NewsELA_How_To_Identify_Rock_Types.pdf - How to identify...

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This article is available at 5 reading levels at .How to identify the three major types of rocksImage 1. This is an outcrop of igneous rock in Iceland. Igneous rock is created by volcanic activity. Photo by: Phil Degginger/Science SourceIn geology, pictures of rocks can be used to help you best determine which of the three major typesa particular rock belongs to: igneous, sedimentary or metamorphic.By comparing your rock sample with photographic examples, you can identify key characteristics,such as how the rock was formed, what minerals and other materials it contains, and where therock may have come from.Sooner or later, you're bound to encounter hard, rock-like substances that aren't rocks. Such itemsinclude man-made substances like concrete and bricks, as well as rocks from outer space (such asmeteorites) that have dubious origins.Before beginning the identification process, make sure that your sample has been washed toremove dirt. You'll also want to make sure you have a freshly cut surface so you can identify color,grain structure, stratification, texture and other characteristics.Igneous RocksBy Andrew Alden, ThoughtCo., adapted by Newsela staff on 09.19.19Word Count819LevelMAX
This article is available at 5 reading levels at .Igneous rock is created by volcanic activity. Theserocks come from magma and lava as they cool andharden. Igneous rock is most often black, gray orwhite. It often has a baked appearance.Igneous rock may form crystalline structures as itcools. This gives it a granular appearance; if nocrystals form, the result will be natural glass.Examples of common igneous rock include: basalt,granite and obsidian.Basalt is formed from low-silica lava. Basalt is themost common type of volcanic rock. It has a fine grainstructure and is usually black to gray in color. Another type of igneous rock is granite. This rockmay range from white to pink to gray, depending on the mix of quartz, feldspar and other mineralsit contains. It is among the most abundant type of rock on the planet. Obsidian is a type of igneousrock that is formed when high-silica lava cools rapidly. This forms volcanic glass. It is usually

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