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Minerals and mineralogy
Mineralogy is the science which analyses minerals. Here we have to define what minerals are. A mineral is a
solid or liquid material with certain chemical and physical properties which is in the earth. In comparison to minerals
rocks are very different. Since thousands of years people are fascinate of minerals. There are about 3000 known minerals,
but only few of them are fascinating got people. Their look is the reason why they pleases to people. Very beautiful
minerals are often transparent and they have got a nice color or form. The popularity of a minerals decides if it is a
precious stone or not.
The formation: 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 volcanos 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
forms 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 which are called geodes. Generelly quartz grows in cracks
of rock. In the sedimentary developing process minerals originate because of many enviromental factors. High temperatures
can cause new chemical connections. Strong frost can have an explosive effect. There also also acid and other substances,
because fo 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 throught the rocks where minerals already exist. Here
the magma alters these minerals. There are special developing processes for organic minerals, too.
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.
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 eample 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 Mohs' hardness scale. It is from1 to 10. A mineral with
the hardness of 1 can be scratched with the finger nail. 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.
- Elements (diamond, gold, silver)
- Sulfides, selenides, tellurides, arsenides, antimonides and bismutides (pyrite)
- Halides (fluorite, rock salt)
- Oxides and hydroxides (corundum, quartz)
- Nitrates, carbonates and borates (calcite, malachite)
- Sulfates, chromates, molybdates and tungstenates (alabaster)
- Phosphates, arsenates and vanadates (turkis)
- Silicates (feldspar, topaz)
- Organic connections (amber)
Mohs' hardness scale
|1 talc||2 gypsum||3 calcite||4 fluorite||5 apatite
|6 feldspar||7 quartz||8 topaz||9 corundum||10 diamond
Many minerals can be splited throught an impact with a hammer. A mineral can be splited 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 quartzs like the
amethyst have got a color, because of admixtures. They are colored minerals. The third group are minerals which have got an
own color, because of their chemical and physical properties. To see wheather 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.
Mineral database (sorted by mineral classes)
- Sulfides, selenides, tellurides, arsenides, antimonides and bismutides
- Oxides and hydroxides
- Nitrates, carbonates and borates
- Sulfates, chromates, molybdates and tungstenates
- Phosphates, arsenates and vanadate
- Organic connections
Author and Webmaster: Lukas Czarnecki
If you have got questions about minerals and mineralogy you can send me an e-mail under the following adress:
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Last Update: 21.01.2006