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 formed from the solidification of molten rock. Most of the Earth is composed of igneous rock. There are 2 major types of igneous rocks; intrusive igneous rocks, and extrusive igneous rocks.INTRUSIVE IGNEOUS ROCKS solidify beneath the Earth's surface.Because the magma cools over a relatively long period of time, Intrusive igneous rocks tend to have large mineral crystals that give the rock a rough granular texture.NTRUSIVE IGNEOUS ROCKS solidify beneath the Earth's surface. Because the magma cools over a relatively long period of time, Intrusive igneous rocks tend to have large mineral crystals that give the rock a rough granular texture.