the bedrock
banded chert
opaque · a true agate glows at the edge
The tell
THE big one. Hold the thin edge up to the sun. An agate glows, because light passes through the rim. Chert stays dead and opaque no matter how thin the edge is.
Chert bands are fuzzy and roughly parallel. Agate bands are sharp and concentric, following the shape of the cavity they grew in. Most "agates" posted to Michigan rock groups are banded chert, and there is no shame in it.
What it gets mistaken for
The facts
- also calledmistaken for an agate · a banded one is a keeper
- ageage varies
- where it turns upevery shore · glacial float
- the field markstays opaque at a thin edge · an agate glows there
10% of every order goes to northern Michigan animal shelters.