Log InRegister
Home PageAbout MindatThe Mindat ManualHistory of MindatCopyright StatusWho We AreContact UsAdvertise on Mindat
Donate to MindatCorporate SponsorshipSponsor a PageSponsored PagesMindat AdvertisersAdvertise on Mindat
Learning CenterWhat is a mineral?The most common minerals on earthInformation for EducatorsMindat ArticlesThe ElementsBooks & Magazines
Minerals by PropertiesMinerals by ChemistryAdvanced Locality SearchRandom MineralRandom LocalitySearch by minIDLocalities Near MeSearch ArticlesSearch GlossaryMore Search Options
Search For:
Mineral Name:
Locality Name:
The Mindat ManualAdd a New PhotoRate PhotosLocality Edit ReportCoordinate Completion ReportAdd Glossary Item
Mining CompaniesStatisticsUsersMineral MuseumsMineral Shows & EventsThe Mindat DirectoryDevice Settings
Photo SearchPhoto GalleriesNew Photos TodayNew Photos YesterdayMembers' Photo GalleriesPast Photo of the Day GalleryMineral Photography

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

This page is currently not sponsored. Click here to sponsor this page.
Lock Map
Latitude & Longitude (WGS84): 41° 24' 11'' North , 72° 27' 5'' West
Latitude & Longitude (decimal): 41.40306,-72.45139
GeoHash:G#: drk7x34w2
Köppen climate type:Cfb : Temperate oceanic climate
Nearest Settlements:
Chester Center1,558 (2017)0.2km
Deep River Center2,484 (2017)2.5km
East Haddam9,042 (2017)5.6km
Essex Village2,495 (2017)7.3km
Moodus1,413 (2017)11.1km

Chester was originally a parish in the town of Saybrook, which was formed from the original English colony (1635-1644). After joining the Connecticut colony, Saybrook was eventually subdivided into Chester (1836), Westbrook (1840), Essex (1852, known as Pettipaug, Pettypaug, or Potopaug until 1854), and Old Saybrook (1854). The remainder, surrounding the original core town of Saybrook, changed its name to Deep River in 1947.

Geologically, Chester is underlain by generally NW-SE-trending metamorphic rock units, mostly of Ordovician age. Under the west and center parts of town are metavolcanics of the Middletown Formation, mixed metasediments of the Collins Hill Formation and a belt of Monson Orthogneiss; these are folded into the Ivoryton Synform. A major tectonic terrane suture, the Cremation Hill Fault Zone, separates these rocks from the Silurian-Ordovician Hebron Formation calc-silicate gneiss, which underlies mostly the extreme NE corner of town. It and a belt of Ordovician Tatnic Hill metavolcanics, which hosts the sillimanite type locality, wrap around the NW nose of a fold in another major tectonic terrane suture, the Honey Hill Fault, SE of which are Neoproterozoic gneisses.

Regions containing this locality

North America PlateTectonic Plate

Select Mineral List Type

Standard Detailed Strunz Dana Chemical Elements

Mineral List

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

10 valid minerals. 1 (TL) - type locality of valid minerals. 1 erroneous literature entry.

Detailed Mineral List:

Formula: Na(AlSi3O8)
Reference: Van King
Albite var: Oligoclase
Formula: (Na,Ca)[Al(Si,Al)Si2O8]
Reference: Van King
Formula: Fe2+3Al2(SiO4)3
Reference: Lundgren, Lawrence, Jr. (1979), The Bedrock Geology of the Haddam Quadrangle. State Geological and Natural History Survey of Connecticut. Quadrangle Report 37.
Formula: KFe2+3(AlSi3O10)(OH)2
Reference: Van King
Formula: ☐{Mg2}{Mg5}(Si8O22)(OH)2
Reference: Lundgren, Lawrence, Jr. (1979), The Bedrock Geology of the Haddam Quadrangle. State Geological and Natural History Survey of Connecticut. Quadrangle Report 37.
Formula: ☐{Mg2}{Mg3Al2}(Al2Si6O22)(OH)2
Reference: Lundgren, Lawrence, Jr. (1979), The Bedrock Geology of the Haddam Quadrangle. State Geological and Natural History Survey of Connecticut. Quadrangle Report 37.
Formula: Fe2+Fe3+2O4
Reference: Van King
Formula: Ce(PO4)
Reference: Nitze, Henry B. C., 1895, Monazite, and Monazite Deposits in North Carolina, Bulletin 9, North Carolina Geological Survey, pp. 47.
Formula: SiO2
Reference: Van King
Formula: TiO2
Reference: Van King
Sillimanite (TL)
Formula: Al2(SiO4)O
Reference: [Nickel & Nichols, 1991, "Mineral Reference Manual"]
Formula: (K,Ca,Na)(Fe2+,Mg,Al)8(Si,Al)12(O,OH)36 · nH2O
Description: Reference says occurs in "Cheshire" and other towns but not Chester.
Reference: Januzzi, 1976. Mineral Localities of CT and Southeastern NY State

List of minerals arranged by Strunz 10th Edition classification

Group 4 - Oxides and Hydroxides
Group 8 - Phosphates, Arsenates and Vanadates
Group 9 - Silicates
var: Oligoclase9.FA.35(Na,Ca)[Al(Si,Al)Si2O8]
Sillimanite (TL)9.AF.05Al2(SiO4)O
Stilpnomelane ?9.EG.40(K,Ca,Na)(Fe2+,Mg,Al)8(Si,Al)12(O,OH)36 · nH2O

List of minerals arranged by Dana 8th Edition classification

Group 51 - NESOSILICATES Insular SiO4 Groups Only
Insular SiO4 Groups Only with cations in [6] and >[6] coordination
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
Sillimanite (TL)52.2.2a.1Al2(SiO4)O
Group 66 - INOSILICATES Double-Width,Unbranched Chains,(W=2)
Amphiboles - Mg-Fe-Mn-Li subgroup
Group 71 - PHYLLOSILICATES Sheets of Six-Membered Rings
Sheets of 6-membered rings with 2:1 layers
Group 74 - PHYLLOSILICATES Modulated Layers
Modulated Layers with joined islands
Stilpnomelane ?,Ca,Na)(Fe2+,Mg,Al)8(Si,Al)12(O,OH)36 · nH2O
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.
var: Oligoclase-(Na,Ca)[Al(Si,Al)Si2O8]

List of minerals for each chemical element

H AnniteKFe32+(AlSi3O10)(OH)2
H Anthophyllite☐{Mg2}{Mg5}(Si8O22)(OH)2
H Gedrite☐{Mg2}{Mg3Al2}(Al2Si6O22)(OH)2
H Stilpnomelane(K,Ca,Na)(Fe2+,Mg,Al)8(Si,Al)12(O,OH)36 · nH2O
O SillimaniteAl2(SiO4)O
O QuartzSiO2
O MagnetiteFe2+Fe23+O4
O RutileTiO2
O AnniteKFe32+(AlSi3O10)(OH)2
O Albite (var: Oligoclase)(Na,Ca)[Al(Si,Al)Si2O8]
O Monazite-(Ce)Ce(PO4)
O AlbiteNa(AlSi3O8)
O AlmandineFe32+Al2(SiO4)3
O Anthophyllite☐{Mg2}{Mg5}(Si8O22)(OH)2
O Gedrite☐{Mg2}{Mg3Al2}(Al2Si6O22)(OH)2
O Stilpnomelane(K,Ca,Na)(Fe2+,Mg,Al)8(Si,Al)12(O,OH)36 · nH2O
Na Albite (var: Oligoclase)(Na,Ca)[Al(Si,Al)Si2O8]
Na AlbiteNa(AlSi3O8)
Na Stilpnomelane(K,Ca,Na)(Fe2+,Mg,Al)8(Si,Al)12(O,OH)36 · nH2O
Mg Anthophyllite☐{Mg2}{Mg5}(Si8O22)(OH)2
Mg Gedrite☐{Mg2}{Mg3Al2}(Al2Si6O22)(OH)2
Mg Stilpnomelane(K,Ca,Na)(Fe2+,Mg,Al)8(Si,Al)12(O,OH)36 · nH2O
Al SillimaniteAl2(SiO4)O
Al AnniteKFe32+(AlSi3O10)(OH)2
Al Albite (var: Oligoclase)(Na,Ca)[Al(Si,Al)Si2O8]
Al AlbiteNa(AlSi3O8)
Al AlmandineFe32+Al2(SiO4)3
Al Gedrite☐{Mg2}{Mg3Al2}(Al2Si6O22)(OH)2
Al Stilpnomelane(K,Ca,Na)(Fe2+,Mg,Al)8(Si,Al)12(O,OH)36 · nH2O
Si SillimaniteAl2(SiO4)O
Si QuartzSiO2
Si AnniteKFe32+(AlSi3O10)(OH)2
Si Albite (var: Oligoclase)(Na,Ca)[Al(Si,Al)Si2O8]
Si AlbiteNa(AlSi3O8)
Si AlmandineFe32+Al2(SiO4)3
Si Anthophyllite☐{Mg2}{Mg5}(Si8O22)(OH)2
Si Gedrite☐{Mg2}{Mg3Al2}(Al2Si6O22)(OH)2
Si Stilpnomelane(K,Ca,Na)(Fe2+,Mg,Al)8(Si,Al)12(O,OH)36 · nH2O
P Monazite-(Ce)Ce(PO4)
K AnniteKFe32+(AlSi3O10)(OH)2
K Stilpnomelane(K,Ca,Na)(Fe2+,Mg,Al)8(Si,Al)12(O,OH)36 · nH2O
Ca Albite (var: Oligoclase)(Na,Ca)[Al(Si,Al)Si2O8]
Ca Stilpnomelane(K,Ca,Na)(Fe2+,Mg,Al)8(Si,Al)12(O,OH)36 · nH2O
Ti RutileTiO2
Fe MagnetiteFe2+Fe23+O4
Fe AnniteKFe32+(AlSi3O10)(OH)2
Fe AlmandineFe32+Al2(SiO4)3
Fe Stilpnomelane(K,Ca,Na)(Fe2+,Mg,Al)8(Si,Al)12(O,OH)36 · nH2O
Ce Monazite-(Ce)Ce(PO4)

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

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: 2743651
Tatnic Hill Formation

Age: Neoproterozoic (541 - 1000 Ma)

Stratigraphic Name: Tatnic Hill Formation

Description: Medium- to dark-gray, medium-grained gneiss or schist composed of quartz, andesine, biotite, garnet, and sillimanite, locally kyanite, muscovite, or K-feldspar, interlayered with locally mappable units and thinner layers of rusty-weathering graphitic pyrrhotitic two-mica schist, amphibolite, and calc-silicate rock.

Comments: Part of Eastern Uplands; Iapetus (Oceanic) Terrane - Merrimack Synclinorium; Brimfield Schist and equivalent formations (includes Tatnic Hill Formation) (Upper? and Middle Ordovician). The age of the Putnam Group, including its Tatnic Hill Formation, is considered to be Late Proterozoic(?) based on the 730 my age of the Fishbrook Gneiss in MA and the 440 my age of the Hedgehog Hill gneiss intruded into the upper part of the younger Brimfield 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:{gneiss,schist}, Incidental:{amphibolite, 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 Macrostrat.org, used under Creative Commons Attribution 4.0 License

External Links

Bedrock geologic map of Connecticut:

Localities in this Region
Show map

This page contains all mineral locality references listed on mindat.org. 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 mindat.org 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.
Mineral and/or Locality  
Mindat.org is an outreach project of the Hudson Institute of Mineralogy, a 501(c)(3) not-for-profit organization. Public Relations by Blytheweigh.
Copyright © mindat.org and the Hudson Institute of Mineralogy 1993-2020, except where stated. Most political location boundaries are © OpenStreetMap contributors. Mindat.org relies on the contributions of thousands of members and supporters.
Privacy Policy - Terms & Conditions - Contact Us Current server date and time: February 25, 2020 22:39:20 Page generated: March 5, 2019 23:27:01
Go to top of page