MADE FROM MAGMA Did you know that there is more than one kind of rock Igneous rock is one of the three kinds of rock found on Earth The other two are sedimentary rock and metamorphic rock Each of these kinds of rock forms differently Igneous rock is formed from a soft fluid substance called magma Magma is often described as molten or When a volcano erupts you can see melted rock pouring out of it 4
melted rock Igneous rock forms when magma cools down and hardens There are many types of igneous rock Granite is one of the most common forms This hard rock is used in building It is also popular for kitchen countertops Obsidian is an igneous rock too Obsidian is a shiny jet-black rock It was once used to make mirrors When a solid is heated it melts and becomes liquid It is called molten when very high heat causes the melting Vocabulary Obsidian can form sharp edges when it breaks It was once used to make knives 5
A MIX OF MINERALS As all rocks are igneous rocks are made up of minerals Minerals are inorganic substances This means that they do not come from an animal or a plant Some minerals such as copper and silver are metals Sulfur quartz and salt are other well known minerals Igneous rocks are made up of a mix of minerals The mineral quartz is quite common in igneous rocks So are a group of minerals known as feldspars Igneous rocks Quartz is the second most common mineral in Earth’s crust 6
Devils Postpile in California is made up of basalt columns that are 40 to 60 feet 12 to 18 meters tall that have a lot of feldspar and silica in them are called felsic from feldspar and silica They are rather light in color Rhyolite and granite are felsic rocks Mafic rocks have larger amounts of magnesium and iron This makes them darker in color Gabbro and basalt are mafic rocks The igneous rock diabase is dark in color Do you think it is a mafic rock or a felsic rock Think About It 7
