When discussing gemstone cutting, it is necessary to have an understanding of three important factors: tradition and advances in polishing technology, the quality of rough material, and the cost of polishing gems. Answers to questions such as, “Why do antique jewelry pieces use rose-cut diamonds?”, “Why is this ruby fashioned as a cabochon?”, and “How did Mumbai (Bombay) become a major diamond cutting center?” become apparent when the three aspects of technology, rough, and cost are considered.

As previously mentioned, diamond is the hardest substance in nature, in Europe during the Middle Ages it was used in its rough from or with the crystal faces polished, not as popular adornments, but in regal accoutrements such as coronation capes, scepters, royal crowns, and scabbards. There is no knowledge of the existence of any diamond polishing industry in Europe until the beginning of the 15th century. With the introduction of diamond powder in the 15th century, more precise cutting of facets became possible. The rose cut was developed in 1520. Its use spread rapidly, and it was commonly used until around the year 1900. The rose cut is suited for bringing out brilliance in flat rough with little weight loss, but it is unable to bring out the beauty of dispersion. Bohemian pyrope garnets, popular during the latter half of the 19th century, were also fashioned into rose cuts.

The brilliant cut was invented in the mid-17th century, and toward the end of that century the Venetian Iapidary Vincenzio Peruzzi improved it by placing 32 facets on the crown. His cut consisted of 32 facets on the crown (top) of the stone, 24 facets on the pavilion (bottom), and one facet each for the table and culet for a total of 58 facets, making it the forerunner of the modern brilliant cut.

Fashioning rough gems requires a balance between placement of facets to maximize the beauty of the gemstone and keeping weight loss to a minimum. In India, weight loss was minimized by removing imperfections in diamonds while keeping the shape close to that of the rough. These thick stones were called “Indian cut,” whereas flat rough was cut into appropriately thin stones. Outside in India, such “thick stones” and “thin stones” were also popular in the Middle East (Persia, Arabia, and Baghdad). The so-called “Mogul cut” diamonds were finished by simply polishing the surface of rough while following its shape to keep weight loss to a minimum.

Gemstone rough is a product of nature, and each piece is completely different from the next. The quality of the rough material is the definitive factor in the quality of the finished gemstone. The shape of the rough and the location of imperfections will influence the quality of the cut of the stone. Products of nature are extremely variable, with some having color only near the surface or concentrated in areas within the stone, and it is up to the skill of the cutter to give the best possible finish based on these factors. No matter how much care is giving to material with poor transparency or a cloudy appearance, it will not become an especially attractive gem. Diamonds of this type will be cut accepting that the stone will be an inexpensive one; in colored stones, such lower-quality material will be fashioned into cabochons or beads, made into carvings, or tumbled. Of course there is a limit even to this, and since material that is fashioned into cabochons often has surface-reaching fractures, it may be oiled or treated after polishing. The degree of surface-reaching fractures is a consideration when determining the degree of treatment to be used.

Rough is usually separated by quality immediately after mining into stones that will be faceted, made into cabochons, or cut into other styles, and material that is useless to polish. At the polishing centers, stones other than those of exceptional size are normally separated into five basic quality levels, and each parcel is assigned a price. Individual stone prices are usually set at the location of final sale. Because the characteristics of colored stones differ widely by source, lapidaries will, as a rule, handle these differently according to source.

The rapid advance of the diamond cutting industry of India during the 1960s was astonishing. The increase in diamond rough output caused an increase in the output of small near-gem rough, and the Indian lapidaries responded to this. Meanwhile, mass popularization of diamonds continued, with the sales volume of diamond jewelry in 1992 reaching $40 billion on sales of 53 million pieces.

Diamond polishing in India is a mind-numbering process that involves taking stones that differ in shape and hand-polishing them on a spinning disk, accurately placing 58 tiny facets on the hardest known substance in nature. Even considering the low cost of labor in India compared to more advanced economies, one most appreciate that current gemstone prices are due to the inexpensive and admirable job that the Indian lapidaries perform. Polishing of ruby and sapphire in Thailand is also flourishing. Costs are slowly rising, but the Thais have been able to maintain their international competitiveness. China is also attracting attention in terms of gemstone demand, as well as gemstone production and polishing.

The number of lapidaries employed by diamond and other gemstone cutting factories, by cutting center, is shown above. These figures are provided for reference purposes, but the number of cutters fluctuates in each country, depending on supply and demand, making collection of precise data difficult.