I think, you’ve see such stones many times. They are in sell everywhere where there are semiprecious stones. They are in the shops, they are n the houses of your friends, they are in museums and in the specialized sites. Here is the photo from one of the museums. Te only difference is they are bigger than thiose you have seen before.
Find the the best place to buyer rough gemstones
Have you ever thought: where they come from? How they are situated in the rocks etc? If you asked you some of these questions, now you can see the answer. I post here 2 photos taken by one friend in Argentina in Minas de Wanda
usually most of the rough gemstones become the loose gemstone after it’s been cut in into a shape and polished. check variety of gemstone here https://gemfame.com