72 



A NATURALIST IN THE GREAT LAKES REGION 



Easily scratched 

 with a knife 

 (continued) 



Scratched with a 

 knife with dif- 

 ficulty 



Scratched by 

 quartz but not { 

 with a knife 



Sphalerite, 3.5-4.0 

 (Zinc blende) 



Yellow, red, brown, black. 

 Luster resinous when yellow. 

 Perfect cleavage. Brittle. 



Chalcopyrite, 3.5-4.0 Brass yellow, often tarnished, 

 (Copper pyrite) then showing iridescence. 



Streak green-black. Softer than 

 pyrite. 



Dolomite, 3.5-4.0 

 (Pearl spar) 



Mica, see above 

 Limonite, 5.0-5.5 



Pyroxene or 

 Augite, 5-6 



Amphibole or 

 Hornblendes, 5-6 



Hematite, 5.5-6.5 



Feldspar,* 6.0-6.5 



Pyrite, 6.0-6.5 

 (Fool's gold) 



White, gray, green, black. 

 Streak white. Transparent to 

 translucent. Crystals curved 

 like saddles. 



Dark brown, streak yellowish 

 brown. Often fibrous; if earthy, 

 color is yellow. In cubical 

 crystals. 



Green to black. Fracture un- 

 even to conchoidal. Usually in 

 short, thick, eight-sided prisms. 

 Cleavage poor; faces meet at 90°. 



Brown, green, or black, darker 

 than augite. Fracture as above. 

 Luster pearly on cleavage faces. 

 Crystals long, slender, six-sided, 

 faces finely cross-striate. Cleav- 

 age faces meet at 1 24°. 



Cherry red to iron black; streak 

 red. Metallic luster, massive or 

 fibrous or scaly. 



Many colors, streak white. 

 Cleavage perfect, faces at nearly 

 right angles. Light colored, 

 orthoclase; darker, plagioclase. 



Brass yellow, tarnishes brown. 

 Streak greenish black. Metal- 

 lic luster. Crystals, cubes or 

 dodecahedra. Harder than 

 chalcopyrite. 



