Hydroxyapophyllite-K with Prehnite - image 1

Hydroxyapophyllite-K with Prehnite

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Colorless blocky pseudo-cubic crystals of hydroxylapophyllite measuring to 0.8 cm in size across a prehnite crystal covered matrix. Some cleaving present as seen. The back of the piece is covered with crystallized prehnite as seen in the video.The Fairfax Quarry, located near Centreville in Fairfax County, Virginia, is a large-scale aggregate operation situated within the Culpeper Basin. Geologically, the site exploits a massive Diabase sill of Jurassic age that intruded into Triassic sedimentary rocks, creating an environment rich in calcium-silicate minerals through contact metamorphism and hydrothermal activity. The quarry is internationally famous for producing world-class specimens of hydroxylapophyllite-(K), which occur as colorless to white, highly lustrous, and often blocky or tabular crystals found within vugs and fractures of the dark diabase. Historically, industrial mining and quarrying at the site began in the early 1950s to provide crushed stone for the rapid suburban development and infrastructure of the Northern Virginia and Washington, D.C. regions. Operated for many years by Luck Stone Corporation, the facility has been a prolific source of diverse secondary minerals, including prehnite and various zeolites, alongside its signature hydroxylapophyllite. As of 2026, the Fairfax Quarry remains an active and vital producer of construction materials while maintaining its status as a premier East Coast locality for mineral collectors and researchers.