Skip to content

The Diamond Cutting And Polishing Process

The process of cutting of a rough diamond crystal into a finished gem is sometimes referred to generally as diamond polishing. While the process of crafting a polished diamond involves many different steps, the final polishing of all the facets is a crucial step in determining the quality and beauty of the finished gem.
 
Before the actual final step of polishing, a rough crystal must be planned, sawn, and shaped. Each rough diamond offers a unique challenge. Determining the best approach requires careful analysis of the potential of the crystal which involves a complex calculus involving clarity features, shape and orientation the crystal, and the economics of different potential yield scenarios. The crystallographic orientation is a critical consideration in the plan as certain directional planes differ in hardness making it impossible to polish in certain directions.
 
 
Planning has been significantly aided in recent years by advance scanning hardware coupled with sophisticated computer software. Once the plan is decided upon, the crystal is sawn into the pieces that will eventually become individual diamonds. Each of these pieces is then blocked into basic shapes.
 
 
 

Screen shot from diamond planning software showing how three diamonds can be cut from an actual piece of rough considering clarity features and crystallographic orientation.

Illustration of two princess cuts that can be produced from an octahedral diamond crysta

The main cutting instrument is the cutting “wheel” called a scaife – a disk impregnated with diamond powder that turns at 4000 rpms. The diamond is held against the scaife in a device called a tang

The main cutting instrument is the cutting “wheel” called a scaife – a disk impregnated with diamond powder that turns at 4000 rpms. The diamond is held against the scaife in a device called a tang.

A mirror finish enables the diamond to possess as much external luster as possible and optimizes the internal reflection of light rays as they bounce from facet to facet before being returned to the eye of the observer. Light rays exiting from a facet with an imperfect polish are degraded in terms of dispersion (fire) or brightness (brilliance). Facets that do not have a high polish are also prone to accumulating dirt and oils that result in further loss of performance. Diamonds with inferior polish require more frequent cleaning in order to look their best.

Polish and symmetry are the two factors of finish that are assessed on a laboratory grading report. A diamond graded as having Ideal polish indicates that each and every facet on the diamond has a mirror finish.