AskDefine | Define prase

User Contributed Dictionary

Czech

Etymology

Proto-Slavic *porsę (piglet). Compare Slovak prasa, Polish prosię, Slovene prašič, Bulgarian прасе, Russian поросёнок.

Pronunciation

Noun

  1. pig

Declension

Extensive Definition

Chrysoprase or chrysophrase is a gemstone variety of chalcedony (a cryptocrystalline form of silica) that contains small quantities of nickel. Its color is normally apple-green, but varies to deep green. 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.)
Chrysoprase is cryptocrystalline, which means that it is composed of crystals so fine that they cannot be seen as distinct particles under normal magnification. This sets it apart from rock crystal, amethyst, citrine, and the other varieties of crystalline quartz which are basically transparent and formed from easily recognized six-sided crystals. Other members of the cryptocrystalline silica family include agate, carnelian, and onyx. Unlike many non-transparent silica minerals, it is the color of chrysoprase, rather than any pattern of markings, that makes it desirable. The word chrysoprase comes from the Greek chrysos meaning 'gold' and prason, meaning 'leek'.
Unlike emerald which owes its green color to the presence of chromium, the color of chrysoprase is due to trace amounts of nickel in the structure. The nickel reportedly occurs as platelets of the talc-like mineral willemsite. Chrysoprase results from the deep weathering or lateritization of nickeliferous serpentinites or other ultramafic ophiolite rocks. In the Australian deposits, chrysoprase occurs as veins and nodules with brown goethite and other iron oxides in the magnesite-rich saprolite below an iron and silica cap.
As with all forms of chalcedony, chrysoprase has a hardness of 6 - 7 on the Mohs hardness scale and a conchoidal fracture like flint.
The best known sources of chrysoprase are Queensland, Western Australia, Germany, Poland, Russia, Arizona, California, and Brazil.

References and external links

prase in Breton: Kryzopras
prase in Catalan: Crisopras
prase in Danish: Krysopras
prase in German: Chrysopras
prase in Spanish: Crisoprasa
prase in Esperanto: Krizopraso
prase in French: Chrysoprase
prase in Italian: Crisoprasio
prase in Hebrew: כריזופראס
prase in Dutch: Chrysopraas
prase in Japanese: クリソプレーズ
prase in Portuguese: Crisoprase
prase in Sicilian: Crisoprasu
prase in Slovak: Chryzopras
prase in Swedish: Krysopras
prase in Turkish: Krizopras
prase in Chinese: 绿玉髓
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