Oval shaped black and white semiprecious stone Tuxedo Agate Designer cabochon 89 mm (3.5 inches!) by 40 mm and 5 mm thick.
This is actually semi precious gemstone Brazilian Agate that has been dyed a rich black!
The natural white lines come through and make a beautiful specialty designer cabochon known as Tuxedo Agate.
Agate is a form of Chalcedony, or a microcrystalline quartz. It forms in concentric layers in a wide variety of colors and textures. It has a hardness of 7 and wears great in jewelry.
Cabochons are stones cut for jewelry and are measured in mm. One inch is equal to about 25 mm.