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Prase is a dull green to yellowish green variety of chalcedony, a cryptocrystalline quartz. It is commonly fashioned en cabochon to show off its leek-green color. Prase can be confused with chrysoprase since they are very similar in appearance, but a darker, less saturated color is typically indicative of prase.

Prase Polished
Prase Classification
Common Name Prase
Species Prase
Prase Optical Properties
Transparency Transparent - Semitranslucent
Dispersion Strength: None
Refractive Index 1.535-1.539
Birefringence 0.004
Optic Character Uniaxial
Optic Sign Positive
Polariscope Reaction Aggregate (AGG)
Fluorescence SWUV: Inert
LWUV: Inert
Pleochroism None
Prase Characteristic Physical Properties
Hardness 6.5-7
Streak White
Specific Gravity 2.550-2.700 Typical:2.600
Toughness Excellent
Inclusions Prase's green color is due to chlorite inclusions, the grayish green color is due actinolite fibers and the blue color is due to crocidolite fibers.
Luster Vitreous, Greasy
Stability Good
Fracture Conchoidal, Granular
Cleavage None
Prase Chemistry & Crystallography
Chemical Name silicon dioxide (aka silica)
Chemical Formula SiO2
Crystal System Trigonal
Chemistry Classification Silicate

Prase Colors

  • Green Prase Green

Countries of Origin

Ecuador; United States of America (the); Spain; Greece; Austria; Morocco; China; Ireland; Russian Federation (the); Brazil; Italy; Australia; Bulgaria; France; Germany; Nepal; United Kingdom of Great Britain and Northern Ireland (the)


Normal care

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This page was created on June 27, 2014.

This page was last edited on October 24, 2019.