What you are looking at is a really interesting "set" of a tourmaline crystal and what is known as a "gem nodule" that formed as the bottom termination of a crystal in a manner that often leaves them as loose or easily pried form the rest of the crystal; it fits perfectly into the concave bottom of the tourmaline crystal, its glassy rounded side facing out. The tourmaline crystal is a gemmy green, with a rough but natural and complete top termination. Miners harvest preferentially the gem nodules for cutting rough, and this makes a set showing the natural full crystal with the nodule as it would be found in some pockets.