GL23C IGNEOUS & METAMORPHIC PETROLOGY LAB 6

STUDENT NAME ____________________________________________________________

Cumulative Igneous Rocks

Describe thoroughly the thin sections provided by your instructor, noting texture, mineralogy, mineral size and shape, and any other special features. Determine the crystallization history on the basis of the inter-relationships of minerals in the rock. Sketch the thin section and label diagram.

In your petrographic description, you must identify and describe in detail the optical properties of the different minerals present in the rock and estimate the modal mineralogy for each. Apply the IUGS nomenclature to the rocks.

List of Cumulative Rocks to be Examined in Lab 6

1. Anorthosite
2. Pyroxenite
3. Dunite

Read ATLAS OF IGNEOUS ROCKS AND THEIR TEXTURES by MacKenzie, Donaldson & Guildford.