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Farmington, Hartford Co., Connecticut, USA

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Latitude & Longitude (WGS84): 41° 43' 35'' North , 72° 49' 29'' West
Latitude & Longitude (decimal): 41.72639,-72.82472
GeoHash:G#: drkjqu49u
Köppen climate type:Dfa : Hot-summer humid continental climate

A town settled by Europeans in 1645. It originally included Avon (until 1830) and Plainville (until 1869), so using Robinson (1825) as a reference is ambiguous. Descriptions in it of prehnite and calcite, for example, clearly refer to the well-known Talcott Mountain locality now in Avon. Coordinates are for the intersection of state Routes 4 and 10.

Most references to trap rock minerals that are not locality specific (such as Schairer (1931), Januzzi (1976), Tschernich (1992)) are typically referring to the old and largely forgotten Farmington Trap Rock Quarry on state Route 4, which became the town dump and has long been covered.

Geologically, Farmington lies in the Early Mesozoic Hartford Mesozoic Basin, part of the Newark Supergroup of rift basins. The western, lowland part of town is underlain by the Triassic New Haven Arkose, while the eastern, upland portion of town is underlain by the ridge forming Jurassic Talcott and Holyoke Basalts (trap rock), with the intervening sediments of the Shuttle Meadow and East Berlin Formations. The very northwest corner of town, between the Farmington River and state Route 177, is underlain by metamorphic bedrock of the Collinsville dome - mostly Ordovician Collinsville Formation hornblende gneiss and amphibolite with a core of light gray Ordovician Bristol Gneiss.

Mineral List

Mineral list contains entries from the region specified including sub-localities

16 valid minerals.

Rock Types Recorded

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Rock list contains entries from the region specified including sub-localities

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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

Early Jurassic - Late Triassic
174.1 - 237 Ma

ID: 2791643
New Haven Arkose

Age: Mesozoic (174.1 - 237 Ma)

Stratigraphic Name: New Haven Arkose

Description: Red, pink, and gray coarse-grained, locally conglomeratic, poorly sorted and indurated arkose, interbedded with brick-red micaceous, locally shaly siltstone and fine-grained feldspathic clayey sandstone.

Comments: Part of Central Lowlands; Newark Terrane - Hartford and Pomperaug Mesozoic Basins; part of Newark Supergroup (Upper Triassic and Lower Jurassic).

Lithology: Major:{arkose}, Minor:{conglomerate,siltstone,sandstone}

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]

201.3 - 252.17 Ma

ID: 3188891
Mesozoic volcanic and intrusive rocks

Age: Triassic (201.3 - 252.17 Ma)

Comments: Connecticut Valley Basin

Lithology: Mafic volcanic rocks; conglomerate,arkose,shale,arenite

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. [154]

Data and map coding provided by, used under Creative Commons Attribution 4.0 License

Localities in this Region
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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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Robinson, Samuel. (1825), A Catalogue of American Minerals, with their localities. Boston.
Longwell & Dana (1932), Walks & Rides in Central Connecticut & Massachusetts: 229.
White, John, and Cook, Robert. (1990), Amethyst Occurrences of the Eastern United States. Mineralogical Record: 21(3): 203-213.
Lunar and Planetary Science XXXIV (2003).

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