All minerals (and stones are minerals) have two important characteristics - mass and density. Moreover, the density of the stone is important in a purely practical sense - to calculate the reserve of a mineral deposit.
What is this feature?
For any substance, density is understood as mass divided by unit volume. Since stones (that is, minerals) have a heterogeneous composition and include elements of different atomic masses, the physical characteristic 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 tightly elementary particles are "packed" in their internal structure.
Mineralogy deals with the study of the density of minerals. The density of a stone is calculated by dividing the mass of a sample mineral per unit volume by the mass of water of the same volume at a temperature of 4 ⁰С. For example, the sample weight is 200 grams. Water in the same volume of 40 grams. In this case, the density of this stone will be equal to 5.
The density of stones is measured in kilograms per cubic meter orgrams per cubic centimeter.
How to find the density of a stone?
How is the density of a stone determined? The procedure is quite simple - we weigh the sample first in air, then in water. According to the law of Archimedes, the resulting difference corresponds to the mass of water that the sample displaces. Density is calculated by dividing the mass of the sample in air by this difference.
Depending on the density, minerals can be light, medium, heavy and very heavy. 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 above 8 g/cm³ are very heavy stones.
Gem 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 (for pearls - in grains).
To understand the ratio of these units, remember: 1 carat corresponds to 200 milligrams, in one grain 50 milligrams, that is, 1 carat is equal to four grains. Gem measurement accuracy is up to two decimal places.
Let's go to the lab
How to measure dredge 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 physics course is as follows: a body immersed in a liquidis pushed out of it by a force that is equal to the weight of the liquid displaced by this body.
To put it simply, if you hang a stone and lower it into water, then its weight will decrease compared to the original one by as much as the volume of water displaced by it weighs. It is clear that this volume will be equal to the stone's own volume.
Thus, by sequentially weighing the stones in the air, and then in the water, we can get all the data we need for the calculation.
Everything - to nature
Now let's turn to natural stone materials. As you know, there are several types. From a practical point of view, any breed is usually classified into one of two groups - strong or low-strength.
Materials of the first group have a high hardness index and, most often, the structure is medium or coarse-grained. In the so-called unweathered state, they have little water absorption. In other (low-strength) breeds, as the name implies, the strength is much lower. They also have a much higher degree of water absorption.
Sometimes, when recognizing types of rock, it is required to determine its hardness. In the field, it is most convenient to do this with the help of the so-called. relative Mohs scale and additional improvised means. Such improvised means can be a stylus, a coin, a piece of glass, a file, a steel needle or a knife, an ordinary or a diamond glass cutter. The average density of a stone is also important in determining its rock. By determining this value, it is possible to identifybreed by referring to special tables.
Calculate the density of natural stones
How to calculate the average density of a sample stone? The equipment needed for this is a scale with a set of weights and the skills to measure the volume of an irregularly shaped sample.
The easiest way to do this is with 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 rocks with low water absorption (no more than 2%). If this characteristic is higher (up to 5%), a dry sample, having previously been weighed, 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 the weight stops growing during absorption of water.
Porous stones (most often limestones or tuffs) have low strength. They are easy to process - cut a sample of the desired shape (for example, a cube) with an ordinary hacksaw and calculate its volume by measuring the edges.
DIY
In the absence of a sufficient volume of a measuring cylinder in the field, the amount of displaced water can be determined by the followingmanner. In any cylindrical metal vessel, just below the top, a hole is punched in the wall with an ordinary nail, then a tube is inserted there, which can also be made independently by rolling any film. Fix it in the wall of the cylinder with plasticine or any similar material.
Thus, you get a travel volume meter. If this unit is used constantly, it makes sense to solder a steel or brass tube.
Human-made stones
Everything written above referred to natural stones. And now it's time to talk about artificial ones. They can be wall, road and side. This should also include concrete roof tiles and paving slabs, as well as all kinds of blind areas, stair steps and chimney elements.
In the production of almost all of the listed stones both in Russia and abroad, strict technical standards are used. They regulate all the main characteristics - the quality of raw materials, the size and shape of the section, physical and mechanical indicators (including the density of concrete stones).
These requirements depend on the expected operating conditions and the material available.
What can be artificial stones?
The concrete from which the stones are made can be either heavy or light. Artificial stones made from it are made full-bodied or hollow. The normative characteristic of the average bulk density for hollow stones should not exceed 1,650 kg / m³, forfull-bodied - 2,200 kg/m³.
Wall stones in terms of medium density (and, in addition, thermal conductivity) are considered effective (density up to 1,400 kg / m³), conditionally effective (1,400-1,650 kg / m³) and heavy (above 1,650 kg/m³). Most of them are now produced from lightweight concrete of low density (up to 1,800 kg/m³).
Heavy concrete (including sand) with high abrasion and low water absorption is used in the production of side or road stones, as well as paving slabs, since their operating conditions are more severe than those of wall ones.
Artificial stones also differ in aggregate, which can be quartz sand (considered fine aggregate) or strong rocks (large aggregate). For example, the density of crushed stone from natural stone can be different depending on the fraction - the degree of grinding. The composition of the aggregate also has a significant effect on the density of artificial stone.
