Methylphenidate is a commonly prescribed psychostimulant and works by increasing the activity of the central nervous system. It produces such effects as increasing or maintaining alertness, combating fatigue, and improving attention. The short-term benefits and cost effectiveness of methylphenidate are well established.
(image copied from here). 1  Igneous Rocks: form by crystallizing melted material (magma). 2  They can form either on the surface (extrusive igneous rocks), or deep in the crust (intrusive or plutonic igneous rocks).
When most people think of igneous rock they vision a volcano erupting pumice and lava. Igneous rocks form directly by crystallization from materials from a magma melt. Igneous rocks crystalize after the magma reaches the earth's surface. Igneous rock is divided into 2 groups, extrusive and intrusive. Extrusive rocks form when magma flows onto the surface of the earth or floor of the ocean through deep cracks or fissures and at volcanic vents, and then cools and hardens.