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Portland, Middlesex Co., Connecticut, USA

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Latitude & Longitude (WGS84): 41° 34' 22'' North , 72° 38' 28'' West
Latitude & Longitude (decimal): 41.57278,-72.64111
Köppen climate type:Dfa : Hot-summer humid continental climate


Known as "Quarrytown" primarily for the large "brownstone" quarries (aeolian arkosic sandstone of the Portland Formation) near the Connecticut River in the western part town, Portland is also host to the most famous pegmatite quarry in the area - the Strickland Quarry. Coordinates are for the downtown intersection of State Routes 17A and 66 in the west, which is far removed from the pegmatite quarries farther east.

European settlers arrived in the 1690s, attracted to the blocks of brownstone along the riverbank. Originally Portland was part of Middletown and was known as East Middletown. In 1767 it became the separate town of Chatham. In 1841, when it separated from the eastern part of Chatham, it changed its name first to Conway then to Portland (because of the fame of quarries in that English town) (The remainder of Chatham changed its name to East Hampton in 1915.)

The bedrock geology is split between continental sedimentary rocks in the west, part of the Mesozoic Hartford Basin of the Newark Supergroup and mostly metaplutonic, metavolcanic and metasedimentary metamorphic rocks of the Ordovician Bronson Hill terrane in the east. These terranes are separated by the Eastern Border Fault of the Hartford Basin. Much of the Bronson Hill terrane rocks in town are mixed schists, calc-silicate rocks, and minor quartzites of the Collins Hill Formation, and its metavolcanic member, which are present just east of the Eastern Border Fault. Farther east the bedrock is mostly metaplutonic Glastonbury Gneiss, which crops out as far south as Great Hill Pond. A thin sliver of Devonian Maromas Granite Gneiss is also present.

Portland lies within the Middletown Pegmatite District, and a swarm of Permian pegmatite dikes lies just east of the Eastern Border Fault, mostly within the Collins Hill Formation, but some further east in the Glastonbury Gneiss. These were heavily quarried from the north at the Glastonbury town line and just east of State Route 17 (particularly the long-lived Hale Quarry) southward onto Collins Hill, which hosted the famous Strickland Quarry and Cramer Mine, where most of Portland's diverse mineralogy originates. Most pegmatite specimens just labeled "Portland" are likely from there, although the small Walden Gem Mine and Case Quarries produced many specimens also. Sharply formed and deeply colored aquamarines hail from the small Pelton's Quarry. Unquarried pegmatites can still be easily seen along State Route 66 in the Riverdale section just north of the Connecticut River in the area known as "The Ledges".


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

Actinolite

Albite

var: Cleavelandite

var: Oligoclase

var: Peristerite

'Allanite Group'

Almandine

Analcime

Anatase

Annite

Anorthite

Aragonite

Arsenopyrite

Augelite

Augite

var: Fassaite

Autunite

Bavenite

Bertrandite

Beryl

var: Aquamarine

var: Goshenite

var: Heliodor

var: Morganite

Bismite

Bismuthinite

Bismutite

Bismutoferrite

Bityite

Brazilianite

Calcite

Cassiterite

Chalcopyrite

'Chlorite Group'

Clinozoisite

Columbite-(Fe)

'Columbite-(Fe)-Columbite-(Mn) Series'

'Columbite-Tantalite'

Cookeite

Cordierite

Cuprobismutite

Dickinsonite-(KMnNa)

Diopside

Elbaite

Eosphorite

Epidote

Epsomite

Fairfieldite

'Feldspar Group'

'var: Perthite'

Ferrimolybdite

Fluorapatite

var: Mn-bearing Fluorapatite

Fluorite

Foitite

Gahnite

Galena

'Garnet'

Gehlenite

Gobbinsite

Goethite

Graphite

Grossular

Groutite

'Gummite'

Gypsum

'Halloysite'

Hematite

Heterosite

Hexahydrite ?

'Hornblende'

Hureaulite

Hydroxylapatite

Hydroxylherderite

Ilmenite

'Indicolite'

Ishikawaite

Kaolinite

Kyanite

Lacroixite

Larnite

'Lepidolite'

Liandratite

'Limonite'

Lithiophilite

Löllingite

Magnesio-hornblende

Magnetite

Malachite

'Manganese Oxides'

'var: Manganese Dendrites'

Masutomilite

Melanterite

Meta-autunite

Metatorbernite

Microcline

var: Amazonite

Microlite Group

Mitridatite

Molybdenite

'Monazite'

Monazite-(Ce)

Montebrasite

Montmorillonite

Moraesite

Muscovite

var: Schernikite

Natrophilite

Opal

var: Opal-AN

Parsonsite

Petalite

Phenakite

Phosphuranylite

Pickeringite

'Pinite'

Pollucite

Purpurite

Pyrite

Pyrochlore Group

Pyrrhotite

Quartz

var: Amethyst

var: Chalcedony

var: Citrine

var: Milky Quartz

var: Rock Crystal

var: Rose Quartz

var: Smoky Quartz

Rhodochrosite

'Rubellite'

Rutile

Samarskite-(Y)

'Scapolite'

Scheelite

Schorl

Sicklerite

Siderite

Sillimanite

Spessartine

Sphalerite

Spodumene

var: Kunzite

Spurrite

Staurolite

'Stilbite'

Sulphur

Tantalite-(Mn)

'Tapiolite'

'Thorogummite'

Titanite

Topaz

Torbernite

'Tourmaline'

'var: Watermelon Tourmaline'

Triphylite

Triplite

Uraninite

Uranophane

'Uranpyrochlore (of Hogarth 1977)'

'Verdelite'

Wardite

Wodginite

Wollastonite

'Zinnwaldite'

Zircon

var: Cyrtolite

Zoisite


120 valid minerals.

Rock Types Recorded

Note: this is a very new system on mindat.org 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

Select Rock List Type

Alphabetical List Tree Diagram

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

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 Macrostrat.org, used under Creative Commons Attribution 4.0 License


Localities in this Region


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.

References

Sort by Year (asc) | by Year (desc) | by Author (A-Z) | by Author (Z-A)
Jarnot, Bruce. (1989): Minerals New to the Portland Area Pegmatites of Central Connecticut. Abstract from the 16th Rochester Mineralogical Symposium April 7, 1989, in Rocks and Minerals, Vol. 64, No. 12, p. 471.

Mineral and/or Locality  
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