Calcite also know as limespar, limestone is found in a range of colours also ranging from transparent to translucent. It is a quite soft gem ranging at only 3 on the mohls hardness scale so great care must be taken when working with this item. It refractive index is 1.486-1.658. It is widely found worldwide but due to the softness is rarely faceted and then only for collectors as normally to brittle for setting.