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Glastonbury, Hartford Co., Connecticut, USA

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Latitude & Longitude (WGS84): 41° 42' 44'' North , 72° 36' 29'' West
Latitude & Longitude (decimal): 41.71222,-72.60806
Köppen climate type:Dfa : Hot-summer humid continental climate

A town on the east side of the Connecticut River, just southeast of Hartford. The bedrock geology consists of continental clastic sedimentary rocks (Portland Formation) within the Mesozoic Hartford Basin under the westernmost part of town, though these are mostly covered by Pleistocene deposits, and, in the Eastern Highlands, metamorphic rocks of the Bronson Hill terrane under the eastern part of the town. Most of the Bronson Hill bedrock is the Ordovician Glastonbury meta-plutonic gneiss, flanked on the east and west by Collins Hill formation, and unconformably overlain by the Silurian-Devonian meta-sedimentary Fitch, Clough, and Littleton formations in a north-northeast trending syncline near the eastern edge of town. Numerous pegmatites intrude these units, most notably just south of the village of South Glastonbury near the Portland line. This swarm is the northern part of the Middletown Pegmatite District.

The diversity of mineralogy found within the town is dominated by the pegmatites, which include both common and mariolitic, lithium-rich types. Rock forming and accessory metamorphic minerals are found in the meta-plutons and meta-sediments, and low temperature hydrothermal minerals are found in later faults and fractures.

Coordinates are for the town center green.

Mineral List

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

48 valid minerals.

Rock Types Recorded

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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.

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Early Jurassic
174.1 - 201.3 Ma

ID: 2968514
Portland Arkose

Age: Early Jurassic (174.1 - 201.3 Ma)

Stratigraphic Name: Portland Arkose

Description: Reddish-brown to maroon micaceous arkose and siltstone and red to black fissile silty shale. Grades eastward into coarse conglomerate (fanglomerate).

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

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

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

Localities in this Region

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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