What is prehnite?

Prehnite is a calcium aluminum phyllosilicate mineral with the formula Ca₂Al(AlSi₃O₁₀)(OH)₂.

  • Color: Prehnite is typically light green, but can also be found in yellow, brown, orange, pink, white, and gray. The green colors are attributed to the presence of iron impurities.

  • Hardness: It has a relatively low hardness, ranging from 6 to 6.5 on the Mohs scale. This means it can be scratched by quartz.

  • Luster: Prehnite exhibits a vitreous (glassy) to pearly luster.

  • Crystal System: It crystallizes in the orthorhombic crystal system, often forming botryoidal (grape-like) or reniform (kidney-shaped) aggregates. Well-formed crystals are rare.

  • Occurrence: Prehnite is a secondary mineral, typically found in cavities and veins of basaltic rocks and other low-grade metamorphic environments. It often occurs with other minerals such as zeolites, calcite, and datolite.

  • Notable Localities: Significant deposits are found in South Africa, Australia, China, Scotland and the USA.

  • Uses: Prehnite is sometimes used as a gemstone, particularly when it exhibits good color and translucency. It's also popular among mineral collectors. Some believe it has metaphysical properties, such as promoting unconditional love and healing.

  • Distinguishing Features: Prehnite is often recognized by its characteristic light green color, botryoidal habit, and association with zeolite minerals.

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