Editing Chalcedony (section)

== Varieties ==

Chalcedony occurs in a wide range of varieties. Many semi-precious [[gemstone]]s are in fact forms of chalcedony. The more notable varieties of chalcedony are as follows:

===Agate===
[[File:Quartz - Agateplate, redbrown-white.jpg|thumb|left|180px|Agate]]
[[Agate]] is a fibrous, banded variety of chalcedony that occurs in a variety of colors and patterns.<ref>{{cite web |title=Agate |url=https://www.mindat.org/min-51.html |website=mindat.org |publisher=Hudson Institute of Mineralogy |access-date=10 February 2025}}</ref> Iris agate shows exceptional [[iridescence]] when light (especially pinpointed light) is shone through the stone. Landscape agate is chalcedony with a number of different mineral impurities making the stone resemble landscapes.<ref name="cibjo">{{Cite web |url=http://www.cibjo.org/index.php?option=com_content&view=article&id=55&Itemid=32 |title=Retailers' Reference Guide: Diamonds, Cemstones, Pearls and Precious Metals |author=CIBJO member laboratories |date=May 2009 |publisher=CIBJO (The World Jewellery Federation, international federation of all national trade organizations and gemological laboratories) |location=Bern, Switzerland }}</ref>
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===Carnelian===
[[File:carnelian sard (mineral specimen).jpg|thumb|left|180px|Carnelian]]
[[Carnelian]] (also spelled cornelian) is a clear-to-translucent reddish-brown variety of chalcedony. Its hue may vary from a pale orange to an intense almost-black coloration.  Similar to carnelian is [[carnelian|sard]], which is brown rather than red.
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===Chrysoprase===
[[File:Chryzopras Polsko.jpg|thumb|left|180px|Chrysoprase]]
[[Chrysoprase]] (also spelled chrysophrase) is a green variety of chalcedony, which has been colored by [[Nickel(II) oxide|nickel oxide]]. (The darker varieties of chrysoprase are also referred to as prase. However, the term prase is also used to describe green [[quartz]] and to a certain extent is a color-descriptor, rather than a rigorously defined mineral variety.)

Blue-colored chalcedony is sometimes referred to as "blue chrysoprase" if the color is sufficiently rich, though it derives its color from the presence of [[copper]] and is largely unrelated to nickel-bearing chrysoprase.

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=== Fire agate ===
[[File:Agate-180670.jpg|left|thumb|Fire agate]]

[[Fire agate]] is a variety of chalcedony with inclusions of goethite or limonite causing an iridescent effect.<ref>{{Cite web|title=Fire Agate|url=https://www.mindat.org/min-7601.html|access-date=2021-04-11|website=www.mindat.org}}</ref> It can display a wide range of iridescent colors including red, orange, yellow, green, blue, and purple.<ref>{{Cite web|last=Page|first=Geology|date=2020-01-13|title=Fire Agate : What is fire agate? How fire agate is formed?|url=http://www.geologypage.com/2020/01/fire-agate.html|access-date=2021-04-11|website=Geology Page|language=en-US}}</ref> {{Clear}}

===Heliotrope===
[[File:Quarz - Heliotrop (Blutjaspis).JPG|thumb|left|180px|Heliotrope, or bloodstone]]
[[Heliotrope (mineral)|Heliotrope]] is a green variety of chalcedony, containing red inclusions of [[iron oxide]] that resemble drops of [[blood]], giving heliotrope its alternative name of bloodstone. In a similar variety known as plasma, the spots are yellow instead.
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===Moss agate===
[[File:mossagate.pebble.750pix.jpg|thumb|left|180px|Tree agate]]
[[Moss agate]] contains green filament-like inclusions, giving it the superficial appearance of [[moss]] or [[blue cheese]]. There is also tree agate which is similar to moss agate except it is solid white with green filaments whereas moss agate usually has a transparent background, so the "moss" appears in 3D. It is not a true form of agate, as it lacks agate's defining feature of concentric banding.
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===Chrome chalcedony===
[[File:Mtorolite zimbabwe trimmed.jpg|thumb|left|Mtorolite]]
[[Chrome chalcedony]] is a green variety of chalcedony, which is colored by [[chromium]] compounds.  It is also known as "mtorolite" when found in [[Zimbabwe]] and "chiquitanita" when found in [[Bolivia]].
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===Onyx===
[[File:Agate-Quartz-49959.jpg|thumb|left|180px|Onyx]]
[[Onyx]] is a variant of agate with black and white banding. Similarly, agate with brown, orange, red and white banding is known as [[sardonyx]].
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===Chalcedony ice-blue===
[[File:Iceblue-all2_hg.jpg|thumb|left|180px|Chalcedony ''Ice-blue'' (boulder, polished section and cabochon in ring]]
In [[Greenland]], white to greyish chalcedony is known from volcanic strata of the [[Paleocene]], in the Disko-Nuussuaq area (West Greenland) and from the Scoresby Sound area (East Greenland). A light blue variety of chalcedony is known from [[Illorsuit]], formed in the volcanic rocks along the southern coast of the island. Because of its bluish, ice-like colour, it has the local name chalcedony "ice-blue".
<ref>[https://www.geus.dk/Media/637588304356429792/Smykkestensrapport_GEUS2021.pdf >Ghisler & Secher (2020) ''Smykkesten fra Grønland i GEUS' prøvesamlinger'' (Gemstones from Greenland in the sample collections of the Geological Survey of Denmark and Greenland), Danmarks og Grønlands Geologiske Untersøgelse Rapport 2020/50]</ref>
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