View the “Rock” Discovery School Video Clip Rocks! View the “Rock” Discovery School Video Clip

Classifying Rocks: Review Rocks are made of mixtures of minerals and other materials. Some rocks contain only a single mineral. Others contain several minerals. Granite: quartz, feldspar, hornblende, and mica. When studying a rock sample, geologists observe the rock’s mineral composition, color, and texture.

Classifying Rocks: Review Grains= particles of other rocks and minerals- give the rock its texture. Texture= the look and feel of the rock’s surface. To determine a rock’s texture: Grain Size: fine, coarse, no visible grain Grain Shape: rounded, jagged Grain Pattern: nonbanded, banded Geologists classify rocks into three major groups: igneous, sedimentary, and metamorphic rock.

Igneous Rocks Form from the cooling of magma or lava. Extrusive= igneous rock that formed from lava that erupted onto Earth’s surface. Example= Basalt (fine grained, glassy texture). Intrusive= igneous rock that formed when magma hardened beneath Earth’s surface. Example= Granite (larger crystals).

Diagram

Use of Igneous Rocks People throughout history have used igneous rock for tools and building materials. Building Materials- Granite: statues, building blocks, bridges, streets (cobblestones), kitchen counters. Basalt: gravel Other Uses: Pumice (cleaning and polishing) Obsidian (cutting and scraping)

Granite Statue Basalt as Gravel

Obsidian Pumice

Sedimentary Rocks Form when particles of other rocks or the remains of plants and animals are pressed and cemented together. Most sedimentary rocks are formed through a series of processes: erosion, deposition, compaction, cementation.

Erosion= running water, wind or ice loosen and carry away fragments of rock. Deposition= sediment settles out of water or wind carrying it. Compaction= presses sediments together Cementation= dissolved minerals crystallize and glue particles of sediment together.

Sandstone Coal

Uses of Sedimentary Rock Sandstone and limestone have been used for building materials for thousands of years. Both are soft enough o be cut easily into blocks. Did you know?? The White House is built of sandstone!

Metamorphic Rocks Form when existing rock is changed by heat, pressure, or chemical reactions. Most metamorphic rock forms deep underground.

Gneiss Slate

Uses of Metamorphic Rocks Marble and slate are two of the most useful metamorphic rocks in building and sculpture. Marble is easy to cut into thin slabs or carved into many shapes (it is also easy to polish). The Lincoln Memorial is made of gleaming white marble!