mineral

Polished/tumbled agate or chalcedony nodule

Microcrystalline quartz (SiO₂), likely agate/chalcedony with weathered outer matrix

AI-generated identification · may be incorrect

Hardness 6.5–7 Mohs; cream, tan, and translucent honey-brown coloration; waxy to dull luster; cryptocrystalline quartz with no obvious cleavage; specific gravity about 2.6.

Identified September 12, 2026More mineral →

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Physical properties

Hardness 6.5–7 Mohs; cream, tan, and translucent honey-brown coloration; waxy to dull luster; cryptocrystalline quartz with no obvious cleavage; specific gravity about 2.6.

Formation & geological history

Forms when silica-rich groundwater fills cavities in volcanic rock, depositing chalcedony and quartz in layers over long periods, commonly during the Cenozoic or older volcanic episodes.

Uses & applications

Used as a lapidary, ornamental, and collecting specimen; suitable for cabochons, carvings, and small polished stones, though this example appears relatively low-grade.

Geological facts

The rounded shape and pale, chalky rind suggest a naturally weathered or lightly tumbled nodule. Honey-colored translucent zones may be quartz-rich chalcedony rather than true banded agate.

Field identification & locations

Identify by testing for glass-scratching hardness, waxy translucence, and absence of acid reaction; common sources include Brazil, Uruguay, Mexico, Madagascar, and volcanic regions worldwide. Exact identification would benefit from a fresh cut surface or magnification.