Prase
A variety of Quartz
What is Prase?
The term "prase" refers to a translucent, leek-green type of quartz, most commonly quartzite, but also some true quartzes and jaspers of similar color. The term is no longer considered to have much scientific meaning, since it covers so many differing types of rocks. Stones of this beautiful color have been carved for decorative purposes since ancient Greece.
Uses & Applications
The second-most valuable variety of chalcedony, prase was a known gem in the times of ancient Greeks and Romans. Today, it is mostly used for making attractive green cabochons and beads. Sometimes pieces of prase are clear enough to be cut into faceted stones. Its availability in the market is limited.
Optical Properties
- Refractive Index
- 1.544-1.553
- Birefringence
- 0.009
- Pleochroism
- Weakly dichroic
- Optical Character
- Biaxial positive
- Dispersion
- 0.013
Market Value Factors
Pricing varies for every rock and mineral, so use these universal factors to gauge Prase before comparing listings or appraisals.
Size & Weight
Larger, intact specimens usually command higher prices.
Rarity & Demand
Scarce material or popular varieties sell at a premium.
Condition & Finish
Chips, repairs, and heavy wear lower value; clean prep helps.
Treatment & Provenance
Untreated specimens with documented locality are prized.
Prase Localities Map
See where Prase is found with a localities map, collecting zones, and geology context. Generate a sample map preview below.
The Meaning
During the Middle Ages, it was believed that this stone had healing and protective properties.
Health & Safety Information
- ⚠️Prase in powdered form can be toxic due to its Crystalline Silica content.
- ⚠️Quartz, silica, crystalline silica and flint are non-toxic materials, but very fine dust containing quartz, known as respirable crystalline silicon (RCS), can cause serious and fatal lung disease. Lapidaries should exercise caution when cutting silica.
- ⚠️Prase is typically non-toxic unless it's in powder form. Long-term exposure to finely ground powder may lead to silicosis. Therefore, when cutting or polishing prase, be sure to wear a dust mask to avoid inhaling its dust.
Quick Facts
Physical Properties
- Color
- Leek-green
- Hardness (Mohs)
- 6.5 - 7
- Density
- 2.64 - 2.69 g/cm³
- Streak
- White
- Luster
- Greasy, Vitreous
- Crystal System
- Trigonal
Chemical Properties
- Chemical Formula
- SiO2
- Elements
- Si, O
Also Known As
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Prase FAQs
How do I identify Prase?
Prase can be identified by its hardness of 6.5 - 7 on the Mohs scale, Leek-green color, Greasy, Vitreous luster, Trigonal crystal system. Look for these key characteristics when examining specimens.
What color is Prase?
Prase typically appears in Leek-green. Color can vary depending on impurities and formation conditions.
How hard is Prase?
Prase has a hardness of 6.5 - 7 on the Mohs scale. This gives it moderate hardness.
