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Fissure Mines

Past Producer in Keweenaw county in Michigan, United States with commodities Copper, Silver, Arsenic
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Sections on this page
  1. Identification information
  2. Geographic coordinates
  3. Site location context
  4. Geographic areas
  5. Commodities
  6. Materials information
  7. Host and associated rocks
  8. Nearby scientific data
  9. Geologic structures
  10. Economic information about the deposit and operations
  11. Production statistics
  12. Bibliographic references
  13. General comments
  14. Reporter information

Geologic information

Identification information

Deposit ID 10310197
MRDS ID LW00197
Record type District
Current site name Fissure Mines
Alternate or previous names Fissure Deposits

Comments on the site names

  • FISSURE DEPOSITS RANGE FROM SMALL FRACTURES FILLED WITH CALCITE AND OTHER GANGUE MINERALS, UP TO LARGE FAULT ZONES THAT CONTAINED LARGE MASSES OF NATIVE COPPER WEIGHING SEVERAL HUNDRED POUNDS. FISSURES DEPOSITS ARE WIDELY DISTRIBUTED THROUGHOUT THE DISTRICT. THE EARLIEST MINED AND MOST FAMOUS FISSURES WERE LOCATED IN THE EXTREME NORTHERN AND SOUTHERN END OF THE DISTRICT. CROSS-CUTTING FISSURES OFTEN ADDED SIGNIFICANT PRODUCTION TO BASALT AND CONGLOMERATE LODE DEPOSITS WHERE THEY CUT THE LODES (WILSON AND DYL, 1992).

Geographic coordinates

Geographic coordinates: -88.3231, 47.3675 (WGS84)

Site location context

Political divisions (FIPS codes)

Keweenaw(county)

Michigan(state)

United States(country)

North America(continent)

Land(continent)

USGS map quadrangles

Mohawk(quadrangle 1:24,000 scale)

Hancock(quadrangle 1:100,000 scale)

Hancock C(quadrangle 1:250,000 scale)

Hydrologic units (watersheds)

Keweenaw Peninsula(hydrologic unit)

Southcentral Lake Superior(hydrologic accounting unit)

Southern Lake Superior(hydrologic subregion)

Great Lakes(hydrologic region)

Geographic areas

Country State County
United States Michigan Keweenaw
United States Michigan Houghton
United States Michigan Ontonagon

Comments on the location information

  • FISSURE MINES WERE FOUND THROUGHOUT THE NATIVE COPPER DISTRICT. THIS LOCATION IS FOR THE CLIFF MINE NEAR THE NORTHERN END OF THE DISTRICT.

Commodities

Commodity Importance
Copper Primary
Silver Secondary
Arsenic Critical Tertiary

Comments on the commodity information

  • NATIVE SILVER WAS AN IMPORTANT BY-PRODUCT OF COPPER MINING IN FISSURE DEPOSITS, AND OFTEN PROVIDED AS MUCH REVENUE AS NATIVE COPPER. THE MINNESOTA FISSURE PRODUCED OVER 61 MILLION POUNDS OF COPER AND 21,000 OUNCES OF SILVER, AS WELL AS THE LARGEST SINGLE MASS OF COPPER IN THE DISTRICT, WEIGHING 527 TONS. THE MASS FISSURE CUTTING THE KEARSARGE LODE IN THE AHMEEK AND MOHAWK MINES YEILED SIGNIFICANT COPPER ARSENATIVE SILVER WAS AN IMPORTANT BY-PRODUCT OF COPPER MINING IN FISSURE DEPOSITS, AND OFTEN PROVIDED AS MUCH REVENUE AS NATIVE COPPER. THE MINNESOTA FISSURE PRODUCED OVER 61 MILLION POUNDS OF COPER AND 21,000 OUNCES OF SILVER, AS WELL AS THE LARGEST SINGLE MASS OF COPPER IN THE DISTRICT, WEIGHING 527 TONS. THE MASS FISSURE CUTTING THE KEARSARGE LODE IN THE AHMEEK AND MOHAWK MINES YEILED SIGNIFICANT COPPER ARSENIDES. THE

Materials information

Materials Type of material
Copper Ore
Silver Ore
Calcite Gangue
Quartz Gangue
Analcime Gangue
Apophyllite Gangue
Barite Gangue
Prehnite Gangue
Epidote Gangue
Pumpellyite-(Mg) Gangue
Datolite Gangue
Adularia Gangue

Host and associated rocks

  • Host or associated Host
    Rock type Volcanic Rock (Aphanitic) > Mafic Volcanic Rock > Basalt
    Rock unit name Portage Lake Volcanics
    Rock description Portage Lake Volcanics
    Stratigraphic age (youngest) Stenian
    Chronological age 1095

Nearby scientific data

(1) -88.3231, 47.3675
ListMap

Economic information

Geologic structures

Type of structure Regional
Structure description Syncline

Comments on the geologic information

  • FISSURES ARE COMMON THROUGHOUT THE DISTRICT, AND OF THE FEW THAT WERE MINERALIZED, FEW WERE PRODUCTIVE. THE FISSURES IN THE NORTH END OF THE DISTRICT ARE TENSION CRACKS ON FOLDS -- THERE IS A SERIES OF FISSURES NEAR THE CREST OF THE ALLOUEZ ANTICLINE. THE MOST PRODUCTIVE FISSURES (CLIFF AND CENTRAL) IN THE NORTH WERE FOUND BENEATH THE GREENSTONE FLOW, WHERE A 'SLIDE' IMMEDIATELY BENEATH THE FLOW (A CHLORITE-RICH GOUGE PRODUCED BY MOVEMENT ALONG THE BASE OF THE FLOW) MAY HAVE ACTED AS AN IMPERMEABLE BARRIER TO ORE-FLUIDS MOVING UPWARDS ALONG FISSURES THAT TERMINATE AT THE BASE OF THE GREENSTONE. IN THE SOUTHERN END OF THE DISTRICT, FISSURES ARE NEARLY PARALLEL TO THE STRIKE OF THE BEDS. MINERALIZATION IN THE FISSURES WAS APPARENTLY CONTROLLED BY THE NATURE OF THE OF THE UNIT CROSSED BY THE FISSURE, AS EXEMPLIFIED BY THE MINNESOTA FISSURE CUTTING THE MINNESOTA CONGLOMERATE AT THE MINNESOTA MINE [NOTE SPELLING DIFFERENCE].

Economic information about the deposit and operations

Development status Past Producer
Commodity type Metallic
Significant No
Discovery year 1845
Year of first production 1890

Production statistics

  • Year 1968
    Period 1845-1968
    Accuracy Estimate
    Importance Item Commodity Group Amount recovered Grade Recovery percentage
    Major recovered Cu Copper Copper 96800mt

Comments on the production information

  • MUCH OF THE COPPER OCCURRED IN SMALL TO LARGE MASSES AND WAS SMELTED DIRECTLY

Comments on the workings information

  • INDIVIDUAL MINES THAT WORKED FISSURES DEPOSITS THAT ARE INCLUDED IN THIS DATABASE ARE: CLIFF, PHOENIX, MASS, DREXEL, ST. CLAIR, NORTHWESTERN, MOHAWKITE, CONNETICUT, MADISON, BABBITT, FULTON, OWL CREEK, HILL, CHILDS, AND MINESOTA.

Comments on development

  • FISSURE DEPOSITS WERE THE EARLIEST (CLIFF) AND MOST SPECTACULAR DEPOSITS (MINESOTA) MINED IN THE COPPER COUNTRY, ALTHOUGH THEY PRODUCED ONLY 2% OF TOTAL COPPER PRODUCTION.

Reference information

Bibliographic references

  • Deposit

    WILSON, M.L. AND DYL, S.J., III, 1992, THE MICHIGAN COPPER COUNTRY: MINERALOGICAL RECORD, V. 23, P. 1-76.

  • Deposit

    BUTLER, R.S. AND BURBANK, W.S., 1929, THE COPPER DEPOSITS OF MICHIGAN: U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 144, 238 P.

  • Deposit

    WHITE, W.S., 1968, THE NATIVE COPPER DEPOSITS OF NORTHERN MICHIGAN: IN J.D. RIDGE, (EDITOR), ORE DEPOSITS OF THE UNITED STATES (1933-1967) (GRATON-SALES VOLUME): AM. INSTIT. MIN. METALL. PETROL. ENG., VOL. 1, 303-325.

  • Production

    WHITE, 1968

General comments

Subject category Comment text
Deposit THE THREE MOST PROFITABLE FISSURE MINES IN THE DISTRICT WERE THE CLIFF AND CENTRAL MINES ON THE NORTHERN END OF THE DISTICT AND THE MINESOTA MINE ON THE SOUTHERN END OF THE DISTRICT. THE CLIFF MINE WAS THE FIRST MINE IN THE COPPER COUNTRY TO PRODUCE COPPER BY SYSTEMATIC MINING TECHNIQUES AND THE FIRST TO SHOW A PROFIT. IT WORKED THE CLIFF FISSURE CUTTING THE GREENSTONE FLOW, AS DID THE NEAR-BY PHOENIX MINE. THE CENTRAL FISSURE WAS MORE THAN A MILE LONG AND WAS MINED FROM 5 SHAFTS. THE MINESOTA MINE WORKED THE MINNESOTA FISSURE [NOTE SPELLING DIFFERENCE]. THE MINNESOTA FISSURE WAS DISCOVERED IN 1847 AT THE BOTTOM OF A PREHISTORIC MINE PIT. ORE WAS MINED FROM THE MINNESOTA FISSURE WHERE IT FOLLOWED THE STRIKE OF THE MINNESOTA CONGLOMERATE.
Deposit DEPOSITS TYPICALLY WORKED FISSURES AND PARTS OF LODES (CONGLOMERATE AND AMYGDALOIDAL) CUT BY FISSURES.

Reporter information

Type Date Name Affiliation Comment
Reporter 29-MAR-2004 Woodruff, Laurel G. U.S. Geological Survey

Beyond USGS

Supplemental information added by qvyshift.com. Not part of the original USGS MRDS record.

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