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Frederick Co., Maryland, USA

Frederick County has very diverse geology, spanning several geologic provinces, each with its own distinctive set of mineral occurrences. The eastern portion of the county is underlain by metamorpohsed Ordovician and Cambrian sedimentary and volcanic rocks, now metamorphosed to phyllites, slates, quartzites and marbles. Some of the marbles are mineralized, forming the deposits of copper, lead and zinc of the Liganore District. A few monadnocks, notably Sugarloaf Mountain, are underlain by resistant quartzites, provide outcrops and great views. The Martic Line Thrust Fault separates these highly metamorphosed rocks from the essentially unmetamorphosed Cambrian and Ordovician limestones of the Frederick Valley. Quarries in these limestones have provided agricultural lime and other products for many years. To the south and west these are unconformable overlain by Triassic “red bed” sandstones and conglomerates, sediments that accumulated in a fault-bounded half graben related to the opening of the Atlantic Ocean. West of this Triassic border fault, rises the Blue Ridge Province, an anticlinorium exposing metamorphosed Proterozoic and Cambrian volcanic and sedimentary rocks. Resistant Cambrian quartzites of the Cambrian Weaverton Formation hold up Catoctin Mountain and South Mountain. Between lies the Middleton Valley, underlain by somewhat less resistant Proterozoic rocks such as the Middletown Gneiss and Catoctin Formation , a metamorphosed series of volcanic rocks (mostly now greenstones) marking the opening of a predecessor to the Atlantic. Blue Ridge geology is well shown in Gambrill and Cunningham Falls State Parks on Catoctin Mountain. The most interesting collecting in the County is in the quarries and few remaining copper, lead and zinc mine dumps of the Liganore district around Libertytown and New London and in the metamorphic rocks of the Blue Ridge, which hosted intriguing small iron and copper deposits.

Mineral List

Mineral list contains entries from the region specified including sub-localities
Actinolite
Amphibole Supergroup
var: Byssolite

Anglesite
Aurichalcite
Azurite
Baryte
Bornite
Calcite
var: Manganoan Calcite
Cerussite
Chalcanthite
Chalcocite
Chalcopyrite
'Chlorite Group'
Chrysocolla
Copper
Covellite
Cuprite
Dolomite
Epidote
Fluorite ?
Galena
Goethite
Gold
Hematite
var: Specularite
Hemimorphite
Hydrozincite
'Limonite'
Magnetite
Malachite
Muscovite
Orthoclase
Ottrélite
'Psilomelane'
Pyrite
Pyrolusite
Quartz
var: Jasper
var: Milky Quartz
var: Rock Crystal
Rosasite
Silver
Smithsonite
Sphalerite
Stibnite ?
Strontianite
Sulphur
Talc
Tenorite
Tetrahedrite
Titanite
'Tourmaline'
'Wad'


60 entries listed. 43 valid minerals.

Localities in this Region

USA
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

Jonas, A. I. & G. W. Stose (1938) Geologic map of Frederick County, Maryland: Maryland Geological Survey.

Stose, A. J. et. al. (1946) Carroll and Frederick Counties: Maryland Dept. of Geology, Mines and Water Resources: Carroll and Fredrick Counties Report, 312 p.

Singewald, J. T. (1946) Mineral resources of Carroll and Frederick Counties: Maryland Dept. of Geology, Mines and Water Resources: Carroll and Fredrick Counties Report: 11-131.

Ostrander, C. W. & W. E. Price (1940) Minerals of Maryland: Natural History Society of Maryland , 92 p.

Heyl, A. & Pearre, N (1965) Copper, zinc, lead, iron cobalt and barite deposits of the Piedmont Upland in Maryland: Maryland Geological Survey: Bulletin 28, 72 p.

Southworth, S. & Brezinski, D. (1996) Geology of the Harper's Ferry Quadrangle, Virginia, Maryland and West Virginia: U.S. Geological Survey Bulletin 2123.

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Copyright © Jolyon Ralph and Ida Chau 1993-2014. Site Map. Locality, mineral & photograph data are the copyright of the individuals who submitted them. Site hosted & developed by Jolyon Ralph. Mindat.org is an online information resource dedicated to providing free mineralogical information to all. Mindat relies on the contributions of thousands of members and supporters. Mindat does not offer minerals for sale. If you would like to add information to improve the quality of our database, then click here to register.
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