Etchison Mine, Montgomery Co., Maryland, USA
|Latitude & Longitude (WGS84):||39° 15' 19'' North , 77° 9' 22'' West|
|Latitude & Longitude (decimal):||39.25540,-77.15631|
|Köppen climate type:||Cfa : Humid subtropical climate|
Chromite mine worked in pre-Civil War times. The workings were largely bulldozed under a road in 1950.
6 valid minerals.
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 Macrostrat.org
|Cambrian - Neoproterozoic|
485.4 - 1000 Ma
|Precambrian-Phanerozoic sedimentary and volcanic rocks|
Reference: Chorlton, L.B. Generalized geology of the world: bedrock domains and major faults in GIS format: a small-scale world geology map with an extended geological attribute database. doi: 10.4095/223767. Geological Survey of Canada, Open File 5529. 
|Early Cambrian - Neoproterozoic|
511 - 1000 Ma
Description: Fine- to coarse-grained, lustrous, greenish-gray to gray, reddish-brown weathering, quartz-rich schist and much lesser mica gneiss. Contains interbedded metagraywacke and some calc-silicate rock. Typical mineral assemblages from west to east and from low to high metamorphic grade are: quartz-muscovite-chlorite-plagioclase-epidote-magnetite-hematite, quartz-muscovite-biotite-garnet-staurolite-plagioclase-magnetite?andalusite, quartz-muscovite-garnet-kyanite-plagioclase-staurolite-magnetite, and quartz-biotite-plagioclase-sillimanite-magnetite. Some sillimanite-bearing rocks also contain microcline. Cordierite has been recognized at a few places. Contains an abundant debris of ultramafic and lesser related mafic rocks (CZu)
Reference: Davis, A.M., C.S. Southworth, J.E. Reddy, J.S. Schindler. Geologic Map Database of the Washington DC Area Featuring Data from Three 30 x 60 Minute Quadrangles: Frederick, Washington West, and Fredericksburg. U.S. Geological Survey Open-File Report 01-227. 
541 - 2500 Ma
|Wissahickon Formation (Undivided)|
Age: Proterozoic (541 - 2500 Ma)
Stratigraphic Name: Wissahickon Formation
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.