Vintage Table Lamps

I recently aquired this pair of table lamps. They look like they are hand carved out of white marble. When I started to clean them up I noticed that they were made of a lot softer material than the regular marble that I'm used to seeing. I was just wondering if someone might be able to tell me more about this pair. I have tryed to look them up on the internet but I'm not sure if they are a soft white marble or parian. I am sure they are vintage table lamps. If you can help identify this pair maybe you could suggest a possible value. Thanks for the help with matter.