Gold mining activity has been interesting in Maryland. Although gold was known to exist on the south side of the Potomac as far back as Colonial times, yet the first authentic record of its discovery on the north side of the Potomac or in Maryland is in the Proceedings of the American Philosophical Society for April, 1849, where mention is made of gold bearing quartz veins on one farm in Montgomery County, some thirty miles west of Baltimore. Reported assays of samples from these veins reported gold.
Many gold-bearing quartz veins were found in the immediate vicinity of Washington, but prospecting was done using gold pans. Nevertheless, the main developments of gold were made in the vicinity of Great Falls, from fifteen to sixteen miles west of the city. Reports say that gold was discovered by California volunteers who camped in the neighborhood during the war. The Maryland mine was opened in 1867 and was located midway between Great Falls and the Harrison state. Early in 1888, gold was discovered by a Georgia miner who after prospecting performed some exploratory work by sinking pits. The following year it was exploited by others. A three-stamp mill was erected and later a ten-stamp mill took its place.
In 1889, owing to the successful operation of the Harrison property, a number of other properties were developed, the most important being the Allerton-Ream, the Pine Hill, Broad Rock and Eagle, which were not far distant from the Harrison property. Although mining begun in 1849, the mint reports show no returns previous to 1868.
The country rock was fine-grained micaceous schists, probably more massive than schistose in structure. Some of the quartz-filling of the veins showed free gold, but the greater part did not show free gold. Epidote and chlorite were found associated with the schists as basic silicates. Some pyrite was found in the oxidized zone, below which the sulphides occurred as in the mines of the southern states. It is clear from the work done that the quartz-veins were irregular in vertical and horizontal directions.