Romantic and poetic encounters by candlelight.
Enchanting jewelry that was all the rage during the Georgian and Victorian eras.
What created its unparalleled charm and popularity during that time?
In this episode, we are going to unveil its mysterious allure.
Join us as we delve into the past and present of Old Mine Cut diamonds!

In the previous episode, we discussed the tools and cutting methods used by craftsmen in the ancient times for diamond cutting. In this episode, we will delve into the design and cutting principles of old cut diamonds.

Due to the scarcity of diamonds and the symbolic power attributed to them, especially in eras when exploration and mining techniques lacked the scientific instruments available today, acquiring each diamond was extremely challenging. This determined that every rough diamond was highly precious. Particularly when diamonds were directly supplied to royalty, craftsmen had to be exceptionally vigilant to prevent any mishap such as over-polishing a diamond ordered by a king or queen, which could potentially result in severe consequences like being sent to the gallows or guillotine.

Therefore, there are two fundamental principles that must be followed during diamond cutting. One is preserve weight, with the goal of maximizing the utilization of the rough diamond. It involves minimizing material loss during each processing step while ensuring the smooth progression to the next stage. It can be said that throughout the entire process of diamond cutting, weight preservation needs to be taken into consideration.

The other principle is pursuing flawlessness. Since the diamond roughs at that time were formed naturally in the environment, it was extremely difficult to find rough stones without any inclusions. Therefore, before cutting diamonds, the lapidary had to carefully examine the rough stone, identify the location of each flaw, and plan ahead so that the flaws could be removed during the polishing process or positioned in less visible areas. However, due to the lack of precise auxiliary instruments available at that time, craftsmen had to rely solely on their experience and elusive luck for cutting, often resulting in loss of carat weight. Nevertheless, this was an inevitable challenge they faced.

Therefore, when unable to clearly see the internal structure and form of flaws within the rough diamond, the craftsmen, after careful examination of the rough stone, would use ink to draw cutting lines on the stone. Then, they would place the ink-marked rough diamond on a mount and use another diamond to grind along the cutting lines, creating a groove. Subsequently, they would place a blade on the groove and repeatedly strike it with force at the back, causing the rough stone to fracture into several pieces due to the stress at the notch—a process known as cleaving. The fractures that occur within the rough stone due to the impact of gravity are called cleavage planes. During the subsequent polishing and shaping of the diamond, if the cut facets are positioned too close to the cleavage planes, it would make the sharp edges of the finished diamond highly susceptible to cracking.

Not only the sharp edges but also the thin girdle of a diamond can make it more prone to developing cracks or chips at the girdle. Therefore, in old cut diamonds, especially those with old mine cut, the girdles are often thickened. Additionally, the corners are rounded, and even the culet is ground flat, leaving only a small facet. This further minimizes the risk of cracking due to stress.

In the next episode, we will discuss the various shapes of old mine cut diamonds and their differences from modern brilliant cuts. Stay tuned for more information.