Download Week #9: INTRODUCTION TO ROCKS

Week #9: INTRODUCTION TO ROCKS
These notes go with the Geo-tour lab
Definition of Rock: Mixture of one or more minerals, volcanic glass, organic matter
or other materials.
If a rock is made up of just one mineral it is homogeneous. (Dunite)
If a rock is made up of more than one mineral it is heterogeneous. (Granite)
If a mineral is made up of one element it is homogenous. (Sulfur)
If a mineral is made up of more than one element it is heterogeneous. (Quartz)
Rocks are classified by their ORIGIN.
By origin we mean:
How they formed
Where they formed
What they are made of (composition)
Rocks are classified into three main groups:
IGNEOUS: rocks that originally were lava or magma. Igneous literally
translates to “born of fire.” A characteristic of igneous rocks that you need to be
able to recognize is that the mineral crystals are randomly arranged. The granite
and basalt rocks from stations 3, 4, and 5 are examples of igneous rocks.
METAMORPHIC: rocks that were originally other rocks. Metamorphic
literally means “changed form.” When a rock changes form due to extreme heat
& pressure its minerals rearrange themselves (recrystallize). A characteristic of
metamorphic rocks you need to be able to recognize is the mineral alignment. The
gneiss rock from station 5 is an example of a metamorphic rock.
SEDIMENTARY: rocks made from sediment. Sediment literally translates to a
settled piece – something that was placed down. Sedimentary rocks are rocks
made from the small bits and pieces of matter that settle on the
earth’s surface and then get compacted and cemented together. Pebbles
glued together (the conglomerate from station 6); sand grains glued together (the
sandstone from station 7); shells glued together (the limestone from station 2); plant
matter glued together (the coal from station 2) are all examples of sedimentary
rocks.