1 It is proven that a cup of hot coffee can help uplift your senses and refresh you. This quality of coffee can be attributed to the presence of caffeine, which is a central nervous stimulant.  Caffeine is basically a bitter white crystalline alkaloid.
1 Igneous rocks that form too quickly for crystals to form have what is called a glassy texture. 2  Obsidian is the only glassy igneous rock, and can be identified by its dark color. 3  This looks like dark black glass. An example of an intrusive rock is granite. 2  When magma is above the earth's crust, it is known as lava. 3  Extrusive rocks form through very fast cooling of lava above the Earth's surface. 4  Extrusive rocks have very small, almost microscopic crystals.
When magma cools and hardens below the Earth's surface, an intrusive igneous rock forms. Because the process of the formation of intrusive igneous rock occurs slowly, these rocks tend to have a grainy texture.Examples of intrusive igneous rock include granite and gabbro.ocks are classified by the way they form. Igneous rocks are those that form when magma cools and hardens. This process can occur on the Earth's surface or underground. The exact location of the formation of the rock determines the type of igneous rock it is. Interesting Igneous Rocks Facts: