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East Village pegmatite, Monroe, Fairfield Co., Connecticut, USA

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Latitude & Longitude (WGS84): 41° 21' 57'' North , 73° 11' 5'' West
Latitude & Longitude (decimal): 41.36583,-73.18472
Köppen climate type:Cfa : Humid subtropical climate


Very little has been written about this obscure locality, best known for its rose quartz. This text is from Crowley (1968):

"About 1 1/2 mi. north of East Village and 800 ft east northeast of the hairpin bend in Boys Halfway River is an old quarry in an extremely coarse-grained pegmatite, which locally exhibits a graphic-granite texture... Schairer (1931) describes it as "a small feldspar quarry where rose quartz, muscovite, biotite, garnet, columbite and feldspar are abundant." This may be the location described by Shepard (1837, p. 137): "A coarse grained granite in the northwestern part of Monroe, has afforded the most interesting variety of well crystallized and handsomely colored beryl .. ." The problem with that statement is that the East Village pegmatite is in the northeastern part of Monroe.

Januzzi (1959) states: "This pegmatite has produced some beautiful specimens of rose quartz, some of which have been cut into semi-precious gemstones. Other minerals found here are muscovite, biotite, garnet, feldspar and columbite."

Ryerson (1976) lists albite, chalcopyrite, columbite, garnet, manganapatite, quartz, and uranophane.

The prospect is a small pit barely 2 meters deep and 5 meters wide, with the mostly milky quartz core of the pegmatite partly exposed.


Mineral List


9 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.

Click on geological units on the map for more information. Click here to view full-screen map on Macrostrat.org

Middle Ordovician
458.4 - 470 Ma



ID: 2922376
Collinsville Formation

Age: Middle Ordovician (458.4 - 470 Ma)

Stratigraphic Name: Collinsville Formation

Description: Mixture of rock types as described for the two members; in many areas felsic and mafic striped metavolcanic rocks predominate.

Comments: Part of Central Lowlands; Iapetus (Oceanic) Terrane - Connecticut Valley Synclinorium; Gneiss Dome Belt. Hawley Formation and equivalent formations (includes Collinsville Formation) (Middle Ordovician). Two members referred to in primary description are units: Ocs and Ocg. Secondary unit description per CT008. Secondary unit description from USGS Geologic Names lexicon (ref. CT017): Metamorphic strata in the report area that lie above the Bristol Gneiss (as it is here revised) and below The Straits Schist are assigned to the Collinsville Formation. Unit is divided into a lower unnamed hornblende gneiss member (was uppermost part of Stanley's (1964) Bristol Member) approximately 400 ft thick, an unnamed metaquartzite member that averages 100 ft, and the upper Sweetheart Mountain Member adopted here as defined by Stanley. Inferred age is Middle Ordovician. Correlates, at least in part, with the Hawley Formation of MA (Simpson, 1990). Also from ref. CT017: Part of Bronson Hill anticlinorium, not part of Rowe-Hawley zone, but discussed in this report to emphasize importance of junction between Rowe-Hawley zone and Bronson Hill anticlinorium. Collinsville is exposed in Granville and Shelburne Falls domes, and to a limited extent in Goshen dome (Hatch and Warren, 1982). Consists of various light-colored, plagioclase-rich gneisses and interlayered amphibolite and hornblende gneiss. Upper part is amphibolite-rich; lower part is predominantly feldspathic gneiss. In places, thin aluminous feldspathic schist, locally containing coticule and amphibolite, forms an upper unnamed member of formation in Granville dome, or is Sweetheart Mountain Member of Stanley (1964) in Collinsville and Bristol domes in CT. Most complete sequence is in Shelburne Falls dome where L.M. Hall (1977, written commun.) has recognized seven mappable subdivisions. With minor modification, they are (ascending) 1) amphibolite with thin felsic gneiss layers; 2) rusty-weathering massive granulites; 3) very homogeneous garnetiferous biotite gneiss; 4) interlayered amphibolite and felsic gneiss; 5) felsic gneiss with scattered biotite +/-magnetite, garnet, and hornblende; 6) interbedded amphibolite and white felsic gneiss; and 7) gray, tan-weathering granulites containing thin coticule layers. Members 4, 5 and 6 are approximately equivalent to Ammonoosuc Volcanics. Member 3 is lithically similar to Monson and Fourmile Gneisses. Age in report is Ordovician. [Papers presented as chapters in U.S. Geological Survey Professional Paper 1366 are intended as explanations and (or) revisions to MA State bedrock geologic map of Zen and others (1983) at scale of 1:250,000.]

Lithology: Major:{gneiss,amphibolite}, Minor:{metavolcanic}, Incidental:{granulite}

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 Macrostrat.org, used under Creative Commons Attribution 4.0 License



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References

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Shepard, Charles U. (1837): A Report on the Geological Survey of Connecticut. p. 137.
Schairer, J. F. (1931): The Minerals of Connecticut. State Geological and Natural History Survey, Hartford, Connecticut Bulletin 51.
Januzzi, Ronald E. (1959): The Minerals of Western Connecticut and Southeastern New York State. The Mineralogical Press, Danbury.
Crowley, William Patrick. (1968): The Bedrock Geology of the Long Hill and Bridgeport Quadrangles. State Geological and Natural History Survey of Connecticut, Quadrangle Report No. 24, p. 73.
Ryerson, Kathleen. (1976): Rock Hound's Guide to Connecticut. Pequot Press.
Weber, Marcelle H. and Earle C. Sullivan. (1995): Connecticut Mineral Locality Index. Rocks & Minerals (Connecticut Issue): 70(6): 397.

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