mineral

Raw green chalcedony (likely chrysoprase or prehnite)

Microcrystalline quartz, SiO₂; possible prehnite, Ca₂Al₂Si₃O₁₀(OH)₂

AI-generated identification · may be incorrect

Translucent green-yellow material with a waxy to vitreous luster and conchoidal-looking fracture; chalcedony has Mohs hardness 6.5–7, whereas prehnite is 6–6.5. The blurry image prevents confident separation; visible granular brown matrix may be host rock or iron staining.

Identified September 2, 2026More mineral →

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Physical properties

Formation & geological history

Green chalcedony forms when silica-rich fluids fill cavities and fractures, commonly in volcanic rocks; chrysoprase is nickel-colored. Prehnite typically forms in low-temperature hydrothermal cavities of basalt, generally during the host rock’s Mesozoic–Cenozoic alteration.

Uses & applications

Used as a lapidary stone, cabochon, bead, and collector specimen; lower-grade material is ornamental rather than industrial.

Geological facts

Chrysoprase’s green color commonly comes from nickel, while prehnite often shows botryoidal or globular surfaces and pale translucent green color.

Field identification & locations

Test hardness against steel or glass, inspect for conchoidal fracture, and use a streak test (white streak); acid testing is not diagnostic. Common sources include Australia, Brazil, Madagascar, India, and volcanic districts worldwide.