Prehnite

Prehnite is a gorgeous mineral which often occurs in stalactites or in botryoidal formations. It is often green or clear, but pink, blue and orange pieces have been found too.

Some gem quality pieces have been faceted for jewellery making. It is also polished for tumblestones, cabochons, etc. Some pieces have needle-like inclusions of Epidote.

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Appearance, Uses and History

Prehnite is often used as an inexpensive gemstone. This was not always the case, though. Recent finds of Prehnite in gem qualities have significantly lowered the price of the material.

It is not widely used in mainstream jewellery, however. It is almost always cut en cabochon, with some rare faceted stones available. Some pieces may show ‘cats eye’ asterism.

Locales

Nice specimens have been found in Australia, China, Czechia, France, Germany, India, Italy, Kazakhstan, Mali, Mexico, Morocco, Namibia, Pakistan, Russia, Spain, Switzerland, and the United States.

Mineralogy

Chemistry
Calcium aluminium silicate, sometimes with Iron. Ca2Al2Si3O10(OH)2+Fe
Colours and Variations
Usually pale green, light green, etc – usually translucent.
May also be yellow-green, brown-green, blue-green. In rare cases, it can be colourless, red, orange, etc.
Often found with inclusions of Epidote.
Streak
Colourless
Luster
Vitreous to pearly to waxy
Fracture
Uneven to conchoidal
Crystal habit
Usually fibrous, can be globular, stalactitic, botryoidal.
Mohs hardness
6.0 – 6.5
Specific Gravity
2.8 – 3.0
Easiest testing method
Common Treatments

Hazards and Warnings

Almost all rocks, minerals (and, frankly, almost all other substances on earth) can produce toxic dust when cutting, which can cause serious respiratory conditions including silicosis.

When cutting or polishing rocks, minerals, shells, etc, all work should be done wet to minimise the dust, and a suitable respirator or extraction system should be used.

Translations

Arabic:

Hindi:

Portuguese:

Bengali:

Indonesian:

Punjabi:

English:

Italian:

Russian:

  • пренит

French:

  • préhnite

Japanese:

  • プレナイト

Spanish:

  • prehnita

German:

  • Prehnit

Korean:

  • 프레 나이트

Thai:

Gujurati:

Mandarin and Traditional Chinese:

  • 葡萄石

Urdu:

Further Reading / External Links