Common Rock Forming Minerals
Calcite Composition
Carbonate CaCO3
Dolomite Composition
Carbonate CaMg(CO3)2
Calcite Uses
Cement
Garnet Uses
gemstone
Olivine Uses
gemstone
Orthoclase Uses
glass and ceramics
Plagioclase Uses
glass and ceramics
Dolomite Color
gray to white
Talc (other properties)
greasy feel, very soft
Olivine Color
green
Talc Harness
1
Biotite Cleavage or Fracture
1 direction
Muscovite Cleavage or Fracture
1 direction
Gypsum Cleavage or Fracture
1 good plane, 2 poor planes
Talc Cleavage or Fracture
1 plane, rarely seen
Gypsum Hardness
2
Augite Cleavage or Fracture
2 fair planes @ 90
Hornblende Cleavage or Fracture
2 planes @ 60 and 120 diamond shape
Orthoclase Cleavage or Fracture
2 planes @ 90
Plagioclase Cleavage or Fracture
2 planes @ 90
Muscovite Hardness
2-2.5
Halite Hardness
2.5
Biotite Hardness
2.5-3
Calcite Hardness
3
Halite Cleavage or Fracture
3 planes @ 90, cubic
Calcite Cleavage or Fracture
3 planes not @ 90 rhombohedral
Dolomite Cleavage or Fracture
3 planes not at 90 rhombohedral
Dolomite Hardness
3.5-4
Fluorite Hardness
4
Fluorite Cleavage or Fracture
4 planes rarely seen (double pyramid)
Hornblende Hardness
5-6
Augite Hardness
5-7
Orthoclase Hardness
6
Plagioclase Hardness
6
Olivine Hardness
6.5-7
Garnet Hardness
7
Calcite Color
Clear to gray-white
Halite Color
Clear to white
Calcite (other properties)
Effervesces readily with acid
Muscovite Composition
Felsic Kal3Si3O10(OH)2
Orthoclase Composition
Felsic KalSi3O8
Plagioclase Composition
Felsic/Mafic NaAlSi3O8-CaAl2Si2O8
Fluorite Composition
Halide CaF2
Halite Composition
Halide NaCl
Hornblende Composition
Mafic (Ca,Fe,Mg,Al)Si8O22(OH)
Garnet Composition
Mafic (Ca,Fe,Mg,Al,Mn)SiO4
Biotite Composition
Mafic Kal3Si3O10(OH)2
Talc Composition
Mafic Mg3(Si4O10)(OH)2
Augite Composition
Mafic/Felsic (Ca,Na)(Mg,Fe,Al)(Si,Al)2O6
Micas
Muscovite, Biotite
Biotite Uses
Paint
Halite Uses
Salt
Halite (other properties)
Salty taste
Biotite (other properties)
Splits into thin sheets, opaque
Gypsum Composition
Sulfate CaSO4(2)H2O
Talc Uses
Talcum Powder
Augite Luster
Vitreous
Biotite Luster
Vitreous
Fluorite Luster
Vitreous
Gypsum Luster
Vitreous
Halite Luster
Vitreous
Calcite Luster
Vitreous to pearly
Hornblende
amphibole
Biotite Color
black to dark green
Augite (other properties)
blocky appearance
Gypsum Color
clear to white
Muscovite Color
clear to yellow-brown
Olivine Cleavage or Fracture
conchoidal fracture
Fluorite (other properties)
cubic shaped crystal
Augite Color
dark green to black
Hornblende Color
dark green to black
Orthoclase (other properties)
does not have striations on one of its cleavage planes
Dolomite (other properties)
effervesces with acid slowly or not at all unless powdered
Fluorite Uses
making steel
Garnet Cleavage or Fracture
none
Muscovite Uses
paint, cosmetics
Talc Luster
pearly
Feldspar
plagioclase, orthoclase
Gypsum Uses
plaster and wall board
Fluorite Color
purple, clear, white, yellow
Augite
pyroxene
Hornblende Uses
railroad ballast
Garnet Color
red, brown, green
Garnet (other properties)
soccer ball shape
Gypsum (other properties)
soft, rhombohedral shape
Dolomite Uses
soil conditioner
Augite Uses
sometimes jewelry
Hornblende (other properties)
splintery surface, needle like crystal form
Muscovite (other properties)
splits into thin sheets, usually transparent or translucent
Plagioclase (other properties)
striations on one of the cleavage planes
Garnet Luster
vitreous
Hornblende Luster
vitreous
Muscovite Luster
vitreous
Olivine Luster
vitreous
Orthoclase Luster
vitreous
Dolomite Luster
vitreous to pearly
Plagioclase Luster
vitreous to pearly
Plagioclase Color
white to gray
Talc Color
white to green
Orthoclase Color
white, gray, salmon
