strange rock with spheres inside, ID please?

[30-hot-06]

My grandmother found this rock in a box of river rock. It raised some question to what it is and how it is formed. I know very little about the different types of rocks and would love to learn more.

This rock is flat, dark, and seems very brittle and would be easy to chip away. Flint? chert? however there are two almost perfect spheres "trapped" inside. Both I can feel on both sides of the rock. One of the spheres is a brownish color on one side and dark on the other, and the other sphere is black on both.

 

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[XGPX0001]

My grandmother found this rock in a box of river rock. It raised some question to what it is and how it is formed. I know very little about the different types of rocks and would love to learn more.

This rock is flat, dark, and seems very brittle and would be easy to chip away. Flint? chert? however there are two almost perfect spheres "trapped" inside. Both I can feel on both sides of the rock. One of the spheres is a brownish color on one side and dark on the other, and the other sphere is black on both.

Looks like shale. You also mentioned brittle and river.

 

[vpnavy]

1st - I noticed this was your very first post - so, Welcome Aboard 30-hot-06! You didn't list your state (or country) in your profile. So, you might consider jumping over to Sub-Forums: Select Your Area.... and selecting location information (i.e., clubs, hunts, finds, legends, maps, etc.) directly related to your state (or country). You might also consider adding your state (or country) to your displayed profile (SETTINGS -> EDIT PROFILE) so if you ask a question, etc. - people may have more success helping you (if necessary)...

2nd - it sure would help if you let us know where the rock was found (if you know it).

 

[30-hot-06]

Looks like shale. You also mentioned brittle and river.

Oh, i'm sorry I had to make an account fast, This rock is in Iowa however it was purchased in a bundle of 'river rock' So it is hard to determine where it came from.

 

[DDancer]

I agree with XGPX, it appears to be shale. Try a streak test and hardness test. The sphere's are likely concretions of another mineral~ the light coloration and grainy look of the one in the first picture makes me think of a carbonate and the dark one is still covered over by the host material.

 

[Eu_citzen]

Shale, indeed. The "bumps" are often small clay lumps.