List the percentages of minerals found in rock 'Z'.
  • feldspar: 60
  • amphibole: 25
  • pyroxene: 15
  • Total: 100
What's the maximum number of minerals that can occur together in one igneous rock?According to the chart, six minerals. Actually, there can be very small quantities of additional minerals.
Can an igneous rock consist of just one mineral? Not according to the chart. But there are unusual occurrences of rocks that geologists have decided are igneous that do consist of just one mineral. The origin of such rocks has been the focus of much investigation.
What are the names of three minerals that do not occur together in the same rock with pyroxene?
  • quartz
  • potassium-rich feldspar
  • sodium-rich feldspar
  • muscovite
  • biotite
Why do you think geologists feel confident in saying that the rock assemblages shown on the chart are typical of igneous rocks? You'll find the answer here:

© 2001, David J. Leveson