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.
Igneous rocks are rocks that formed directly from magma and can form either in the earth or on its surface. Igneous rocks can weather and be compressed to form sedimentary rocks, rock made up eroded material broken off of other rocks and cemented together, and both of these can be transformed into metamorphic rock.ll magma that solidifies becomes one of two types of igneous rock: either extrusive rocks, rocks that form on the earth's surface, or intrusive rocks, rocks that form under the earth's surface. Hawaii is made up mostly of extrusive rock called basalt that came from the volcanic activity common to the area.