Prehnite after Laumontite with Gyrolite

specimen number:
1115638

location:
Mumbai, Maharashtra, India

description:
Classic Indian specimen with crystallized prehnite replacing prismatic crystals of laumontite across the top of matrix. Gyrolite is present as well.

The prehnite after laumontite specimens from the Mumbai region of India form within the tholeiitic basalts of the Deccan Traps, specifically associated with the Salsette Subgroup. Geologically, these unique pseudomorphs developed during late-stage hydrothermal alteration and low-grade metamorphism, where mineral-rich fluids circulated through volcanic cavities and coated or replaced earlier-formed prismatic laumontite crystals with a durable layer of green prehnite. Historically, these mineral treasures have been uncovered primarily through industrial quarrying, road construction, and infrastructure expansion across the region, yielding world-class specimens prized by collectors globally.

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