Stilbite

specimen number:
2102374

location:
Fairfax Quarry, Centreville,Fairfax Co., Virginia, USA

description:
Attractive orange sparkling lustrous crystals of stilbite across the top of matrix. In good condition and nice for this famous locality.

The Fairfax quarry (also known as the Centreville quarry), located along Route 29 near Centreville in Fairfax County, Virginia, was a massive open-pit industrial aggregate operation renowned among mineralogists for producing outstanding, world-class pocket specimens of prehnite, apophyllite, and byssolite-inclusion quartz. Geologically, the quarry was excavated into a thick Triassic-age diabase sill, a tabular igneous intrusion belonging to the Central Atlantic Magmatic Province that cut through sedimentary sandstones and shales of the Newark Supergroup. High-temperature hydrothermal fluids circulating through cooling fractures, shear zones, and extensive fault planes within the dense diabase deposited an abundance of secondary calcium-aluminum silicates, creating rich mineral-lined vugs filled with light-green botryoidal prehnite disks, prismatic apophyllite crystals, and fibrous actinolite networks. Historically, large-scale commercial open-pit quarrying commenced at the site in the early twentieth century, specifically around 1934, operating under corporate names like the Fairfax Quarries Company and later the Vulcan Materials Company to supply crushed diabase stone for regional highway construction and concrete production. Underground and surface blasting regularly breached spectacular mineral pockets from the 1960s through the 1980s, attracting intense field-collecting activity from local mineral clubs and research institutions until active quarrying operations officially ceased and the site was reclaimed in the late 1990s. Following its closure, the deep pit was systematically converted into a stabilized municipal water storage reservoir for the Fairfax County Water Authority, an infrastructure role it continues to fulfill through 2026.

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