Rock crystal thumbstone from Brazil (Thumbstones are super hot right now!)

Thumbstones are gemstones that are first sawn into slices and then polished. This ensures beautiful flat stones that fit well in the hand and are easy to carry. The name thumb stone arose because each stone has a recess cut into an oval shape where you place your thumb when you grip the stone. So you can "keep your fingers crossed" for good luck by rubbing it with your thumb, but the stone is also very popular for massage.