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Howard Co., Maryland, USA

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Location is approximate, estimate based on other nearby localities.
Latitude & Longitude (WGS84): 39° North , 76° West (est.)
Margin of Error:~9km

Except for a band of unconsolidated Cretaceous rock along its eastern edge (essentially the I-95 corridor), Howard County is underlain by metamorphic and igneous rocks of the Piedmont Province. They are intruded by several generations of granite and pegmatites, as well as bodies of maifc rock from the Baltimore Gabbro Complex. Several domes, most notably the Woodstock Dome near Marriottsville, bring up the oldest rock in Maryland, the 1.0 to 1.3 billion year old Baltimore Gneiss. The gneiss is surrounded by Cambrian quartzite, marble and schist. These are well exposed along the Patapsco River, on the border with Baltimore County. Development has restricted access to or obliterated many of the occurrences, however the diversity of the geology means that any new excavation is worth exploring for new mineral occurrences.

Mineral List

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

42 valid minerals.

Rock Types Recorded

Entries shown in red are rocks recorded for this region.

Note: this is a very new system on and data is currently VERY limited. Please bear with us while we work towards adding this information!

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

Localities in this Region

The above list 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.


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

Cloos, E. et. al. (1964) Howard and Montgomery Counties, Maryland: Maryland Geological Survey: County Report: 373 p.

Crowley, W. P. et. al. (1971) New interpretations of the eastern Piedmont geology of Maryland: Maryland Geological Survey, Guidebook Series 2, 32 p.

Bernstein, Lawrence (1980) Minerals of the Washington D. C. area: Maryland Geological Survey Educational Series 5, 148 p.

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