Prehnite is an orthorhombic mineral which is rarely found as distinct crystals. Found in association with volcanic rocks, it usually forms in aggregates with botryoidal habit. Prehnite is typically pale green to yellowish green with a white streak. It is named after a Dutchman, Colonel H. von Prehn, who discovered the mineral at the Cape of Good Hope, South Africa, and brought the first specimens to Europe.
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| Known Facts |
| Color Key: |
yellow green, brown, yellow brown, oil green |
| Refractive Index: |
1.61 - 1.64 |
| Chemical Composition: |
(CA2Al2SI3O10(OH)2) |
| Hardness: |
6 |
| Density: |
2.80 - 2.95 |
| Crystal Group: |
Orthorhombic |
| Ocurrence: |
China, France, U.S.A., Scotland, Australia |
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Prehnite occurs most commonly in veins and cavities in igneous rocks, often in association with zeolites. Prehnite is never clean enough to produce bright faceted gemstones but beautiful yellow to blue green cabochons can be cut from the right material. |
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