In this video I show how a raw peridot stone is prepared for grinding and the shape of the cut is first roughly sketched on one side. The stone is then fixed to a so-called dop with a 2-component adhesive. With this dop, the stone is later attached to a faceting machine.
From Rough Stone to Jewel - Faceting a Gemstone. While the glue hardens, I use a computer program (Gem Cut Studio) to create the most favorable cut angles for the refractive index of this mineral (RI = 1.65). I am planning a light stone in a navette shape (also called marquise, boat or pointed oval).
Various scenarios can be visualized using computer calculations. In this way, unwanted effects (fisheye, window) can be avoided or at least minimized. When everything is calculated as desired, a cutting plan is created with appropriate angles and so-called index settings. In addition to the angles and index settings, this plan, which can be printed out, also includes a grinding schedule. This allows the facets to be "processed" in the correct order and at the exact angle.
Four facets for the center point of the lower part, the so-called pavilion, are first ground on a beveling machine (in this case an Ultra Tec V5). This is followed by the facets on the outer edges and the remaining lower facets. Polishing follows grinding with ever finer diamond discs. Special care is required here, because with perfectly polished facet surfaces, the finished cut stone gains immensely. I am polishing peridot on a tin/lead wheel, the abrasive is Aloxide 0.3.
From the yield point of view, the raw stone was not optimally suited for a cut in this form. A round stone with a lower body, e.g. SRB (standard round brilliant), would have been more profitable (in carats). But since navette stones are selling well at the moment, I decided on this shape.
The inclusions that are visible in the stone do not detract from the beauty of the stone - on the contrary: they give the stone depth and liveliness.
Thanks to Arya Akhavan for uploading “Marquise 1” from 2012 to www.facetdiagramms.org
While Arya designed the design for small tourmalines, it appears to work for larger stones as well. I was attracted by the simple and clear design language and have slightly modified its grinding angles for peridot.
Bernd Alexander Mansholt