Victorian Scottish Agate Brooch.

Chalcedony is cryptocrystalline quartz. It is semitransparent to opaque and, depending on it's color, the chalcedony is further divided in several varieties.

History

All varieties of chalcedony were very popular in Victorian jewelry. Moss agate, known for its green tree-like patterns was a particular favorite. Bloodstone was often used for cameos and intaglios for gentleman's jewelry. Carnelian, also popular for intaglios, is often found in beads from the Victorian Era. Banded stones like sardonyx and onyx were used extensively for cameos and some of the most interesting beads feature banded agate. The term "hardstone" used in reference to a cameo usually refers to some form of chalcedony.

Victorian Era Scottish jewelry features many and varied combinations of chalcedony cut en cabochon and faceted sent in silver and sometimes gold. Often the pieces are fitted together mosaic style. Scottish agate or pebble jewelry as it is sometimes called, became fashionable after Victoria bought Balmoral Castle in 1848.

Chalcedony Varities
Agate	Various Colors, Banded or Interwoven
Bloodstone	Dark Green with Red Spots
Carnelian	Orangish to Brownish Red
Chrysocolla	Light Blue or Blue-Green
Chrysoprase	apple green
Fire Agate	Brown with Multicolor Iridescence
Jasper	All Colors Except Black
Onyx	Black & White
Petrified Wood	Multicolored Silicified Wood
Prase	Dull Green
Sardonyx	Brownish Red & White
Sard	Brownish Red to Orange

Gemological Information

Gemological information for chalcedony
Color	All colors
Crystal structure	Trigonal (polycrystalline quartz)
Family	Quartz
Refractive index	~1.54
Durability	Very durable
Hardness	7
Treatments	Dying
Country of origin	World wide deposits
Chalcedony care
Ultrasonic cleaning	Usually safe
Steam cleaning	Usually safe
Warm soapy water	Safe
Chemical attack	Avoid
Light sensitivity	Stable (unless dyed)