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Harford Co., Maryland, USA

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Location is approximate, based on center of defined region.
Latitude & Longitude (WGS84): 39° North , 76° West (est.)

Harford County is mostly underlain by complex igneous and metamorphic rocks of the Piedmont Province. This includes schists, gneiss and amphibolites of metasedimentary and metavolcanic origin, various granites and rocks of the Cambrian Baltimore Mafic Complex. All of the Piedmont rocks were caught up and deformed in the Ordovician Taconic Orogeny. These rocks are well exposed along the Susquehanna River gorge around Conowingo Dam and in several state parks. At Rocks State Park are good outcrops of schist and metaconglomerate. Palmer State Park features exposures of the Baltimore Gabbro complex. Serpentinite masses, often intruded by odd desilicified albitite dikes have provided some production of feldspar, decorative serpentinite and chromite, generally pre-1914. Lower grade metamorphic rock of the Peach Bottom slate were produced along the north and northwest edge of the County. The southern part of Harford County (generally south of I-95) is underlain by loosely consolidated Cretaceous, Tertiary and Quaternary sediments of the Coastal Plain Province.

Mineral List

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

31 valid minerals.

Localities in this Region

This page contains all mineral locality references listed on 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 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.


Pearre, N. & A. V. Heyl (1960) Mineral deposits in serpentine rocks of the Piedmont Upland, Maryland, Pennsylvania and Delaware: U. S. Geological Survey: Bulletin 1082K: 707-833.

Southwick, D. , J. Owens & J. Edwards (1969) The Geology of Harford County, Maryland: Maryland Geological Survey: County Report: 133 p.

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