types of agates found in michigan?

Question

stones or rocks in michigan

Answer 1

Lake Superior agates are the name given for banded agates commonly found on beaches of Lake Superior, formed originally when silica filled in vesicles (gas bubbles) that formed in molten lava. The silica is mostly in the form of iron-stained transluscent chalcedony-andis commonly banded. Some of the agates are amygdaloidal. and some have copper inclusions.
These agates are found in Minnesota as well. Here's a Minnesota department of Natural Resources site that gives a nice description of how the rock formed: