COMMON ROCK-FORMING MINERALS

PART II - Silicate Minerals

MUSCOVITE

  • Chemical Formula:KAl2(AlSi3)O10(OH)2
  • Mineral Group: non-ferromangnesian silicate
  • Luster/Color: non-metallic, glassy/colorless
  • Cleavage: 1 perfect direction
  • Hardness: 2 to 3
  • Other Characteristics: splits into thin elastic sheets, transparent to translucent

    • BIOTITE

  • Chemical Formula: K(Mg,Fe)3(Al,Fe)Si3O10(OH)2
  • Mineral Group: ferromagnesian silicate
  • Luster/Color: non-metallic, glassy/black
  • Cleavage: 1 perfect direction
  • Hardness: 2 to 3
  • Other Characteristics: splits into thin elastic sheets, opaque to barely translucent

    • OLIVINE

  • Chemical Formula: (Fe,Mg)2SiO4
  • Mineral Group: ferromagnesian silicate
  • Luster/Color: green
  • Cleavage: absent
  • Hardness: 6.5 to 7
  • Other Characteristics: transparent to translucent, commonly occurs as small granular aggregates

    • PYROXENE

  • Chemical Formula: complex solid solution
  • Mineral Group: ferromagnesian silicate
  • Luster/Color: non-metallic/green to black
  • Cleavage: 2 directions at 90o
  • Hardness: 6
  • Other Characteristics: breaks into columnar fragments

    • AMPHIBOLE

  • Chemical Formula: complex solid solution
  • Mineral Group: ferromagnesian silicate
  • Luster/Color: non-metallic/ green to black
  • Cleavage: 2 directions at 56o and 124o
  • Hardness: 6
  • Other Characteristics: breaks into wedge-shaped splintery fragments

    • QUARTZ

  • Chemical Formula: SiO2
  • Mineral Group: non-ferromagnesian silicates
  • Luster/Color: non-metallic, glassy/variable
  • Cleavage: absent
  • Hardness: 7
  • Other Characteristics: conchoidal fracture, high hardness

    • CALCIUM-PLAGIOCLASE

  • Chemical Formula: CaAl2Si2O8
  • Mineral Group: non-ferromagnesian silicates
  • Luster/Color: non-metallic, glassy/blue-gray
  • Cleavage: 2 directions at 90o
  • Hardness: 6 to 6.5
  • Other Characteristics: striations, gray color with iridescence (play of colors)

    • SODIUM-PLAGIOCLASE

  • Chemical Formula: NaAlSi3O8
  • Mineral Group: non-ferromagnesian silicate
  • Luster/Color: non-metallic, glassy/ white to light gray
  • Cleavage: 2 directions at 90o
  • Hardness: 6 to 6.5
  • Other Characteristics: striations, light color

    • POTASSIUM-FELDSPAR

  • Chemical Formula: KAlSi3O8
  • Mineral Group: non-ferromagnesian silicate
  • Luster/Color: non-metallic, glassy/pink to white
  • Cleavage: 2 directions at 90o
  • Hardness: 6 to 6.5
  • Other Characteristics: absence of striations

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