposits as a result of the deep weathering and lateritization of these rocks.

Primarily used as a gemstone in jewelry, including cabochons, beads, and carvings. It is also used for ornamental objects and sculptures. Its affordability compared to other green gemstones like emerald makes it a popular choice.

Chrysoprase is one of the most valued varieties of chalcedony. Its vibrant green color makes it a popular gemstone. Historically, it was used in decorative arts and jewelry by the Greeks and Romans. Unlike many other green stones, its color is stable and does not fade with light exposure.

Chrysoprase is identified by its apple-green color, its translucency, and its waxy luster. In the field, it is often found in association with weathered nickel deposits. Common locations include Australia (especially Queensland), Brazil, California (USA), Poland, Russia (Urals), Tanzania, and Germany. When identifying, look for its distinctive green hue (which sets it apart from jade or emerald), its lack of visible crystals, and its hardness (it will scratch glass). It often occurs in veins or as nodular masses within its host rock.