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Unnamed pegmatites, Wildcat Ridge Wildlife Management Area, Rockaway Township, Morris Co., New Jersey, USA

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Latitude & Longitude (WGS84): 40° 56' 0'' North , 74° 29' 30'' West
Latitude & Longitude (decimal): 40.93333,-74.49167
GeoHash:G#: dr70bgsvf
Köppen climate type:Cfa : Humid subtropical climate

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.

Select Mineral List Type

Standard Detailed Strunz Dana Chemical Elements

Mineral List

3 valid minerals.

Detailed Mineral List:

'Allanite Group'
Formula: {A12+REE3+}{M3+2M32+}(Si2O7)(SiO4)O(OH)
Reference: XRD via Morris Museum resource
Reference: Mr. Modris Baum.
Reference: Mr. Modris Baum.
'Garnet Group'
Formula: X3Z2(SiO4)3
Reference: Mr. Modris Baum.
Reference: Mr. Modris Baum.
Formula: Fe2+TiO3
Reference: Mr. Modris Baum.
Formula: SiO2
Reference: Mr. Modris Baum.
Quartz var: Milky Quartz
Formula: SiO2
Reference: Mr. Modris Baum.
Formula: Zr(SiO4)
Reference: Mr. Modris Baum.

List of minerals arranged by Strunz 10th Edition classification

Group 4 - Oxides and Hydroxides
var: Milky Quartz4.DA.05SiO2
Group 9 - Silicates
Unclassified Minerals, Rocks, etc.
'Allanite Group'-{A12+REE3+}{M3+2M32+}(Si2O7)(SiO4)O(OH)
'Garnet Group'-X3Z2(SiO4)3

List of minerals arranged by Dana 8th Edition classification

Group 51 - NESOSILICATES Insular SiO4 Groups Only
Insular SiO4 Groups Only with cations in >[6] coordination
Group 75 - TECTOSILICATES Si Tetrahedral Frameworks
Si Tetrahedral Frameworks - SiO2 with [4] coordinated Si
Unclassified Minerals, Rocks, etc.
'Allanite Group'-{A12+REE3+}{M3+2M32+}(Si2O7)(SiO4)O(OH)
'Garnet Group'-X3Z2(SiO4)3
var: Milky Quartz

List of minerals for each chemical element

H Allanite Group{A12+REE3+}{M23+M32+}(Si2O7)(SiO4)O(OH)
O Allanite Group{A12+REE3+}{M23+M32+}(Si2O7)(SiO4)O(OH)
O Garnet GroupX3Z2(SiO4)3
O IlmeniteFe2+TiO3
O Quartz (var: Milky Quartz)SiO2
O QuartzSiO2
O ZirconZr(SiO4)
Si Allanite Group{A12+REE3+}{M23+M32+}(Si2O7)(SiO4)O(OH)
Si Garnet GroupX3Z2(SiO4)3
Si Quartz (var: Milky Quartz)SiO2
Si QuartzSiO2
Si ZirconZr(SiO4)
Ti IlmeniteFe2+TiO3
Fe IlmeniteFe2+TiO3
Zr ZirconZr(SiO4)

Regional Geology

This geological map and associated information on rock units at or nearby to the coordinates given for this locality is based on relatively small scale geological maps provided by various national Geological Surveys. This does not necessarily represent the complete geology at this locality but it gives a background for the region in which it is found.

Click on geological units on the map for more information. Click here to view full-screen map on Macrostrat.org

1000 - 1200 Ma

ID: 2915959
Hornblende Granite

Age: Stenian (1000 - 1200 Ma)

Stratigraphic Name: Byram Intrusive Suite

Description: Pinkish-gray- to medium-buff-weathering, pinkish-white or light-pinkish-gray, medium- to coarse-grained, gneissoid to indistinctly foliated granite and sparse granite gneiss composed principally of microcline microperthite, quartz, oligoclase, and hornblende. Some phases are quartz syenite or quartz monzonite. Includes small bodies of pegmatite and amphibolite not shown on map. U-Pb age approximately 1,090 Ma (Drake and others, 1991b).

Comments: Byram Intrusive Suite (Middle Proterozoic) (Drake, 1984) Original map source: Dalton, R.F., Herman, G.C., Monteverde, D.H., Pristas, R.S., Sugarman, P.J., and Volkert, R.A., 1999, New Jersey Department of Environmental Protection, Bedrock Geology and Topographic Base Maps of New Jersey: New Jersey Geological Survey CD Series CD 00

Lithology: Major:{granite}, Minor:{gneiss,quartz syenite,quartz monzonite}, Incidental:{pegmatite, amphibolite}

Reference: Horton, J.D., C.A. San Juan, and D.B. Stoeser. The State Geologic Map Compilation (SGMC) geodatabase of the conterminous United States. doi: 10.3133/ds1052. U.S. Geological Survey Data Series 1052. [133]

1000 - 1600 Ma

ID: 3188605
Mesoproterozoic crystalline metamorphic rocks

Age: Mesoproterozoic (1000 - 1600 Ma)

Lithology: Paragneiss; paragneiss

Reference: Chorlton, L.B. Generalized geology of the world: bedrock domains and major faults in GIS format: a small-scale world geology map with an extended geological attribute database. doi: 10.4095/223767. Geological Survey of Canada, Open File 5529. [154]

Data and map coding provided by Macrostrat.org, used under Creative Commons Attribution 4.0 License

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