Where is Prehnite found?
Ca2Al(AlSi3O10)(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
Historic localities like Paterson and Prospect Park are known for excellent prehnite specimens, often found in diabase quarries.
Australia
Various localities, particularly in the Northern Territory and Western Australia, yield significant prehnite occurrences, sometimes with epidote.
India
The Deccan Traps basalts are a source of prehnite, often found in association with other secondary minerals.
China
Several regions produce prehnite, including specimens with good crystal forms.
Collecting tips
- Look in Mafic Igneous Rocks. Focus your search on areas with basalt, gabbro, or diabase, especially where these rocks show signs of hydrothermal alteration or contain vugs and amygdales.
- Check Veins and Cavities. Prehnite commonly forms in open spaces within rocks. Look for veins, fractures, and cavities that may be lined with or filled by prehnite.
- Associated Minerals. Prehnite often occurs with other secondary minerals such as zeolites (e.g., stilbite, heulandite), calcite, epidote, and quartz. The presence of these minerals can be an indicator.
- Botryoidal Habit. The distinctive grape-like or kidney-shaped habit is a strong indicator for prehnite. Look for these rounded, often translucent masses.
- Color and Luster. The characteristic pale green to yellowish-green color and vitreous to pearly luster are key visual identifiers.
Quick Check
- Color:
- Pale green to yellowish-green (most common), white, gray, colorless
- Luster:
- Vitreous to pearly
- Streak:
- White
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