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Prasiolite  (variety of Quartz)
Current inventory:  0 gems
 

  
Prasiolite is named from the Greek words prasio meaning leek, referring to the vegetable's green color, and lithos for stone.

Discovered in Prehistory;   IMA status: Not Valid (trade name).

Chemistry

Chemical Formula:

SiO₂  +  Fe²⁺

Silicon Dioxide  +  Iron

Molecular Weight:

60.08 gm (Quartz)

Composition: 

Classification

Mineral Classification:

Oxides

Strunz 8th Ed. ID:

4/D.01-10

Nickel-Strunz 10th Ed. ID:

4.DA.05

4 : OXIDES (Hydroxides, V[5,6] vanadates, arsenites, antimonites, bismuthites, sulfites, selenites, tellurites, iodates)
D : Metal: Oxygen = 1:2 and similar
A : With small cations: Silica family

Related to:

Quartz Group

Synonyms:

Green Quartz

Crystal Data

Crystallography:

Trigonal - Trapezohedal

Crystal Habit:

Widely variable; but typically long prismatic with steep pyramidal terminations, but may be short prismatic to nearly bipyramidal; fibrous (Agate & Chalcedony)

Twinning:

Very common, penetration twins on the Dauphiné law, about [0001], and the Brazil law, with [1120] as contact plane; contact twins on the Japan law, with [1122] as contact plane, may be repeated; and several other laws.

Physical Properties

Cleavage:

[0110] Indistinct

Fracture:

Conchoidal

Tenacity:

Brittle, tough when massive

Moh's Hardness:

7.0

Density:

2.60 - 2.65 (g/cm³)

Luminescence:

may be Triboluminescent

Radioactivity:

Not Radioactive

Other:

Piezoelectric and Pyroelectric

Optical Properties

Color:

Medium to Dark Green, Olive Green

Transparency:

Transparent to nearly Opaque

Luster:

Vitreous, waxy to dull when massive

Refractive Index:

1.540 - 1.553  Uniaxial ( + )

Birefringence:

0.0090

Dispersion:

0.013 (low)

Pleochroism:

None

Occurances

Geological Setting:

In hydrothermal veins, epithermal to alpine; characteristic of granites and granite pegmatites; in sandstones and quartzites, less abundant in other rock types; in hydrothermal metal deposits. Common in carbonate rocks; a residual mineral in soils and sediments.

Common Associations:

Calcite, Chlorite, Epidote, Feldspars, Fluorite, Micas, Zeolites, many other species.

Type Locality:

n/a

Year Discovered:

Prehistoric

View mineral photos:

Quartz Mineral Photos and Locations

More Information

Mindat.org  (Quartz)
Webmineral.com  (Quartz)

Prasiolite is the green variety of the macro-crystalline Quartz Group of minerals that also includes Amethyst, Ametrine, Citrine, Rose Quartz and Smoky Quartz. Prasiolite is a green, macro-crystalline variety of Quartz with fairly large, well formed crystals, whereas Chrysoprase is a green cryptocrystalline variety of Quartz, where the individual crystals are too small to be seen. The term prase is often wrongly used for any green Quartz and is from the Greek word prasinon (or prason) meaning leek, referring to the vegetable's green color.

Most Prasiolite gems on the market are irradiated or heat treated Amethyst. These heated gems are often refered to as "green amethyst" or "vermarine" but are not true Prasiolite. Naturally occuring Prasiolite is actually quite rare. Natural Prasiolite gets its green color from iron (Fe²⁺) compounds in the chemical mixture. Some colorless quartz crystals contain green Chlorite inclusions or phantoms. These would not be considered Prasiolite however.

Natural Prasiolite crystals are known to be found in Southern Bahia and Minas Gerais, Brazil; and Lower Silesia in Poland.
 

  
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