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VIRTUAL FIELD TRIP TO THE KEWEENAW PENINSULA, MICHIGAN -  MINERALOGY    

 

     There are three major assemblages of minerals found on the Keweenaw peninsula. The first are the minerals that make up the volcanic rocks. The second are the minerals that are found in the fissures and amygdaloids of the volcanics and conglomerates. A third group are the minerals that formed from the weathering of the primary ore minerals.

Mineralogy of the district (after Heinrich, 1976)

   Basalt rock forming minerals - albite, andesine, apatite, augite, bytownite, chamosite, hematite, hornblende, hypersthene, iddingsite, ilmenite, labradorite, magnetite, oligoclase, olivine, pigeonite, sphene.

   Rhyolite rock forming minerals - apatite, hematite, orthoclase, quartz, sanidine, tourmaline.

   Ore vein minerals - albite, algodonite, analcite, anhydrite, ankerite, apophyllite, arsenical copper, babingtonite, barite, bornite, brucite, chabazite, chalcocite, chalcopyrite, chloanthite, copper, covellite, datolite, delessite, diabanite, digenite, α-domeykite, β-domeykite, epidote, faujasite, fluorite, gypsum, hematite, heulandite, laumontite, leonhardite, maucherite, mesolite, microcline (adularia), monazite, muscovite (sericite), natrolite, niccolite, pararammelsbergite, pennine, phillipsite, powellite, prehnite, prochlroite, pumpellyite ( including var. chlorastrolite), pyrite, quartz, rammelsbergite, saponite, silver, smaltite, sphalerite, stilbite, thomsonite, thuringite, wairakiite, xonotlite.

   Supergene minerals - annabergite, anthonyite, atacamite, azurite, buttenbachite, calumetite, cerargyrite, chrysocolla, covellite, cuprite, dioptase, erthyrite, freirinite, gephardtite, guerinite, gypsum, halite, kaolinite, kinoite, malachite, mirabilite, nantokite, olivenite, paramelaconite, paratacamite, picropharmacolite, plancheite, rauenthalite, tenorite, trichalcite, tyrolite, vladimirite.

Cliff mine mineralogy –  adularia, albite, analcime, azurite, babingtonite, barite, calcite, chalcocite, chamosite, chrysocolla, copper, covellite, cuprite, datolite, epidote, fluorapophyllite, galena, gypsum, hematite, laumontite, microcline, natrolite, prehnite, pumpellyite, pyrite, quartz, silver, sphalerite, tenorite, thomsonite.

Mineralogy of the conglomerate lodes –  barite, calcite, chalcocite, chrysocolla, copper, cuprite, epidote, laumontite, malachite, microcline, orthoclase, powellite, pumpellyite, quartz, silver, and tenorite.

Mineralogy of the White Pine Mine

   Original minerals in Nonesuch shale - chlorite, epidote, illite, orthoclase, plagioclase, quartz.

   Diagenetic minerals in Nonesuch shale - calcite, chlorite, laumontonite, pyrite, quartz.

   Stratiform copper deposit minerals - bornite, chalcocite, chalcopyrite, copper, covellite, digenite, djurleite, galena, greenockite, hematite, pyrite, silver, sphalerite.

   Vein minerals - barite, bastnaesite, bismuth, bornite, calcite, calumenite, chalcocite, chalconatronite, chalcopyrite, chlorite, copper, covellite, cuprite, dolomite, domeykite, galena, greenockite, graphite, illite, malachite, microcline, montmorillonite, molybdenite, pyrite, quartz, silver, sphalerite, synchysite.

 

Calcite from the district often had inclusions of copper which gives the calcite a distinctive pinkish hue ( specimen is 7.5 cm high). Analcime, Phoenix Mine, (largest crystal is 2.5 cm. across).

        

Calcite (with copper inclusions) Quincy mine. Seaman Museum specimen 22 cm tall.

 

Calcite twin with inclusions of copper (probably from the Quincy mine) Seaman museum specimen 7.5 cm. across.

 

Seaman Museum Calcite page 1 

 

Quartz crystals ( specimen is 7 cm across) from the district are relatively rare, although most ore contained some associated quartz. Quincy Mine Pewabic lode. Thomsonite - Michigan 5cm across.   

 

Group of chalcocite crystals from the White Pine mine( 4.5 cm across). These were some of the first mineral specimens to come from the mine.

 Group of copper crystals with a crystals of barite ( largest barite is 2.5cm long) from White Pine Mine.

Adularia on copper wire. Osceola mine. Seaman Museum Specimen #957. 3 cm. high. Analcite. Franklin Jr. Mine. Seaman Museum specimen. 5 cm. high.

 
Datolite (crystal) on prehnite, Osceola mine. Crystalline datolite is relatively rare in the district. Seaman Museum specimen. Prehnite, Tamarck Jr. mine. Seaman museum specimen.

 

Natrolite from the St. Clair mine. Seaman museum specimen

Seaman Museum other minerals page.

Other photographs of minerals from the district.