Minerals are the building blocks of stone and surround us in the environment. Deposit mineral grains are found in soil, gravel, sand and rocks. There are even mineral deposits in the air we breathe.
German crystallographer, Fredrich Mohs, was the first person to rank minerals in order of relative hardness by their ability to scratch one another. His scale is still used today by mineralogists.
Minerals form when and where temperature, pressure and chemical environment exists over a long period of time. The length of time allows the component atoms to become ordered into a crystalline structure. Formation time may occur over limited or broad range conditions.
Rocks actually contain a record of events that occurred during our Earth’s long history. There are three major types of rock families; Igneous, Sedimentary and Metamorphic.
The word “igneous “ comes from the Latin ignis, meaning “fire”. These rocks are formed by molten or partly molten rock material which is consolidated and generally called (magma or lava) which flows out of a volcano onto land surface. This magma is derived from the Earth’s mantle or existing rocks made molten by extreme temperature and/or pressure changes. There are over 700 types, most of them formed beneath the Earth’s surface crust. (example: granite)
Most sedimentary rocks are layered and many contain fossils. They hold important and fascinating history of the earth. The preserved remains of ancient plants, animals and the composition of sediments give us clues to the original rock. The different layers record the environmental changes of the earth over great spans of time. This type of rock forms at temperatures and pressures that preserve fossil remains. They form in three main ways—by the deposits of biogenic activity; by weathered remains of other rocks (clastic sedimentary rocks); and precipitation from solution. As particles of sediment are deposited from air, ice or water they build up and the over burden or pressure squeezes the sediment into layered solids (rock formation) and the original fluids are expelled. Sedimentary rock covers a great amount of the Earth’s crust but represent only a thin veneer over this crust which consist mainly of igneous and metamorphic rocks. (example limestone & travertine)
These rocks are found in areas of intense distortion such as zones in the Earth’s crust where large masses of rock have been ground against one another or where heat and vapors have permeated the nearby rocks or where large volumes of buried rock are under tons and tons of pressure which fosters heat build up and causes them to change or morph . On close examination, you can observe how flattened some of the grains in the rock have become. Therefore, Metamorphic rocks are transformation of pre-existing rocks given sufficient time to respond or change form—the process of metamorphism. (example: marble & slate)