Rock Identifier
Tumbled yellow jasper or yellow chalcedony (Microcrystalline quartz (SiO₂), likely jasper/chalcedony; exact identification requires testing) — mineral
mineral

Tumbled yellow jasper or yellow chalcedony

Microcrystalline quartz (SiO₂), likely jasper/chalcedony; exact identification requires testing

AI-generated identification · may be incorrect

Opaque to slightly translucent mustard-yellow, waxy to dull luster, massive with no visible cleavage; quartz hardness ~6.5–7 Mohs and specific gravity ~2.6. The rounded shape indicates mechanical tumbling and polishing.

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Physical properties

Opaque to slightly translucent mustard-yellow, waxy to dull luster, massive with no visible cleavage; quartz hardness ~6.5–7 Mohs and specific gravity ~2.6. The rounded shape indicates mechanical tumbling and polishing.

Formation & geological history

Forms from silica-rich fluids filling cavities or replacing rock, with iron oxides producing the yellow color; generally a relatively young, sedimentary or volcanic-associated silica deposit. Geological age cannot be determined from the photograph.

Uses & applications

Used as a decorative tumbled stone, cabochon, bead, and low-cost lapidary material; not typically used structurally. Commercial value is usually modest.

Geological facts

The specimen may be sold as yellow jasper, mookaite, lemon quartz, or yellow chalcedony, though trade names are often inconsistent. A streak, hardness, and translucency test can distinguish it from dyed materials or amber.

Field identification & locations

Commonly found in silica-rich volcanic and sedimentary regions, including Australia, Madagascar, Brazil, India, and the western United States. It should scratch ordinary glass but not be scratched by a steel knife; a white streak and lack of fizz support quartz.