Mineral Identification key

Directions: Use this key to identify the minerals.

  1. Is the luster metallic?
    1. Yes - Metallic Luster
      Streak Color Description Mineral
      black, gray, or dark green streak black, strongly magnetic, harder than glass (H=6) Magnetite
      gray to black, smudges fingers, shiny, slippery, softer than fingernail (H=1) Graphite
      shiny silver-gray, very heavy, occurs in cubes, harder than fingernail (H=2.5) Galena
      shiny pale yellow-gold, often in cubes, harder than glass (H=6.5) Pyrite
      brass yellow, weakly magnetic, same hardness as steel (H=4.5) Chalcopyrite
      red to brown streak red-brown to black, earthy or powdery, same hardness as glass (H=5-6) Hematite
      steel gray, shiny, same hardness as glass (H=5-6) Specular Hematite
    2. No...go to 2.
  2. Non-metallic Luster: Is the color dark?
    1. Yes...go to 3.
    2. No...go to 4.
  3. Non-metallic Luster, Dark Color: Does the mineral scratch glass?
    1. Yes - Harder than Glass
      Cleavage or
      fracture?
      Description Mineral
      Cleavage light to dark pink, blocky, 2 cleavage planes at almost 90°, harder than steel (H=6) Orthoclase Feldspar
      black to dark green, cleavage planes at almost 90°, same hardness as glass (H=6) Pyroxene
      black to dark green, cleavage planes at 60° and 120°, same hardness as glass (H=6) Amphibole
      Fracture gray to black, glassy, curved fracture, harder than glass (H=7) Smokey Quartz
      black, brown or gray, curved fracture, harder than glass (H=7) Flint (quartz)
      brown with some green or purple, dull, harder than glass (H=9) Corundum
      bright to dark green, glassy, usually in granular masses, harder than glass (H=6) Olivine
      black, strongly magnetic, irregular masses or chunks, harder than glass (H=6) Magnetite
    2. No - Softer than Glass
      Cleavage or
      fracture?
      Description Mineral
      Cleavage colorless, green or purple, glassy, 4 good cleavage planes, harder than penny (H=4) Fluorite
      black to brown, one perfect cleavage plane (basal), thin flexible sheets, same hardness as fingernail (H=2.5) Biotite Mica
      green, basal cleavage, platy masses or fine particles,same hardness as fingernail (H=2.5) Chlorite
      Fracture red to red-brown streak, earthy, softer than fingernail (H=1) Hematite
      green, basal cleavage, platy masses or fine particles,same hardness as fingernail (H=2.5) Chlorite
      gray, pink or white, greasy or soapy feel, softer than fingernail (H=1) Talc
     
  4. Non-metallic Luster, Light Color: Does the mineral scratch glass?
    1. Yes - Harder than Glass
      Cleavage or
      fracture?
      Description Mineral
      Cleavage light to dark pink, blocky, 2 cleavage planes at almost 90°, harder than steel (H=6) Orthoclase Feldspar
      gray to white, blocky, 2 cleavage planes at almost 90°, harder than steel (H=6) Oligoclase (Sodium Feldspar)
      Fracture transparent (or almost so), glassy, curved fracture, crystals common, harder than glass (H=7) Quartz
      milky white, glassy, curved fracture, harder than glass (H=7) Milky Quartz
      pink, glassy, curved fracture, harder than glass (H=7) Rose Quartz
      white, yellow, gray, black, or brown, sometimes banded, dull and opaque, curved fracture, harder than glass (H=7) Chert
      bright to dark green, glassy, usually in granular masses, harder than glass (H=6) Olivine
    2. No - Softer than Glass
      Cleavage or
      fracture?
      Description Mineral
      Cleavage colorless, white or pale orange, forms cubes, perfect cubic cleavage, salty taste, same hardness as fingernail (H=2.5) Halite (salt)
      white or colorless, perfect rhombohedral cleavage (squashed cube), fizzes with acid, harder than fingernail (H=3) Calcite
      colorless to light yellow, one perfect cleavage plane, thin flexible sheets, same hardness than fingernail (H=2.5) Muscovite Mica
      white to pink, thick transparent plates or fibrous, softer than fingernail (H=2) Gypsum
      colorless, green, purple, yellow or brown, glassy, 4 good cleavage directions, harder than penny (H=4) Fluorite
      Fracture white, fibrous or granular masses, softer than fingernail (H=2) Gypsum
      gray, pink or white, greasy or soapy feel, softer than fingernail (H=1) Talc
      bright yellow, waxy luster, odor, same hardness as fingernail or slightly harder (H=1.5-2.5) Sulfur