Any Rock Collectors? What is this?

My aunt just gave me a box of rocks she said she found and picked up all over the US. Most of the rocks were normal looking rocks, except this one. It looks perfectly shaped and it's smooth except for one side has a small rough spot that you wouldn't know unless you rubbed your finger over it. My aunt said she did not polish it, she found it this way. This was posted to a rock/mineral forum, but no replies. Thought maybe some ATS'ers might have a clue.

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Not sure what type of rock it is..but I see these at the dollar store/ craft store all the time.
People use them for decorative purposes.
It looks like it was tumbled smooth.
Just because it was found outside doesn't mean it originated there.

It could very well be a decorative stone, but I don't know anything about stones or rocks and I was curious about it. I know she's had it about 30 yrs. and that's about all I know. I might just bust it open with a hammer to see what the inside looks like.

It looks like onyx to me, a soft form of quartz.

See if you put on an LED flashlight and any light shines through. Also you can do a scratch test with a pocket knife. Onyx tends to be about 7 on the Mohs scale, where pure quartz is about 100.

Don't smash it though, it's a nice little stone.