Latitude: 40°22'16"N
Longitude: 74°47'15"W
This is one of several baryte occurrences in west-central New Jersey and adjacent Pennsylvania. The mine is located just off Stoney Brook Road, across from the Stoney Brook Golf Course, between Stoney Brook and the Conrail (Reading) Railroad tracks. It is slightly less than 2000 feet north of the former Moore's Station on the Reading Railroad. The site is marked by a leaf-filled pit, a collapsed shaft, and a small dump. 30 years ago fragments of the barite ore, often 6 to 8 inches, were fairly common scattered in the nearby woods. Now these are rare. Material is still abundant on the small dump adjacent to the collapsed shaft.
The Hopewell Barite Mine is a fracture filling in a fault associated with the Hopewell Fault, a major intrabasin fracture that passes approximately 1/2 mile north of the locality. The vein filling is baryte and subordinate quartz with minor chloritized gouge. Deposition occurred while fault movement was active. The baryte is brecciated and rehealed. Open cavities with free standing crystals are uncommon.
Surface outcrops at the site are nonexistent. The area is underlain by the upper-middle portion of the Passaic formation and by a small mass of diabase. The vein prospected at this site was in diabase. Many fragments on the dump contain altered diabase wall rock. Perhaps a vein wide enough to attract attention developed here because of contrasting competency between the diabase and the sedimentary mudstones.
Nearly all the baryte localities in the Newark Basin are in the lower portion of the stratigraphic section. It may be that the older units contained less saline formation brines, at least less sulphate-rich. This allowed barium to be mobile. The upper part of the Passaic formation was deposited in a drier, more saline environment as evidenced by numerous layers containing evaporite casts (gypsum, glauberite). Barium-bearing solutions that encountered the more sulphate-rich brines deposited baryte.
References
New Jersey State Geologist Annual Report (1893): 433.
Mineral List
3 entries listed. 2 valid minerals.
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