Where is Prehnite found?
Ca2Al2Si3O10(OH)2
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Open the appPrehnite occurs in specific geological environments. Knowing where to look, and in what kind of rock, is the difference between going home empty-handed and finding a great specimen.
Where to find Prehnite
Karoo Basin, South Africa
Famous for producing large, high-quality botryoidal prehnite specimens, often associated with zeolites in basaltic amygdales.
New Jersey, USA
Notable localities include the Paterson and Prospect Park quarries, where prehnite occurs in diabase sills, often with copper minerals and zeolites.
Australia
Various localities, particularly in the Northern Territory and Western Australia, yield fine prehnite specimens, sometimes with epidote.
China
Several provinces, including Sichuan and Yunnan, produce significant quantities of prehnite, often in attractive botryoidal forms.
India
The Deccan Traps basalts are a source of prehnite, often found in association with other secondary minerals.
Scotland, UK
Occurrences in the Tertiary volcanic rocks, such as on the Isle of Skye.
Collecting tips
- Look in Mafic Igneous Rocks. Focus your search on areas with basalt, diabase, or gabbro, particularly in vesicles, amygdules, and fracture fillings.
- Hydrothermal Veins. Examine hydrothermal veins in metamorphic and igneous terrains, as prehnite can precipitate from circulating fluids.
- Associated Minerals. Prehnite often occurs with zeolites (e.g., stilbite, heulandite), calcite, epidote, datolite, and native copper. Finding these minerals can indicate the presence of prehnite.
- Botryoidal Habit. Keep an eye out for grape-like or kidney-shaped aggregates, which are characteristic forms of prehnite.
- Color and Luster. The pale green to yellowish-green color and vitreous to pearly luster are good indicators.
Quick Check
- Color:
- Pale green to yellowish-green, white, gray, colorless
- Luster:
- Vitreous to pearly
- Streak:
- White
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