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Pewabic Amygdaloid

Past Producer in Houghton county in Michigan, United States with commodities Copper, Silver
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Sections on this page
  1. Identification information
  2. Geographic coordinates
  3. Site location context
  4. Geographic areas
  5. Public Land Survey System information
  6. Commodities
  7. Materials information
  8. Alteration
  9. Mineral occurrence model information
  10. Host and associated rocks
  11. Nearby scientific data
  12. Geologic structures
  13. Ore body information
  14. Controls for ore emplacement
  15. Economic information about the deposit and operations
  16. Mining district
  17. Ownership information
  18. Production statistics
  19. Bibliographic references
  20. General comments
  21. Reporter information

Geologic information

Identification information

Deposit ID 10082606
MRDS ID W060039
Record type Site
Current site name Pewabic Amygdaloid
Alternate or previous names Pewabic Lode, Pewabic Amygdaloid Lode
Related records 10194755, 10146511

Comments on the site names

  • MINES THAT WORKED THE PEWABIC AMYGDALOID LODES AT ONE TIME OR ANOTHER ARE; QUINCY, ALBANY & BOSTON, FRANKLIN, FRANKLIN JR., PEWABIC, RHODE ISLAND, AND HANCOCK. THE QUINCY HAD 9 SHAFTS ON THE PEWABIC LODE.

Geographic coordinates

Geographic coordinates: -88.56672, 47.13333 (WGS84)

Site location context

Political divisions (FIPS codes)

Houghton(county)

Michigan(state)

United States(country)

North America(continent)

Land(continent)

USGS map quadrangles

Hancock(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)

Federal lands

Keweenaw National Historical Park(National Historical Park)

National Historical Park NPS(Type of land area)

NPS(Federal land areas administered by NPS)

Geographic areas

Country State County
United States Michigan Houghton

Public Land Survey System information

Meridian Township Range Section Fraction State
055N 034W 24 SW 4 OF SW 4 Michigan

Comments on the location information

  • LOCATION ASSUMED AS THE NO. 1 SHAFT FOR THE QUINCY MINE (IN TOWN OF FRANKLIN MINE)

Commodities

Commodity Importance
Copper Primary
Silver Secondary

Materials information

Materials Type of material
Copper Ore
Silver Ore
Quartz Gangue
Calcite Gangue
Pumpellyite-(Mg) Gangue
Epidote Gangue
Chlorite Gangue

Alteration

  • (Local) Oxidized and bleached

Mineral occurrence model information

Model code 96
USGS model code Unassigned
Deposit model name Native Cu
Mark3 model number 99

Host and associated rocks

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

Nearby scientific data

(1) -88.56672, 47.13333
ListMap

Economic information

Geologic structures

Type of structure Local
Structure description Hancock fault

Ore body information

  • General form AMYGDALOIDAL LODE

Controls for ore emplacement

  • Amygdaloidal flow tops

Comments on the geologic information

  • The Pewabic amygdaloid lodes consists of at least 6 separate relatively thin amygdaloidal andesite flows. These overlap so that it is possible to follow amygdaloid continuously and still pass from the amygdaloid of one flow to that of another. It is difficult to correlate the flows certainly from one point to another unless the top of the flow has been actually followed, as one flow may give place to another within a few hundreds or, in the thinner flows, a few tens of feet. Texturally the flows are glomeroporphyrites and feldspathic melaphyres, with ophitic texture in some of the thicker beds. All or nearly all the flows are porphyritic, containing well-developed feldspar phenocrysts. Fragmental tops are not characteristic of the Pewabic lodes as a whole. The amygdaloidal flow tops are of the coalescing type, though different lodes vary in the degree of development, and there may also be a decided difference in its development in different parts of a single flow.

Economic information about the deposit and operations

Operation type Underground
Development status Past Producer
Commodity type Metallic
Deposit size Large
Significant Yes
Year of first production 1857
Year of last production 1931
Production years VARIOUS MINES INTERMITTENTLY PRODUCED FROM THIS AMYGDALOID FROM 1857 AT LEAST THROUGH 1925. ALL REMAINING MINES IN DISTRICT CLOSED IN 1968

Mining district

District name Keweenaw Copper

Ownership information

  • Type Operator
    Owner Quincy Mining Co.
  • Type Operator
    Owner Pewabic Mining Co.
  • Type Operator
    Owner Franklin Mining Co.
  • Type Operator
    Owner Rhode Island Copper Co.
  • Type Operator
    Owner Albany and Boston Mining Co.

Production statistics

  • Year 1945
    Period 1855-1945
    Accuracy Accurate
    Importance Item Commodity Group Amount recovered Grade Recovery percentage
    Major recovered Cu Copper Copper 488502.7mt

Comments on the production information

  • Ore graded 1.26 % Cu.

Comments on development

  • Due to the increasing cost of mining at such great depth (over 6000 feet vertical depth) and the low price of copper during the depression years, the Quincy Mine ('Old Reliable', and the last mine operating on the Pewabic) ceased its underground mining activity in 1931. Government regulated copper pricing allowed the mine to open briefly during World War II, but the continuing low price of copper after September 1945 forced the company to confine its operations to reclamation work on older mill tailings and custom smelting work

Reference information

Bibliographic references

General comments

Subject category Comment text
Deposit MOST PRODUCTION WAS FROM WHAT IS NOW THE QUINCY MINE (ENCOMPASSING OLDER MINES OF OLD QUINCY, PEWABIC, FRANKLIN, MESNARD, PONTIAC, AND OTHERS) AND THE HANCOCK AND FRANKLIN JUNIOR MINES
Deposit PEWABIC AMYGDALOID LODES IS SERIES OF THIN FLOWS, ANDESITIC. LODE IS TYPICALLY 3-5 FEET THICK.

Reporter information

Type Date Name Affiliation Comment
Reporter 01-JUL-1995 Nicholson, Suzanne U.S. Geological Survey
Updater 01-MAR-1997 Sutphin, D.M. U.S. Geological Survey
Editor 01-MAY-1997 Mason Jr., G.T. U.S. Geological Survey
Editor 12-JAN-2004 Woodruff, Laurel G. U.S. Geological Survey MERGED RECORDS; DELETED MP90034

Beyond USGS

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

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