A quarry in Precambrian gneissic rock. Located East of State route 23 and North of State route 94.

Hamburg Quarry, currently (2007) operated by Eastern Concrete Materials, Inc. is located 5000 feet north of the intersection of Routes 23 and 94, just beyond the northern edge of the Boro. of Hamburg in Hardyston Township, New Jersey. The quarry is excavated in rocks of the Losee Metamorphic Suite (Volkert and Drake, 1999 ), a collection of lithologies that, at this location, is predominantly granulite facies quartz oligoclase gneiss, with local streaks of amphibolite, and post orogenic pegmatites. Along the margins of the property, especially along the northwest side of the old quarry, now mostly filled with slimes from the sand plant, the very sharp unconformity between the Proterozoic metamorphic rocks and the overlying Cambrian Leithville dolomite is well exposed. At Hamburg Quarry the Leithsville formation rests directly on the Precambrian rocks. The Hardyston Quartzite is essentially absent, represented only by abundant sand grains in the lowermost few inches of the dolomite.

Mineralogical interest in this quarry has only come about in the last few years. Sometime prior to 1996 a fracture filling vein of very coarsely crystalline, pinkish orange (salmon) calcite was exposed. Quarrying eventually exposed a strike length of over 2000 feet. Flanking this vein the gneiss was replaced by a banded skarn. The inner band was composed mainly of pyroxene (diopside – hedenburgite) with variable amounts of biotite and quartz. Locally, additional minor components of the mineral assemblage included pyrite, sphene, zircon and molybdenite. At the inner margin of the inner band and in the adjacent calcite vein filling, apatite was locally abundant. Apatite and pyroxene occurred as euhedral crystals up to 3 inches.

The outer band of the skarn is composed almost entirely of scapolite. The scapolite contains scattered, small, ragged inclusions of gneiss. The transition into unaltered gneiss, at the outer edge of the skarn, is abrupt.

The calcite-apatite-pyroxene vein at Hamburg Quarry bears many similarities to the carbonatitic vein-dikes of Quebec and Ontario, Canada (Lentz, 1998). In this author’s experience the visual similarities between the Hamburg Quarry vein and the Matte Zone at Yates Uranium Mine, north of Otter Lake, Que. are striking. Like the Canadian examples the Hamburg Quarry vein was likely emplaced during the period 1000 – 950 Ma when the region was intruded by pegmatites and experienced widespread hydrothermal activity (Volkert, et al, 2005)

In the current workings (late 2007) of the pit the vein seems to have terminated. New exposures of the down dip extension will probably be found if and when another lower level is begun.

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