I'm gonna say a type of marble or onyx. These imported decorative items are generally made of a soft stone so they can be carved, shaped and polished with ease, so they can be somewhat mass produced with minimal powered hand tools. There are many sources of various types of onyx and marble found almost on every continent. Here in Colorado we have a large deposit of white marble called Colorado yule marble. These types of rocks are mostly made up of calcite and have many other names.