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Good evening everyone. Thanks for coming. yes you know My name is Rose Refezedyan and her name is Svetlana Tsaregorodtseva. Today i am going to speak about Minerals.
So, Lets get started.
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A mineral is a naturally occurring chemical compound. Most often, they are crystalline and abiogenic in origin. A mineral is different from a rock, which can be an aggregate of minerals or non-minerals and does not have one specific chemical composition, as a mineral does. The exact definition of a mineral is under debate, especially with respect to the requirement that a valid species be abiogenic, and to a lesser extent with regard to it having an ordered atomic structure.
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The study of minerals is called mineralogy. There are over 5,300 known mineral species. The silicate minerals compose over 90% of the Earth's crust. The diversity and abundance of mineral species is controlled by the Earth's chemistry. Silicon and oxygenconstitute approximately 75% of the Earth's crust, which translates directly into the predominance of silicate minerals.
Minerals are distinguished by various chemical and physical properties. Differences in chemical composition and crystal structure distinguish the various species, which were determined by the mineral's geological environment when formed. Changes in the temperature, pressure, or bulk composition of a rock mass cause changes in its minerals.
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Minerals are classified by key chemical constituents; the two dominant systems are the Dana classification and the Strunz classification.
The general definition of a mineral encompasses the following criteria:
Naturally occurring
Stable at room temperature
Represented by a chemical formula
Usually abiogenic (not resulting from the activity of living organisms)
Ordered atomic arrangement
Minerals are chemical compounds, and as such they can be described by fixed or a variable formula. Many mineral groups and species are composed of a solid solution; pure substances are not usually found because of contamination or chemical substitution.
"A mineral is an element or chemical compound that is normally crystalline and that has been formed as a result of geological processes."
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Mineral classes
As the composition of the Earth's crust is dominated by silicon and oxygen, silicate elements are by far the most important class of minerals in terms of rock formation and diversity. However, non-silicate minerals are of great economic importance, especially as ores.
The largest grouping of minerals by far are the silicates; most rocks are composed of greater than 95% silicate minerals, and over 90% of the Earth's crust is composed of these minerals. The two main constituents of silicates are silicon and oxygen, which are the two most abundant elements in the Earth's crust. Other common elements in silicate minerals correspond to other common elements in the Earth's crust, such aluminium, magnesium, iron, calcium, sodium, and potassium. Some important rock-forming silicates include the feldspars, quartz, olivines, pyroxenes, amphiboles, garnets, and micas.
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Rocks, ores, and gems
Minerals are not equivalent to rocks. A rock is either an aggregate of one or more minerals, or not composed of minerals at all. Rocks like limestone or quartzite are composed primarily of one mineral—calcite or aragonite in the case of limestone, and quartz in the latter case. Other rocks can be defined by relative abundances of key (essential) minerals; a granite is defined by proportions of quartz, alkali feldspar, and plagioclase feldspar. The other minerals in the rock are termed accessory, and do not greatly affect the bulk composition of the rock. Rocks can also be composed entirely of non-mineral material; coal is a sedimentary rock composed primarily of organically derived carbon.
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In rocks, some mineral species and groups are much more abundant than others; these are termed the rock-forming minerals.
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The major examples of these are quartz, the feldspars, themicas, the amphiboles, the pyroxenes, the olivines, and calcite; except the last one, all of the minerals are silicates. Overall, around 150 minerals are considered particularly important, whether in terms of their abundance or aesthetic value in terms of collecting.
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