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East Haddam, Middlesex Co., Connecticut, USAi
Regional Level Types
East Haddam- not defined -
Middlesex Co.County

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Latitude & Longitude (WGS84): 41° 27' 51'' North , 72° 26' 36'' West
Latitude & Longitude (decimal): 41.46417,-72.44333
GeoHash:G#: drk7zs267
Köppen climate type:Cfb : Temperate oceanic climate
Nearest Settlements:
East Haddam9,042 (2017)1.9km
Moodus1,413 (2017)4.3km
Chester Center1,558 (2017)7.0km
Deep River Center2,484 (2017)9.1km
Higganum1,698 (2017)10.1km

Located on the east side of the Connecticut River from Haddam, from which it split and then incorporated as a separate town in 1734, the first permanent European settlers established homesteads there in 1685. The town covers a large area and includes several villages such as Moodus, Millington, Bashan, Middle Haddam, Hadlyme, Leesville, and East Haddam center. The latter is located on the Connecticut Riverand includes the Goodspeed Landing where ferry service across the river operated until replaced by the swing bridge in 1913, which now carries state Route 82 across.

East Haddam's bedrock geology consists mostly of metamorphic rocks of the Merrimack and Central Maine oceanic terranes, with some of the Proterozoic Avalonian metamorphic micro-continental terrane in the southeast part of town. The Merrimack Terrane rocks are mostly the Silurian-Ordovician Hebron Formation calc-silicate gneiss and granofels (well exposed at Goodspeed Landing), while the Central Maine Terrane includes the Ordovician Brimfield siliceous schist and gneiss. A small klippe of Bronson Hill Terrane (Middletown formation meta-volcanics) lies just southwest of Lake Hayward. The Eastford Fault, responsible for the audible minor earthquakes known as the Moodus Noises, passes through the NW part of town along a NE-SW trend that takes it along Pickerel Lake Road and Sillimanville Road and just north of Black Birch Golf Course and Machimoodus State Park. It eventually links up with the Ponset Brook Fault in Haddam.

East Haddam mineralogy mostly consists of rock-forming and accessory metamorphic minerals, with minor pegmatite minerals most notably at Mt. Tom in Moodus, and low-temperature hydrothermal minerals in fractures and faults. Hitchcock (1823) and Robinson (1825) lists some minerals from non-specific town localities.

Coordinates are for the intersection of State Routes 82 and 151.

Regions containing this locality

North America PlateTectonic Plate

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Standard Detailed Strunz Dana Chemical Elements

Mineral List

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

9 valid minerals.

Rock Types Recorded

Note: this is a very new system on and data is currently VERY limited. Please bear with us while we work towards adding this information!

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

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Alphabetical List Tree Diagram

Detailed Mineral List:

Formula: Na(AlSi3O8)
Reference: Barton and Goldsmith (1968): New England Beryllium Investigations. US Bureau of Mines Report of Investigation 7070.
Formula: Be3Al2(Si6O18)
Colour: yellow to pale green
Description: Some gem material was recovered.
Reference: Rocks & Minerals (1995) 70:396-409; Schooner (1961)
'Columbite-(Fe)-Columbite-(Mn) Series'
Description: Schooner (1961) reports that some "good crystals" were found.
Reference: Schooner (1961): Mineralogy of Connecticut
Formula: K(AlSi3O8)
Reference: Barton and Goldsmith (1968): New England Beryllium Investigations. US Bureau of Mines Report of Investigation 7070.
Formula: MoS2
Description: “sulphuret of molybdena” (Hitchcock, 1823), (Robinson, 1825 - with reference to Cleaveland's Mineralogy)
Reference: Hitchcock, Edward. (1823): A Sketch of the Geology, Mineralogy, and Scenery of the Regions contiguous to the River Connecticut. AJS Vol 6. p. 235.; Robinson (1825) A Catalogue of American Minerals, With Their Localities
Colour: yellow-brown
Description: "beautiful yellowish-brown monazite crystals, up to a couple of inches long and quite glassy, are sometimes found. [David] Seaman has established their identity by an x-ray test." Schooner (1961).
Reference: Rocks & Minerals (1995) 70:396-409; Schooner (1961)
Formula: KAl2(AlSi3O10)(OH)2
Reference: Barton and Goldsmith (1968): New England Beryllium Investigations. US Bureau of Mines Report of Investigation 7070.
Formula: SiO2
Description: “rose-red quartz” (Hitchcock, 1823), "good specimens have been obtained" (Robinson, 1825)
Reference: Hitchcock, Edward. (1823): A Sketch of the Geology, Mineralogy, and Scenery of the Regions contiguous to the River Connecticut. AJS Vol 6. p. 213.; Robinson (1825) A Catalogue of American Minerals, With Their Localities
Quartz var: Rose Quartz
Formula: SiO2
Habit: massive
Colour: pink
Description: “rose-red quartz” (Hitchcock, 1823), "good specimens have been obtained" (Robinson, 1825), probably as glacial erratics, which can still be found around town.
Reference: Hitchcock, Edward. (1823): A Sketch of the Geology, Mineralogy, and Scenery of the Regions contiguous to the River Connecticut. AJS Vol 6. p. 213.; Robinson (1825) A Catalogue of American Minerals, With Their Localities
Quartz var: Smoky Quartz
Formula: SiO2
Reference: Barton and Goldsmith (1968): New England Beryllium Investigations. US Bureau of Mines Report of Investigation 7070.
Formula: Na(Fe2+3)Al6(Si6O18)(BO3)3(OH)3(OH)
Reference: Rocks & Minerals (1995) 70:396-409
Formula: Al2(SiO4)O
Habit: massive, fibrous
Colour: white
Description: Forming lineations and aggregates with quartz in schist.
Reference: Harold Moritz collection
Formula: CaTi(SiO4)O
Colour: light brown
Description: small crystals in Hebron Formation calc-silicate gneiss
Reference: Wesleyan University collection

List of minerals arranged by Strunz 10th Edition classification

Group 2 - Sulphides and Sulfosalts
Group 4 - Oxides and Hydroxides
var: Rose Quartz4.DA.05SiO2
var: Smoky Quartz4.DA.05SiO2
Group 9 - Silicates
Unclassified Minerals, Rocks, etc.
'Columbite-(Fe)-Columbite-(Mn) Series'-

List of minerals arranged by Dana 8th Edition classification

Group 2 - SULFIDES
AmBnXp, with (m+n):p = 1:2
Group 52 - NESOSILICATES Insular SiO4 Groups and O,OH,F,H2O
Insular SiO4 Groups and O, OH, F, and H2O with cations in [4] and >[4] coordination
Insular SiO4 Groups and O, OH, F, and H2O with cations in [6] and/or >[6] coordination
Group 61 - CYCLOSILICATES Six-Membered Rings
Six-Membered Rings with [Si6O18] rings; possible (OH) and Al substitution
Six-Membered Rings with borate groups
Group 71 - PHYLLOSILICATES Sheets of Six-Membered Rings
Sheets of 6-membered rings with 2:1 layers
Group 75 - TECTOSILICATES Si Tetrahedral Frameworks
Si Tetrahedral Frameworks - SiO2 with [4] coordinated Si
Group 76 - TECTOSILICATES Al-Si Framework
Al-Si Framework with Al-Si frameworks
Unclassified Minerals, Mixtures, etc.
'Columbite-(Fe)-Columbite-(Mn) Series'-
var: Rose Quartz
var: Smoky Quartz-SiO2

List of minerals for each chemical element

H SchorlNa(Fe32+)Al6(Si6O18)(BO3)3(OH)3(OH)
H MuscoviteKAl2(AlSi3O10)(OH)2
Be BerylBe3Al2(Si6O18)
B SchorlNa(Fe32+)Al6(Si6O18)(BO3)3(OH)3(OH)
O Quartz (var: Rose Quartz)SiO2
O BerylBe3Al2(Si6O18)
O SchorlNa(Fe32+)Al6(Si6O18)(BO3)3(OH)3(OH)
O AlbiteNa(AlSi3O8)
O MicroclineK(AlSi3O8)
O Quartz (var: Smoky Quartz)SiO2
O MuscoviteKAl2(AlSi3O10)(OH)2
O SillimaniteAl2(SiO4)O
O QuartzSiO2
O TitaniteCaTi(SiO4)O
Na SchorlNa(Fe32+)Al6(Si6O18)(BO3)3(OH)3(OH)
Na AlbiteNa(AlSi3O8)
Al BerylBe3Al2(Si6O18)
Al SchorlNa(Fe32+)Al6(Si6O18)(BO3)3(OH)3(OH)
Al AlbiteNa(AlSi3O8)
Al MicroclineK(AlSi3O8)
Al MuscoviteKAl2(AlSi3O10)(OH)2
Al SillimaniteAl2(SiO4)O
Si Quartz (var: Rose Quartz)SiO2
Si BerylBe3Al2(Si6O18)
Si SchorlNa(Fe32+)Al6(Si6O18)(BO3)3(OH)3(OH)
Si AlbiteNa(AlSi3O8)
Si MicroclineK(AlSi3O8)
Si Quartz (var: Smoky Quartz)SiO2
Si MuscoviteKAl2(AlSi3O10)(OH)2
Si SillimaniteAl2(SiO4)O
Si QuartzSiO2
Si TitaniteCaTi(SiO4)O
S MolybdeniteMoS2
K MicroclineK(AlSi3O8)
K MuscoviteKAl2(AlSi3O10)(OH)2
Ca TitaniteCaTi(SiO4)O
Ti TitaniteCaTi(SiO4)O
Fe SchorlNa(Fe32+)Al6(Si6O18)(BO3)3(OH)3(OH)
Mo MolybdeniteMoS2

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

Devonian - Silurian
358.9 - 443.8 Ma

ID: 3186140
Paleozoic sedimentary and volcanic rocks

Age: Paleozoic (358.9 - 443.8 Ma)

Lithology: Mudstone-carbonate-sandstone-conglomerate

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]

541 - 1000 Ma

ID: 2744518
Hebron Gneiss

Age: Neoproterozoic (541 - 1000 Ma)

Stratigraphic Name: Hebron Gneiss

Description: Interlayered dark-gray, medium- to coarse-grained schist, composed of andesine, quartz, biotite, and local K-feldspar, and greenish-gray, fine- to medium-grained calc-silicate rock, composed of labradorite, quartz, biotite, actinolite, hornblende, and diopside, and locally scapolite. Local lenses of graphitic two-mica schist.

Comments: Part of Eastern Uplands; Iapetus (Oceanic) Terrane - Merrimack Synclinorium; Hebron Gneiss and equivalent formations (including equivalents of Paxton and Oakdale Formations of Massachusetts) (including Bigelow Brook and Southbridge Formations) (Silurian and Ordovician). The Hebron Formation is here restricted to rocks in the area south and west of the Willimantic dome, south of the Wangumbaug Lake fault, and west of a fault in the Fitchville quad delineated by the Lebanon Gabbro. It includes the type area of the Hebron. Other rocks formerly mapped as Hebron are here assigned to the Oakdale, Dudley, and Southbridge Formations. It is separated from all other stratigraphic units by fault or intrusive contacts across which no stratigraphy can be correlated. Age is Late Proterozoic(?) based on correlation with part of the Paxton Group (Pease, 1989) per CT013. Original map source: Connecticut Geological and Natural History Survey, DEP, in cooperation with the U.S. Geological Survey, 2000, Bedrock Geology of Connecticut, shapefile, scale 1:50,000

Lithology: Major:{schist,calc silicate rock}

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


Sort by

Year (asc) Year (desc) Author (A-Z) Author (Z-A)
Hitchcock, Edward. (1823), A Sketch of the Geology, Mineralogy, and Scenery of the Regions contiguous to the River Connecticut. American Journal of Science: s. 1: 6: 213, 218, 235.
Robinson, Samuel. (1825), A Catalogue of American Minerals, With Their Localities; Including All Which Are Known to Exist in the United States and British Provinces, And Having the Towns, Counties, and Districts in Each State and Province Arranged Alphabetically. With an Appendix, Containing Additional Localities and a Tabular View. Cummings, Hilliard, & Co., Boston.
Altamura, R. J. & R. T. Marple. (2015): The Eastford Fault and Lineament of Eastern Connecticut: A Regional Neotectonic Structure Responsible for the 1987 Moodus Earthquake Swarm. New England. Intercollegiate Geological Conference Guidebook for Field Trips in Conn. and Mass.

Localities in this Region
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