Rock Identifier
Tumbled yellow chalcedony (likely honey agate or yellow quartz) (Microcrystalline quartz, SiO₂; coloration likely from iron oxides or included minerals) — mineral
mineral

Tumbled yellow chalcedony (likely honey agate or yellow quartz)

Microcrystalline quartz, SiO₂; coloration likely from iron oxides or included minerals

AI-generated identification · may be incorrect

Mohs hardness 6.5–7; translucent yellow to honey-colored, waxy-to-glassy luster, cryptocrystalline structure, no visible cleavage, conchoidal fracture, specific gravity about 2.6. Its smooth rounded form indicates human tumbling and polishing.

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Physical properties

Mohs hardness 6.5–7; translucent yellow to honey-colored, waxy-to-glassy luster, cryptocrystalline structure, no visible cleavage, conchoidal fracture, specific gravity about 2.6. Its smooth rounded form indicates human tumbling and polishing.

Formation & geological history

Chalcedony forms when silica-rich groundwater deposits microscopic quartz fibers in cavities and fractures, commonly in volcanic rocks; iron staining produces yellow hues. Deposits range from relatively young volcanic terrains to Paleozoic and older sedimentary-hosted occurrences.

Uses & applications

Used for cabochons, beads, carvings, ornaments, and inexpensive jewelry; polished pieces are popular as lapidary and metaphysical specimens.

Geological facts

Chalcedony is quartz whose crystals are too fine to see individually; agate is a banded or patterned variety, so this specimen may simply be massive yellow chalcedony rather than true agate.

Field identification & locations

Identify by its waxy translucence, lack of cleavage, hardness, and conchoidal fracture; it should scratch glass but not be scratched by a steel knife. Common sources include Brazil, Uruguay, India, Madagascar, and the United States.