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Canton Lead Mines (Cherry Brook lead mine; Dyer Farm zinc mine), Rattlesnake Mountain, Canton, Hartford Co., Connecticut, USA

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Latitude & Longitude (WGS84): 41° 50' 9'' North , 72° 54' 47'' West
Latitude & Longitude (decimal): 41.83611,-72.91306
Köppen climate type:Dfa : Hot-summer humid continental climate

Very little has been written about this old locality, most references give only the briefest mention. A 1910 postcard shows what was called the zinc mine on the Dyer Farm, Collinsville, Conn. The 1869 map of Canton shows a house owned by "D. Dyer" on the road close to the mine location. The Town of Canton web site (see link below) gives a brief history of the Dyer house and property at 1 Dyer Cemetery Road, near the same spot, that had "...a farm of six hundred acres. Over the years it had a sawmill; “silver mine” that produced small quantities of zinc, lead, copper and beryl..." Given the size of the farm and the proximity of the house with the mine, the mine in the postcard must be the Canton lead mine.

Shepard (1837) presaged, or perhaps inspired, the mining of lead here with this short sentence:

Rolled masses [boulders] of quartz including galena have been found in Canton near Collinsville...indicating the existence of veins of such ores in these regions.

A hydrothermal fault vein deposit, probably related to Mesozoic rifting as large-scale faults associated with the Hartford and Cherry Brook rift basins are close by. Minor amounts of galena, sphalerite, and lead secondary minerals occur here. But the locality is most famous for its amethyst, which occurs lining cavities in breccia and varies from larger lavender, mottled and translucent crystals to smaller, clearer, deeply colored druses. Colorless and milky quartz also occurs. Any beryl found must be related to a pegmatite in the host rock that the mine intersected.

Commodity List

This is a list of exploitable or exploited mineral commodities recorded at this locality.

Mineral List

7 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

Middle Ordovician
458.4 - 470 Ma

ID: 2927585
Sweetheart Mountain Member [of Collinsville Formation]

Age: Middle Ordovician (458.4 - 470 Ma)

Stratigraphic Name: Sweetheart Mountain Member

Description: Gray and silvery (not rusty), medium- to coarse-grained, poorly layered schist, composed of quartz, oligoclase, biotite, muscovite, and garnet, and in places kyanite or sillimanite. Amphibolite layers common; also layers of quartz-spessartine rock (coticule). In the Bristol quad., CT, Collinsville Formation is revised to include a basal unnamed hornblende gneiss member (was upper part of Stanley's (1964) Bristol Member), a middle unnamed metaquartzite member, and the upper Sweetheart Mountain Member. Bristol Member of Stanley (1964) is raised in rank to Bristol Gneiss in the report area. Collinsville unconformably underlies The Straits Schist. Inferred age is Middle Ordovician (Simpson, 1990).

Comments: Part of Central Lowlands; Iapetus (Oceanic) Terrane - Connecticut Valley Synclinorium; Gneiss Dome Belt, Hawley Formation and equivalent formations (includes Collinsville Formation) (Middle Ordovician). Secondary unit description per CT008.

Lithology: Major:{schist}, Minor:{amphibolite}, Incidental:{metamorphic}

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.


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Shepard, Charles Upham. (1837), Report on the Geological Survey of Connecticut.
Schairer, John F. (1931), Minerals of Connecticut. State Geological and Natural History Survey of Connecticut Bulletin 51.
Schooner, Richard. (1961), The Mineralogy of Connecticut. Fluorescent House, Branford, Connecticut.
Hiller, John, Jr. (1971), Connecticut Mines and Minerals. Privately published.
White, John, and Cook, Robert. (1990), Amethyst Occurrences of the Eastern United States. Mineralogical Record: 21(3): 203-213.
Weber, Marcelle H. and Earle C. Sullivan. (1995), Connecticut Mineral Locality Index. Rocks & Minerals (Connecticut Issue): 70(6): 399.

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