General Geology

Petrology (Rocks)

Objective: Classify and analyze igneous, sedimentary, and metamorphic rocks.

Key points:

Igneous rocks:

  • Intrusive (granite, diorite) → visible crystals

  • Extrusive (basalt, rhyolite) → fine or glassy texture

Sedimentary rocks:

  • Clastic (sandstone, conglomerate) → cemented grains

  • Chemical/organic (limestone, evaporites)

Metamorphic rocks:

  • Foliated (gneiss, schist) → banded or layered

  • Non-foliated (marble, quartzite) → granular texture

Lab techniques:

  • Observation of thin sections under a microscope

  • Comparison of textures and compositions