SLE102 Study Guide - Midterm Guide: Porphyritic, Feldspar, Hornblende

• School: Deakin University
• Department: Science, Engineering and Built Environment
• Course: SLE102
• Professor: Nick Porch

Document Summary

Igneous rocks: primary rock type on earth, form by the crystallization of liquid molten material called magma, formed at high temperatures, randomly interlocking network of crystals. Formed from lava erupted onto the earths surface. Rapid cooling tiny crystals form fine-grained rocks. Slow cooling large crystals develop coarse-grained rocks (rocks have long time to grow because they are cooling down slowly) Igneous rocks are classified by their: texture: grain relationship/grain size, features: vesicles, phenocrysts, minerals: high/low temp, dark/pale. Magma has cooled slowly, underneath earth surface. Igneous minerals are classified mineralogically on the basis of the: abundance of quartz, proportion of orthoclase to plagioclase (pale minerals, nature of dark minerals olivine, pyroxene, hornblende, biotite. Quartz: grey (sometimes black) mineral, glassy lustre, distinctive fracture. Orthoclase in coarse-grained rocks is pink; otherwise milky-white colour. Crystals (>1cm) in coarse even-grained rocks are usually orthoclase. Olivine: distinctive green, gassy crystals, obvious fracture. Pyroxene, hornblende and biotite: distinguished by hardness and cleavage (prac 1)