Great Video on mining of Marble..worth viewing..
We used to carry thousands of pounds in many varieties. However, we simply got very tired of the heavy equipment and labor intensive end of the business.
The best and most fun stone for beginning carvers. It is soft and plentiful.
The best for purity (no asbestos) is Brazilian. For a local supplier: Google "Soapstone" and check availability.
For Brazilian Soapstone:
You may have to buy a whole pallet (2000 pounds) from Canada and pay duties, so it is best to go in with friends and split the cost.
A soft stone, it is colorful and available in the United States.
It varies in hardness, but is easily carved by beginners.
Marble is the stone of choice for many sculptors.
I prefer Carrara, but you may want to go Carrara Italy for it.
In the United States, you can find it.
Onyx and harder stones: You are on your own.