All minerals (and stones relate specifically to minerals) have two important characteristics - mass and density. Moreover, the density of the stone is important in a purely practical sense - to calculate the stock of a mineral deposit.
What is this characteristic?
For any substance, density means mass divided by unit volume. Since stones (i.e. minerals) have a heterogeneous composition and include elements of different atomic masses, the physical characteristics of their density can vary significantly. Also, the density of stones depends not only on the severity of the elements that make them up, but also on how closely elementary particles are "densely packed" in their internal structure.
The study of the density of minerals deals with mineralogy. The density of the stone is calculated by dividing the mass of the mineral sample in a unit volume by the mass of water of the same volume at a temperature of 4 ° C. For example, the weight of the sample is 200 grams. Water in the same volume of 40 grams. In this case, the density of this stone will be 5.
The density of stones is measured in kilograms per cubic meter or grams per centimeter cubic.
How to find the density of the stone?
How is the density of the stone determined? The procedure is quite simple - weigh the sample first in air, then in water. According to the law of Archimedes, the difference obtained corresponds to the mass of water that the sample displaces. Density is calculated by dividing the mass of the sample in air by a given difference.
Minerals can be light, medium, heavy, and very heavy, depending on their density. For example, the density of granite stone is 2 600 kg / m³. For reference: the density of the lungs does not exceed 2.5 g / cm³, medium - ranges from 2.5 to 4 g / cm³, heavy - from 4 to 8 g / cm³. Minerals with a density higher than 8 g / cm³ belong to very heavy stones.
Gemstone density
In addition to density and another characteristic - hardness, gem minerals or precious stones also have such an important component as mass, measured in grams or carats (in pearls - in grains).
To clarify the ratio of these units, remember: 1 carat corresponds to 200 milligrams, 50 milligrams in one face, that is, 1 carat is equal to four grains. Gem measurement accuracy - up to two decimal places.
Let's go to the lab
How to measure drag density. stones in the laboratory? The hydrostatic method is best suited for this. Its principle was proposed by the Greek scientist Archimedes many centuries ago. The essence of the principle known from the school course in physics is as follows: a body immersed in a liquid is pushed out of it by force, which is equal to the weight of the liquid displaced by the given body.
Simply put, if you hang a stone and lower it into water, then its weight will decrease compared to the original by as much as the volume of water displaced by it. It is clear that this volume will be equal to the own volume of the stone.
Thus, by sequentially weighing the stones in the air, and then in the water, we can get all the data we need to calculate.
Everything is in nature!
Let us now turn to natural stone materials. There are several types of them, as you know. From a practical point of view, it is customary to attribute any breed to one of two groups - strong or low-strength.
The materials of the first group have a high hardness index and, most often, the structure is medium or coarse-grained. In the so-called non-weathering state, they have little water absorption. In other (low-strength) rocks, as the name implies, the strength is significantly lower. They also have a much higher degree of water absorption.
Sometimes, when recognizing the types of rock of a stone, it is necessary to determine its hardness. In the field, it is most convenient to do this using the so-called. Mohs relative scale and additional tools available. Such improvised tools can be a stylus, a coin, a piece of glass, a file, a steel needle or knife, an ordinary or diamond glass cutter. The average density of a stone is also important in determining its breed. Having determined this value, one can identify the breed by referring to special tables.
We calculate the density of natural stones
How to calculate the average density of the sample stone? The equipment necessary for this is a balance with a set of weights and skills to measure the volume of a sample having an irregular shape.
The easiest way to do this is to have a graduated graduated cylinder with a volume of about half a liter. 200-300 ml of water is poured into such a cylinder and a piece of the studied stone material is placed.
The total volume of samples placed in water is recognized by the amount of water displaced by them. Then, by dividing their mass by the calculated volume, the average density of the material is obtained.
What is important to consider?
It should be noted that this method is suitable only for dense rock with insignificant water absorption (no more than 2%). If this characteristic is higher (up to 5%), a dry sample, after weighing it, must first be placed in an aqueous medium for saturation. Then, the average density is determined by the above method. Saturation is considered complete if, during water absorption, the weight ceases to grow.
Porous stones (most often limestones or tuffs) are of low strength. They are easy to process - with a conventional hacksaw, cut out a sample of the desired shape (for example, a cube) and calculate its volume by measuring faces.
Do it yourself
In the absence of sufficient volume in the measuring cylinder in the field, the amount of water displaced can be determined as follows. In any metal vessel of cylindrical shape, just below the top, a hole in the wall is punched with an ordinary nail, then a tube is inserted there, which can also be made independently by folding any film. Fix it in the cylinder wall with plasticine or any similar material.
Thus, a field volume meter is obtained. If this unit is used constantly, it makes sense to solder a tube of steel or brass.
Stones made by human hands
Everything written above related to natural stones. And now it's time to talk about artificial ones. They can be wall, road and side. This also includes concrete roofing tiles and paving slabs, as well as all kinds of blind areas, stair steps and chimney elements.
In the production of almost all of these stones, both in Russia and abroad, strict technical standards are used. They govern all the basic characteristics - the quality of the starting materials, the size and shape of the cross section, physical and mechanical properties (including the density of concrete stones).
These requirements depend on the intended operating conditions and the material available.
