What is a mineral? Classification of minerals by origin

Despite the fact that many people approximately imagine what it is, some people can not define the concept of "mineral". The classification of minerals includes a large number of very diverse elements, each of which has found application in one or another field of activity due to its advantages and features. Therefore, it is important to know what properties they have and how they can be used.

Minerals are products of artificial or natural chemical reactions that occur both within the earth's crust and on its surface, and are homogeneous chemically and physically.

Classification

To date, more than 4,000 different breeds are known, which are classified as "mineral". Classification of minerals is carried out on the following grounds:

• Genetic (depending on the origin);
• Practical (raw materials, ore, precious stones, fuel, etc.);
• Chemical.

Chemical

At the moment, the most common is the classification of minerals by chemical composition, which is used by modern mineralogists and geologists. It is based on the nature of the compounds, the types of chemical bonds between the various structures of the elements, the types of packaging and many other features that a mineral can have. Classification of minerals of this kind provides for their division into five types, each of which is characterized by the predominance of a certain character of the relationship between certain structural units.

Types:

• Native elements;
• Sulfides;
• Oxides and hydroxides;
• Salts of oxygen acids;
• Halides.

Further on the nature of the anions, they are divided into several classes (in each type, their division), within which they are already divided into subclasses, from which one can distinguish: frame, chain, island, coordination and layered mineral. Classification of minerals, which are close in composition and have a similar structure, provides for their association in different groups.

Characteristics of the types of minerals

• Native elements. This includes native metalloids and metals, such as iron, platinum or gold, as well as non-metals like diamond, sulfur and graphite.
• Sulphites, as well as their various analogues. Chemical classification of minerals includes in this group salts of hydrogen sulfide, such as pyrite, galena and others.
• Oxides, hydroxides and other analogues thereof, which are a compound of a metal with oxygen. Magnetite, chromite, hematite, goethite are the main representatives of this category, which distinguish the chemical classification of minerals.
• Salts of oxygen acids.
• Halides.

It is also worth noting that in the group "salts of oxygen acids" there is also a classification of minerals by classes:

• Carbonates;
• Sulfates;
• Tungstates and molybdates;
• Phosphates;
• Silicates.

There are also rock-forming minerals that are divided into three groups:

• Magmatic;
• Sedimentary;
• Metamorphic.

By origin

The classification of minerals by origin includes three main groups:

• Endogenous. Such processes of mineral formation in the majority of cases involve the introduction of earth into the crust and subsequent solidification of underground incandescent alloys, which are commonly called magmas. In this case, the formation of minerals is carried out in three steps: magmatic, pegmatite and postmagmatic.
• Exogenous. In this case, the formation of minerals is carried out completely in other conditions in comparison with the endogenous. Exogenous mineral formation provides for the chemical and physical decomposition of substances and the simultaneous formation of neoplasms that have resistance to another environment. Crystals are formed as a result of weathering of endogenous minerals.
• Metamorphic. Regardless of the ways of formation of rocks, their strength or stability, they will always change under the influence of certain conditions. Breeds that are formed due to changes in the properties or composition of the original samples, it is customary to call metamorphic.

According to Fersman and Bauer

The classification of minerals according to Fersman and Bauer includes several rocks, intended primarily for the manufacture of various products. It includes:

• Gems;
• Colored stones;
• Organogenic stones.

Physical properties

The classification of minerals and rocks by origin and composition includes many names, and each element has unique physical properties. Depending on these parameters, the value of a particular breed is determined, as well as the possibility of its application in various spheres of human activity.

Hardness

This characteristic is the resistance of a certain solid body to the scratching effect of the other. Thus, if the mineral under consideration is softer than the one with which its surface is scratched, traces will remain on it.

The principles of mineral classification by hardness are based on the use of the Mohs scale, which is represented by specially selected breeds, each of which is capable of scratching its previous names with its sharp end. It includes a list of ten items, which starts with talc and gypsum, and ends, as we all know, with diamond - the hardest substance.

Initially, it is customary to carry a rock along the glass. If there is a scratch on it, then in this case the classification of minerals by hardness already provides for assigning to it more than 5th grade. After that, the firmness is already specified on the Mohs scale. Accordingly, if there is a scratch on the glass, then a sample from the 6th grade (feldspar) is taken next, after which they try to draw them on the required mineral. Thus, if, for example, feldspar left a scratch on the sample, and apatite, which is number 5, did not leave, it is assigned the class 5.5.

Do not forget that depending on the value of the crystallographic direction, some minerals may have different hardness. For example, in the distane on the cleavage plane, the hardness along the long axis of the crystal has a value of 4, while across the same plane it increases to 6. Very hard minerals can be found exclusively in the group with non-metallic sheen.

Shine

The formation of gloss in minerals is due to the reflection from their surface of the rays of light. In any manual on minerals, the classification provides for division into two large groups:

• With metallic luster;
• With a non-metallic sheen.

The first include those rocks that give a black line and are opaque even in fairly thin fragments. This includes magnetite, graphite and coal. As an exception, minerals with a non-metallic luster having a colored line are also considered here. This applies to gold with a greenish dash, copper with a peculiar red, silver with a silver-white, and a number of others.

Metallic in nature is similar to the sheen of fresh fracture of various metals, and it can be seen quite well on the fresh surface of the sample, even if rock-forming minerals are considered . The classification of products with such gloss also includes opaque patterns that are heavier than the first category.

Metallic shine is characteristic of minerals, which are an ore of various metals.

Colour

It is worth noting that color is a constant sign only for some minerals. Thus, malachite always remains green, gold does not lose its golden yellow color, etc., while for many others it is unstable. To determine the color, you must first obtain a fresh chip.

Particular attention should be paid to the fact that the classification of the properties of minerals also provides for a concept such as the color of a dash (ground powder), which often does not differ from the standard one. But there are also such breeds, in which the color of the powder differs significantly from their own. For example, they include calcite, which can be yellow, white, blue, blue and many other variations, but the powder will remain white anyway.

Powder, or a feature of the mineral, is obtained on porcelain, which should not be covered with any glaze and among professionals is simply called "biscuit." On its surface, a line is drawn by the mineral to be determined, after which it is slightly spread out with a finger. Do not forget that hard as well as very hard minerals do not leave a trace behind themselves because they will simply scratch this "biscuit", so you must first scrape off a certain part of them on white paper and then rub it To the desired state.

Cleavage

This concept implies the property of the mineral to split or to split in some direction, while leaving a brilliant smooth surface. It is worth noting the fact that Erasmus Bartolin, who discovered this property, sent the results of the conducted research to a rather authoritative commission including such well-known scientists as Boyle, Hooke, Newton and many others, but they recognized the discovered phenomena as accidental and the laws invalid , Although literally in a century it turned out that all the results were correct.

Thus, there are five main gradations of cleavage:

• Very perfect - the mineral can easily be split into small plates;
• Perfect - for any hammer blows the sample will split into fragments that are confined to cleavage planes;
• Clear or medium - when attempting to split a mineral, they form fragments that are limited not only by cleavage planes, but also by uneven surfaces in random directions;
• Imperfect - is detected with certain difficulties;
• Very imperfect - cleavage is practically absent.

Certain minerals have several directions of cleavage at once, which often becomes the main diagnostic sign for them.

Fracture

By this concept is meant the surface of the split, which was not in cleavage in the mineral. To date, it is common to distinguish the main five types of kinks:

• Flat - there are no noticeable bends on the surface, but it is not mirror-like, as in the case of cleavage;
• Stepped - is typical for crystals that have more or less clear and perfect cleavage;
• Uneven - manifested, for example, in apatite, as well as a number of other minerals that have imperfect cleavage;
• Zanozisty - typical for minerals of fibrous addition and is somewhat similar to the fracture of wood across fibrous;
• Conchoid - in form of its surface is similar to the shell;

Other properties

A sufficiently large number of minerals has such a diagnostic or distinguishing feature as magnetism. To determine it, it is customary to use a standard compass or special magnetized knife. Carrying out the tests in this case is carried out in the following way: a small piece or a small amount of powder of the test material is taken, after which it is touched by a magnetized knife or horseshoe. If after this procedure the particles of the mineral begin to attract, this indicates that it has a certain magnetic strength. When using a compass, it is placed on some level surface, after which the arrows are aligned and the mineral is brought to it, without touching the device itself. If the arrow begins to move, this indicates that it is magnetic.

Certain minerals, which contain carbonate salts, under the influence of hydrochloric acid begin to release carbon dioxide, which is manifested in a visa of bubbles, so many call it "boiling." Among such minerals are: malachite, calcite, chalk, marble and limestone.

Some substances can also be dissolved in water. This ability of minerals is easy to determine for taste, and in particular, it refers to rock salt, as well as potassium salts and others.

If it is required to conduct studies of minerals for fusibility and combustion, you must first detach a small piece from the sample, then with tweezers, bring it directly into the flame from a gas burner, an alcohol lamp or a candle.

Forms of their presence in nature

In the predominant majority of cases in nature, various minerals are found in the form of intergrowths or single crystals, and can also be displayed in the form of clusters. The latter consist of a large number of grains having an internal crystalline structure. Thus, there are three main groups that have a distinctive appearance:

• Isometric, equally developed in all three directions;
• Elongate, having more elongated forms in one of the directions;
• Stretched in two directions while maintaining the third in a short form.

It should be noted that some minerals can form naturally fused crystals, which are then called twins, tees and other names. Such samples often are the result of intergrowth or mutual germination of crystals.

Kinds

Do not confuse regular splices and irregular aggregates of crystals, for example, with "brushes" or druses, which grow on the walls of caves and various cavities in the rocks. Druses are splices formed from several more or less regular crystals, and at the same time growing at one end to some kind of rock. To form them requires an open cavity, which provides for the possibility of free growth of minerals.

Among other things, many crystalline minerals are distinguished by rather complex irregular forms, which leads to the formation of dendrites, sintering forms and others. The formation of dendrites is due to the too rapid crystallization of minerals located in thin cracks and pores, and the rocks in this case begin to resemble rather quaint branches of plants.

Often there are situations where minerals almost completely fill a small empty space, which leads to the formation of secretion. They use a concentric structure, and the mineral substance fills it to the center from the periphery. Large enough secretions, in which there is an empty space inside, are called zheodes, while small formations are called amygdala.

Nodules are inclusions of an irregular round or spherical shape, the formation of which arises because of the active deposition of mineral substances around a certain center. Quite often, they are characterized by radial-radiant internal construction, and unlike secretions, growth is, on the contrary, to the periphery from the center.