Mineralogy. Crystalline matter and its constitution.

Crystalline matter and its constitution. Crystals - solid bodies having the many-sided moulding box, and fragments composing them (atoms, molecules, ions) are laied out naturally. The surface of crystals is restricted by plains which one wear the name of facets. Conjunctions of facets are termed as ribs which one intersection points are termed as vertexes or angles. Facets, ribs and vertexes of crystals are bundled by dependence: number of facets + number of vertexes = number of ribs + 2. In most cases crystalline matters have no clearly faceted moulding box though possess a natural interior crystalline constitution. It is fixed, that crystals are constructed of the material fragments - ions, atoms or molecules, geometrical in position in room.

Properties of crystalline matters. The basic properties the following:

1. Anisotropy. Anisotropic term such matters which one have identical properties in parallel directions and unequal - in not parallel. Various physical properties of crystals, such as a thermal conduction, hardness, resiliency, spreading of light, etc., are inflected with a veering. Contrary to anisotropic, isotropic bodies have identical properties in all directions.
2. Ability to semi-facete. This particular feature crystalline matters possess only. At the free growth crystals are restricted to plane facets and direct ribs, taking over the many-sided moulding box.
3. Symmetry. Symmetry terms natural repeatability in a location of subjects or their parts on a plain or in room. All crystals are bodies symmetrical

Lattice structure. The material fragments (atoms, ions, molecules) in crystalline matter are disposed not chaotically, and in the certain strict order. They are laied out by parallel rows, and spacing intervals between the material fragments of these rows are identical. This legitimacy in a constitution of crystals is expressed geometrical in the form of a space lattice which is as though a skeleton of matter.

To introduce a space lattice it is possible as perpetually major number identical under the moulding box and the size of the parallelepipeds moved concerning another and stacked so, that they execute room without gaps. Vertexes of parallelepipeds in which one there are atoms, ions or molecules, are termed as space lattice knots, and the straight lines made through them, - rows. Any plain, which one drives through three knots of a space lattice (not laying on one straight line), it is termed as a plane mesh. The elementary parallelepiped in which one vertexes there are lattice sites, wears the name of a mesh of the yielded space lattice.

Thus, crystalline matter has strictly natural (reticular) constitution.

Physical properties of minerals, as reflex of their interior. All major properties of crystalline matters are a consequence of their interior natural constitution. So, for example, anisotropy of crystals can be understood easily if to lead gauging of any properties in various directions. Specially accurately direction properties come to light in optical properties of crystals on what one of the major methods of their analysis is grounded, applied in mineralogy and petrography.

Ability of crystals to semi-facete also is a natural consequence of their interior. Facets of crystals correspond to plane meshes, ribs - to rows, and vertexes of angles - to space lattice knots. The space lattice has the perpetual set of plane meshes, rows and knots. But to real facets there can correspond only those plane meshes of a grating which one have the greatest reticular density i.e. on which one the greatest number of fragments drawing up it (atoms will have per acre, ions). It is a little such plane meshes, from here and crystals have quite certain number of facets.

Pattern of a crystal, i.e. location in it of separate fragments, is symmetrical. Hence and the crystal will possess plains and symmetry axes.

Formation and crystal growth. Crystals arise at transition of matter from any modular state in the solid. Thus fragments can appear rather each other in a chaotic standing or there can be a legitimacy of their location. In case of the former we will have amorphous solid, and in second the crystalline.

Crystals can be formed at transitions of matter of a gaseous state in solid, from liquid in solid and from solid in the solid.

Formation of crystals of sulphur, sal ammoniac, fumarole acid, etc. originates at refrigeration of gases in craters of volcanoes and fumaroles. The most usual example is snow formation.

Specially widespread in the nature and the technician formation of crystals at transition of matter from liquid state in the solid. Here it is necessary to distinguish two cases of formation of crystals: from melting and from a solute. An example of the maiden case is magma crystallisation. Magma - it is vulcanic - the liquid silicate melting containing various chemical combinations, including gases. At slow cooling of magma the set of crystallisation centres is formed, crystals grow, stirring each other and as a result crystalline granulated soil is formed.

As examples of formation of crystals from solutes formation of ice and a deposition of various salts can serve.

At transition from solidity in the solid it is necessary to score two cases. At one processes crystalline matter can be formed of the amorphous. So, about time fluxion glasses and containing glasses igneous rocks are crystallised. Other process - a recrystallization: pattern of one matters new crystals with diverse pattern are blasted and formed. All metamorphic soils are to some extent recrystallized. Under temperature effect, pressure and other factors chalkstone transfers in marble. The phenomenon of a recrystallization widespread in the nature.

Crystal growth. Small chips routinely have major number of facets, but in the course of growth some facets grow. Normal lines to facets are directions of their growth, i.e. in the course of facet growth move to itself. Not all facets grow with identical velocity. Those from them which one grow more promptly, relieving in sizes and can disappear, therefore the moulding box of a crystal in the course of its growth is inflected.

Sometimes there are so-called zonal crystals. Their zonality can be caused interruptions in crystallisation or any impurities and painting matters which one were present during the certain moments of crystallisation.