Directory
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CHALCEDONY
| CHALCEDONY | Waxy lustre |
| Origins | Brazil, India, Madagascar, Mexico, South Africa, Tanzania & US |
| Colours Found | Black, blue, brown, buff, green, grey, red, tan, white & yellow |
| Family | Quartz |
| Hardness | 6.50 - 7.00 |
| Refractive Index | 1.53 - 1.54 |
| Relative Density | 2.58 - 2.64 |
Chalcedony’s (also spelt Calcedony, it is correctly pronounced as “Kal-ced-on-ee” and is the catch all term for cryptocrystalline Quartz) name is derived from Chalcedon or Calchedon, an ancient port of Bithynia, near present day Istanbul, Turkey.
It has a waxy lustre and appears in a great variety of colours including blue, white, buff, tan, green, red, grey, black, yellow or brown. Different coloured varieties of Chalcedony have individual names including Agate (banded), Bloodstone (green with red spots), Chalcedony (blue to brownish blue), Chrysoprase (apple green), Cornelian (orange to red), Flint (dull grey to black), Jasper (spotted red, yellow, brown or green) and Sard (light to dark brown).
Legends and lore
The Romans prized Chalcedony as seals, and in the New Testament (Revelations 21:19) Chalcedony is one of the twelve gemstones set in the foundations of the city walls of Jerusalem. As compiled by Andreas, Bishop of Caesurae, one of the earliest writers to tie the Apostles with the symbolism of the twelve gems of Jerusalem, Chalcedony represented the Apostle St. Andrew.
Chalcedony was used during the Renaissance as a magic amulet to promote health and safety.
Chalcedony is one of the gemstones used in commesso or Florentine mosaic. Developed in Florence in the late 16th century, commesso is a technique of fashioning pictures with thin, cut-to-shape pieces of brightly coloured gems.
Just the facts
Quartz gemstones are commonly separated into two groups based on the size of their individual crystals. The macrocrystalline Quartz (large crystal) group includes many popular gemstones such as Amethyst, Ametrine, Citrine and Green Amethyst (Prasiolite). Cryptocrystalline Quartz includes species whose individual crystals are too small to be easily distinguished. Apart from being a variety within the group, Chalcedony is also a catch all term to describe cryptocrystalline Quartz and includes many gems that have been coveted since antiquity.
Normally faceted as a cabochon it is often used to great effect in both necklaces and bracelets.
