Prehnite with Fluorapophyllite-K

specimen number:
2072289

location:
Eagle Rock Quarry, Roseland, New Jersey, USA

description:
Light green crystallized prehnite covering the top of matrix with minor fluorapophyllite. In good condition.

The Eagle Rock Quarry, located in Roseland, Essex County, New Jersey, is situated within the First Watchung Mountain, a massive basaltic ridge formed during the Early Jurassic period. Geologically, the site consists of tholeiitic basalt flows where cooling-related gas vesicles and fractures were later mineralized by hydrothermal fluids, creating a rich suite of secondary silicates. The quarry is particularly noted for its specimens of prehnite, which occurs as translucent, pale green to apple-green botryoidal masses, and fluorapophyllite-K, which typically forms as sharp, colorless to white pearly crystals often perched atop the prehnite. Historically, the quarry was a major industrial operation focused on the extraction of trap rock for road construction and regional infrastructure projects. Industrial quarrying activities were most intensive during the mid-20th century, with the site being a prime destination for mineralogists and collectors from the 1940s through the 1970s. While large-scale commercial mining has since ceased and the area has undergone significant land redevelopment for office complexes and residential use, the material recovered during its active years remains a classic representation of the Watchung basalt mineralogy.

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