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Brighton Dam Road Quarry (Howard-Montgomery Quarry), Howard Co., Maryland, USA

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Latitude & Longitude (WGS84): 39° 11' 44'' North , 76° 59' 9'' West
Latitude & Longitude (decimal): 39.19556,-76.98583
Köppen climate type:Cfa : Humid subtropical climate

This quarry was in a somewhat schistose to gneissic phase of the Cockeysville Marble along the southern flank of the Clarksville gneiss dome. It was operated by the Howard-Montgomery Crushed Stone Company, a division of Contee Sand and Gravel. The Howard/Montgomery Quarry is now filled with water and is located in the middle of an upscale residential neighborhood. The grounds of the quarry are posted "No Trespassing."

Mineral List

14 valid minerals.

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

541 - 2500 Ma

ID: 2935545
Cockeysville Marble

Age: Proterozoic (541 - 2500 Ma)

Stratigraphic Name: Cockeysville Marble

Description: Metadolomite, calc-schist, and calcite marble are predominant; calc-gneiss and calc-silicate marble widespread but minor; thickness about 750 feet.

Comments: secondary unit description from USGS Geologic Names lexicon (ref MD004): Author has erected a six-fold stratigraphy for the Cockeysville consisting of five unnamed members and one lens to accommodate the variety of rock types. These are the layered marble member (0 to 200 m), the massive metadolostone member (0 to 400 m), the layered metadolostone member (0 to 1.4 km), the massive metalimestone member (0 to 450 m), which includes the calc-gneiss lens (0 to 225 m), and the phlogopitic metalimestone member (0 to 300 m). Each member is described in detail. Thickness of the Cockeysville overall varies from 0 to 1.4 km, the range of the layered metadolostone. The relative ages of these units are uncertain. Unit as a whole is mapped as Cambrian to Ordovician(?).

Lithology: Major:{marble}, Minor:{calc silicate schist}, Incidental:{calc silicate gneiss}

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]

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

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.


Edwards, J. (1971) Directory of mineral producers in Maryland: Maryland Geological Survey Information Circular 11: 15.

MESA Health and Safety Inspection Report January 31 & February 1, 1972.

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

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