Prase
Silicon dioxide (SiO2)
An old name for a dull leek-green variety of quartz or chalcedony colored by green mineral inclusions, historically called mother of emerald.
- Mohs hardness
- 6.5-7
- Color
- Leek-green to dull grass-green
- Type
- crystal
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Overview
Prase is a traditional name for a translucent, leek-green to grass-green variety of quartz, including both microcrystalline chalcedony and crystalline quartz whose color comes from included green minerals such as actinolite, hedenbergite, or chlorite rather than from the silica itself.
The name derives from the Greek prasios, meaning leek-green. Historically, lapidaries called prase the mother of emerald because it was sometimes found alongside or mistaken for the precious green beryl. It has been used as a decorative and carving material since antiquity.
Prase should not be confused with prasiolite (green amethyst), a separate green quartz colored by iron rather than by mineral inclusions.
Formation & geology
Prase forms when silica crystallizes in environments rich in green ferromagnesian minerals. The green color is caused by myriad microscopic to fine fibrous inclusions of minerals like actinolite, hedenbergite, or chlorite that became enclosed as the quartz or chalcedony grew.
It occurs in metamorphic and contact-metamorphic settings, in skarns, and in hydrothermal veins where iron- and magnesium-bearing silicates coexisted with silica-rich fluids. Notable historic localities include the Serifos and other Greek islands, Austria, and Finland.
Because the color is inclusion-based, prase intensity varies with the density and type of included minerals, ranging from pale dull green to deep grass-green.
How to identify it
Prase appears as a translucent dull green stone with a vitreous to slightly waxy luster and a white streak. Hardness is about 6.5 to 7, and it shows conchoidal fracture with no cleavage, consistent with quartz.
Under magnification you can often see the fibrous or granular green inclusions responsible for the color, which helps separate it from prasiolite (uniform iron-colored green) and from chrysoprase (apple-green, colored by nickel, more evenly translucent).
It is harder than green serpentine or fluorite. Distinguish it from emerald by hardness and the dull, non-gemmy color: emerald is harder (7.5-8), more vividly green, and a beryl, not quartz.
Uses & significance
Historically prase was carved into seals, cabochons, beads, and ornamental objects, valued as an affordable green stone before brighter chrysoprase and chrome chalcedony became popular.
Today it is mostly a collector and lapidary curiosity, cut into cabochons and tumbled stones. Its toughness makes it suitable for jewelry, though its muted color limits commercial demand compared with brighter green quartzes.
In metaphysical circles prase is associated with calm, emotional healing, and connection to nature, though such uses are traditional rather than scientific.
Frequently asked questions
What gives prase its green color?
Tiny included green minerals such as actinolite, hedenbergite, or chlorite tint the quartz; the silica itself is colorless.
Is prase the same as prasiolite?
No. Prase is green from mineral inclusions, while prasiolite (green amethyst) is crystalline quartz colored green by iron, usually through heating amethyst.
Why is prase called mother of emerald?
Old lapidaries used the term because prase was sometimes found near or confused with emerald due to its green color.
Is prase a rare stone?
It is uncommon in the modern gem trade and mostly of interest to collectors, having been displaced by brighter green stones like chrysoprase.
How can I tell prase from chrysoprase?
Chrysoprase is a brighter, more even apple-green colored by nickel, while prase is a duller leek-green with visible mineral inclusions under magnification.
Prase guides
In-depth guides for identifying, valuing, and understanding Prase.
Prase identified by the community
Real specimens identified with Rock Identifier.
