Factors affecting the selection of building stones (price and color)

Choosing the right stone is very important. Inappropriate selection of stones may cause a high cost of repair or replacement during or after installation. In choosing the right stone, first, by answering the following questions, the expectations ofthe stone’s work should be  determined:

• Is the stone used indoors or outdoors?

• Is the stone exposed to moisture after installation?

• Is the stone exposed to the daily traffic of  many people?

• Will the stone be exposed to acidic materials after installation?

• Does the stone require surface operation to retrofit against slippage and slippage?

• Is the stone exposed to detergent?

• Is the stone exposed to direct heat?

• Does the stone need a special design and color according to the design of the space décor used?

In general, price, color, durability and technical specifications  are more important factors in choosing suitable building stones.

Price

 From the  distant past to the present day, one of the basic parameters in choosing stones is the cost or in other words,  the cost of it, if 2,500 years ago the Palace  of PersepolisD was built from  limestone stones or at that time they were able to  inscription Ganj-e-Letter.  Carved on stone only on the backing of the state budget and cheap labor at the time (Farhadian, 1991).

The price of building stones depends on the following:

1.  The type of stone and the ability to work on it, especially in terms of the hazingof extraction and processing.

2.  Access to the deposit and proximity to transportation routes

3.  Changes in color and texture in stone and its abundance

4. Local Conditions

Any of the above factors may overshadow other factors depending on the market conditions.

Color

Color is an important factor for determining the value of stone and its elasticity in the market.   Color has  a wide impact  on the  decisionof the end  consumer (architects, designers, etc.) this factor is more important than the architects, although engineers are also sure to consider the color  of the stone.  Limestone  is more important, and most  of the dark colorsof limestone inthe exterior of the building do not last due to sunlight and air pollution.

In nature, the color of the stones is different, with little change in the chemical composition or conditions during the formation of the stone, its color changes  and according to the market demand and people’s tastes, the economic value of the stone is  fluctuating dramatically.   For example, red and walnut travertine, which is not different from white travertine, even in some cases white travertine resistance is more than its color type, but they differ considerably in price.

The color of the stone is one ofthe  most  economically important.   Green, azure and red stones that are rare are more valuable, in addition, some stones may be  sold more expensive than other types of  stones due to their  experience and designs.  The price of stone is effective in the market and disrupts the above mentioned basis.

Sometimes the distance of vision is important in the diagnosis of stone color. A medium-sized  granite with pink feldspars will not be seen in the distance with this feature, and a multicolored piece of it  will be monochrome in the distance, so the monochrome or multicolor of the stone  should be considered at a distance of about 20 to 50 cm from the eye  .

 Granite stones except in low cases due to the presence of various heavy crystals and the presence of some alvan materials in its paste (stone text) are not composed of one color and the overall color of the stone is considered as its color  , while the combination  of colors and coarse crystals of the donor mattress is very important if the   group of limestone stones is very important.  The sub-materials do not penetrate them, in white, and if there are ancillary materials  in different  colors, sometimes this color affects the  whole text of the stone and  removes the  stone from white to another color  , and sometimes  it can be seen as different designs. Sometimes, various minor materials penetrate the stone and make it multi-colored from a monochrome form  .

The color of   igneous rocks and silicate metamorphism in relation  to the color of feldspars is a donor mattress, which according to its type can take on pink, cream, red, green and white  colors in sedimentary main minerals are  usually B-color  (such as quartz and calcite) but there is a small amount of  Impurities  make these rocks colored  ,  which are more important than  carbon and iron oxides.     Black and blue colors due to the presence of organic carbon and  green, red and yellow colors can be caused by iron oxides and hydroxides in Table 1-1 the relationship between the color of the stone and  its  mattress cans is listed.

The relationship between the color of the  stone and  the minerals of the mattress.

The color stability of the stones is    one of   their most important and functional jags, and the color of some stones changes  , and those made up of organic materials (gray and black)  will have more changes, the black color of a gabbro with durable  pyroxene minerals.  But the black color of limestone with hydrocarbon materials is  not durable, but the  pink color of granite obtained from feldspars is  durable, but the green color of sandstone will not be durable if it is caused by iron compounds  .

Changing the color of the stone harms the goals of the  design and its beauty, so these points should be considered in choosing the stone:

1. When choosing the desired stone, pay attention to its function in  existing buildings with similar climatic conditions.  Miners and     stone companies dealing with the stone can be good advisors in this field.

2.  Most   black limestone stones outside the building are exposed to atmospheric conditions and sunlight to change color.

3.  Unstable minerals, even to a small extent, cause discoloration  before choosing stones, this issue can be investigated by the  study of petrology.

4. Polishing the stone will help to durable its color.

The color stability of the stone   depends on where the stone is used, if it is used inside the building, the color of the stone will change for a long time,   but if it is exposed to certain atmospheric conditions, especially with high humidity, its color change occurs very quickly, the  main causes of the color change  are:

A- Exposure to acid

    Usually, acid is used to remove slurry residuals or rust stains on the stone, if acid can remove the slurry,  it can also attack the carbonate part of the stone, if the acid can remove the bell, it should also be expected to remove the color of the stone that is made of iron oxides (rust).    Acid rains and polluted urban air have caused   many buildings to lose color over the years (Conklin, 1993).

B-  Exposure to UV light

 Sunlight can eliminate the  color of many materials, including stones, often  from  metal oxides of  M.G. Rand  , which  are  resistant to color loss, but there are exceptions to black marbles under sunlight, and their  color from organic matter.   M.G.Rand decomposing by ultraviolet light  (Conklin, 1993).       Gray limestone gradually turns white  , and  black limes tend to be pale gray or gray yellow, in  sandstones and clays the azure and green color caused by iron sulfur, M.A.D., The oxidation squash is first converted to yellow, L to green, and then to yellow or red.

C- The existence of  unstable minerals

  Unstable minerals are    easily converted into  other minerals, and color changes occur in  white rocks, usually they become opaque  and due  to chemical interactions in the vicinity of moisture. The stains   on their surface are caused  by the exhaustion of these types of stones mostly in industrial cities and at least hot and humid  M.A.D., while in dry and clean weather the durability of these stones    It will be more, the opacity of the stone on its surface is not uniform and in the place of the seams and holes is more in the  next table the  color of the different  minerals in the stone is inserted in the healthy and weathered sample.

D – Dandruff

 Dandruff  covers the surface of  the  rock  as stains,  usually composed of calcium carbonate particles or calcium sulfate, and sometimes associated with chlorides and terats, rather than related to the  type of stone used.  I’ll go back to installing  it.   Salts form crystals on the  surface  if surface evaporation occurs,  and if evaporation occurs on the underlying surface, the salt accumulates inside the  rock.

 The color of different minerals in the stone in the healthy and weathered sample