Traditional Origin of Gem Cutting

Natural uncut gemstones are usually very different from ordinary gemstones after being cut and polished. Only after a fine cutting process can the gemstone show its beauty. The process of cutting and polishing is able to make the gemstone give off a bright light, showing hidden color beauty, sparkle and other unique characteristics.

In this article, we will reveal the precise and traditional process of gem cutting technology.

The Origin of Gem Cutting

The origin of gemstone cutting can be traced back to the end of the 18th century, when mineralogy began to develop as a science. Before that, the study of gemstones was more like superstition and traditional knowledge. The Arabs were ahead of the Europeans in gemstone cutting, and in 1048, different stone cutting techniques were described in a paper written by Abu Rehan Biluni, and this knowledge may then spread to Europe.

In the 14th century, it was possible to learn about gemstone cutting in Bohemia by looking at some art objects such as the crown of St. Vaclav and the paneling of the Church of the Holy Cross in Karlstein. These works demonstrated a higher level of cutting and polishing techniques, as well as some uncommon techniques at that time. However, it was a pity that there were no detailed written records during this period.

The Gemmarum et Lapidum Historia, published in 1609, is an important document describing gemstone cutting and processing techniques by Anselmus Boetius de Boot. The book is also the source of pictures from Quadrant, a cutting machine that can cut minerals into facets and circular shapes, which is still in use today. In the 17th century, cutting the bottom of the stone into a pointed shape was an important change. Before, the stones were all cut with a flat base, and this was the first time that light was consciously used to improve the glittering effect of gemstones.

During the Renaissance, gem cutters were already able to cut minerals with a hardness of 8. They used a diamond abrasive paste for cutting, but this abrasive paste contained grit and would leave dents on gems. This became one of the typical features of Renaissance jewelry works.

In Bohemia, the town of Turnov and the surrounding area became the center of gemstone cutting. In addition to minerals, glass also began to be cut here for making Jablonec jewelry. The gemstone cutting artisans were divided into two groups, one specialized in mineral cutting and the other in glass manufacturing and cutting.

Faceted gem

Facets are the cutting of the surface of a gemstone into many flat areas, and they play a key role in completing the appearance of the gemstone. These facets reflect and transmit light according to the angle at which it is irradiated, and each facet has its specific function. The cutting of gemstones is an elaborate process that makes use of the principle of refraction in physics.

The purpose of the facets is to allow as much light as possible to enter the gem and reflect back to the human eye through the gem's countertop (the flat part at the top) and facets. By precisely cutting and polishing the facets, light can be reflected multiple times inside the gem, increasing the shining and refractive effects of the gem. The setting of different types of facets and their relative angles, can affect the optical properties of the gem, such as refractive index, dispersion, and luster.

The number and shape of facets depends on the type, size, and cutting style of the gemstone. Common facets include countertops, wedge-shaped facets, diamond-shaped facets, circular facets, etc. Their design and layout are designed to maximize the use of light so that the gemstone presents the best optical effect.

Practical gemstone cutting methods

For gemstone cutters, it is crucial to understand the characteristics of gemstones, because this will guide them to choose the appropriate cutting method. At the same time, they also need to pay attention to the specific gemstone they are dealing with and its special qualities, including transparency, the number of contents and, most importantly, the number of cracks. The job of a gemstone cutter is to choose the most suitable cutting method for the gemstone to highlight its best characteristics.

Diamond Cutting

The cutting of diamond required special techniques. Before starting the cutting process, the original diamond was first scanned, and then a three-dimensional model was created in the computer. According to the model and any defects that might appear, the most suitable shape and cutting type were selected. During the initial processing, the cleavage nature of the diamond would be utilized. The area to be cleaved was marked on the stone by using a laser, and then a hammer or mallet was used to cut and cleave. In a professional processing workshop, a special round diamond saw would be used to cut the diamond.

Diamond Cutting Company

Amsterdam is home to the most famous diamond-cutting workshop, and later the industry center moved to Antwerp, where many Dutch cutters also moved. One of the well-known companies is the famous Coster Diamonds BV, who once cut Koh-I-Noor diamonds decorated with British royal jewelry. The oldest diamond-cutting company is Van Moppes Diamonds, which was established in 1828. Although the Netherlands is no longer the only cutting center in the world, many Dutch diamond cutters still have a reputation today. In addition, Israel has become a competitor, and the ancient Jewish families in Antwerp have also continued this tradition. Currently, other gem-cutting centers include India, China, and Africa.

Evaluate gem cutting

Every cut had clearly defined parameters that had to be followed in order to maximize the use of light. However, this did not always happen. It could be due to improper cut selection, mismatching with the raw stone shape, or deliberately not following the guidelines to increase the carat weight of the gemstone (thus increasing the price). This evaluation category was called proportions and was very important.

At the same time, when evaluating the cut, it was also necessary to consider small details that could only be seen through careful inspection by the magnifying glass. The gemologist observed the size and symmetry, sharpness, and mutual continuity of the individual facets, as well as the symmetry of the entire cut and the good centering of the main facets. The surface finish was also very important, and the quality of the stone polishing needed to be considered, and the surface should be completely smooth and free of any scratches.

In addition, the evaluation also involves the consideration of the internal characteristics of the gemstone, such as brightness, fire color, and flicker. Brightness refers to the degree of reflection of white light, while fire color refers to the amount of light emitted by the diamond that breaks down into spectral colors. Flicker occurs when the diamond moves from one side to the other, and the number and pattern of bright and dark areas inside the gemstone are also evaluated.

These evaluation factors together determine the cutting quality and beauty of the gem, which has an important impact on the overall value and attractiveness of the gem.

A complex system designed by GIA (Gemological Institute of America) helps to grade diamond cutters. It divides diamond cutters into five categories:

• Excellent: These are the best quality diamonds, labeled EX, accounting for about 3% of the world's total diamond production. They almost perfectly reflect all the light that shines on them.

• Very Good: Very good diamonds are marked as VG, and for the untrained, they are almost indistinguishable from perfect diamonds. They reflect almost all the light that shines on them, but they are slightly less perfect. They account for about 15% of the total global diamond production.

• Good: Good cut diamonds are marked as G, and about a quarter of cut diamonds fall into this category. They are able to reflect most of the light.

• Fair: Fair-level diamonds are marked as F and still belong to high-quality cut, but their luster is less than the previous level.

• Poor tailoring (Poor): The last level is P, diamonds with poor tailoring are rated as poor, and they do not meet the quality cut standards. The light is actually not completely reflected back, but leaks out through the diamonds. These diamonds look darker, have no glitter, and are not attractive.

These cut grades help buyers understand the quality and optical properties of diamonds, and have an important impact on the price and beauty of diamonds.