Any idea what these are?

[Rattlehead]

Found this one in a local creek bed in Grand Rapids, MI area

Found this 2.3 pounder on a rock beach on Lake Superior near Marquette, MI

Additional pic after cutting the rock in half...very pretty inside:

 

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[DanB]

it looks like a piece of quartz and host bed rock that has been rolling down that river bed for a very long time.....

good luck db

 

[phantomfinder]

I think Dans right , But its still a good looking stone.

 

[Eu_citzen]

Does it have a blue shimmer? A effect that only is visable from certain angles?

Looks like a mix of Quartz, Moonstone and possibly some other form of feldspar with an optical effect.

Adding a picture of moonstone for reference.

 

[goldinmypan]

If you have access to a saw, you might want to cut off a slab to see what the rock really looks like on the inside.

 

[Rattlehead]

I cut the small one open and added the picture above. Could it be some kind of agate?

 

[goldinmypan]

Chalcedony is my guess. It often has a blue tinge. Could also be an agate. They along with quartz and a bunch of other minerals are all SiO2. What ever trace minerals are present determine the difference.