What's That Rock?Agate
Banded, fine-grained quartz (chalcedony). It forms in cavities in volcanic rock, often filling them layer by layer.
How to identify Agate
- Fine curved or concentric bands, visible when cut or where weathered
- Waxy, smooth look; translucent when held to light
- Breaks with curved surfaces; hardness about 7
Often confused with
Real or fake?
- Bright blue, pink or green agate slices are almost always dyed; colors that pool in cracks show dye
- Natural agate colors are earthy: grays, browns, whites, soft reds
Is Agate valuable?
Common and inexpensive. Rare patterns such as moss, fire or lace agate cost more.
Typical retail prices
Tumbled stone$1–5each
Rough$5–25per pound
Polished piece$5–40each
Typical retail ranges in US dollars, compiled from public dealer and marketplace listings in October 2026. Real prices vary widely with quality, size and origin. This is general information, not an appraisal.
What changes the price
- Pattern: sharp, even bands or rare types (moss, lace, fire, plume) cost far more than plain gray
- Natural color: earthy tones are normal; bright blue, pink or green is almost always dyed and worth much less
- Size and cut: a clean polished slice or a hollow geode half beats a rough lump
- Origin: Lake Superior, Brazilian and Mexican agates have collector followings, but most are inexpensive
Uses
- Slices, bookends, jewelry, mortars
Care
Safe to wash. Dyed pieces can lose color in strong sun.
Identifying a stone from a description or a photo is an estimate. Many stones look alike. Ask an expert or a gem lab before you buy, sell or rely on an identification.
Updated October 2026