|Chemical composition||Silicon dioxide SiO2|
|Refractive index||1.535 - 1.539|
Chalcedony is microcrystalline (cryptocrystalline) quartz. The name is often used to encompass all varieties of microcrystalline quartz such as jasper, carnelian, chrysoprase and bloodstone. The mineral is very abundant and found all over the world. The most common variety is a muted blue-gray tone (unnamed) found in geodes and vugs.