mineral
Tumbled chalcedony/agate (likely iron-stained quartz)
Microcrystalline quartz, SiO₂; chalcedony with possible agate banding and iron-oxide inclusions
AI-generated identification · may be incorrectHardness 6.5–7 Mohs; translucent cream, orange, brown, and reddish colors with a waxy-to-glassy luster. It has a cryptocrystalline quartz structure, no obvious cleavage, conchoidal fracture, and typical specific gravity near 2.6; the rounded surface indicates tumbling or water wear.
Identified More mineral →
Explore Tumbled chalcedony/agate (likely iron-stained quartz) in the encyclopedia →Identify your own rocks.
Get a report just like this from any photo, free.
Physical properties
Hardness 6.5–7 Mohs; translucent cream, orange, brown, and reddish colors with a waxy-to-glassy luster. It has a cryptocrystalline quartz structure, no obvious cleavage, conchoidal fracture, and typical specific gravity near 2.6; the rounded surface indicates tumbling or water wear.
Formation & geological history
Forms when silica-rich groundwater fills cavities and fractures in volcanic rocks, depositing chalcedony and quartz in layers; orange-red coloration commonly comes from hematite or limonite. The specimen’s exact geological age and locality cannot be determined from the image.
Uses & applications
Used as a decorative stone, cabochon, bead, polishing material, and collector specimen; common quality has modest value.
Geological facts
Agate is a variety of chalcedony distinguished by visible color or texture banding, though this piece may be massive chalcedony rather than clearly banded agate.
Field identification & locations
Look for translucency, waxy luster, conchoidal edges, and hardness sufficient to scratch glass; it should not fizz in dilute acid. Common sources include Brazil, Uruguay, Mexico, India, Madagascar, and the western United States.
