|A variety or type of:||Quartz|
Agate - A banded variety of Chalcedony.
Iris Agate - An iridescent variety of Agate.
Onyx - A monochromatic Agate with black and white banding.
Sardonyx - A monochromatic Agate with red/brown and either black or white banding.
Binghamite - Chatoyant Chalcedony with fibres of hematite/goethite.
Bloodstone - A dark green/greenish-blue Chalcedony with small red blood-like spots.
Carnelian - A red to orange variety of Chalcedony.
Chrome-Chalcedony - Emerald green Chalcedony, colored by chromium.
Chrysoprase - A green Chalcedony coloured by inclusions of Ni minerals.
Dendritic Agate - A chalcedony containing contrasting branching, or dendritic, mineral inclusions.
Moss Agate - A translucent chalcedony containing green strands of chlorite.
Fire Agate - A variety of Agate containing iridescent spheroids of limonite.
Jasper - Jasper is a dense, opaque, microcrystalline variety of Chalcedony.
Dallasite - A variety of Jasper from Vancouver Island, British Columbia, Canada.
Orbicular Jasper - Jasper containing numerous spherical inclusions.
Petrified Wood - A decorative type of fossil wood where the original organic material has been replaced - usually by chalcedony, agate, opal, etc.
Pietersite - Chalcedony with embedded fibers of amphibole minerals, causing chatoyancy.
Sard - A brown to brownish-red translucent variety of Chalcedony.
|Photos of natural/un-cut material from mindat.org|
|Routinely dyed, tests limited: look for dye concentration between grain boundaries, in fractures. Transmitted light: may show mosaic-like marking - Blue Chart Gem Identification, Herve Nicolas Lazzarelli, 2010, p 7|
|Physical Properties of Chalcedony|
|Mohs Hardness||6.5 to 7Blue Chart Gem Identification (2010) , More from other references|
|Specific Gravity||2.55 to 2.70Blue Chart Gem Identification (2010) , More from other references|
|Cleavage Quality||NoneGemstones of the world (2001) ,|
|Fracture||UnevenGemstones of the world (2001) , Shell-likeMore from other references|
|Optical Properties of Chalcedony|
|Refractive Index||1.530 to 1.543Blue Chart Gem Identification (2010) , More from other references|
|Optical Character||Uniaxial/+Gemmological Tables (2004) ,|
|Birefringence||0.003 to 0.009Blue Chart Gem Identification (2010) , More from other references|
|Pleochroism||AbsentGemstones of the world (2001) ,|
|Dispersion||NoneGemstones of the world (2001) ,|
|Colour (General)||All coloursGemmological Tables (2004) , Commonly bandedMore from other references|
|Causes of Colour||Purple, microscopic sugilite inclusions. Purple, color center similar to that found in amethyst. Blue to greenish blue (chrysocolla quartz), microscopic to sub-microscopic inclusions. Green (chrysoprase), microscopic inclusions of nickeliferous clay-like material. Orange to red (carnelian, jasper), submicroscopic to microscopic inclusions of hydrous Fe oxidesPragmatic Spectroscopy For Gemologists (2011) ,|
|Transparency||Translucent,OpaqueBlue Chart Gem Identification (2010) , Semi-transparent to opaqueMore from other references|
|Lustre||WaxyGems, Sixth Edition (2006) , More from other references|
|Fluorescence & other light emissions|
|Fluorescence (General)||Often yellowish-greenBlue Chart Gem Identification (2010) ,|
|Crystallography of Chalcedony|
|Crystal System||TrigonalGemmological Tables (2004) ,|
|Habit||Fibrous to grained aggregateGemmological Tables (2004) , More from other references|
|Where found:||Chalcedony is deposited in a variety of environments and deposition is commonly at low temperatures. Light-coloured material with no marked banding is often found as a late hydrothermal deposit or an alteration product in acidic to basic igneous rocks, tuffs and breccias. It is|
vary common as crusts, as vein and cavity fillings.Gems, Sixth Edition (2006) ,
Click spectra for more information
|Mineral information:||Chalcedony information at mindat.org|
|Significant Gem Localities|