What valuable rocks/minerals naturally occur in Mid Michigan?

Question

Anything interesting looking or valuable that occur in mid Michigan?

rock,meteorites,gems,minerals, IS THERE ANYTHING WORTH SEARCHING FOR OUTSIDE IN THIS STATE?

Answer 1

Not so valuable: Petoskey stones

http://www.petoskeystones.com/

http://www.bernardine.com/gemstones/peto...

Better but not "mid-Michigan": Lake Superior agates:

http://www.dayooper.com/LSAgates.htm

http://www.alleycatbead.com/advanced_sea...

????? Isle Royale greenstones:

http://www.alleycatbead.com/greenstone.p...

??? Kona Dolomite:

http://www.alleycatbead.com/advanced_sea...