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Northwestern Mine, Central, Keweenaw Co., Michigan, USAi
Regional Level Types
Northwestern MineMine
Central- not defined -
Keweenaw Co.County
MichiganState
USACountry

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Latitude & Longitude (WGS84): 47° 24' 32'' North , 88° 11' 29'' West
Latitude & Longitude (decimal): 47.40889,-88.19139
GeoHash:G#: f03m9nsbz
Locality type:Mine
Köppen climate type:Dfb : Warm-summer humid continental climate
Nearest Settlements:
PlacePopulationDistance
Ahmeek146 (2017)19.7km
Copper City187 (2017)20.3km
Copper Harbor108 (2017)23.7km
Calumet703 (2017)26.8km
Laurium1,941 (2017)26.9km


The Northwestern Mine consists of 4 shafts and at least 1 adit. The Northwestern Mining Company was organized in 1845 and then reorganized in 1848. Work continued until 1857 and resumed again in 1863. All work ceased in 1865 and was absorbed by the Central Mining Company shortly after. 313,000 lbs. of refined copper was recovered from the mine. Copper, silver, analcime, and prehnite can be found on the poor-rock piles.

Regions containing this locality

North America PlateTectonic Plate
Keweenaw Peninsula, Michigan, USAPeninsula

Select Mineral List Type

Standard Detailed Strunz Dana Chemical Elements

Mineral List


12 valid minerals.

Detailed Mineral List:

Analcime
Formula: Na(AlSi2O6) · H2O
Habit: trapazohedra to 2.5cm in diameter
Colour: reddish
Reference: Rocks & Min.:58:111; Tschernich, R. (1992): Zeolites of the World, 66; Rocks & Minerals 84:298-323.
'Apophyllite'
Reference: Tschernich, R. (1992): Zeolites of the World, 66
Calcite
Formula: CaCO3
Reference: Rocks & Min.:58:111.; Rocks & Minerals 84:298-323.; Rosemeyer, T. 2011 New from the Keweenaw: Part 4 - Recent Mineral Finds in Michigan's Copper Country. Rocks & Minerals 86:205-227
Chalcocite
Formula: Cu2S
Reference: Electron Backscatter Diffraction (EDS) on Scanning Electron Microscope (SEM) (Joshua Richardson)
'Chlorite Group'
Reference: Rocks & Minerals 84:298-323.
Chrysocolla
Formula: Cu2-xAlx(H2-xSi2O5)(OH)4 · nH2O
Reference: Mineralogy of Michigan (2004) Heinrich & Robinson
Copper
Formula: Cu
Reference: Henwood, W.J. (1871): Transactions of the Royal Geological Society of Cornwall 8(1), 385-489; Rocks & Min.:58:111.; Rocks & Minerals 84:298-323.; Rosemeyer, T. 2011 New from the Keweenaw: Part 4 - Recent Mineral Finds in Michigan's Copper Country. Rocks & Minerals 86:205-227
Datolite
Formula: CaB(SiO4)(OH)
Reference: Rocks & Min.:58:111.
'K Feldspar'
Reference: Mineralogy of Michigan (2004) Heinrich & Robinson; Rocks & Minerals 84:298-323.; Rosemeyer, T. 2011 New from the Keweenaw: Part 4 - Recent Mineral Finds in Michigan's Copper Country. Rocks & Minerals 86:205-227
'K Feldspar var: Adularia'
Formula: KAlSi3O8
Reference: Mineralogy of Michigan (2004) Heinrich & Robinson; Rocks & Minerals 84:298-323.; Rosemeyer, T. 2011 New from the Keweenaw: Part 4 - Recent Mineral Finds in Michigan's Copper Country. Rocks & Minerals 86:205-227
Microcline
Formula: K(AlSi3O8)
Reference: Rocks & Min.:58:111.
Prehnite
Formula: Ca2Al2Si3O10(OH)2
Reference: Rocks & Min.:58:111.
'Pumpellyite'
Reference: Rocks & Min.:58:111.
Pumpellyite-(Mg)
Formula: Ca2MgAl2(Si2O7)(SiO4)(OH)2 · H2O
Reference: Mineralogy of Michigan (2004) Heinrich & Robinson
Pumpellyite-(Mg) var: Chlorastrolite
Formula: Ca2MgAl2(Si2O7)(SiO4)(OH)2 · H2O
Reference: Mineralogy of Michigan (2004) Heinrich & Robinson
Quartz
Formula: SiO2
Reference: Rocks & Minerals 84:298-323.
Saponite
Formula: Ca0.25(Mg,Fe)3((Si,Al)4O10)(OH)2 · nH2O
Reference: Rocks & Min.:58:111.
Silver
Formula: Ag
Reference: Henwood, W.J. (1871): Transactions of the Royal Geological Society of Cornwall 8(1), 385-489

List of minerals arranged by Strunz 10th Edition classification

Group 1 - Elements
Copper1.AA.05Cu
Silver1.AA.05Ag
Group 2 - Sulphides and Sulfosalts
Chalcocite2.BA.05Cu2S
Group 4 - Oxides and Hydroxides
Quartz4.DA.05SiO2
Group 5 - Nitrates and Carbonates
Calcite5.AB.05CaCO3
Group 9 - Silicates
Analcime9.GB.05Na(AlSi2O6) · H2O
Chrysocolla9.ED.20Cu2-xAlx(H2-xSi2O5)(OH)4 · nH2O
Datolite9.AJ.20CaB(SiO4)(OH)
Microcline9.FA.30K(AlSi3O8)
Prehnite9.DP.20Ca2Al2Si3O10(OH)2
Pumpellyite-(Mg)9.BG.20Ca2MgAl2(Si2O7)(SiO4)(OH)2 · H2O
var: Chlorastrolite9.BG.20Ca2MgAl2(Si2O7)(SiO4)(OH)2 · H2O
Saponite9.EC.45Ca0.25(Mg,Fe)3((Si,Al)4O10)(OH)2 · nH2O
Unclassified Minerals, Rocks, etc.
'Apophyllite'-
'Chlorite Group'-
'K Feldspar'-
'var: Adularia'-KAlSi3O8
'Pumpellyite'-

List of minerals arranged by Dana 8th Edition classification

Group 1 - NATIVE ELEMENTS AND ALLOYS
Metals, other than the Platinum Group
Copper1.1.1.3Cu
Silver1.1.1.2Ag
Group 2 - SULFIDES
AmBnXp, with (m+n):p = 2:1
Chalcocite2.4.7.1Cu2S
Group 14 - ANHYDROUS NORMAL CARBONATES
A(XO3)
Calcite14.1.1.1CaCO3
Group 54 - NESOSILICATES Borosilicates and Some Beryllosilicates
Borosilicates and Some Beryllosilicates with B in [4] coordination
Datolite54.2.1a.1CaB(SiO4)(OH)
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)
Pumpellyite-(Mg)58.2.2.7Ca2MgAl2(Si2O7)(SiO4)(OH)2 · H2O
Group 71 - PHYLLOSILICATES Sheets of Six-Membered Rings
Sheets of 6-membered rings with 2:1 clays
Saponite71.3.1b.2Ca0.25(Mg,Fe)3((Si,Al)4O10)(OH)2 · nH2O
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
Prehnite72.1.3.1Ca2Al2Si3O10(OH)2
Group 74 - PHYLLOSILICATES Modulated Layers
Modulated Layers with joined strips
Chrysocolla74.3.2.1Cu2-xAlx(H2-xSi2O5)(OH)4 · nH2O
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
Microcline76.1.1.5K(AlSi3O8)
Group 77 - TECTOSILICATES Zeolites
Zeolite group - True zeolites
Analcime77.1.1.1Na(AlSi2O6) · H2O
Unclassified Minerals, Mixtures, etc.
'Apophyllite'-
'Chlorite Group'-
'K Feldspar'-
'var: Adularia'-KAlSi3O8
'Pumpellyite'-
Pumpellyite-(Mg)
var: Chlorastrolite
-Ca2MgAl2(Si2O7)(SiO4)(OH)2 · H2O

List of minerals for each chemical element

HHydrogen
H AnalcimeNa(AlSi2O6) · H2O
H DatoliteCaB(SiO4)(OH)
H PrehniteCa2Al2Si3O10(OH)2
H SaponiteCa0.25(Mg,Fe)3((Si,Al)4O10)(OH)2 · nH2O
H ChrysocollaCu2-xAlx(H2-xSi2O5)(OH)4 · nH2O
H Pumpellyite-(Mg) (var: Chlorastrolite)Ca2MgAl2(Si2O7)(SiO4)(OH)2 · H2O
H Pumpellyite-(Mg)Ca2MgAl2(Si2O7)(SiO4)(OH)2 · H2O
BBoron
B DatoliteCaB(SiO4)(OH)
CCarbon
C CalciteCaCO3
OOxygen
O AnalcimeNa(AlSi2O6) · H2O
O CalciteCaCO3
O DatoliteCaB(SiO4)(OH)
O MicroclineK(AlSi3O8)
O PrehniteCa2Al2Si3O10(OH)2
O SaponiteCa0.25(Mg,Fe)3((Si,Al)4O10)(OH)2 · nH2O
O K Feldspar (var: Adularia)KAlSi3O8
O ChrysocollaCu2-xAlx(H2-xSi2O5)(OH)4 · nH2O
O Pumpellyite-(Mg) (var: Chlorastrolite)Ca2MgAl2(Si2O7)(SiO4)(OH)2 · H2O
O QuartzSiO2
O Pumpellyite-(Mg)Ca2MgAl2(Si2O7)(SiO4)(OH)2 · H2O
NaSodium
Na AnalcimeNa(AlSi2O6) · H2O
Na SaponiteCa0.25(Mg,Fe)3((Si,Al)4O10)(OH)2 · nH2O
MgMagnesium
Mg SaponiteCa0.25(Mg,Fe)3((Si,Al)4O10)(OH)2 · nH2O
Mg Pumpellyite-(Mg) (var: Chlorastrolite)Ca2MgAl2(Si2O7)(SiO4)(OH)2 · H2O
Mg Pumpellyite-(Mg)Ca2MgAl2(Si2O7)(SiO4)(OH)2 · H2O
AlAluminium
Al AnalcimeNa(AlSi2O6) · H2O
Al MicroclineK(AlSi3O8)
Al PrehniteCa2Al2Si3O10(OH)2
Al SaponiteCa0.25(Mg,Fe)3((Si,Al)4O10)(OH)2 · nH2O
Al K Feldspar (var: Adularia)KAlSi3O8
Al ChrysocollaCu2-xAlx(H2-xSi2O5)(OH)4 · nH2O
Al Pumpellyite-(Mg) (var: Chlorastrolite)Ca2MgAl2(Si2O7)(SiO4)(OH)2 · H2O
Al Pumpellyite-(Mg)Ca2MgAl2(Si2O7)(SiO4)(OH)2 · H2O
SiSilicon
Si AnalcimeNa(AlSi2O6) · H2O
Si DatoliteCaB(SiO4)(OH)
Si MicroclineK(AlSi3O8)
Si PrehniteCa2Al2Si3O10(OH)2
Si SaponiteCa0.25(Mg,Fe)3((Si,Al)4O10)(OH)2 · nH2O
Si K Feldspar (var: Adularia)KAlSi3O8
Si ChrysocollaCu2-xAlx(H2-xSi2O5)(OH)4 · nH2O
Si Pumpellyite-(Mg) (var: Chlorastrolite)Ca2MgAl2(Si2O7)(SiO4)(OH)2 · H2O
Si QuartzSiO2
Si Pumpellyite-(Mg)Ca2MgAl2(Si2O7)(SiO4)(OH)2 · H2O
SSulfur
S ChalcociteCu2S
KPotassium
K MicroclineK(AlSi3O8)
K K Feldspar (var: Adularia)KAlSi3O8
CaCalcium
Ca CalciteCaCO3
Ca DatoliteCaB(SiO4)(OH)
Ca PrehniteCa2Al2Si3O10(OH)2
Ca SaponiteCa0.25(Mg,Fe)3((Si,Al)4O10)(OH)2 · nH2O
Ca Pumpellyite-(Mg) (var: Chlorastrolite)Ca2MgAl2(Si2O7)(SiO4)(OH)2 · H2O
Ca Pumpellyite-(Mg)Ca2MgAl2(Si2O7)(SiO4)(OH)2 · H2O
FeIron
Fe SaponiteCa0.25(Mg,Fe)3((Si,Al)4O10)(OH)2 · nH2O
CuCopper
Cu CopperCu
Cu ChrysocollaCu2-xAlx(H2-xSi2O5)(OH)4 · nH2O
Cu ChalcociteCu2S
AgSilver
Ag SilverAg

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

Stenian
1000 - 1200 Ma



ID: 3184728
Mesoproterozoic volcanic rocks

Age: Stenian (1000 - 1200 Ma)

Comments: Mid-Continent Rift

Lithology: Bimodal volcanic rocks

Reference: Chorlton, L.B. Generalized geology of the world: bedrock domains and major faults in GIS format: a small-scale world geology map with an extended geological attribute database. doi: 10.4095/223767. Geological Survey of Canada, Open File 5529. [154]

Stenian
1000 - 1200 Ma



ID: 2928161
Portage Lake Volcanics

Age: Stenian (1000 - 1200 Ma)

Stratigraphic Name: Portage Lake Volcanics

Description: Lava flows, mostly basalt, andesite and felsite flows and subordinate interflow sedimentary rocks.

Comments: This unit is the same as unit Yp on paper map of Sims (1992). Description is taken from that unit description. Original map source: Cannon, W.F., Kress, T.H., Sutphin, D.M., Morey, G.B., Meints, Joyce, and Barber-Delach, Robert, 1997, Digital Geologic Map and mineral deposits of the Lake Superior Region, Minnesota, Wisconsin, Michigan: USGS Open-File Report 97-455 (version 3, Nov. 19

Lithology: Major:{basalt}, Minor:{basaltic andesite}, Incidental:{rhyolite, sandstone mudstone}

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

References

Sort by

Year (asc) Year (desc) Author (A-Z) Author (Z-A)
Henwood, W.J. (1871): Observations on Metalliferous Deposits: On the Native Copper of Lake Superior. Transactions of the Royal Geological Society of Cornwall 8(1), 385-489.
Tschernich, R. (1992): Zeolites of the World, 66
Butler, B.S., and Burbank, W.S., 1929, The Copper Deposits of Michigan. U.S. Geological Survey. Professional Paper 144. 238 pp.


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