The value and evaluation of diamonds.
The most important factors, on which depends the value and price of a diamond: barwa, cleanliness (faultlessness), cut quality and size.
The size of diamonds. Diamond crystals vary in size - they can be very small, up to several centimeters in diameter. Large diamonds only make up a small percentage of the stones found; usually there are fine crystals and their crumbs. The largest diamond ever found, known as Cullinan, it was the size of a fist; originally it was probably even bigger, because on the one hand it was limited by the cleavage plane.
Time, and therefore the size of diamonds, just like other Gemstones, is defined in karatach. The former Arabic name kirat comes from the Greek keration - carob seed (Ceratonia siliqua). The Romans called carob Greek pods, and the Roman name for the mass of gemstones was Siliqua. According to other assumptions, the name carat comes from the seeds of the coral tree Erythrina corallodendron, called kuara, growing in India and Africa. The average weight of these seeds is approx 0,2 g, was taken as the basis for measuring the mass of gemstones. Time 1 the carat in different countries and commercial centers varied, most often it was 0,205 g. The resulting difficulties and misunderstandings were only removed by introducing v 1913 r. a single carat weighing 0,2 g, called metric carat. In the past, this carat was abbreviated as ct, mtc; now - kr. In the international system of units, SJ does not have a carat as the weight unit for gemstones. This SI mass is measured in grams (1 kr = 0,2 g, lg = 5 kr).
The carat is now divided into tenths and hundredths. Formerly, division into parts was used: 1/2, 1/4, 1/8, 1/16, 1/32, 1/64. Was used also the division into played (1 karat = 4 played). In Florence, an ounce was used as the unit of mass 144 karatom. Points were also used as a measure (points); this unit equaled 0,01 kr. Carat concepts, used as a unit of weight for diamonds and other gemstones, and sometimes also pearls, not to be confused with the carats for the pure gold content of the alloys, Pure gold is defined as 24 carat gold, alloy content 50% gold - 12 carat gold, a containing only 15% gold - as 6 carat gold. Hence, 18 carat gold has 75% gold content, that is, an attempt 750/1000, and gold 14 carat fineness 583/1000, sometimes 585/1000.
The size of diamonds is measured with special gauges - caratometers.
Regardless of the situation on the world markets, assess the value of stones, especially the big ones, may vary considerably, because there are no strictly established rules and regulations in this area. There are stones of the first water, i.e.. colorless and error free, that is, not containing inclusions and cracks, stones of the second water, which are also colorless and contain only slight errors or are very weakly colored, but they do not contain errors, and finally the stones of the third water - colorless, with greater errors or with a distinct color.
Coloring - except for a pale blue shade – generally lowers the value of a diamond. However, rarely seen clearly colored diamonds cost much more than colorless ones. In these cases, the evaluation depends particularly on the individual opinion of the diamond expert, and the two estimates can differ significantly.
Common errors are the content of the infixes and the presence of cracks. Errors visible to the naked eye essentially affect the value of the stone, lowering it sometimes very significantly. Errors visible through a 10x magnifying glass are considered less important, but also affect the value of the stone.
A microscope is more and more often used to recognize errors, which allows for an accurate recognition of the nature of the error. Error (the presence of ingrowths or internal cracks) only visible under a microscope, and invisible through a magnifying glass, however, it is considered irrelevant.
There is widespread conviction, that the diamond is contaminated with hard coal, because the infixes appear black or dark when viewed with the naked eye or through a magnifying glass. However, detailed studies have shown, that particles of hard coal or graphite are very rare in diamond, however, more often they are found in infixes of other minerals, created simultaneously with the diamond. Next to zircon, which occurs mostly in well-formed crystals, the presence of quartz was found, grenades (pirop), hematytu, enstatytu i in.