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Mansfield Hollow Dam, Windham, Windham Co., Connecticut, USAi
Regional Level Types
Mansfield Hollow DamDam
Windham- not defined -
Windham Co.County
ConnecticutState
USACountry

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Key
Latitude & Longitude (WGS84):
41° 44' 56'' North , 72° 10' 26'' West
Latitude & Longitude (decimal):
Locality type:
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


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 Strunz Dana Chemical Elements

Mineral List


13 valid minerals.

Detailed Mineral List:

Albite
Formula: Na(AlSi3O8)
Reference: Former Fred Schuster collection
'Allanite Group'
Formula: {A12+REE3+}{M3+2M32+}(Si2O7)(SiO4)O(OH)
Reference: Weber, Marcelle H. and Earle C. Sullivan. (1995): Connecticut Mineral Locality Index. Rocks & Minerals (Connecticut Issue): 70(6): 403.
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).
Reference: Eric Quinter collection
Beryl
Formula: Be3Al2(Si6O18)
Habit: prismatic
Colour: aqua
Description: Subhedral crystals to 4 cm embedded in smoky quartz, albite, rosy microcline and fluorite.
Reference: Weber, Marcelle H. and Earle C. Sullivan. (1995): Connecticut Mineral Locality Index. Rocks & Minerals (Connecticut Issue): 70(6): 403.
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).
Reference: Eric Quinter collection
'Chlorite Group'
Habit: granular masses
Colour: dark green
Description: In veins with calcite, annite, pyrite, and rutile cutting annite gneiss (probably Tatnic Hill Formation).
Reference: Eric Quinter collection
Fluorite
Formula: CaF2
Colour: colorless to smoky
Fluorescence: blue under long wave UV
Description: massive grains with aquamarine, usually crumble out leaving voids
Reference: Weber, Marcelle H. and Earle C. Sullivan. (1995): Connecticut Mineral Locality Index. Rocks & Minerals (Connecticut Issue): 70(6): 403.
Goethite
Formula: α-Fe3+O(OH)
Reference: Former Fred Schuster collection
'Hornblende'
Reference: Schooner, Richard. (1961): The Mineralogy of Connecticut. Fluorescent House, Branford, Connecticut.
Magnetite
Formula: Fe2+Fe3+2O4
Reference: Weber, Marcelle H. and Earle C. Sullivan. (1995): Connecticut Mineral Locality Index. Rocks & Minerals (Connecticut Issue): 70(6): 403.
Microcline
Formula: K(AlSi3O8)
Habit: massive
Colour: rosy
Description: Host mineral, with quartz, for beryl crystals.
Reference: Former Don Miller collection
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).
Reference: Weber, Marcelle H. and Earle C. Sullivan. (1995): Connecticut Mineral Locality Index. Rocks & Minerals (Connecticut Issue): 70(6): 403.
Pyrrhotite
Formula: Fe7S8
Reference: Weber, Marcelle H. and Earle C. Sullivan. (1995): Connecticut Mineral Locality Index. Rocks & Minerals (Connecticut Issue): 70(6): 403.
Quartz
Formula: SiO2
Habit: massive
Colour: smoky
Description: Host mineral, with microcline, for beryl crystals.
Reference: Former Don Miller collection
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).
Reference: Eric Quinter collection
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."
Reference: Schooner, Richard. (1961): The Mineralogy of Connecticut. Fluorescent House, Branford, Connecticut.

List of minerals arranged by Strunz 10th Edition classification

Group 2 - Sulphides and Sulfosalts
Pyrite2.EB.05aFeS2
Pyrrhotite2.CC.10Fe7S8
Group 3 - Halides
Fluorite3.AB.25CaF2
Group 4 - Oxides and Hydroxides
Goethite4.00.α-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
Albite9.FA.35Na(AlSi3O8)
Annite9.EC.20KFe2+3(AlSi3O10)(OH)2
Beryl9.CJ.05Be3Al2(Si6O18)
Microcline9.FA.30K(AlSi3O8)
Titanite9.AG.15CaTi(SiO4)O
Unclassified Minerals, Rocks, etc.
'Allanite Group'-{A12+REE3+}{M3+2M32+}(Si2O7)(SiO4)O(OH)
'Chlorite Group'-
'Hornblende'-

List of minerals arranged by Dana 8th Edition classification

Group 2 - SULFIDES
AmXp, with m:p = 1:1
Pyrrhotite2.8.10.1Fe7S8
AmBnXp, with (m+n):p = 1:2
Pyrite2.12.1.1FeS2
Group 4 - SIMPLE OXIDES
AX2
Rutile4.4.1.1TiO2
Group 6 - HYDROXIDES AND OXIDES CONTAINING HYDROXYL
XO(OH)
Goethite6.1.1.2α-Fe3+O(OH)
Group 7 - MULTIPLE OXIDES
AB2X4
Magnetite7.2.2.3Fe2+Fe3+2O4
Group 9 - NORMAL HALIDES
AX2
Fluorite9.2.1.1CaF2
Group 14 - ANHYDROUS NORMAL CARBONATES
A(XO3)
Calcite14.1.1.1CaCO3
Group 52 - NESOSILICATES Insular SiO4 Groups and O,OH,F,H2O
Insular SiO4 Groups and O, OH, F, and H2O with cations in [6] and/or >[6] coordination
Titanite52.4.3.1CaTi(SiO4)O
Group 61 - CYCLOSILICATES Six-Membered Rings
Six-Membered Rings with [Si6O18] rings; possible (OH) and Al substitution
Beryl61.1.1.1Be3Al2(Si6O18)
Group 71 - PHYLLOSILICATES Sheets of Six-Membered Rings
Sheets of 6-membered rings with 2:1 layers
Annite71.2.2b.3KFe2+3(AlSi3O10)(OH)2
Group 75 - TECTOSILICATES Si Tetrahedral Frameworks
Si Tetrahedral Frameworks - SiO2 with [4] coordinated Si
Quartz75.1.3.1SiO2
Group 76 - TECTOSILICATES Al-Si Framework
Al-Si Framework with Al-Si frameworks
Albite76.1.3.1Na(AlSi3O8)
Microcline76.1.1.5K(AlSi3O8)
Unclassified Minerals, Mixtures, etc.
'Allanite Group'-{A12+REE3+}{M3+2M32+}(Si2O7)(SiO4)O(OH)
'Chlorite Group'-
'Hornblende'-

List of minerals for each chemical element

HHydrogen
H Allanite Group{A12+REE3+}{M23+M32+}(Si2O7)(SiO4)O(OH)
H Goethiteα-Fe3+O(OH)
H AnniteKFe32+(AlSi3O10)(OH)2
BeBeryllium
Be BerylBe3Al2(Si6O18)
CCarbon
C CalciteCaCO3
OOxygen
O Allanite Group{A12+REE3+}{M23+M32+}(Si2O7)(SiO4)O(OH)
O BerylBe3Al2(Si6O18)
O MagnetiteFe2+Fe23+O4
O TitaniteCaTi(SiO4)O
O CalciteCaCO3
O RutileTiO2
O Goethiteα-Fe3+O(OH)
O AnniteKFe32+(AlSi3O10)(OH)2
O QuartzSiO2
O MicroclineK(AlSi3O8)
O AlbiteNa(AlSi3O8)
FFluorine
F FluoriteCaF2
NaSodium
Na AlbiteNa(AlSi3O8)
AlAluminium
Al BerylBe3Al2(Si6O18)
Al AnniteKFe32+(AlSi3O10)(OH)2
Al MicroclineK(AlSi3O8)
Al AlbiteNa(AlSi3O8)
SiSilicon
Si Allanite Group{A12+REE3+}{M23+M32+}(Si2O7)(SiO4)O(OH)
Si BerylBe3Al2(Si6O18)
Si TitaniteCaTi(SiO4)O
Si AnniteKFe32+(AlSi3O10)(OH)2
Si QuartzSiO2
Si MicroclineK(AlSi3O8)
Si AlbiteNa(AlSi3O8)
SSulfur
S PyrrhotiteFe7S8
S PyriteFeS2
KPotassium
K AnniteKFe32+(AlSi3O10)(OH)2
K MicroclineK(AlSi3O8)
CaCalcium
Ca TitaniteCaTi(SiO4)O
Ca CalciteCaCO3
Ca FluoriteCaF2
TiTitanium
Ti TitaniteCaTi(SiO4)O
Ti RutileTiO2
FeIron
Fe MagnetiteFe2+Fe23+O4
Fe PyrrhotiteFe7S8
Fe Goethiteα-Fe3+O(OH)
Fe PyriteFeS2
Fe AnniteKFe32+(AlSi3O10)(OH)2

References

Sort by

Year (asc) Year (desc) Author (A-Z) Author (Z-A)
Schooner, Richard. (1961): The Mineralogy of Connecticut. Fluorescent House, Branford, Connecticut.
Weber, Marcelle H. and Earle C. Sullivan. (1995): Connecticut Mineral Locality Index. Rocks & Minerals (Connecticut Issue): 70(6): 403.

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North America PlateTectonic Plate

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