Igneous Rocks Worksheet
Assess each of your igneous rock samples and make your notes on this worksheet. Make sure that every box is completed. For help with dominant minerals and composition, consult the Lab Directions for more information. Use the Igneous Rock Key for help with identifications. Sample
Color (Describe the colors
you see)
Texture Present (Aphanitic, Phaneritic,
Porphyritic, Vesicular, or
Glassy)
Extrusive or Intrusive
(Where the rock formed) Dominant minerals
in rock Composition
(Felsic, Intermediate or
Mafic)
Rock Name
1
dark-colored
rock
Phaneritic Texture
intrusive
Plagioclase feldspar
mafic
dolerite
2
cream to light
gray
Vesicular
Extrusive
Feldspar (usually
potassium feldspar)
Felsic
Pumice
3
black
Glassy
Extrusive
(non-crystalline) glass
Felsic
Obsidian
4
black
Phaneritic
Intrusive
Plagioclase feldspar
mafic
Gabbro
5
pink, gray
Phaneritic
Intrusive
Feldspar
Felsic
Granite
6
gray in color
porphyritic
Extrusive
Plagioclase feldspar
Intermediate
Andesite
BC Online - Physical Geology Lab (GLY1010L)
