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.
Rocks resulting from cooled-off lava include obsidian, lava rock, basalt or pumice. These are known as extrusive igneous rocks because they are formed outside of the crust. There are about 700 different types of igneous rock. More examples of igneous rocks include tuff, diorite and andesite.Here are some uses of igneous rocks: Granite is used for building and construction because of its strong properties. It is also used for head stones and kitchen counter tops.here are about 700 different types of igneous rock. More examples of igneous rocks include tuff, diorite and andesite. Here are some uses of igneous rocks: Granite is used for building and construction because of its strong properties. It is also used for head stones and kitchen counter tops.