An underground copper mine consisting of 3 shafts located near Delaware. The Connecticut Mining Company was organized in 1853 and mining began shortly after. The mine worked the Connecticut Fissure, a series of 2 parallel veins approximately 200 feet apart. The veins were similar in nature; fine prehnite and quartz set in a coarse calcite. Copper was discovered in the veins and the Company drove 3 shafts along the veins in hopes of finding more copper; however, very little copper was found after the initial strike. Between 1853 and 1856, 116,800 pounds of copper was recovered. Beginning in 1857, the mine was worked on tribute until 1860 when the Amygdaloid Copper Company took control. In 1864 the Eagle Harbor Mining Company took control and split the lands up into 3 separate strips of land to organize 3 new companies. Today, the mine piles are known to produce datolite with translucent interiors, a prized find. Also from the Connecticut are copper, prehnite, thomsonite, and greenstone as well.

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Standard Detailed Gallery Strunz Chemical Elements

Commodity List

This is a list of exploitable or exploited mineral commodities recorded at this locality.

ⓘ Copper

Mineral List

8 valid minerals.

Detailed Mineral List:

ⓘ Analcime

Formula: Na(AlSi₂O₆) · H₂O

References:

Yalmer Primeau collection

ⓘ Copper

Formula: Cu

References:

USGS PP144

Rosemeyer, T. (2009) Copper-bearing Fissure Veins, Keweenaw County, Michigan, Lake Superior Native Copper District. Rocks & Minerals: 84(4): 298-323.

ⓘ Datolite

Formula: CaB(SiO₄)(OH)

References:

Heinrich, E. W., Robinson, George Willard (2004) Mineralogy of Michigan (2nd ed.) A.E. Seaman Mineral Museum and Michigan Technological University. 252pp.

Rosemeyer, T. (2009) Copper-bearing Fissure Veins, Keweenaw County, Michigan, Lake Superior Native Copper District. Rocks & Minerals: 84(4): 298-323.

Rosemeyer, T. (2011) New from the Keweenaw: Part 4 - Recent Mineral Finds in Michigan's Copper Country. Rocks & Minerals: 86(3): 205-227

ⓘ Malachite

Formula: Cu₂(CO₃)(OH)₂

References:

Yalmer Primeau collection

ⓘ Microcline

Formula: K(AlSi₃O₈)

References:

Rosemeyer, T. (2022). News from the Keweenaw: Part 5—Recent Mineral Finds in Michigan’s Copper Country: Twenty-ninth in a series of articles on the mines and minerals of Michigan’s Copper Country. Rocks & Minerals, 97(4), 354-363.

ⓘ Natrolite

Formula: Na₂Al₂Si₃O₁₀ · 2H₂O

References:

Heinrich, E. W., Robinson, George Willard (2004) Mineralogy of Michigan (2nd ed.) A.E. Seaman Mineral Museum and Michigan Technological University. 252pp.

ⓘ Prehnite

Formula: Ca₂Al₂Si₃O₁₀(OH)₂

ⓘ Quartz

Formula: SiO₂

References:

Gallery:

CaB(SiO₄)(OH)ⓘ Datolite

List of minerals arranged by Strunz 10th Edition classification

Group 1 - Elements
ⓘ	Copper	1.AA.05	Cu
Group 4 - Oxides and Hydroxides
ⓘ	Quartz	4.DA.05	SiO₂
Group 5 - Nitrates and Carbonates
ⓘ	Malachite	5.BA.10	Cu₂(CO₃)(OH)₂
Group 9 - Silicates
ⓘ	Datolite	9.AJ.20	CaB(SiO₄)(OH)
ⓘ	Prehnite	9.DP.20	Ca₂Al₂Si₃O₁₀(OH)₂
ⓘ	Microcline	9.FA.30	K(AlSi₃O₈)
ⓘ	Natrolite	9.GA.05	Na₂Al₂Si₃O₁₀ · 2H₂O
ⓘ	Analcime	9.GB.05	Na(AlSi₂O₆) · H₂O

List of minerals for each chemical element

H	Hydrogen
H	ⓘ Analcime	Na(AlSi₂O₆) · H₂O
H	ⓘ Datolite	CaB(SiO₄)(OH)
H	ⓘ Malachite	Cu₂(CO₃)(OH)₂
H	ⓘ Natrolite	Na₂Al₂Si₃O₁₀ · 2H₂O
H	ⓘ Prehnite	Ca₂Al₂Si₃O₁₀(OH)₂
B	Boron
B	ⓘ Datolite	CaB(SiO₄)(OH)
C	Carbon
C	ⓘ Malachite	Cu₂(CO₃)(OH)₂
O	Oxygen
O	ⓘ Analcime	Na(AlSi₂O₆) · H₂O
O	ⓘ Datolite	CaB(SiO₄)(OH)
O	ⓘ Malachite	Cu₂(CO₃)(OH)₂
O	ⓘ Microcline	K(AlSi₃O₈)
O	ⓘ Natrolite	Na₂Al₂Si₃O₁₀ · 2H₂O
O	ⓘ Prehnite	Ca₂Al₂Si₃O₁₀(OH)₂
O	ⓘ Quartz	SiO₂
Na	Sodium
Na	ⓘ Analcime	Na(AlSi₂O₆) · H₂O
Na	ⓘ Natrolite	Na₂Al₂Si₃O₁₀ · 2H₂O
Al	Aluminium
Al	ⓘ Analcime	Na(AlSi₂O₆) · H₂O
Al	ⓘ Microcline	K(AlSi₃O₈)
Al	ⓘ Natrolite	Na₂Al₂Si₃O₁₀ · 2H₂O
Al	ⓘ Prehnite	Ca₂Al₂Si₃O₁₀(OH)₂
Si	Silicon
Si	ⓘ Analcime	Na(AlSi₂O₆) · H₂O
Si	ⓘ Datolite	CaB(SiO₄)(OH)
Si	ⓘ Microcline	K(AlSi₃O₈)
Si	ⓘ Natrolite	Na₂Al₂Si₃O₁₀ · 2H₂O
Si	ⓘ Prehnite	Ca₂Al₂Si₃O₁₀(OH)₂
Si	ⓘ Quartz	SiO₂
K	Potassium
K	ⓘ Microcline	K(AlSi₃O₈)
Ca	Calcium
Ca	ⓘ Datolite	CaB(SiO₄)(OH)
Ca	ⓘ Prehnite	Ca₂Al₂Si₃O₁₀(OH)₂
Cu	Copper
Cu	ⓘ Copper	Cu
Cu	ⓘ Malachite	Cu₂(CO₃)(OH)₂

Other Regions, Features and Areas containing this locality

North America PlateTectonic Plate

Mid-continent DomainDomain

USA

Michigan
- Keweenaw PeninsulaPeninsula
Midcontinent RiftGeologic Province

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References

The Copper Country Rock & Mineral Club (2001) Red Gold and Tarnished Silver, 2nd edition. Self-Published. 44 pages.

Kaminski-Hamka, T. (2011) The Copper Mines of Keweenaw County, Michigan. Copperlady Press. 150 pages.

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Connecticut Mine, Eagle Harbor, Keweenaw County, Michigan, USAiRegional Level TypesConnecticut MineMine Eagle HarborTownship Keweenaw CountyCounty MichiganState USACountry function showexplain() { $("#locexplain").toggle(); if (typeof movemap === "function") movemap(); }

Select Mineral List Type

Commodity List

Mineral List

Detailed Mineral List:

Gallery:

List of minerals arranged by Strunz 10th Edition classification

List of minerals for each chemical element

Other Regions, Features and Areas containing this locality

References

Connecticut Mine, Eagle Harbor, Keweenaw County, Michigan, USA i
Regional Level Types
Connecticut Mine Mine
Eagle Harbor Township
Keweenaw County County
Michigan State
USA Country