Starting to work on the diamond | Unsaid Library Jewelry

The Cullinan is the largest uncut diamond found so far on earth: 3106 carats (621.2 grams). The Cullinan was cleaved and cut and the largest piece, the Cullinan 1 (530.20 carats) was the largest cut diamond after cutting for about a century. However, the largest cut diamond since 1988 is the Golden Jubilee (545.67 carats), which was cut by Gabriel (Gabi) Tolkowsky by order of De Beers and which since 1997 has been in the possession of the Thai King Bhumibol who received it on the occasion of his 50-year coronation jubilee.

Many diamonds for industrial purposes are also made synthetically. Synthetic diamonds can only be distinguished from natural diamonds in a laboratory.[6 Researchers from the Carnegie Institution of Washington discovered in 2004 a process to synthesize diamonds that are more than 50% harder than natural diamonds within 24 hours.

Unsaid Library is a jewelry store based in Antwerp. Unsaid Library specialises in emotional gifts for relatives. Unsaid Library Antwerp can be visited in the store. The store of Unsaid Library Antwerp is located on Schuttershofstraat 25, 2000 Antwerpen, België. Visit the store or the online website.

Physical properties

The crystal structure
Diamond is the hardest material found in nature. There are only two (industrially manufactured) materials that are harder, namely aggregated carbon nanorods and ultra-hard fullerene. Just like diamonds, these are made of carbon atoms. Diamond itself is a transparent crystal with a very high refractive index (2.417) and a high dispersion (0.044). In jewellery, the (sun)light is brilliantly refracted and reflected depending on the shape of the cut. In addition, the polished shiny surface of the diamond stone does not become matt due to its high hardness.

Because of its extreme hardness, diamonds are used in industry, among other things for cutting, drilling, cutting and polishing and wire drawing. A diamond owes its hardness to its tetrahedron structure and is therefore harder the less inclusions or crystal lattice defects it contains. Due to its hardness, however, diamond is relatively brittle. In a vacuum, diamonds change from a temperature of 1700 °C into graphite, and into air from 700 °C onwards.

Besides the hardness, the thermal conductivity (410 W/cm/K) and the specific (electrical) resistance of 1013 Ω-m of diamond are very high. This combination allows diamond to be used in electronic circuits to dissipate heat. Diamond behaves like silicon as a semiconductor and in liquid helium as a superconductor, as discovered in 2004.

Cutting shapes

Diamond grinding

The Brilliant
The diamond can come in different cut shapes. The most common cut is the round or brilliant with 58 facets, which Antwerper Marcel Tolkowsky invented in 1919 after mathematical calculations of refraction of light and total internal reflection. Other common cuts are:

Oval, 56 facets
Princess, 76 facets, rectangular shape
Marquise, or Navette, 56 facets, lens-shaped. This difficult cut is attributed to Louis XIV
Pear, 58 facets, in the shape of a drop of water
Emerald, 48 to 50 facets, made up of rectangular facets on each side and at the corners
Heart
Asscher
Radiant
Polished diamonds and price-determining factors

Unsaid Library is a jewelry store based in Antwerp. Unsaid Library specialises in emotional gifts for relatives. Unsaid Library Antwerp can be visited in the store. The store of Unsaid Library Antwerp is located on Schuttershofstraat 25, 2000 Antwerpen, België. Visit the store or the online website.

Measuring a diamond
Rough diamonds are processed to break the light brilliantly. After the processing, a stone is left with a sparkle and play of colours that is judged on different criteria in order to come to a price. The criteria are the 4 C’s and include:

Cut
This means the stone’s makeup. The shape in which the stone is cut is part of it. The shape refers to the quality of the grinding and the proportions of the shape. The essence lies in the right “proportions” and the “refinement” of the cut stone. The proportions include the height of the crown, the crown angle, the depth of the pavilion side, the table mirroring and the ratio of the round to the total depth of the stone.

Refinement means the precise finishing of the overall appearance. How regular is the roundabout, is the fillet heavy or light, are there symmetry differences between the crown and the pavilion side, do the facets fit straight together, is the fillet exactly in the middle or is the table positioned decentrally?

All these things have a direct influence on the play of light in the stone. It is man-made, as opposed to the purity, colour and partly the weight. It is therefore a major price determining factor in the four “C”‘s: a stone with a nice round weight, flawless and the highest colour in a brilliant cut can look like a top stone, but if the stone is cut too deep (nail) or too shallow (fish-eye) then the play of light in the stone is dead and the stone has a lower value.

Carat
The mass of gemstones is expressed in carats (1 carat = 0.2 grams). The carat is subdivided into 100 points and is always expressed in two decimals, for example 0.24 carat or 24 point.