gemstone

Polished chrysoprase (likely dyed or treated)

Chalcedony, cryptocrystalline quartz (SiO₂), colored green by nickel

AI-generated identification · may be incorrect

Mohs hardness 6.5–7; waxy to vitreous luster; opaque to translucent; typically apple-green, here with unusually dark/black areas and a rounded tumbled form. Quartz has no visible cleavage and conchoidal fracture; specific gravity about 2.6.

Identified August 16, 2026More gemstone →

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Physical properties

Formation & geological history

Chrysoprase forms when nickel-bearing groundwater alters ultramafic rocks, depositing microcrystalline quartz in fractures and cavities, commonly during Cenozoic weathering. The dark coloration may indicate included matrix, iron/manganese staining, or artificial treatment.

Uses & applications

Used for cabochons, beads, carvings, and inexpensive jewelry; polished pieces are mainly decorative and collectible.

Geological facts

Chrysoprase is the rarest and most valuable green chalcedony variety, historically used in Greek, Roman, and Art Nouveau jewelry. Strongly saturated natural green material is uncommon.

Field identification & locations

Identify by its smooth waxy polish, hardness, quartz-like conchoidal fracture, and green body color; it should not fizz in dilute acid. Common sources include Australia, Poland, Brazil, Tanzania, and the United States.