Chalcedony Rosettes Crystal Mineral Specimen

Chalcedony is a form of quartz that is found in deposits all over the world, particularly in Brazil, Madagascar and Turkey. It forms fine inter-growths as quartz which has a trigonal crystal structure and morganite which has a monoclinic crystal structure that results in fibrous layers or “aggregates”.

Chalcedonies vary in color, pattern and name. It is said that its name is derived from the Greek port city of Chalcedon where it is reported to have first been found. Chalcedony has been used as a decorative stone in carvings and jewelry since antiquity from cultures that span the globe. Chalcedony seals have been found in the Mediterranean that date back to 1800 BC, three varieties of chalcedony were used in the Jewish High Priest’s breastplate, objects from Afghanistan have been found, and it is said to be used in Native American ceremonies.

Chalcedony also varies in its formation habits, occurring in geodes, it forms pseudomorphs after organic material like petrified wood, and another pseudomorph is chalcedony after coral and tigers eye.

“Blue chalcedony” is a blue, translucent variety of chalcedony or microcrystalline quartz. Its soft, distinctive, blue color is due to the interference of light caused by the reflection from microcrystalline interfaces. Blue chalcedony is a popular gemstone and decorative stone.