Desert Terrains, Rocky Lands and the Minerals we obtain from this Earth

This earth has a vast range of terrains to offer in its topography. Talking about rocky lands first; there are three kinds of rocks that we come across – igneous, sedimentary and metamorphic. Igneous rocks are formed when the magma from the earth cools down, forming hot liquid rock. Sedimentary rocks are formed from older rocks that break down are get worn out into small fragments. Metamorphic rocks have also formed on account of heat and the pressure that exist within the crust of the earth. Rocks and minerals are found in the Earth’s outer layer. A rock is a solid collection of minerals. Both rocks and minerals have commercial value. Rocks are essential for their minerals, while minerals are widely used in the manufacturing industry. A rock is any natural substance composed of solid crystals of various minerals fused together to form a solid lump, while a mineral is any naturally occurring inorganic mass having a specific composition and orderly arrangement of the atoms. What is a metamorphic rock? It is a rock that is formed by the modification in colour, consistency, hardness and arrangement of the pre-existing rocks is known as a metamorphic rock. Marble, slate and schist are examples of metamorphic rock. What is a metallic and non-metallic mineral? Give three examples of metallic and three examples of non-metallic minerals. The mineral containing one or more metal elements is known as a metallic mineral. In contrast, the mineral that does not contain any metal element is known as a non-metallic mineral. No new product is generated by melting a non-metallic mineral. Examples of metallic minerals Iron, Copper, and Nickel Examples of non-metallic minerals Marble, Dolomite and Clay Rocks and subterranean caves offer us minerals and gemstones. The most important among gemstones is the diamond. It is also one of the hardest natural substances that are known to man. Diamond crystals have mostly eight sides are shaped in the form of double pyramids. Some diamonds may have more sides while others may have the shape of a cube. Diamonds will show off their true beauty only when they are cut and then polished. These stones are cut with flat-faced series that are known as facets and they help to reflect light, making these gems sparkle. The diamonds are often colourless but some may have few impurities that may tint them. For example, the Hope Diamond is deep blue in colour and the Tiffany Diamond gives a deep yellow tint. After the diamond stone, the second hardest mineral is corundum. It is dull grey in colour. Some stones may look like transparent crystals and their colour may vary as per their impurity that they contain. Ruby is a red type of corundum and it is red in colour on account of the presence of chromium oxide. Sapphires are blue in colour from the traces of titanium and iron. These gemstones are usually found embedded in other kinds of rocks. One of the wonders of sedimentary rocks is the way they have preserved themselves with the remains of fossils. Many fossils are mineral replicas of the original matter which ultimately turned to stone. Fossils of this type are also known as moulds. Some fossils are formed by volcanic action, in ashes or lava. When the Vesuvius erupted in Pompeii in 79 Anno Domini, hot ash and cinders buried the bodies of animals and people then and hardened around them. They got asphyxiated and died. Speaking of deserts, the largest one is Sahara that stretches across Northern Africa. In such regions, rainfall is erratic. The rain may come down intensely for few hours and disappear for several months and in few cases; for many years. The soil of these deserts is surprisingly fertile and one of the miracles of nature is the way in which deserts become a field of colourfully growing flowers, whenever there is sufficient rain. The seeds of desert plants have tougher outer casings which resist drought. Some desert areas may support a range of animal and plant life. Take for example, the Namib Desert lying between Luderitz and Walvis Bay in Namibia – it is a typical desert with dunes, stony areas and exposed rock. You will find that it has scattered plant life. Single Rocks, Minerals and Gemstones One of the largest single rocks found in this world is Ayers Rock that is found in the Northern Territory of Australia. It is a massive outcrop of rough and red sandstone which is laid down by glacial sediments. This monolith spreads to more than two and a half kilometres. The Aborigines have embellished it with rock paintings and they call it `Uluru’ or the `Great Pebble’. In Vera Cruz, Mexico, you will come across an amethyst crystal which is about two inches high. It is a violet variety of quartz and when it is heated; it will turn yellow. Mineralogists consider that its violet colour source is from organic impurities. Amethysts have been in use as gemstones since ancient Egyptian days. In the Bryce Canyon National Park in Utah, USA, rain and wind have worn the limestone and sandstone rocks into a variety of bizarre shapes. Gold is one of the most valuable and useful of all metals and for thousands and thousands of years, it has evinced interest and excitement. It is found in a natural state, mostly. It may also be found in combination with others, as in the case of metals found in the Lizard peninsula of Cornwall, England in the United Kingdom where it is amalgamated with silicon and oxygen quartz. In such a case too, the gold is separate within the rock.