Chalcedony

This page kindly sponsored by Amir C. Akhavan

Byšta, Trebišov Co., Košice Region, Slovakia
© Albert Russ

System:	Trigonal	Colour:	colorless, white, gray, ...
Hardness:	6½ - 7

A variety of Quartz

Traditionally defined as a fibrous cryptocrystalline variety of Quartz, more recently, it has been shown that much Chalcedony is a mixture of Quartz and Mogánite, another silica mineral.

When it is concentrically banded (often in rather wild patterns) it is called by the subvariety name Agate. When it is in flat layers/bands it is called by the subvariety name Onyx.

[Note: Many non-banded forms of chalcedony - such as Moss agate - are often erroneously called 'agates'. True agate is concentrically banded. Mottled and included chalcedonies are more properly called simply 'chalcedony.' Petrified wood (agatized wood) is the name given to fossil wood where the replacement of the wood is by chalcedony, but the banding in this case is due to the wood structure - not concentric deposition of the chalcedony - and the material is chalcedony, not true agate.]

Chalcedony: Agate, Mexico

Chalcedony: Chalcedony Rose, New Mexico

Chalcedony: Red Jasper, Arizona

Chalcedony: Flint Nodule, England

Chalcedony: Chrysoprase, Poland

Chalcedony: Heliotrope, Brazil

Classification of Chalcedony

mindat.org URL:

http://www.mindat.org/min-960.html
Please feel free to link to this page.

Physical Properties of Chalcedony

Lustre:

Waxy, Dull

Diaphaneity (Transparency):

Translucent

Comment:

vitreous when polished

Colour:

colorless, white, gray, blue, any color due to embedded minerals, multicolored specimen not uncommon.

Streak:

White

Hardness (Mohs):

6½ - 7

Tenacity:

Brittle

Cleavage:

None Observed

Fracture:

Conchoidal

Density (measured):

2.6 g/cm³

Comment:

varies with amount and type of impurities

Crystallography of Chalcedony

Crystal System:

Trigonal

Other Names for Chalcedony

Synonyms:

Ceracahtes	Cerachates	Chalcedone	Chalcedonite	Chalcedononyx
Merlinite

Other Languages:

Basque:	Kaltzedonia
Breton:	Kalkedon
Catalan:	Calcedònia
Czech:	Chalcedon
Dutch:	Chalcedoon
Esperanto:	Kalcedono
Estonian:	Kaltsedon
Finnish:	Kalsedoni
French:	Calcédoine
German:	Chalcedon Chalcedonit Chalzedon Kalzedon
Hebrew:	כלקדון
Italian:	Calcedonio
Japanese:	石髓
Korean:	옥수
Latin:	Calcedonius
Latvian:	Halcedons

Lithuanian:	Chalcedonas
Norwegian (Bokmål):	Kalsedon
Polish:	Chalcedon
Portuguese:	Calcedônia
Romanian:	Calcedon
Russian:	Халцедон
Serbian (Cyrillic Script):	Калцедон
Simplified Chinese:	玉髓
Slovak:	Chalcedón
Spanish:	Calcedonia
Swedish:	Kalcedon
Turkish:	Kalsedon
Ukrainian:	Халцедон

Varieties:

Abakusz-kö	Agate	Agate-Jasper	Amarillo Stone	Amberine
Azurchalcedony	Ball Jasper	Basanite	Bayate	Beekite
Binghamite	Bloodstone	Blue Chalcedony	Blue Lace Agate	Botswana Agate
Brecciated Agate	Buhrstone	Carnelian	Chrome-Chalcedony	Chrysojasper
Cloud Agate	Crazy Lace Agate	Creolite	Cubosilicite	Dallasite
Damsonite	Darlingite	Dendritic Agate	Diackethyst	Egyptian Jasper
Enhydro Agate	Eye Agate	Fairburn Agate	Fire Agate	Fortification Agate
Fossil Agate	Haema-ovoid-agates	Herbeckite	Iris Agate	Irnimite
Jasper	Keystonite Chalcedony	Kinradite	Laguna Agate	Lake Superior Agate
Landscape Agate	Mexican Lace Agate	Mocha Stone	Moss Agate	Myrickite
Nipomo Agate	Onyx	Orbicular Jasper	Owyhee Jasper	Pastelite
Pietersite	Pigeon Blood Agate	Plasma	Plume Agate	Quartzine
Quetzalitztli	Riband Agate	Riband Jasper	Sard	Sardonyx
Schlangenhautachat	Seftonite	Snakeskin Agate	Vogelaugenachat	Vogelaugenjaspis
Watercolour jasper	Wilkite	Youngite

Other Information

Fluorescence in UV light:

None in pure specimen, however green fluorescence in short-wave UV light is very common at many localities.

Other Information:

Certain sub-varieties like jasper may be opaque.

Health Warning:

No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.

References for Chalcedony

Reference List:

- +

Flörke, O.W. et al. (1991) Nomenclature of micro- and non-crystalline silica minerals based on structure and microstructure. Neues Jahrbuch Miner. Abh., Vol 163, 19-42

Graetsch, H. (1994) Structural characteristics of opaline and microcrystalline silica minerals. Reviews in Mineralogy, Vol.29, Silica - Physical behavior, geochemistry and materials applications.