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Hopkinton, Washington Co., Rhode Island, USA

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Latitude & Longitude (WGS84): 41° 28' 35'' North , 71° 45' 9'' West
Latitude & Longitude (decimal): 41.47639,-71.75250
Köppen climate type:Cfb : Temperate oceanic climate

Hopkinton is a town, incorporated in 1757.

Commodity List

This is a list of exploitable or exploited mineral commodities recorded from this region.

Mineral List

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

5 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

541 - 635 Ma

ID: 2922422
Sterling Igneous Suite - alaskite gneiss

Age: Ediacaran (541 - 635 Ma)

Stratigraphic Name: Sterling Plutonic Suite

Description: Pale pink, orange, or gray, fine- to medium-grained granite gneiss, rarely with porphyroclasts of microcline/orthoclase. Composition is granite with generally less than 3% dark minerals. Composed of sodic plagioclase, quartz, microcline/orthoclase, minor biotite, and opaque minerals; minor muscovite (in part secondary), and rare garnet and sphene in some rocks; accessory apatite and zircon; secondary chlorite. Varies from massive to layered. Strongly foliated and locally well lineated. Includes most rock mapped formerly as Hope Valley Alaskite Gneiss.

Comments: Part of Hope Valley Subterrane. Age of 601 +/-5 Ma by U/Pb methods on zircon is reported by Hermes and Zartman (1985) from a sample in RI per RI005. Per printed map: age of rock based on radiometric data from RI005, RI009, and RI012.

Lithology: Major:{gneiss}

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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