Scrub Oaks Mine

PETROLOGYThe rare-earth rocks in the Scrub Oaks mine are distinctly coarser grained than the country rock and the typical magnetite ore; and they have sharp contacts with the granitic wall rocks. Magnetite ore containing rare earths consists mainly of magnetite, hematite, and quartz, and some reddish opalescent albite-oligoclase, perthite, antiperthite (Sims' microperthite and microantiperthite) and microline. The albite-oligoclase has partly replaced the other feldspars. Rare-earth minerals in dull brick-red aggregates of xenotime and synchysite and gray bastnaesite and сhevkinite constitute about

3 percent of the rocks. Microbreccias, partly healed by calcite veins that contain sulfides, are present throughout the rock. Calcite and rare-earth fluocarbonates constitute 2 to 5 percent of the rock. The rare-earth part of the pegmatite consists mainly of antiperthite, perthite, microline, and quartz, and lesser amounts of magnetite and rare-earth minerals, hornblende, and biotite. Albite-oligoclase occurs as a replacement of antiperthite and perthite. The rock is spotted with aggregates of the gray and red rare-earth minerals. The microantiperthite granite wall rocks have been altered near the contacts with the rare-earth rock. Locally much epidote, albite-oligoclase with peculiar checkerboard twin pattern, calcite, and uralite have replaced the antiperthite and microline, suggesting an increase in sodium and calcium at.the expense of potassium. The amphibole and biotite have been altered to chlorite, which is clouded with finegrained inclusions of magnetite and hematite. Ghlorite-rich masses are particularly abundant at the contact between the rare-earth deposit and its wall rocks.

MINERALOGY

The rare-earth deposit consists of about 30 minerals, including the silicates and the iron and titanium oxides and sulfides. Most of the known minerals in the deposit are typical of the magnetite ore deposits, pegmatites, and late sulfide-carbonate veins of the Dover district. Potassium feldspar, plagioclase, quartz, and other silica-rich minerals are abundant, as well as magnetite and hematite. The minerals containing rare earths are synchysite, bastnaesite, xenotime, сhevkinite, zircon, sphene, apatite, and monazite. Some rare-earth minerals or aggregates in the deposit have not yet been identified. Other minerals that are minor constituents of the rocks are anatase, augite, biotite, bornite, chalcopyrite, chlorite, epidote, garnet, hornblende, ilmenite, pumpellyite(?), pyrite, rutile, spinel, sericite, and tremolite. The most distinctive feature of the deposit is the abundance of rareearth fluocarbonates and calcite. Minerals such as nepheline, sodalite, and soda pyroxenes that are common in other rare-earth deposits are absent.

References

1. https://pubs.usgs.gov/bul/1082b/report.pdf

2. RADIOACTIVE RARE-EARTH DEPOSIT AT SCRUB OAKS MINE, MORRIS COUNTY NEW JERSEY Paperback – 1959 by Harry Et Al Klemic (Author)

3. https://www.yumpu.com/la/document/view/49180511/morris-county-municipal-utilities-authority-scrub-oaks-mine-storage-