Characteristics of Chalcedony:

Chemical Name: Silicon dioxide

Formula: SiO2

Colors: All colors

Structure: Hexagonal/Trigonal

Hardness: 7

Specific Gravity: 2.65

Refractive Index: 1.54-1.55

Lustre: Vitreous

Locations: USA, Peru, Morocco, Scotland, Netherlands, Czech Republic, Poland, Russia, Sri Lanka, Madagascar, Myanmar

What is Chalcedony? 

Chalcedony is a compact verity of quartz, composed of crystals that are microscopic (microcrystalline) or too small even for a standard optical microscope (cryptocrystalline). It forms in cavities, cracks, and by replacement when low-temperature, silica-rich waters percolate through preexisting rocks, in particular volcanic rocks. It is relatively porous, and much Chalcedony on the commercial market has been dyed to enhance or color it artificially. Chalcedonies of all kinds have been used as gems, beads, carvings, and in seals for thousands of years. The earliest stone tools were generally made of some form of Chalcedony.

Chalcedony Varieties

Pure Chalcedony is white. However, when trace elements or microscopic inclusions of other minerals occur, it can yield a range or colors. Many of these have their own variety names: Chalcedony that shows distinct banding is called agate; blood-red to reddish-orange translucent Chalcedony colored by inclusions of iron oxide is known as carnelian; bloodstone is dark, opaque green colored by traces of iron silicates and white patches of bright red jasper. Chrysoprase is translucent apple-green variety, colored by nickel; sard is light to dark brown Chalcedony; while sardonyx is color-banded sard; jasper, chert, and flint are opaque, fine-grained of dense, impure varieties of cryptocrystalline quartz.

Chalcedony’s name is thought to originate form the ancient port of Kalkedon in Asia Minor (modern Turkey).