Prasiolite Identification Guide
How to identify prasiolite (green amethyst), a leek-green quartz, by its transparency, hardness, and crystal habit, and how to separate it from peridot, green beryl, and prase.
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What Prasiolite Looks Like
Prasiolite, often marketed as "green amethyst," is a transparent pale leek-green to yellowish-green quartz, most of it produced by heat-treating amethyst or yellowish quartz from specific deposits (natural prasiolite is rare). It has a vitreous luster, is transparent, and shows quartz's typical hexagonal prismatic crystals when in crystal form, often cut as faceted gems. The color is usually soft and slightly minty.
Step-by-Step Field ID Checklist
- Confirm quartz. Hardness 7 (scratches glass and steel), conchoidal fracture, no cleavage.
- Note the pale green. A soft, even leek-green to mint tone is typical; deep saturated green suggests a different stone.
- Check crystal habit. Hexagonal prisms with rhombohedral terminations confirm quartz.
- Look for weak pleochroism. Quartz shows little to none, helping rule out strongly pleochroic gems.
- Assess clarity. Usually eye-clean and transparent, unlike opaque prase.
Key Diagnostic Tests
- Mohs hardness: 7 — scratches glass and steel.
- Cleavage: None; conchoidal fracture.
- Streak: White.
- Specific gravity: About 2.65.
- Refractive index: Low (~1.54–1.55), with weak birefringence.
- Acid: No reaction to dilute HCl.
Common Look-Alikes and How to Tell Them Apart
- Peridot: Brighter olive-green, strongly doubly refractive (back facets appear doubled), denser (SG ~3.3), and only Mohs 6.5–7; prasiolite is single-toned with weak doubling.
- Green beryl/emerald: Higher hardness (7.5–8), higher density, hexagonal but different RI; emerald is usably included.
- Green tourmaline: Strong pleochroism, triangular striated prisms; prasiolite is hexagonal with weak pleochroism.
- Prase: Opaque to translucent, dull inclusion-colored quartz; prasiolite is transparent and evenly colored.
- Green glass: May show bubbles, mold marks, warm to touch, and is softer (~5.5); won't scratch quartz.
Where Prasiolite Is Found
Most commercial prasiolite is heat-treated amethyst from Montezuma, Minas Gerais (Brazil) and from Arizona (USA). Rare naturally green prasiolite has been reported from Poland (Lower Silesia), Brazil, and Canada (Thunder Bay area).
Frequently asked questions
What is prasiolite?
Prasiolite, also called green amethyst, is a transparent leek-green to yellow-green quartz, most of which is produced by heat-treating amethyst or yellow quartz, since natural prasiolite is rare.
How can you tell if it's real prasiolite?
Confirm quartz hardness of 7, conchoidal fracture, no cleavage, a soft transparent green color, low refractive index with weak doubling, and a white streak. These rule out peridot, beryl, and glass.
Prasiolite vs peridot: how do you tell them apart?
Peridot is a brighter olive-green, denser, and strongly doubly refractive so back facets look doubled, while prasiolite has a softer green and only weak birefringence.
Is prasiolite natural or treated?
Most prasiolite on the market is heat-treated amethyst from Brazil or Arizona. Naturally green prasiolite exists but is rare, reported from Poland, Brazil, and Canada.
Prasiolite identified by the community
Recent Prasiolite specimens identified with Rock Identifier.
