Prase Gem Guide and Properties Chart

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.

General Information

Classification
Optical Properties
Characteristic Physical Properties
Chemistry & Crystallography

Common Name

Prase

Species

Prase

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

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

Chemical Name

silicon dioxide (aka silica)

Chemical Formula

SiO₂

Crystal System

Trigonal

Chemistry Classification

Silicate

Prase Colors

Green

Countries of Origin

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

Care

Normal care