Rock Identifier
Tumbled yellow chalcedony (likely yellow jasper or citrine-colored quartz) (Microcrystalline quartz, SiO₂; coloration may come from iron oxides or fine inclusions) — mineral
mineral

Tumbled yellow chalcedony (likely yellow jasper or citrine-colored quartz)

Microcrystalline quartz, SiO₂; coloration may come from iron oxides or fine inclusions

AI-generated identification · may be incorrect

Smooth, opaque-to-translucent yellow oval with a waxy-to-dull luster; quartz hardness is about 7 Mohs, lacks visible cleavage, and has a microcrystalline structure. The image cannot reliably distinguish chalcedony, jasper, dyed material, or glass.

Identified More mineral
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Physical properties

Smooth, opaque-to-translucent yellow oval with a waxy-to-dull luster; quartz hardness is about 7 Mohs, lacks visible cleavage, and has a microcrystalline structure. The image cannot reliably distinguish chalcedony, jasper, dyed material, or glass.

Formation & geological history

Chalcedony forms when silica-rich groundwater fills cavities and fractures, commonly in volcanic rocks; iron staining produces yellow tones. Formation ages vary widely, from relatively young cavities to ancient Paleozoic and older deposits.

Uses & applications

Used as a lapidary and decorative stone, cabochon, bead, and inexpensive collector specimen; polished pieces have modest jewelry value.

Geological facts

Chalcedony is cryptocrystalline quartz composed of intergrown quartz varieties. A scratch test, specific-gravity test, and close inspection for bubbles or dye concentration are needed for confident identification.

Field identification & locations

Common sources include Brazil, Uruguay, India, Madagascar, Mexico, and the western United States. It should resist scratching by a steel knife; glass-like bubbles or perfectly uniform color may indicate an imitation.