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 Igneous rocks form from the solidification of magma (molten rock). A reminder: magma is molten rock beneath the Earth s surface and lava is magma that is on the Earth s surface.The main characteristics of an Igneous rock are crystal size (grain size) and texture. The crystal size and texture of an igneous rock is dependant on where in the earth the rock formed.edimentary rocks are formed from the burial/compaction and cementing of earth materials. These earth materials (sediments) are carried by natural agents such as wind, water, and glaciers and then are deposited on land or underwater.