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How Diamond Cutting Has Evolved Over the Past 150 Years
How Diamond Cuts Have Changed
The shapes and proportions that we associate with modern diamonds are not commonly seen in truly Antique jewelry. The terms used for several older cutting styles tend to be abused today, and these names should only be used when appropriate: Old Mine Cut and Old European Cut. Without getting too technical, I will try to explain how identify these stones properly, and explain how and why cutting styles have changed in the last 150 years.
The Modern round brilliant cut only became readily available as diamond cutting technology improved. Marcel Tolkowsky, a mathematician, studied diamond as an optical medium. In 1919, he published his work, Diamond Design, which displayed diagrams of the proportions that a diamond could be cut to, to achieve maximum brilliancy. While others like certain variations from Tolkowsky's original proportions, it is the standard on which all high quality variations of the modern round brilliant are based.
Tolkowsky's theories supported cutting styles that had actually been pioneered by Henry Morse, a Boston area jeweler, who had opened his own cutting factory, around 1860. His shop foreman, Charles Field, made some major innovations in diamond cutting, including development of mechanized bruting, a process that gives the finished diamond its circular outline. The Morse operation, the first diamond cutting plant in the United States, also favored a set of proportions that resembled Tolkowsky's later recommendations. Morse felt that the crown of the diamond, that portion above the girdle line, should constitute one third of the total depth, with the pavilion, the portion below the girdle line, making up the remaining 2/3 of the total depth of the finished stone. It is said that these stones were marketed as Boston Cuts.
Antique vs. Modern Cuts
These modern cutting standards favored the production of the most brilliant diamond possible, one which would capture the light and release it through the top of the stone. To produce a stone like this would mean losing much of the weight of the rough diamond being cut, and the diamondaires of Morse's time though this was simply wasteful. They continued to produce the Old Mine Cuts and Old European Cuts, known for their maximum retention of rough diamond weight.
Before the development of modern mechanized fashioning methods, rough diamonds became finished shapes through 2 basic processes: Cleaving and grinding. In cleaving, the directional weakness of a diamond is taken advantage of. The rough diamond has planes of cleavage, related to its crystallographic form. A small notch is made in the rough diamond, with another piece of diamond. A small blade is placed in the notch, and the blade is struck. If properly planned and executed, the diamond is split, as planned. An error in planning or execution may lead to a shattered and unusable piece of rough. The rough shape often has a squarish outline, which is obvious in the shape of the Old Mine Cut Diamond.
Steam powered diamond sawing was developed by the 1840s. However, it was not widely utilized at the time. Most Old Mine Cut stones were fashioned by hand, with the cutter holding his diamond to a grinding wheel, known as a scaife, in a special holder, or dop. Field's mechanized bruting process, where 2 steam powered lathes would turn two rough diamonds against each other, appeared in use in the mid-1870s. The convergence of theory, tools, and taste caused the demise of the Squarish Old Mine Cut, and the emergence of the Old European Cut. The Old European Cut was dominant until after World War One, although many hybrids and transitional cuts exist. European cutters adopted or adapted Morse's bruting methods. Morse also was known for Morse gauges, devices which would precisely measure angles to be used in fashioning the individual facets of the stone. The round shapes also lent themselves to the development of mechanical dop arms, automating much of the fashioning procedure.
There is an actual cutting style known as the European Cut. It was never commonly adopted, and is it has a pavilion angle of 28.4 degrees and a crown angle at the main facets of 41.6 degrees. The table is 56% of the girdle diameter, with a crown height equal to 19% of the girdle diameter. The pavilion depth is equal to 40% of the girdle diameter of the stone. This cut was probably developed by Johnson and Roesch in 1926. Most well cut modern brilliant stones will have a deeper pavilion, a smaller crown height, a shallower crown angle, and a larger pavilion angle.
The term European Cut has become rather meaningless. It may be being used incorrectly, to describe an Old European Cut. It may be used to indicate that the stone was cut in Europe. On rare occasions, it may be used correctly, to actually describe a stone cut to the proportions introduced by Johnson and Roesch in 1926. If a seller is merely trying to indicate that the stone was cut in Europe, the use of the term European Cut may be confusing. If the stone is an older cutting style, such as an Old Mine Cut or Old European Cut, the correct terminology should be used.
Cutting Style Indicates Age
The actual cutting style of the stone can help provide some dating information on a piece of jewelry. Please remember, however, that jewelry pieces can be refashioned. Stones may be reused in more modern settings, and older diamonds themselves may be re-cut, refashioned, and repaired, to remove signs of previous damage. This type of work may create a “hybrid” that falls outside of normal categorization. A 150 year old Old Mine Cut can be placed in a modern piece of jewelry. Modern stones may be used to replace a missing stone in a vintage jewelry item. However, the type of cuts present in the stones of a jewelry piece can be used to help date the piece and to indicate if replacement work of any type has been done. Please be aware that it is possible for a contemporary cutter to duplicate any diamond cutting style of the past. All the diamond styles discussed here can be beautiful gems, and all are worthy of proper identification.
Resource: How to Buy An Antique Diamond Engagement Ring
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