mineral
Chalcedony (rough)
Microcrystalline quartz, SiO₂; likely gray chalcedony with iron-oxide staining
AI-generated identification · may be incorrectHardness 6.5–7; gray to bluish-gray, with a waxy to dull luster and translucent edges. Trigonal quartz in microscopic fibers; no true cleavage, with uneven to conchoidal fracture. Specific gravity about 2.6.
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Physical properties
Hardness 6.5–7; gray to bluish-gray, with a waxy to dull luster and translucent edges. Trigonal quartz in microscopic fibers; no true cleavage, with uneven to conchoidal fracture. Specific gravity about 2.6.
Formation & geological history
Silica-rich fluids deposited quartz in cavities and fractures, commonly in volcanic rocks; iron-bearing material caused the brown surface staining. Chalcedony forms across many geologic ages.
Uses & applications
Used for beads, cabochons, carvings, and decorative stone; this rough piece is suitable for cutting or collecting.
Geological facts
Chalcedony is a broad term for compact, very fine-grained quartz and includes varieties such as agate and carnelian.
Field identification & locations
Look for waxy luster, translucence at thin edges, and hardness sufficient to scratch glass; a fresh surface or magnification can help distinguish it from other silica-rich stones. Found worldwide, especially in volcanic terrains and silica-bearing veins.
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