Rocks Rock
Dana Willson
What IS a rock?
Not everything you find in the ground is a rock. Some are minerals. Minerals are naturally occurring substances formed by geologic processes. A rock is a combination of several different minerals.
Quartz
Quartz is an example of a mineral. It is made of only one substance, SiO4.
Granite
Granite is a rock. If you look closely, you can see the different minerals that make up granite, such as quartz.
Emerald
Jewels such as emeralds are minerals, like quartz.
Are all rocks the same?
No!
Not all rocks are the same. There are three main types of rocks. These are sedimentary, igneous, and metamorphic. Sedimentary rocks
Limestone
Limestone is an example of a sedimentary rock. In this sample of limestone, you can see fossilized shells.
Marble
Marble is an example of a metamorphic rock. It is the metamorphosed version of limestone
Basalt
Basalt is an example of an igneous rock.
Sit and Wait
Sedimentary rocks are made by sitting and waiting. Pieces of shell collect together over time forming sediment. Eventually, the layers of sediment harden into rock. But, this type of rock is usually very soft and crumbly.
Pressure; pushing down on me
Metamorphic rocks are formed deep underground when a sedimentary rock experiences intense heat (but not enough to liquefy the rock) and pressure. Metamorphic rocks usually have ribbon like layers
The heat was hot
Igneous rocks are liquid rock that cooled and hardened. If the rock cooled underground, it probably cooled very slowly and came from magma. These rocks can have crystals or air pockets. If the rock cooled very fast, it probably cooled above ground and came from lava. These rocks are usually glass like
Basalt
Basalt is an igneous rock that is formed by cooling lava somewhat rapidly. This causes slight grainy texture.
Obsidian
Obsidian is an igneous rock that is also formed very quickly from lava. That's why it looks like glass.
Pumice
Pumice is another igneous rock that is formed from lava that is ejected from the volcano as small blobs. It gets its appearance from cooling almost instantaneously.
Photo works cited
- Picture of quartz
- picture of granite
- picture of emerald
- picture of limestone
- picture of marble
- picture of gneiss attributed to Siim Sepp
- picture of slate attributed to Sprok
- picture of basalt
- picture of obsidian
- picture of pumice
Text works cited
- types of rocks the Annenberg Foundation
- http://www.sciencekids.co.nz/sciencefacts/earth/rocksandminerals.html