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MINERALS AND MINERALOGY There are three developing processes: the macmatic developing process, the sedimentary developing process and the metamorphically developing process. The magma is known as the material which comes out of volcanoes and is called lava. It is a liquid in the earth with a temperature of 1300 degrees. When the magma comes out of the earth to the surface it becomes colder and it crystallizes. The first minerals are formed which are deep in the earth. On the way to the earth surface the magma becomes high liquid and it crystallizes. One of the last phases is the hydrothermal phase. In this phase some gases leave the magma und flow to the top. Often these gases form rooms in the rocks. These rooms are later filled with magma. In this phase quartz (rock crystal, amethyst) originate. This is the reason why quartz is often in closed rooms of rock that are called geodes. Generally quartz grows in cracks of rock. In the sedimentary developing process minerals originate because of many environmental factors. High temperatures can cause new chemical connections. Strong frost can have an explosive effect. There is also acid and other substances, because of the rain. Water and the oxygen in the air can also react with minerals and so new minerals are formed. In the metamorphically developing process it is so that magma flows again through the rocks where minerals already exist. Here the magma alters these minerals. There are special developing processes for organic minerals, too.
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Chemical and physical properties: every mineral has got certain chemical and physical properties. Every mineral has got a structure. The easiest structure is an element, but most of the minerals are molecules or ions and so they have got a chemical formula. The chemical formulas are described in the chapters about the minerals. Here we will look at the 9 mineral classes in which the minerals are arranged. 1. Elements (Diamond, Gold, Silver) 2. Sulfides, Selenides, Tellurides, Arsenides, Antimonides and Bismutides (Pyrite) 3. Halides (Fluorite, Rock Salt) 4. Oxides and Hydroxides (Corundum, Quartz) 5. Nitrates, Carbonates and Borates (Calcite, Malachite) 6. Sulfates, Chromates, Molybdates and Tungstenates (Alabaster) 7. Phosphates, Arsenates and Vanadates (Turkis) 8. Silicates (Feldspar, Topaz) 9. Organic Connections (Amber)
Most of the minerals form crystals. Crystals are a symmetric order of atoms, molecules or ions. It is called crystal lattice. An arbitrary order is called Amorph. There are 7 different crystal systems for minerals (Cubical, Monoclinical, Triclinical, Hexagonal, Trigonal, Tetragonal, Rhombical). Rock salt for example crystallizes in the cubical system. Because rock salt (Nacl) is also common salt (Nacl), we can see little cubes in the common salt. It is easier to see in bigger pieces. So minerals which crystallize in the cubical system have got the form of a cube. Quartz and corundum (Ruby, Sapphire) crystallize in the trigonal system. When the material does not comes regular during the formation of a mineral then the crystal would not be perfect. Other factors have also an influence of a wrong form of a crystal. A too small room or other materials can change the crystal form, too. Nearly never we can find perfect crystals. The relation between the perimeter and the height is not always the same. When the room is too small then often one crystal grows into another crystal. Another property of minerals is their density. The density is the mass per volume. It is gram per cubic centimetre (g/cm3). Water for example has got a density of 1 g/cm3. Most of the minerals have got a higher density than water and so they sink in water. The hardness is another property. The hardness is the possibility to break into a mineral. There is the moths' hardness scale. It is from1 to 10. A mineral with the hardness of 1 can be scratched with the fingernail. The diamond with a hardness of 10 cannot be even scratched with a knife. A mineral with a higher hardness can scratch a mineral with a lower hardness. |
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MOHS' HARDNESS SCALE :
1 Talc
2 Gypsum
3 Calcite
4 Fluorite
5 Apatite
6 Feldspar
7 Quartz
8 Topaz
9 Corundum
10 Diamond |
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Many minerals can be split through an impact with a hammer. A mineral can be split well in one direction, but for example not in another. There are also minerals without a certain fissileness. They break casual. Here we can see the break. The color is the easiest property. There are colorless minerals like the rock crystal and the diamond. Other quartz like the amethyst has got a color, because of admixtures. They are colored minerals. The third group is minerals which have got an own color, because of their chemical and physical properties. To see whether a mineral is colored or has got an own color we can pass it over a surface and look at the abrasion. It is the line color. The gloss of a mineral is another property. There is diamond gloss, glass glos, fat gloss and metal gloss. The transparency is very important, too. Clear minerals have got a high transparency, but the transparency is caused by the chemical and physical properties of the mineral. |
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