Chalcedone (mineral)

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The chalcedone (latinized form of ) or in Germanized inscription chalcedone is a micro- to cryptocrystalline microstructure variety of the mineral quartz.

According to older sources, the term chalcedone applies to all fibrous forms of microcrystalline quartz (including quartz), to all weakly to not at all colored, massive occurrences of microcrystalline SiO2 or is used as a generic term for all manifestations of finely crystalline quartz (fleet, hornstone, agate, onyx, jasper ...). In fact, these are rocks consisting of various microstructure varieties of quartz, the SiO2 modifications Mogánite and other coloring impurities. In modern mineralogy, the term chalcedone is narrowed (see structure).

Chalcedone is colorless to bluish gray. Impurities cause a wide variety of colorations, usually brown, reddish or green. Chalcedone is translucent, cloudy, has a waxy shine and, with a Mohs hardness of 6.5–7, is almost as hard as quartz.

For other shades, different names are used. Red to brown chalcedones are known as carnelol (sarder), the green variety colored by nickel oxide is called chrysoprase (artificially colored are called green-dressed agate) or plasma, emerald-green chalcedones obtained by iron oxide their dark green color.
Plasma is sometimes found with small jasper dots that resemble blood drops, which is why it is called heliotrope (blood jasper) or misleadingly bloodstone. The mineral widely known as bloodstone is hematite, an iron oxide.

Other names found for chalcedone are jasponix, massik, quartz, zoesit, blue or California moonstone and milkstone.

Etymology and History
The name first appeared with Pliny the Elder in his Latin Naturalis Historia (around 77 AD). He names a stone called “Calchedon” under a list of translucent jasper species. The reddish-sparkling, but slightly blackened stone "Carchedon" (English: the Carthaginian; possibly it is garnet) was also identified with the chalcedon in the Middle Ages. This, along with the arguably around 95 N. The Greek word χαλκηδών (school Greek pronunciation chalkēdón), a hapax legomenon handed down only in a single ancient source, namely the revelation of John (John's apocalypse), where χαλκηδών denotes the third of the twelve stones in the foundation of the city wall of heavenly Jerusalem after the jasper and sapphire and before the emerald ():

The word was known in antiquity as the place name of the Bithynian port city Kalchedon, located at the southern exit of the Bosporus and still corresponds to the usual form of the place name χαλκηδών. In addition, the predominant form καλχηδών, especially in inscriptions