Like thousands of years ago, we use natural stones for building houses, constructing roads and bridges, creation of beautiful churches, decoration of interiors and making jewelry. Stones are really essential for man’s life! Just recollect that the first tools were made of stones. What is the significance of natural stones nowadays? Just ask yourself a question: what kind of house you wish to live in? Is it a house built of natural stones or of concrete? The answer is evident. And what do we know about natural stones, their properties, strength, durability of various rocks, decoration and kinds of stone finishing?

Mechanical action on rocks and processing of rocks produce stone materials and articles made of natural stones. Depending on their formation, all rocks are subdivided into three groups: primary (eruptive), secondary (sedimentary) and modified (transformed or metamorphic). 

Most often used for lining houses and facilities are the erupted rocks: granites, syenites, diorites (greenstones), gabbro, labradorites, porphyrites, andesites, volcanic tuffs; sedimentary rocks: lime stones, dolomites, travertines and sandstones; and the metamorphic rocks: marbleized lime stones, quartzites and gneisses.

Natural stones used for decorating houses are characterized by such factors as unit weight, breaking strength, frost resistance, water absorption, hardness, abradability and shock resistance.

The rocks used for making the elements of lining or facing are intended to ensure not only durability of houses and facilities but also to convey their architectural expression. Therefore they should possess high strength characteristics and long service life and, on top of that, certain decorative properties (colouring and pattern, tracery).

Some characteristics of natural stones are listed below. It is necessary to know them so as to choose correct stones for a specific application.  

«Stone structure» means the structure characterized by the shape, content and quantitative ratio of the minerals making up the rock.

«Stone texture» means a spatial arrangement of mineral grains and cavities between them. There are massive textures where grains are arranged uniformly dense: banded-type where the areas of various mineral; composition or various structures alternate; The texture creates beauty of stones.

Porosity means a degree of pores in the rock and is defined as a percentage ratio of pore volume to the entire volume of the stone.

Water absorption means a material capacity to absorb and keep water in pores. It is determined as a percentage ratio of the mass of a stone sample saturated with water to its mass when absolutely dry.

Frost resistance means a capacity of a stone to withstand repeated and alternate freezing and melting, being saturated with water, without visible signs of destruction fracturing, lamination) and considerable reduction of the mechanical strength and mass

The main mechanical properties of stones are strength, brittleness, hardness and abradability.

Strength means a stone capacity to withstand destruction under the action of external loads. Breaking strength of a material means the stress which corresponds to the load when destruction of the material takes place.

Brittleness is a property of a material to be destructed at once under the action of external forces without developing any considerable deformations. Slabs of granite, marble and other rocks are weak to impacts.

Hardness characterizes the property of a material to resist penetration of harder solid objects in it. Hardness of stones is approximately estimated by Mohs hardness scale, however, if it is required to measure hardness more precisely, a special instrument – scleroscope – is applied.

Abradability means an ability of a stone to reduce its mass and volume if abraded.

Physical and mechanical properties (mechanical strength, abradability, resistance to frost and atmospheric factors, colour stability, difficulties in processing) predetermine the differences in application of natural stones to line and finish the houses and facilities.

Hygienic safety of natural stones

In recent years great attention is being paid in construction to ensure that houses and facilities are environmentally-friendly and that the used materials are natural, not artificial. Having refused from all kinds of synthetic substitutes, we are coming back to the materials that have been used in construction and finishing works for many a century – to wood and natural stones.

It should be mentioned, however, that many substitutes made of laminated wood particle boards emit phenol-formaldehyde resins which, same as the vapour of plastics used to produce all other substitutes of granite, bring much more evident harm to human health than the infinitesimally small radioactivity of natural stones.