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US Route 6 Willimantic Bypass expressway road cuts, Coventry, Tolland Co., Connecticut, USAi
Regional Level Types
US Route 6 Willimantic Bypass expressway road cutsGroup of Road Cuttings
Coventry- not defined -
Tolland Co.County

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Latitude & Longitude (WGS84):
41° 43' 24'' North , 72° 16' 9'' West
Latitude & Longitude (decimal):
Locality type:
Group of Road Cuttings
Nearest Settlements:
Willimantic17,737 (2017)5.3km
Mansfield City26,439 (2017)5.6km
South Coventry1,483 (2017)6.0km
Mansfield Center947 (2017)7.5km
Coventry Lake2,990 (2017)7.6km

Completed in the early 1980s, the U.S. Route 6 Willimantic Bypass expressway is casually referred to as being in Willimantic, the nearby city. Actually it is not in the city's incorporated boundary and instead is situated in four towns - from west to east: Columbia, Coventry, Windham (which includes the city of Willimantic) and Mansfield. At the time of construction, it was intended to be part of Interstate I-84, but those plans were eventually abandoned. Because of this, old or incorrect labels may refer to the locality as I-84 or Route 84. Before the bypass, U.S. Route 6 used to pass through downtown Willimantic on a stretch of road that is now part of state Route 66.

The expressway begins in the town of Columbia, at a 4-way at-grade intersection with State Route 66. From here the expressway heads northeast and immediately crosses into the town of Coventry where the eastbound and westbound sides of the expressway split, with a hill in between them. The Coventry section contains by far the major road cuts on the expressway and produced specimens found in old collections. The road cuts expose gneiss of the Ordovician Tatnic Hill Formation (part of the Putnam-Nashoba Terrane), which here and in other places around the state can host sillimanite crystals in quartz-rich segregations. Fractures in the gneiss host drusy epidote, quartz, prehnite and zeolites. The locality coordinates are for this portion of the expressway.

The expressway then crosses the Willimantic River and enters the town of Windham. At the interchange with State Route 32 there are additional road cuts exposing gneiss of the Waterford Group (part of the Avalonian Terrane) and a small pegmatite dike, mostly on the ramps rather than on the highway, which include part of a small quarry. But these cuts are minor compared to those in Coventry.

After the Rt 32 interchange, the expressway enters the town of Mansfield. There are no bedrock road cuts in this section. After U. S. Route 6 Willimantic Bypass crosses the Natchaug River it once again enters Windham. 0.5 miles (0.80 km) after entering Windham, the U.S. Route 6 Willimantic Bypass ends at an interchange with State Route 66 and U. S. Route 6. There are no bedrock road cuts in this final section.

Regions containing this locality

North America PlateTectonic Plate

Select Mineral List Type

Standard Detailed Strunz Dana Chemical Elements

Mineral List

11 valid minerals.

Detailed Mineral List:

Formula: Na(AlSi3O8)
Colour: white to pink
Description: As rock forming matrix and as microscopic crystal overgrowths lining fractures.
Reference: Former Ed Force collection
'Amphibole Supergroup'
Formula: AX2Z5((Si,Al,Ti)8O22)(OH,F,Cl,O)2
Reference: Former Ed Force collection
'Amphibole Supergroup var: Byssolite'
Formula: AX2Z5((Si,Al,Ti)8O22)(OH,F,Cl,O)2
Habit: capillary
Colour: white
Description: Scattered capillary crystals in fracture voids.
Reference: Former Ed Force collection
Formula: CaCO3
Habit: massive
Colour: white
Description: Massive material filling fracture voids.
Reference: Former Ed Force collection
Habit: rhombohedral
Colour: white
Description: drusy crystals on epidote in fractures in gneiss
Reference: Harold Moritz collection
Formula: Mg5Al(AlSi3O10)(OH)8
Habit: massive
Colour: dark green
Description: In matrix near hydrothermally altered fractures.
Reference: Former Ed Force collection
Formula: {Ca2}{Al2Fe3+}(Si2O7)(SiO4)O(OH)
Habit: prismatic
Colour: yellow-green to dark green to black
Description: drusy crystals in fractures in gneiss, crystallized in two generations, an initial one with elongated, larger and darker crystals and a second one of much finer-grained, short and lighter colored crystals. The second generation coats the first and some other minerals like quartz.
Reference: Harvard Mineralogical Museum No. 119199; Former Ed Force collection.
Formula: α-Fe3+O(OH)
Habit: cubic (pseudomorph)
Colour: brown
Description: Pseudomorphs of microscopic pyrite crystals in fractures.
Reference: Former Ed Force collection
'Heulandite subgroup'
Colour: colorless to white
Description: micro drusy crystals with epidote and zeolites in fractures in gneiss
Reference: Harold Moritz collection
Formula: K(AlSi3O8)
Habit: massive
Colour: white
Fluorescence: deep red
Description: in pegmatites cross-cutting the gneiss within the road cuts
Reference: Harold Moritz collection
Formula: MoS2
Habit: tabular, subhedral
Colour: silvery gray
Description: crystal 23 mm collected by Fred Schuster during construction
Reference: Harold Moritz collection
Formula: Ca2Al2Si3O10(OH)2
Habit: platy aggregates
Colour: pale green
Description: drusy crystal aggregates with zeolites and epidote in fractures in gneiss
Reference: Harold Moritz collection
Formula: FeS2
Habit: cubic
Description: Microscopic crystals in fractures altered to goethite.
Reference: Former Ed Force collection
Formula: SiO2
Habit: elongated prismatic
Colour: colorless to white
Description: drusy crystals with epidote and zeolites in fractures in gneiss
Reference: Harold Moritz collection
Formula: Al2(SiO4)O
Habit: elongated prisms
Colour: brown
Description: Crystals to 7 cm in subparallel alignment in quartz-rich segregations, just like at Chester, Norwich and Willimantic - all from exposures of the Tatnic Hill Formation.
Reference: Wesleyan University collection
'Stilbite subgroup'
Habit: platy
Description: drusy crystals with epidote and zeolites in fractures in gneiss
Reference: Harold Moritz collection

List of minerals arranged by Strunz 10th Edition classification

Group 2 - Sulphides and Sulfosalts
Group 4 - Oxides and Hydroxides
Group 5 - Nitrates and Carbonates
Group 9 - Silicates
Unclassified Minerals, Rocks, etc.
'Amphibole Supergroup'-AX2Z5((Si,Al,Ti)8O22)(OH,F,Cl,O)2
'var: Byssolite'-AX2Z5((Si,Al,Ti)8O22)(OH,F,Cl,O)2
'Heulandite subgroup'-
'Stilbite subgroup'-

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
Group 58 - SOROSILICATES Insular, Mixed, Single, and Larger Tetrahedral Groups
Insular, Mixed, Single, and Larger Tetrahedral Groups with cations in [6] and higher coordination; single and double groups (n = 1, 2)
Group 71 - PHYLLOSILICATES Sheets of Six-Membered Rings
Sheets of 6-membered rings interlayered 1:1, 2:1, and octahedra
Group 72 - PHYLLOSILICATES Two-Dimensional Infinite Sheets with Other Than Six-Membered Rings
Two-Dimensional Infinite Sheets with Other Than Six-Membered Rings with 4-membered rings
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.
'Amphibole Supergroup'-AX2Z5((Si,Al,Ti)8O22)(OH,F,Cl,O)2
'var: Byssolite'-AX2Z5((Si,Al,Ti)8O22)(OH,F,Cl,O)2
'Heulandite subgroup'-
'Stilbite subgroup'-

List of minerals for each chemical element

H Epidote{Ca2}{Al2Fe3+}(Si2O7)(SiO4)O(OH)
H PrehniteCa2Al2Si3O10(OH)2
H Amphibole Supergroup (var: Byssolite)AX2Z5((Si,Al,Ti)8O22)(OH,F,Cl,O)2
H Amphibole SupergroupAX2Z5((Si,Al,Ti)8O22)(OH,F,Cl,O)2
H Goethiteα-Fe3+O(OH)
H ClinochloreMg5Al(AlSi3O10)(OH)8
C CalciteCaCO3
O Epidote{Ca2}{Al2Fe3+}(Si2O7)(SiO4)O(OH)
O SillimaniteAl2(SiO4)O
O PrehniteCa2Al2Si3O10(OH)2
O QuartzSiO2
O Amphibole Supergroup (var: Byssolite)AX2Z5((Si,Al,Ti)8O22)(OH,F,Cl,O)2
O Amphibole SupergroupAX2Z5((Si,Al,Ti)8O22)(OH,F,Cl,O)2
O MicroclineK(AlSi3O8)
O CalciteCaCO3
O AlbiteNa(AlSi3O8)
O Goethiteα-Fe3+O(OH)
O ClinochloreMg5Al(AlSi3O10)(OH)8
F Amphibole Supergroup (var: Byssolite)AX2Z5((Si,Al,Ti)8O22)(OH,F,Cl,O)2
F Amphibole SupergroupAX2Z5((Si,Al,Ti)8O22)(OH,F,Cl,O)2
Na AlbiteNa(AlSi3O8)
Mg ClinochloreMg5Al(AlSi3O10)(OH)8
Al Epidote{Ca2}{Al2Fe3+}(Si2O7)(SiO4)O(OH)
Al SillimaniteAl2(SiO4)O
Al PrehniteCa2Al2Si3O10(OH)2
Al Amphibole Supergroup (var: Byssolite)AX2Z5((Si,Al,Ti)8O22)(OH,F,Cl,O)2
Al Amphibole SupergroupAX2Z5((Si,Al,Ti)8O22)(OH,F,Cl,O)2
Al MicroclineK(AlSi3O8)
Al AlbiteNa(AlSi3O8)
Al ClinochloreMg5Al(AlSi3O10)(OH)8
Si Epidote{Ca2}{Al2Fe3+}(Si2O7)(SiO4)O(OH)
Si SillimaniteAl2(SiO4)O
Si PrehniteCa2Al2Si3O10(OH)2
Si QuartzSiO2
Si Amphibole Supergroup (var: Byssolite)AX2Z5((Si,Al,Ti)8O22)(OH,F,Cl,O)2
Si Amphibole SupergroupAX2Z5((Si,Al,Ti)8O22)(OH,F,Cl,O)2
Si MicroclineK(AlSi3O8)
Si AlbiteNa(AlSi3O8)
Si ClinochloreMg5Al(AlSi3O10)(OH)8
S MolybdeniteMoS2
S PyriteFeS2
Cl Amphibole Supergroup (var: Byssolite)AX2Z5((Si,Al,Ti)8O22)(OH,F,Cl,O)2
Cl Amphibole SupergroupAX2Z5((Si,Al,Ti)8O22)(OH,F,Cl,O)2
K MicroclineK(AlSi3O8)
Ca Epidote{Ca2}{Al2Fe3+}(Si2O7)(SiO4)O(OH)
Ca PrehniteCa2Al2Si3O10(OH)2
Ca CalciteCaCO3
Ti Amphibole Supergroup (var: Byssolite)AX2Z5((Si,Al,Ti)8O22)(OH,F,Cl,O)2
Ti Amphibole SupergroupAX2Z5((Si,Al,Ti)8O22)(OH,F,Cl,O)2
Fe Epidote{Ca2}{Al2Fe3+}(Si2O7)(SiO4)O(OH)
Fe Goethiteα-Fe3+O(OH)
Fe PyriteFeS2
Mo MolybdeniteMoS2

This page contains all mineral locality references listed on 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 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.
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