# About mineralogy

Mineralogy is the science of minerals. Minerals surrounded the person always and interest to them showed scientists in ancient times. The impulse to the birth and development of **mineralogy** in the first period was the finding of natural crystals quartz, pyrite, hematite, calcite, native copper. And already Aristotle (384-322 BC) and Theophrastus (372-287 BC) refer to the work of previous researchers in the field of mineralogy. Aristotle mentions mineralogy in his Meteorology; Theophrastus wrote a treatise on the "stones", which was, apparently, one of the first special works on mineralogy. One can not help but mention the so-called Platonic bodies (Figure 1), which attracted the attention of ancient Greek mathematicians and philosophers of the Pythagorean school even before Plato. Platonic bodies are geometric forms with identical faces, identical vertices and identical ribs.

**Fig.1. Geometric representation of Platonic solids.**

Five such bodies, namely: tetrahedron with four faces in the form of equilateral triangles, octahedron, which consists of eight faces in the form of equilateral triangles, a cube with six square faces, an icosahedron with twelve faces in the form of equilateral triangles and a dodecahedron with twelve faces in the form regular pentagons, symbolized four basic elements: fire (tetrahedron), air (octahedron), water (icosahedron) and earth (cube). According to the logic of Greek philosophers, to destroy water (icosahedron) by fire (tetrahedron) and air (octahedron), one particle of fire and two air particles are needed, since the number of icosahedron faces is equal to the sum of the number of faces of one tetrahedron and two octahedra. Plato divided the equilateral triangles by medians into six right-angled triangles, the hypotenuse of which is twice as long as the smaller ones, laying down the idea of the "necessity" of the six crystallographic systems behind which they are grouped for the time being crystals.

Many know the "Natural History" of the Roman scientist Pliny the Elder, which included four treatises on mineralogy; it was written in the 40-50's. After the decline of the Roman Empire until the Middle Ages, no scientific publications on mineralogy are known. In the Middle Ages, the most bizarre features of nature attracted the attention of a number of authors whose descriptions closely intertwine both observations and prejudices. Minerals were attributed to magical or healing properties in accordance with their appearance or rare occurrence.

In 1280, Albert Magnus for the first time expressed an interesting idea that minerals are characterized by a certain concrete form - an idea that was later developed by the French crystallograph Gauja and became the basic law of crystal chemistry. It is to this time include "Lapidarii" - a book about the magical properties of stones.

Later, however, more serious mineralogical studies began, and in the monograph "On the Nature of Fossils" by the Czech scientist George Bauer (1494-1555), known as Georgius Agricola, there is a section where minerals are classified on the basis of diagnostic properties-density, hardness and etc. In the work "The History of Precious Stones and Lapidary Art" (1609) of De Boadt, we find views that are much closer to the modern views of mineralogy, and some of the author's observations have not lost significance even in our day. In 1611, the famous mathematician and astronomer Kepler, on the basis of the features of the geometry of the heel of the Platonic solids, showed the possibility of obtaining some forms from others by dulling their edges, and thereby developed the idea of the tarnishing of crystalline forms and the possibility of coexistence in different crystals of different crystalline forms ). In addition, Kepler attempted to explain the correct form of snowflakes (Figure 2).

**Fig.2. A crystal of water is a snowflake.**

The date of the birth of scientific mineralogy is considered to be in 1669, when the Danish doctor N. Stensen, better known under the Latinized name N. Stenon published in Florence a thesis in which the results of various geological and mineralogical observations were presented - namely, the results of measurements of quartz crystals (Fig. ), on the basis of which it was concluded that the angles between the corresponding faces of these crystals are always the same regardless of the shape and size of the crystals.

**Fig.3. Crystals of quartz (SiO**

_{2}).In 1784, the French professor of mineralogy and crystallography Rene Juste Guyui, known as an honorary member of the Paris Academy and as abbot of Gauja, developed his theory of the structure of crystals, the so-called "theory of reduction", and formulated the second basic law of crystallography - the law of rational parameter relations. To this period is the development by the German mineralogist and crystallographer K. Weiss of the third fundamental law of crystallography, known as the law of zones, which establishes the relationship between the arrangement of the faces and edges of the crystal. The fundamentals of the internal structure of minerals can be related to the name of the outstanding Russian crystallograph E.S. Fedorov. In his famous work "Symmetry of regular systems of figures" (1890), all possible geometric laws are deduced that control the arrangement of atoms, ions, and molecules in crystals.