Unnamed pegmatites, Wildcat Ridge Wildlife Management Area, Rockaway Township, Morris County, New Jersey, USAi

Regional Level Types
Unnamed pegmatites	- not defined -
Wildcat Ridge Wildlife Management Area	Area
Rockaway Township	Township
Morris County	County
New Jersey	State
USA	Country

Ref.: http://www.njfishandwildlife.com/wldcthwk.htm

The Wildcat Ridge Wildlife Management Area is best known as a major watch site for hawk migrations (The view from the observation deck is very fine). Mineralogically, the area is best known for its iron mines but granite pegmatites are quite common. According to John C. Puffer ("Iron Ore Deposits of the New Jersey Highlands" - a guidebook) the "magnetite concentrations of the New Jersey Highlands are emplaced in a Precambrian complex of metamorphic and igneous rocks." "The Precambrian rock units include Granite, Quartz-Oligoclase Gneiss, Pyroxene Gneiss, Amphibolite, and Marble."

Some of the pegmatites are very coarsely crystallized but they are all very "tight" (open cavities are not present). Consequently, any euhedral crystals are always embedded and very difficult to extract undamaged.

The primary mineral of interest is zircon, which is found in light reddish brown (and highly fluorescent) to almost black (and non fluorescent), doubly terminated prisms up to 5.5 cm.

On one occasion a large mass of allanite was found. This pegmatite was exposed during blasting for a house foundation. The allanite is somewhat metamict but provided a sufficiently clear XRD pattern. Presumably it is allanite-(Ce) but no chemistry was done. (This pegmatite was actually just south of the current Management Area boundary.)

The pegmatite mineralogy is usually very simple: feldspar and (ferro)hornblende. Quartz occurs in very large, but completely anhedral, milky concentrations. Other minerals encountered are large books of biotite, badly weathered apatite, totally altered garnets, and ilmenite (near the magnetite veins). Some large (50+ cm) parting planes in relatively fine grained gray granite from another construction site fluoresced bright green - presumably due to uranium salts. Nothing was visible even under a scope.

If you go there now you are more likely to find copperhead snakes (shy but poisonous), black bears (with cubs - Grrr!), ticks (Lyme disease infested) and deer flies (very hungry), than to find collectible specimens.

The area is slightly to the north of the terminal moraine of the last continental glaciation and has been scraped clean of most of its soil. Nevertheless, most pegmatites show only small outcrops above ground. In some cases it is difficult to tell if a specimen comes from a nearby pegmatite or is a glacial erratic that has been carried a long way.

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