What is a stone?

It refers to the materials of the earth’s crust, which are composed of one or several minerals.
Stone or soil

In geological terms, stone is the materials of the earth’s crust, which are composed of one or several minerals. In contrast, soil is a pile of detached or loose particles that results from weathering of rocks in place. However, in engineering and construction terminology, drilling capacity of geological materials as an indicator is used as an index to classify them into two groups of stone and soil.
Kinds of building stones
These stones have a wide variety of names, where sometimes the name of the quarry is used as the name of the stone. The most common building stones are :

Granite
Sandstone
Limestone
Quartzite
Claystone
Travertine

Granite

Granite is a common type of felsic intrusive igneous rock, and therefore it has medium to large granular texture and contains quartz, feldspar and some other minerals. Its color depending on the mineralogy and chemistry of rocks, varies from pink to dark gray or even black. This stone is among the heaviest stones with a density of 2.75 g/cm3.
Granite is one of the strongest and hardest stones, therefore widely used as a building material. Their resistance to corrosion makes extensive use of the stone in laboratories. Resistance and high hardness of the stone allows building sheets with a thickness of only a few millimeters.

It is worth noting that the word granite is originated from Latin.
Granite is a stone resulted from cooling the molten rocks. It is a symbol of hardness, resistance and durability. Granite comes in a variety of colors such as white, gray, orange, green, black, red, etc. It is harder but more uniform than limestone. Granite will not scratch easily, and are resistant to high temperatures. Granite is an ideal option for outdoor pavements and in places exposed to heavy traffic, but it can also be used in exterior and interior façades as well as stairs. The majority of these stones are obtained from the Central Asian countries such as India, China, Taiwan and Vietnam and are of very high quality. In terms of color, there are two types of granite stones, natural or artificial colored, such as peachy and peas and red, Black Galaxy, Black chance, Carmen Red, Baltic brown, Maple Red, Juparana, Multicolor Red, Volga Blue, Bidasar Brown, Bidasar Green, Paradiso Bash, Tan Brown, Silver Pearl, and so on.

Travertine

Travertine (Travertin in French) is a kind of porous limestone that is a type of decorative stones. The stone is made of deposits in caves, hot water springs or seabed and river sediments that are found in large areas.
Among types of travertine, white travertine with colored rays and uniform porosity are of higher quality. The reason behind pale travertine is the iron oxide pigment dispersed in the context of travertine. Colored travertine is formed according to the percentage of iron oxide pigments and come in red, nuts, lemon, and other colors. Beautiful appearance of travertine is caused by differences in the amount of iron oxide in different layers.

Appearance

Travertine has different colors and various textures strip, created by the presence of iron compounds, calcium and other impurities. The stone occurs in yellow, brown, red, lime, gray, black, and white. Travertine stone are randomly with or without Shawl.

Properties

Travertine has thermal and acoustic properties due to its cavities. Travertine has an acceptable resistance. This stone can be cut in both straight and corrugated forms. Travertine has holes and cavities that need to be filled in when processing the surface. The holes in travertine makes the installation of stone more secure, as cement mortar penetrates into the pores and prevent from detachment. The most unfavorable property of travertine is the non-uniformity of color and pattern. Another defect is that it is loose and muddy so that if it gets wet and reach freezing temperatures, it will destroy easily. That is why the slabs are covered in the factory.

Uses

Travertine is used in buildings’ exterior and interior as well as for paving.

The stones used in the construction must meet the following specifications:

1 – The texture of the stone has to be solid, i.e. without grooves, cracks and loose veins (not wormy)
2 – it has to be non-porous
3 – Should not be decomposed
4 – Should be smooth, uniform and homogeneous
5 – The building stone should not absorb a lot of water, so it should not:
A – be disintegrated or dissolved in water
B – All or part of it absorb water more than 8% of its weight
6 – Building stone should not be contaminated with natural and artificial materials
7 – Stone must withstand the physical and chemical conditions of the environment, so it must be:
A – Resist against wind, freezing, temperature changes and water flow if water is present, as well as all deterioration factors.
B – Resist against acid and alkaline environments, hydrolysis and oxidation
8 – The compressive strength for the load bearing parts should not be less than 150 kg/cm2
9 – Resistant to abrasion

General characteristics of granite stones

Most granites are hard and dense and thus are considered durable construction materials. They are resistant to water penetration and physical impact, and tolerate industrial environments as well. The appearance of granite is affected by the work done on the final surface, which may look hammered, chamottised, spiky or polished. The finest finish of granite is a polished state, which displays the beauty of color and the reflection of the crystals. The surface of the granite looks burnt due to heat and the effect of expansion and contraction between its various crystalline components. The combined use of polished and burnt granite in the buildings creates an interesting beauty due to the visual contrast. There are many mines in Iran where granite stones from of different colors are extracted. Granite stone is relatively expensive due to the heavy cost of extraction, cutting and polishing, which is why it is more used in the façade of important buildings. It is also used for flooring, pedestrian pavement and road construction.
The origin of the formation of rocks and rubbles
Mountain-formation and mountain-erosion are the two processes create stone products.
Mountain-formation factors
The pressures from molten core toward the Earth’s solid crust are responsible for mountain formation process.
Weathering or mountain-erosion factors

Any of several processes that lead to fragmentation and deformation of hard surface that are in contact with the atmosphere are collectively called weathering. Erosion or weathering factors are divided into two groups: physical and chemical.

Chemical weathering

It is the result of hydration, dissolution, hydrolysis, oxidation or reactions of acidic waters with minerals in the stone.

Physical weathering

This phenomenon is formed by factors such as frost, temperature changes in the atmosphere and thus expansion and contraction, geomagnetism, plants growth, wind, water and animals activities and alike, leading to changes in form and shattering the rocks and change their shape and creating fine grains.
Classification of rocks in terms of formation
Rocks are divided into three groups in terms of formation processes:
Sedimentary rocks
Igneous rocks
Metamorphic rocks
Sedimentary rocks

Some of the rocks are formed through sedimentation of materials in the water. Rivers carry massive materials into the seas and lakes. These materials deposit at the bottom of the sea due to their weight. They are called sedimentary rocks after they become hard. Sedimentary rocks are layered and layer has a different color. Sedimentary rocks are found in abundance in Alborz and Zagros mountains. Sand, gravel and limestone are examples of sedimentary rocks.

Igneous rocks

Another group of rocks has been developed by cooling very hot materials in the earth. The temperature of the earth’s core is very high and melts some rocks. The rocks below or on the earth’s surface cool down again and develop what is called as igneous rocks. The rocks of the mountains such as Damavand and Alvand are of igneous type. Igneous rocks are composed of coarse or grained crystals.
Metamorphic rocks
If some igneous rocks remain too long in the depths of the earth, they endure a lot of pressure and heat. These stones are then baked like bricks, losing their initial form. That is why they are called metamorphic rocks. (Like marble)

Uses

Rocks and minerals are used in construction, industries, medicine, etc.
Corruption in rock

The main cause of decomposition in the rocks is the effect of dissolved salts on them. Pollution, frost and decomposition in metal parts and the existence of weak layers as well as poor processing lead to destruction of rocks.
The effect of dissolved salts
If water with soluble salts evaporates from the stone, it creates a layer of dandruff and leaves crystals in the pores. Continuation of the moisture – evaporation cycle increases the size of the crystals, thus scaling surface of the stone. Therefore, porous rocks are more sensitive to dissolved salts.

Pollution

Stone with calcium carbonate mineral are particularly sensitive to acidic environments. Sulfur dioxide and oxygen in the air produce sulfuric acid in a moist environment that will affect the limestone and produce calcium sulfate. Limestones and calcareous sandstones in this case are more sensitive.
In the case of limestone, the calcium sulfate produced at the surface is washed off by water. But in surfaces that cannot be washed, the surface is blackened by the soot and is converted into hard shells and bulges that contain round limestone

around it.

In a variety of magnesium calcareous stones, the formation of magnesium sulfate accelerates the process of corruption.
In sandstone the pores are filled with gypsum (calcium sulfate), hardened shells often collapse due to the difference in thermal expansion. Silica sandstones, although not directly damaged by the invasion of acids in the air, but the gypsum produced by limestone causes them to break down due to evaporation resulted from crystallization at their surface.
Marble, which is essentially calcium carbonate, is attacked by acids in the air and its polished surface coarsens over time. However, due to its denser texture it is less affected by crystallization.

Frost effect

Frost damage occurs in parts of the building such as covers, shades, basement seats, and windows bases. Generally, limestone and dolomite are more likely to be exposed to ice aggression than sandstones.
Marble, sheath and granite are not affected by glacial effects due to less porosity.

Corruption of metals

When rainwater spills from the surface of copper and alloys to the surface of limestone, green spots are resulted. Rusting from steel and iron is hard and difficult to be removed from porous rocks. The greatest damage is due to the expansion and rusting of iron and steel parts planted into the façade stone. For this reason, all the metal parts used in installing stone should be stainless.

Fire

Fire rarely causes general damage to stone works. However, the surface of the granite, marble and sandstone may be crushed or blackened.
Calcareous stones are not generally affected by fire; only brightly colored stones become permanently pink due to the oxidation of iron in them.

Chemical structure of rocks

The rocks are made of simpler parts called mineral. Minerals are solid, natural, usually crystalline, inorganic, homogeneous and with distinctive chemical compounds. So far, more than 3,000 minerals are known in the nature, while only about 24 minerals found in rocks in the earth’s crust are abundant, which are called rocky minerals.

Chemical classification of rocks

Since the minerals that make up the rocks are diverse, they are divided into four categories depending on the presence of some other chemical compounds in them:

Carbonates
Sulfates
Oxides
Silicates

Building Materials

They are the material used for construction. Many of the naturally occurring materials (such as clay, sand, wood, stone, and even small branches) are used for construction. Apart from natural materials, some materials made by humans are also used in combination for construction. In many countries, the production of building materials has become an industry. In addition, the use of these materials has created many businesses and jobs, such as carpentry, plumbing, roofing and insulation. These types of artisans are made for decoration and beauty of buildings and houses.
Marble stone
Marble is made up of metamorphic rocks that have been transformed from limestone. The main mineral is calcite. The stone has been widely used for sculpture. The facade of the Taj Mahal is marble.

Marble

The limestone is formed from the sediment of the warm and endless seas millions of years ago. The marble has veins and fossils that give it a special beauty. The marble has chains called stylolites, which looks like electrocardiograph lines. Due to the presence of impurities, these stones can be seen in bright or dark colors such as crème, red, brown, pink, black, mustard, green, and so on. Marble has a good application in the interior and exterior façade and pavement. Most of these rocks come from India and a minority from China, and they have a very good market in Iran. Examples of marble rocks include Green Marbles, Enix, Emperador Light, and Dark.

Curbstone

Educational materials
Arman Stone Industries Co. provides customers with a variety of stones including curbstone, cobblestone, pearl granite, staircase stone and other types of stones that are produced at the Granite Factory in Mashhad. You can contact our sales staff for the price or technical characteristics of Pearl granite, or order a variety of curbstones.