Gemstone Cutting: Five Steps to a Perfect Cut
Gemstones are a beautiful gift of nature in their pure, rough form. However, their true potential is brought to life by the human touch of a skilled lapidarist - the person who cuts the gem. Cut is everything. A rough gemstone, when cut well, releases its inner fire, colour and mesmerising sparkle, which makes it so captivating to the human eye. Here, we give a brief overview of the five main processes involved in cutting a gemstone.
ANATOMY OF A ROUND BRILLIANT CUT
Before we jump into the stages of cutting a gemstone, this diagram shows the different facets and parts of a round brilliant cut gemstone, one of the most common and popular cuts used in gemstone cutting. To get to this finished stage with any cut, the lapidarist will go through the following stages:
01. HANDLING THE ROUGH
The process of gem cutting begins with rough gemstones, which come in all shapes and sizes. Some are still in their crystal form, and others have been broken down due to the mining process. Others still are 'alluvial' and carry the appearance of sea-worn glass.
With less rare gems produced in quantity, the gems are usually cut as calibrated sizes such as an 8mm x 6mm oval. With fine quality rarer gemstones, the size and shape of the rough usually determine the shape and size of the final piece, as the lapidarist will want to lose as little of the gemstone as possible.
Creating a good cut while preserving the gemstone size is the most crucial balance the lapidarist will need to find to ensure the best light return from the gemstone. Gems that are cut purely to maintain gemstone size don't always produce the best symmetry, beauty and brilliance. A bad cut can essentially ruin a great piece of rough. Here at Gemporia Craft, we always cut our gemstones to maximise beauty over size.
02. PLANNING THE CUT
This stage of the process is critical. The lapidarist needs to consider the shape of the rough and any inclusions before cutting begins. Any bad inclusions need to be removed, colour banding, or 'zoning' (colour variations within the gem), will affect the orientation of the table. The cutter will then decide how to orientate the cut – where the table sits and where the pavilion will be (see diagram at the top of page).
Once the lapidarist has weighed up their options, they will begin to clean the rough, grinding off inclusions with a special lap. If a piece of stone needs slicing, it will be done using a machine.
03. PRE-SHAPING AND DOPPING
The next part of the process is pre-shaping. This is done freehand. The lapidarist holds the rough gem and grinds it with an ultra-fast spinning machine called a grinding lap. The lap is primed with Diamond powder. Diamond powder is one of the hardest abrasives, so it is perfect for shaping gemstones.
This process will produce the basic cut of the final gemstone. The pre-shaped gemstone is then attached to a metal rod called a 'dop' with special dopping wax. The rod is then connected to a hand faceter.
This is where the gemstone starts to really take shape. The grinding lap is replaced with the faceting lap, which is primed with ultra-fine Diamond powder. The lapidarist then places hundreds of tiny facets on the table or pavilion of the pre-shaped rough. This is an extremely difficult and specialised skill and takes years to perfect.
The lapidarist uses a handheld faceter to make precise cuts, first determining what angles will best return light. Due to differences in critical angles, these measurements will be different for every gemstone.
05. POLISHING: FOLLOWING THE LIGHT
The final stage of the process is polishing. The lapidarist will use a polishing lap, again primed with fine Diamond powder. They will polish each facet to a high sheen, giving the gem a high lustre.
An exceptional lapidarist will perform each stage with intuition and finesse to create the most symmetrical, dazzling and beautiful finished piece. It takes lapidarists many years to obtain a high level of expertise. However, highly skilled cutters are revered in the trade for their ability to visualise the best outcome for a piece of rough gem whilst balancing a variety of considerations and challenges during the process to 'follow the light' through the gem. Each carefully and skillfully cut jewel is then set into jewellery or sold loose.
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