Igneous rocks (fiery rocks) are made when molten material inside or outside the earth cools and becomes solid. This melted rock is called magma when it is inside the earth. When magma finds its way to the surface through cracks or volcanoes, it is called lava.

To identify an igneous rock, first determine its approximate mineral composition by judging its overall color and labeling it as felsic, intermediate, mafic, or ultramafic. Next, observe its texture based on the crystal grain sizes present in the rock. Then, compare your observations to known igneous rock types.

Understanding how to identify igneous rocks is crucial not only for rock and fossil collectors, but also for anyone interested in geology. This article synthesizes the essential techniques and knowledge needed for effective identification.

2024年1月31日 · Identifying igneous rocks involves two key steps: first, distinguishing them from sedimentary and metamorphic rocks, and then determining their specific type. Here is a list of practical tips for identifying a rock:

Extrusive igneous rocks erupt onto the surface, where they cool quickly to form small crystals. Some cool so quickly that they form an amorphous glass. These rocks include: andesite, basalt, dacite, obsidian, pumice, rhyolite, scoria, and tuff. Pictures and brief descriptions of some common igneous rock types are shown on this page.

2019年6月2日 · Learn more about the major types of igneous rock, which includes plutonic, intrusive, and extrusive igneous rocks.

2017年5月17日 · Igneous rocks are rocks which solidify from molten material (magma). Cooling of the magma can occur beneath the surface (plutonic) or on the surface (volcanic). Igneous rocks can be identified by the determination of the composition and texture of the rock.

Rocks rich in magnesium (Mg) and iron (Fe) tend to contain olivine, pyroxene, amphibole, and biotite. These minerals tend to be strongly (dark) colored. On the basis of the amount of color versus white, a color index can be set up that relates to the composition.

2024年7月16日 · Here's how to identify 44 of the most common igneous, sedimentary, and metamorphic rock types with a handy rock identification chart.