Alternative Names: When concentrically banded it is called by the sub-variety name Agate. When it is in flat layers/bands it is called by the sub-variety name Onyx. Many other sub-variety names exist, including Jasper, Chrysoprase, Flint etc.
Mineral Species: Quartz
Mineral Group: Oxides
Chemical Formula: SiO2
Crystal System: Trigonal
Colour: Usually colourless, white, grey or blue, but most colours exist due to other embedded minerals.
Typical Appearance: Traditionally defined as a fibrous cryptocrystalline variety of Quartz. When it is concentrically banded, it is called by the name Agate. When it is in flat layers or bands it is called Onyx.
Birthstone: Elemental birthstone of Cancer & Sagittarius
Chakra Alignment: Throat, Third Eye and Bindu Visarga
Element: Air, water
Origin of Name & Mythology: Mentioned by Agricola (1546) of a stone named for the town of Chalcedon, now called Kadikoy, and is a district within the city of Istanbul, Turkey.
Properties: The properties of chalcedony tend to be related to colour and formation. Please click on some chalcedony varities below.