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مشرفة
عدد المساهمات : 21
 |  موضوع: what is geology  8/6/2009, 5:58 am | |
| Geology…
is the study of the Earth, its substances, shapes, processes and history.
Rocks….
are solid mixtures of at least one mineral. While minerals have crystals and chemical formulas, rocks instead have textures and mineral compositions. On that basis, rocks are divided into three classes reflecting three environments: igneous rocks come from a hot melt, sedimentary rocks from accumulation and burial of sediment, metamorphic rocks from altering other rocks by heat and pressure. This classification points to an active Earth that circulates matter through the three rock classes, on the surface and underground, in what is called the rock cycle.
Rocks are important as ores—economic sources of useful minerals. Coal
Minerals…
are natural, inorganic solids with a consistent composition—a chemical formula. Each mineral also has a unique arrangement of atoms, expressed in its crystal form (or habit) and its hardness, fracture, color and other properties. Organic natural substances, like petroleum or amber, are not called minerals.
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