| Basis for focus area |
Balmat-Edwards ore bodies are found in siliceous dolomitic marbles of the Upper Marble Formation, which was deformed during the Grenville orogeny. Massive stratabound and stratiform sphalerite is localized in channels of microbrecciation. Ore deposits are in the southern overturned limb of the Sylvia Lake Syncline. In the Rossie district east-west-trending nearly vertical veins carry calcite and galena, with minor fluorite and barite. |
| Identified resources |
Identified resources and historical production of zinc. |
| Production |
Balmat district produced over 43 million tons of Zn ore from 1915-2001. A calcite vein south of Rossie produced 6,000 tons of Pb. Minor fluorite was produced from only two of several fissure veins in the Rossie district. |
| Status |
Past mining. |
| Estimated resources |
In 2003 estimated diluted recoverable reserves for Balmat-Edwards were estimated at 4 million tons of ore at 12.9% Zn; resources unknown, but likely minor for Rossie. |
| Geologic maps |
Brown and Engel (1956), scale 1:27,500; Brown (1989), scale 1:18,000. |
| Geophysical data |
Inadequate Rank 3 and 4 aeromagnetic and Rank 5 aeroradiometric coverage. |
| Favorable rocks and structures |
Steeply dipping veins aligned along extensional fractures in metamorphic rocks of the Grenville Complex, including marble and calc-silicates in possibly Paleozoic sedimentary rocks. Rocks are generally older than ~1600-1000 Ma paragneiss, amphibolite, migmatites. |
| Deposits |
Balmat-Edwards district (MRDS dep_id: 10073156), Hyatt mine (MRDS dep_id: 10199530), Pierrepont mine (MRDS dep_id: 10082073), Rossie-Bigelow-Macomb mines (MRDS dep_id: 10175575). |
| Evidence from mineral occurrences |
MRDS; published company data. |
| Geochemical evidence |
At Balmat-Edwards, ore consists primarily of pyrite-sphalerite-galena replacements of metasedimentary rocks of the Proterozoic Grenville Supergroup that were metamorphosed and deformed during the Grenville orogeny. |
| Geophysical evidence |
Unknown. |
| Evidence from other sources |
Unknown. |
| Comments |
Balmat discovered 1838, drilled 1927, productive period 1930-2001, 2004-2008. Edwards discovered 1903, productive period 1915-1980. Hyatt discovered 1917, productive years 1918-22, 1930-49, 1974- 983. Pierrepont discovered 1979, productive years 1982-2001. |
| Cover thickness and description |
Variable. |
| Authors |
Nora K. Foley, Bernard E. Hubbard. |
| New data needs |
Geologic mapping, geophysics. |
| Geologic mapping and modeling needs |
1:24,000 scale mapping. |
| Geophysical survey and modeling needs |
High resolution aeromagnetic and aeroradiometric coverage. Aeromagnetic and aeroradiometric data can assist with framework geology such as structural features and contacts. |
| Digital elevation data needs |
Lidar adequate. |
