Topsham pegmatite district

Region East, Northeast
Mineral systems
Deposit types
Critical minerals
Other minerals

Information leading to the delineation of this focus area

Basis for focus area Topsham district of Cameron and others (1954); extended district to include Larrabee deposit.
Identified resources Historical production of beryllium (beryl), feldspar, and mica.
Production Unknown.
Status Past mining.
Estimated resources Unknown.
Geologic maps Hussey and Marvinney (2002), scale 1:100,000; Hussey and West (2018), scale 1:24,000; West and Hussey (2020), scale 1:24,000; West (2019), scale 1:24,000.
Geophysical data Inadequate Rank 5 aeromagnetic and aeroradiometric coverage.
Favorable rocks and structures Pegmatite cutting granite.
Deposits Coombs feldspar quarry (MRDS dep_id: 10107755), Todd mine (MRDS dep_id: 10291536), McKay Farm prospect (MRDS dep_id: 10291300) Consolidated quarries (MRDS dep_id: 10194708), Fisher quarry (MRDS dep_id: 10242337), Golding's quarry (MRDS dep_id: 10242241), Rumrill, William Willes, Trufant, Alice Staples, Larrabee.
Evidence from mineral occurrences MRDS.
Geochemical evidence Favorable mineralogy and rock type.
Geophysical evidence Unknown.
Evidence from other sources Unknown.
Comments It is reported that masses of columbite-tantalite weighing as much as 15 lbs were recovered from the Coombs mine (Cameron and others, 1954).
Cover thickness and description Variable limited cover and glacial cover estimated at less than 2-50 m.
Authors Gregory J. Walsh, Bernard E. Hubbard.
New data needs Modern maps at 1:24,000 scale and 1:100,000 scale show good coverage. Geochemical sampling needed.
Geologic mapping and modeling needs Additional mapping at 1:24,000 scale may be needed, geophysics may not be useful for pegmatites.
Geophysical survey and modeling needs High resolution aeromagnetic and aeroradiometric coverage can assist with framework geology such as structural features and contacts.
Digital elevation data needs Lidar complete.