Lockwood, Byram Township, Sussex Co., New Jersey, USA

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Ref.: The Minerals of New York City & Its Environs, New York Mineralogical Club Bull., Vol. 3, No. 1, Manchester, J.G. (1931): 79.

Lockwood is an area around the intersection of Rt. 206 and Watreloo road, just north of Stanhope. The area is underlain by granitic rocks of the Losee Metamorphic Suite and pyroxene synenite gneiss . However, the minerals listed for Lockwood are typical of the Franklin marble and, for the most part, could only have come from that unit or a similar one. Lockwood is 9 airline miles southwest of Lime Crest and 10 miles from the southern end of the main outcrop belt of the Franklin marble. Precambrian marble outcrops sporadically along the northwest margin of the Reading Prong highlands southwestward into Pennsylvania. Many of these areas are small and poorly exposed. Their precise relationship to the Franklin marble is uncertain. Two small areas of marble, in close proximity to each other, outcrop a short distance north of Lockwood.

The nearest marble outcrop is approximately 5400 feet north of the Rt. 206 and Watreloo road intersection and a few hundred feet east of Rt. 206, in the quarry now operated by Tilcon. This marble is associated with calc silicate rocks including diopsidite and a scapolite-amphibole gneiss. The outcrop of this group of lithologies is small, 500 X 300 feet and is surrounded by granitic intrusive rocks. In exposures available in the 1980’s and 90’s the calcite ranged from near white to salmon. Euhedral crystals of diopside, up to 2 inches , were common. These crystals were typically light green and contained inclusions of a light to moderate brown mica, probably phlogopite.

The largest diopside crystals, up to 4 or 5 inches, came from a transition zone between marble and diopsidite. Locally the diopsidite contained enough coarsely crystalline calcite to allow the development and recovery of euhedral crystals. In this material much of the diopside was superficially altered to fiberous amphibole. Apatite was locally abundant. The crystals ranged up to 3 inches, were often crude and distorted by deformation and were typically dull, off white with a vaguely purplish gray cast. The diopsidite also contained a dark, coarsely crystalline mica, possibly phlogopite but more likely biotite. Most of the diopsidite was coarsely crystalline, massive and did not have a gneissic texture.

Beyond the diopsidite was an amphibolite containing tiny, blue, subhedral apatite grains. This rock had a gneissic texture for the most part but contained areas that did not.

This author has never seen spinel, chondrodite, talc or graphite in the quarry exposure.

Beginning approximately 2000 feet northwest of the quarry outcrop is a poorly exposed band of marble. This band is mostly on the west side of Rt. 206 and extends north to Cranberry Lake. (Volkert, et al, 1989). The southern portion of this marble band is far enough from the highway that it was not exposed during an extensive road project that took place in recent years. There were limited exposures in a commercial development excavation.

The nature and collecting history of this marble band is unclear. It seems likely that any specimens collected in this more northerly marble area, especially in the era preceding extensive automobile travel, would have been assigned to Cranberry Lake, which could be reached by railroad and was in much closer proximity to this marble band than Lockwood.

Ref’s: Volkert, R. A., Monteverde, D. H., and Drake, A. A., Jr., 1989, Geologic Map of the Stanhope Quadrangle, Morris and Sussex Counties, New Jersey: U. S. Geological Survey Geological Quadrangle Map GQ-1671, scale 1:24000.


Drake, A. A., Jr., 1984, The Reading Prong of New Jersey and Eastern Pennsylvania: An Appraisal of Rock Relations anjd Chemistry of a Major Proterozoic Terrane in the Appalachians, in Bartholomew, M. J., ed., The Grenville Event in the Appalachians and Related Topics: Geol. Soc. of Amer. Special Paper 194, p.75-109.

Mineral List

Augite Calcite

Chondrodite Graphite

Phlogopite Quartz

Spinel Talc

8 entries listed. 8 valid minerals.