Typical faceting defects on a diamond’s surface
Cutting is the most laborious and crucial stage of the operation to turn a diamond into a diamond. The diamond cutter is faced with the difficult task of finding a compromise between the size of a crystal and the quality of its faceting. The purpose of the master is to find a form that would allow him to keep as much as possible the volume of the stone and ensure the flawlessness of all its faces.
When cutting, most diamonds lose up to 50% or more of their initial weight. The end result depends on the experience of the cutter and the technology used by him in working the stone. The decision is made on the basis of the natural form of the diamond, the characteristics of the crystal structure, the presence of inclusions and other defects.
The quality of cut is one of the most important indicators for expert evaluation of a diamond, which seriously affects its value. When buying jewelry, consumers give this characteristic as much attention as to the purity, color and weight of the stone. The improvement of technology has led to the appearance of diamonds with an excellent grade cut, characterized by impeccable proportions.
Unfortunately, to achieve the perfect cut is not always obtained. When grinding, cutting and polishing, defects may appear on the surface of the crystal, which spoil the appearance of the diamond and reduce its price in the jewelry market.
Just a couple of decades ago, the jeweler could, just looking at the stone, tell where it was cut. Especially highly valued “Russian” and “Belgian” cut. Today, the quality of the cut does not depend on the place of residence of the master – the diamonds from India, Israel, Hong Kong, and the United States have achieved commercial success.
“Beard” on the girdle. The girdle is the border that divides the diamond into the upper part — the crown, and the lower — the pavilion. According to the quality of this very thin “belt”, the craftsmanship is evaluated. The “beard” of the girdle is called the minor cuts and cracks that go from its surface deep into the stone. They appear with an excessively rough impact during diamond stripping and adversely affect the purity of the cut diamond.
Porous girdle. When the girdle is cut at too high speed with increased pressure, the probability of formation of dimples and open pores is high. The surface becomes not shiny and silky, but similar in texture to the surface of lump sugar. This stone is quickly polluted. Dust and grease fill the voids, giving the diamond jewelry an unattractive gray tint.
Facet Girdle. Height differences, irregularity throughout the central “belt”, the formation of many miniature faces on it – all this reduces the value of the diamond. An immaculate girdle should not have its facets, its surface is polished to absolute smoothness.
Porous or large culet. The smaller it is, the better. Ideally, all faces should converge at one point. Light falling perpendicular to the culet passes through it. Accordingly, a large culet, when viewed from the side of the site, looks like an unpresentable black spot, destroying the visual impression of even the most pure and transparent diamond. When chips appear on the surface of the culet, it becomes white and ceases to transmit light.
Additional faces. The number of faces depends on the type of cut. A classic round cut diamond contains 57 facets, “marquis” – 55, “pear” – 56, “princess” – 65. To the patterned number anywhere in the stone (most often in the girdle area) during the initial cut or when grinding off small defects, formed during operation, can be added to the face, not covered by the standard.
Traces of grinding and polishing. These operations are performed using diamond paste, and the direction of movement of the polishing disk must be carefully verified. Otherwise, on the surface of the face of a diamond, bands and strokes that are visible at 10-fold magnification and worsen the visual characteristics of the stone will appear.
Traces of burning. They appear after a repeated increase in the temperature of the stone during processing or when it is fixed in the ornament by the method of soldering. Visible traces are spots of a milky white shade. They can be removed by re-polishing, with the weight of the stone slightly reduced.
In addition to the surface defects of the diamond, there are other shortcomings that have a negative impact on the evaluation of the stone: the error of proportions and symmetry breaking. We’ll talk about them in the next articles about diamonds.