Chalcedony is a mixture of cryptocrystalline quartz and another silicon mineral called moganite. Chalcedony is usually divided into translucent varieties such as (blue) chalcedony, carnelian, chrysoprase, or banded varieties under the name agate, as well as opaque varieties known as jasper.

Physical properties:

Chemistry: SiO2
Hardness: 6½-7
SG: 2.58-2.64
Cleavage: None
Fracture: Low
Heat sensitivity: None

Optical properties:

RI: 1.53-1.54
Transparency: Translucent to opaque

Grinding wheel:

All grit sizes

Facet polishing:

Usually not faceted, but if so, it is polished like regular crystalline quartz

Cabochon polishing:

Olson: Tin or cerium oxide on felt
Christiansen: Aluminum, tin, or cerium oxide on felt, leather, or wood
Cox: Cerium oxide on felt or leather
Covington: Cerium oxide on felt or leather


According to shape and color


Due to its fibrous or granular structure, chalcedony can be easily dyed.


LightningLap with cerium oxide is excellent for polishing large facets.

Kalcedon on Gemdat

There are no products to list in this category.

This web site uses cookies only to keep track of your chosen language and currency, and a id number for your shopping basket. It stores no information for marketing or statistics.
I accept these cookies