Hydroxyapophyllite-K with Prehnite

specimen number:
2102195

location:
Fairfax Quarry, Centreville, Virginia, USA

description:
A fine large thick pseudo-cubic lustrous and translucent crystal of hydroxylapophyllite 3.0 cm on edge coming off of a prehnite crystal matrix with numerous smaller crystals. This is in good condition and very nice for this classic North American locality and species.

The Fairfax Quarry, located near Centreville in Fairfax County, Virginia, is a classic American mineral locality renowned for its diverse suite of secondary minerals. Geologically, the quarry exploited a large diabase sill of the Culpeper Basin, which is part of the early Jurassic Central Atlantic Magmatic Province. As the cooling diabase underwent hydrothermal alteration, mineral-rich fluids filled fractures and vesicles, leading to the formation of high-quality zeolites and related silicates. The site is particularly famous for its exceptional specimens of hydroxyapophyllite-K, which typically occur as colorless to white, highly lustrous, blocky or tabular crystals often associated with green prehnite and delicate needles of byssolite. Historically, the quarry was an active producer of crushed stone for construction and road aggregate throughout the mid to late 20th century. While industrial operations have fluctuated over the decades, the locality remains a hallmark for Virginia mineralogy, specifically noted for the chemical purity and crystal clarity of its apophyllite group minerals.

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