Carved Druzy Agate Turtle
Carved black druzy agate turtle.
The geological process that forms a druzy, the layer of crystals on the rock, occurs when water brings minerals onto a rock's surface. When the water evaporates, cooling occurs and the minerals are left behind to form crystals on top of the rock. Depending on the minerals, druzy gemstones can be almost any color of the rainbow, including white, pink, blue, purple, green or black.
Most druse forms as cavity lining in geodes. The botryoidal agate mass of the geodes are irregular, lumpy like a cluster of grapes. As a result, typically the surface area for cutting a cab is small. Large stones are less common. Many cutters keep a border of plain agate around the druse covered area of the cab to produce larger cabs.