The science that explores the formation and classification of rocks is called petrology An important point to note is that rocks make up the lithosphere – a solid mass of rocks with a thickness of 5 to 70 kilometers, which encompasses the Earth's crust (the solid surface layer of the planet Earth) and the Earth's upper mantle (the thickest layer containing the majority of our planet's material). Just beneath the solid lithosphere lies the central part of the Earth's mantle – the asthenosphere – a layer of molten rock called magma. The lower part of the Earth's mantle maintains a solid state as a result of high pressure and reaches a depth of 2,900 kilometers. Beneath the mantle all the way to the center lies the Earth's core, which is made up mostly of iron.

By their origin, rocks are classified as igneous, sedimentary, and metamorphic. Igneous rocks make up about 95% of the lithosphere, whereas the other two types of rock are only 5% of the lithosphere. In fact, rocks are aggregates of one or more minerals – structures formed by natural physical and chemical processes, with a specific chemical composition and crystal structure, as well as stability under certain temperature and pressure condition.

Many countries have issued stamps to display their mineral wealth (gold mining), diamond industry, and industrial use of minerals.  The beauty of crystals has often been displayed on commemorative stamps.  While some of these beautiful crystals and gems can cost a fortune for someone seeking actual specimens, collecting the images on stamps provides a much less expensive avenue to own and admire a gem and mineral collection.

Mar 17th 2023

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