KC, my guess is that it is marble. It is cold to the touch, has a slight ring to it if tapped with something and the wife says it weighs about 2 pounds.
It is polished everywhere except the flat parts of the bottoms of the front paws and hind quarters and on them one can see what appears to me to be saw marks that are at 45 degrees to the longitudal length of the body.
We have had it for several years and we got it in a "box of junk" at an auction.
I guess its origin would have to be traced via the type of stone is is made from.