GL23C IGNEOUS & METAMORPHIC PETROLOGY LAB 1

STUDENT NAME ____________________________________________________________

Below is the modal mineralogy for a variety of igneous plutonic rocks. You are asked to classify these rocks using the IUGS Mineralogical Classification and to determine the Colour Index (CI) for each rock. Write your answers on the right-hand section of the sheet.

Modal Mineralogy C.I. Rock Name

  1. Quartz 30%
    Plag. Feld. 20%
    Alk. Feld. 25%
    Biotite 20%
    Magnetite 5%

  2. Quartz 20%
    Plag.Feld. 30%
    Alk.Feld. 15%
    Hornblende 20%
    Biotite 10%
    Magnetite 5%

  3. Plag.Feld.(An60) 30%
    Augite 45%
    Olivine 20%
    Spinel 5%

  4. Quartz 5%
    Plag. Feld. 20%
    Alk. Feld. 30%
    Diopside 20%
    Hornblende 20%
    Magnetite 5%

  5. Quartz 30%
    Plag.Feld. 40%
    Biotite 20%
    Hornblende 5%
    Magnetite 5%

  6. Nepheline 30%
    Plag.Feld.(An40) 30%
    Alk. Feld. 10%
    Biotite 20%
    Hornblende 5%
    Magnetite 5%