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Mansfield Hollow Dam, Windham, Windham County, Connecticut, USAi
Regional Level Types
Mansfield Hollow DamDam
WindhamTown
Windham CountyCounty
ConnecticutState
USACountry

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PhotosMapsSearch
04094430017272039969264.jpg
Garnet Group

Mansfield Hollow Dam, Windham, Windham County, Connecticut, USA
05734580017272039974042.jpg
Beryl, etc.

Mansfield Hollow Dam, Windham, Windham County, Connecticut, USA
02459810017272039994901.jpg
Beryl, etc.

Mansfield Hollow Dam, Windham, Windham County, Connecticut, USA
07772850017272040017350.jpg
Titanite, etc.

Mansfield Hollow Dam, Windham, Windham County, Connecticut, USA
04094430017272039969264.jpg
Garnet Group

Mansfield Hollow Dam, Windham, Windham County, Connecticut, USA
05734580017272039974042.jpg
Beryl, etc.

Mansfield Hollow Dam, Windham, Windham County, Connecticut, USA
02459810017272039994901.jpg
Beryl, etc.

Mansfield Hollow Dam, Windham, Windham County, Connecticut, USA
07772850017272040017350.jpg
Titanite, etc.

Mansfield Hollow Dam, Windham, Windham County, Connecticut, USA
03168390017272040108981.jpg
Garnet Group

Mansfield Hollow Dam, Windham, Windham County, Connecticut, USA
02543490017272040134445.jpg
Beryl, etc.

Mansfield Hollow Dam, Windham, Windham County, Connecticut, USA
Latitude & Longitude (WGS84):
41° 44' 56'' North , 72° 10' 26'' West
Latitude & Longitude (decimal):
41.74889,-72.17389
GeoHash:
G#: drktt8hsf
GRN:
N28W39
Type:
Dam
Köppen climate type:
Dfb : Warm-summer humid continental climate
Nearest Settlements:
PlacePopulationDistance
Mansfield Center947 (2017)2.7km
Willimantic17,737 (2017)5.1km
Mansfield City26,439 (2017)5.3km
Windham23,072 (2017)5.6km
South Windham1,421 (2017)7.7km
Mindat Locality ID:
16106
Long-form identifier:
mindat:1:2:16106:7
GUID (UUID V4):
0


A rolled earth fill dam with stone slope protection created by the U. S. Army Corps of Engineers between 1949 and 1952. Most of the subsequent lake is in Mansfield, Tolland Co., but the dam itself is in Windham. Coordinates are for the approximate mid-point of the 4.8-km-long dam. Uncertain where the stone came from, but Hope Valley Alaskite Gneiss is exposed in the state park and matches specimens found on the dam. Beryl (variety aquamarine)/fluorite/quartz occur in a 3-4 cm vein cross-cutting the gneiss.

Select Mineral List Type

Standard Detailed Gallery Strunz Chemical Elements

Mineral List


15 valid minerals.

Detailed Mineral List:

ⓘ Albite
Formula: Na(AlSi3O8)
ⓘ 'Allanite Group'
Formula: (A12+REE3+)(M13+M23+M32+)O[Si2O7][SiO4](OH)
ⓘ Annite
Formula: KFe2+3(AlSi3O10)(OH)2
Habit: micaceous
Colour: black
Description: Most obvious in calcite-rich veins cutting annite gneiss (probably Tatnic Hill Formation).
ⓘ Beryl
Formula: Be3Al2(Si6O18)
Habit: prismatic
Colour: aqua
Description: Subhedral crystals to 4 cm embedded in smoky quartz, albite, rosy microcline and fluorite.
ⓘ Calcite
Formula: CaCO3
Habit: anhedral
Colour: white
Description: Cleavable masses in veins with annite, pyrite, chlorite and rutile cutting annite gneiss (probably Tatnic Hill Formation).
ⓘ 'Chlorite Group'
Habit: granular masses
Colour: dark green
Description: In veins with calcite, annite, pyrite, and rutile cutting annite gneiss (probably Tatnic Hill Formation).
ⓘ Epidote
Formula: (CaCa)(AlAlFe3+)O[Si2O7][SiO4](OH)
ⓘ Fluorite
Formula: CaF2
Colour: colorless to smoky
Fluorescence: blue under long wave UV
Description: massive grains with aquamarine, usually crumble out leaving voids
ⓘ 'Garnet Group'
Formula: X3Z2(SiO4)3
ⓘ Goethite
Formula: Fe3+O(OH)
ⓘ 'Hornblende Root Name Group'
Formula: ◻Ca2(Z2+4Z3+)(AlSi7O22)(OH,F,Cl)2
ⓘ Magnetite
Formula: Fe2+Fe3+2O4
ⓘ Microcline
Formula: K(AlSi3O8)
Habit: massive
Colour: rosy
Description: Host mineral, with quartz, for beryl crystals.
ⓘ Molybdenite
Formula: MoS2
ⓘ Pyrite
Formula: FeS2
Habit: cubic, pyritohedral
Description: Crude crystals to 1.5 cm in calcite/annite/chlorite/rutile veins cutting annite gneiss (probably Tatnic Hill Formation).
ⓘ Pyrrhotite
Formula: Fe1-xS
ⓘ Quartz
Formula: SiO2
Habit: massive
Colour: smoky
Description: Host mineral, with microcline, for beryl crystals.
ⓘ Rutile
Formula: TiO2
Habit: elongated prism
Colour: black
Description: Micro crystals embedded in calcite with granular chlorite, in veins with annite and pyrite cutting annite gneiss (probably Tatnic Hill Formation).
ⓘ Titanite
Formula: CaTi(SiO4)O
Habit: rectangular, tabular prisms
Colour: yellow-green
Description: Schooner (1961) states: "Golden crystals, up to a couple of inches across, and fairly thick, have been collected, by the author, at the Mansfield Hollow Dam; they accompany hornblende."

List of minerals arranged by Strunz 10th Edition classification

Group 2 - Sulphides and Sulfosalts
ⓘPyrrhotite2.CC.10Fe1-xS
ⓘMolybdenite2.EA.30MoS2
ⓘPyrite2.EB.05aFeS2
Group 3 - Halides
ⓘFluorite3.AB.25CaF2
Group 4 - Oxides and Hydroxides
ⓘGoethite4.00.Fe3+O(OH)
ⓘMagnetite4.BB.05Fe2+Fe3+2O4
ⓘQuartz4.DA.05SiO2
ⓘRutile4.DB.05TiO2
Group 5 - Nitrates and Carbonates
ⓘCalcite5.AB.05CaCO3
Group 9 - Silicates
ⓘTitanite9.AG.15CaTi(SiO4)O
ⓘEpidote9.BG.05a(CaCa)(AlAlFe3+)O[Si2O7][SiO4](OH)
ⓘBeryl9.CJ.05Be3Al2(Si6O18)
ⓘAnnite9.EC.20KFe2+3(AlSi3O10)(OH)2
ⓘMicrocline9.FA.30K(AlSi3O8)
ⓘAlbite9.FA.35Na(AlSi3O8)
Unclassified
ⓘ'Chlorite Group'-
ⓘ'Hornblende Root Name Group'-◻Ca2(Z2+4Z3+)(AlSi7O22)(OH,F,Cl)2
ⓘ'Garnet Group'-X3Z2(SiO4)3
ⓘ'Allanite Group'-(A12+REE3+)(M13+M23+M32+)O[Si2O7][SiO4](OH)

List of minerals for each chemical element

HHydrogen
Hⓘ AnniteKFe32+(AlSi3O10)(OH)2
Hⓘ Epidote(CaCa)(AlAlFe3+)O[Si2O7][SiO4](OH)
Hⓘ GoethiteFe3+O(OH)
Hⓘ Hornblende Root Name Group◻Ca2(Z42+Z3+)(AlSi7O22)(OH,F,Cl)2
Hⓘ Allanite Group(A12+REE3+)(M13+M23+M32+)O[Si2O7][SiO4](OH)
BeBeryllium
Beⓘ BerylBe3Al2(Si6O18)
CCarbon
Cⓘ CalciteCaCO3
OOxygen
Oⓘ AlbiteNa(AlSi3O8)
Oⓘ AnniteKFe32+(AlSi3O10)(OH)2
Oⓘ BerylBe3Al2(Si6O18)
Oⓘ CalciteCaCO3
Oⓘ Epidote(CaCa)(AlAlFe3+)O[Si2O7][SiO4](OH)
Oⓘ GoethiteFe3+O(OH)
Oⓘ MagnetiteFe2+Fe23+O4
Oⓘ MicroclineK(AlSi3O8)
Oⓘ QuartzSiO2
Oⓘ RutileTiO2
Oⓘ TitaniteCaTi(SiO4)O
Oⓘ Hornblende Root Name Group◻Ca2(Z42+Z3+)(AlSi7O22)(OH,F,Cl)2
Oⓘ Garnet GroupX3Z2(SiO4)3
Oⓘ Allanite Group(A12+REE3+)(M13+M23+M32+)O[Si2O7][SiO4](OH)
FFluorine
Fⓘ FluoriteCaF2
Fⓘ Hornblende Root Name Group◻Ca2(Z42+Z3+)(AlSi7O22)(OH,F,Cl)2
NaSodium
Naⓘ AlbiteNa(AlSi3O8)
AlAluminium
Alⓘ AlbiteNa(AlSi3O8)
Alⓘ AnniteKFe32+(AlSi3O10)(OH)2
Alⓘ BerylBe3Al2(Si6O18)
Alⓘ Epidote(CaCa)(AlAlFe3+)O[Si2O7][SiO4](OH)
Alⓘ MicroclineK(AlSi3O8)
Alⓘ Hornblende Root Name Group◻Ca2(Z42+Z3+)(AlSi7O22)(OH,F,Cl)2
SiSilicon
Siⓘ AlbiteNa(AlSi3O8)
Siⓘ AnniteKFe32+(AlSi3O10)(OH)2
Siⓘ BerylBe3Al2(Si6O18)
Siⓘ Epidote(CaCa)(AlAlFe3+)O[Si2O7][SiO4](OH)
Siⓘ MicroclineK(AlSi3O8)
Siⓘ QuartzSiO2
Siⓘ TitaniteCaTi(SiO4)O
Siⓘ Hornblende Root Name Group◻Ca2(Z42+Z3+)(AlSi7O22)(OH,F,Cl)2
Siⓘ Garnet GroupX3Z2(SiO4)3
Siⓘ Allanite Group(A12+REE3+)(M13+M23+M32+)O[Si2O7][SiO4](OH)
SSulfur
Sⓘ MolybdeniteMoS2
Sⓘ PyriteFeS2
Sⓘ PyrrhotiteFe1-xS
ClChlorine
Clⓘ Hornblende Root Name Group◻Ca2(Z42+Z3+)(AlSi7O22)(OH,F,Cl)2
KPotassium
Kⓘ AnniteKFe32+(AlSi3O10)(OH)2
Kⓘ MicroclineK(AlSi3O8)
CaCalcium
Caⓘ CalciteCaCO3
Caⓘ Epidote(CaCa)(AlAlFe3+)O[Si2O7][SiO4](OH)
Caⓘ FluoriteCaF2
Caⓘ TitaniteCaTi(SiO4)O
Caⓘ Hornblende Root Name Group◻Ca2(Z42+Z3+)(AlSi7O22)(OH,F,Cl)2
TiTitanium
Tiⓘ RutileTiO2
Tiⓘ TitaniteCaTi(SiO4)O
FeIron
Feⓘ AnniteKFe32+(AlSi3O10)(OH)2
Feⓘ Epidote(CaCa)(AlAlFe3+)O[Si2O7][SiO4](OH)
Feⓘ GoethiteFe3+O(OH)
Feⓘ MagnetiteFe2+Fe23+O4
Feⓘ PyriteFeS2
Feⓘ PyrrhotiteFe1-xS
MoMolybdenum
Moⓘ MolybdeniteMoS2

Other Regions, Features and Areas containing this locality

North AmericaContinent
North America PlateTectonic Plate

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

Schooner, Richard. (1961), The Mineralogy of Connecticut. Fluorescent House, Branford, Connecticut.
Weber, Marcelle H., Sullivan, Earle C. (1995) Connecticut Mineral Locality Index. Rocks & Minerals, 70 (6) 396-409 doi:10.1080/00357529.1995.11761569p.403
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