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French Creek Mines, St. Peters, Warwick Township, Chester Co., Pennsylvania, USA

This page kindly sponsored by Dragon Minerals
 
Latitude & Longitude (WGS84): 40° 10' 60'' North , 75° 43' 0'' West
Latitude & Longitude (decimal): 40.1833333333, -75.7166666667


This mine includes the old Klein (lower) and Elizabeth (upper) mines and the Crossley pits. Located near St. Peters. Dumps have produced specimens to now.

The French Creek iron ores are a “Cornwall type” iron ore deposit (Lapham and Gray, 1972). Many examples of this type of iron deposit, including two very large ones, occur in the east-west neck that connects the Newark and Gettysburg Basins. This neck is filled by late Triassic age clastic and lacustrian sediments and has been heavily intruded by thick sheets of early Jurassic age diabase.

The margins of the neck are complexly faulted. In some places the diabase intrudes the older country rocks on which the Triassic-Jurassic Basin has been superimposed. In most cases the intruded older rocks are Paleozoic shelf carbonates. In places where a diabase sheet intrudes into the complex basin margin and isolates a mass of carbonate rock above it the magnetite skarn of a Cornwall type iron deposit can develop. However, many aspects of the ore forming process remain to be resolved.

The French Creek ore deposit is a little different because the carbonate rock replaced by magnetite skarn is proterozoic marble (Smith, 1931). In the French Creek area the southern margin of the Triassic sediments rest on the Precambrian metamorphic rocks of the Honeybrook upland. The Precambrian rocks are graphitic biotite gneiss with a few local pods or bands of marble. The marble occurrences are similar to those in the eastern block of the Reading Prong Highlands in New Jersey and thhe adjacent Hudson Highlands in New York.

At French Creek Jurassic diabase intrudes the Honeybrook rocks that included two significantly large pods of marble. The smaller marble lens was in close proximity to the diabase while only the lower part of the larger lens was in contact with the intrusive rocks. The marble was replaced to varying degrees by magnetite skarn.

Mineral List

Mineral list contains entries from the region specified including sub-localities

56 valid minerals.

Localities in this Region

USA

The above list contains all mineral locality references listed on mindat.org. This does not claim to be a complete list. If you know of more minerals from this site, please register so you can add to our database. This locality information is for reference purposes only. You should never attempt to visit any sites listed in mindat.org without first ensuring that you have the permission of the land and/or mineral rights holders for access and that you are aware of all safety precautions necessary.

References

Grant (1974), Pennsylvania Minerals (PM)(134) (February), Keystone Newsletter.

Lapham, D.M., and Gray, C., 1972, Geology and origin of the Triassic magnetite deposit and diabase at Cornwall, Pennsylvania: Pennsylvania Topographic and Geologic Survey Mineral Resources Report M56, 343 pp.

Reed, Juliet C. (1976), Annotated Bibliography of Minerals New to the Pennsylvania List 1965-1974, The Mineralogical Society of Pennsylvania, Inc.: 19 & 26, 50-51, 53.

Rocks & Minerals (1989): 64(7).

Smith, L., 1931, Magnetite deposits of French Creek, Pennsylvania: Pennsylvania Geol. Survey, 4th ser.. Bull. M 14, pp. 35-37.



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