What is a concave faceted gemstone?

Concave faceting involves cutting facets to curve inward, usually with at least one flat facet, the table, on the crown. The curved facets scatter more light into the interior of the stone than traditional flat facets, resulting in a more brilliant gem. The difference is noticeable even to the untrained eye. The other difference is that they can show some very unusual optical effects. For the best results light to medium coloured rough is the best. Naturally that means a lot of stones aren't concave faceted. 

How does concave faceting create so much more brilliance than regular flat faceting?

Imagine a typical flat, square mirror. Now push the top and bottom closer together so that the reflective side curves toward you. Then take the left and right edges and curve them away from you so that the whole thing is slightly cylindrical. The result would be shaped like a single pavilion facet in a concave-faceted gem. If you were to shine a light on the curved mirror's surface, it would act more like a mirror ball than a flat mirror, scattering light away from it in all directions rather than as a single beam. In a faceted stone, that reflected light in turn bounces off other facets, and the scattering effect is magnified. Because the reflected light is diffused rather than concentrated in a single beam, the body color of a pastel gem doesn't get washed out. Conversely, in a gem with a dark color, the reflected light isn't strong enough to illuminate the interior of the gem, and the stone appears darker than it would with flat faceting. Because of this effect concave faceted gemstones look brilliant in most light conditions, they don't require bright lights to dazzle.

Why haven't I seen it before?

Concave faceting started in America in approximately 1993. In Australia it is still an unappreciated form of cutting, and part of the problem is that Australia's most abundant gemstone, the sapphire, is mostly unsuitable for concave faceting as it is to dark. In addition because of the time involved in cutting a concave faceted stone they are usually sold a premium. The other problem is that in the USA concave faceted gemstones are represented in nearly all jewellery competitions, either set in jewellery or by themselves. This is not the case in Australia because most competitions insist on the use of Australian gemstones. There are very few readily available Australian gemstones suitable for concave faceting.

The other major problem is that there are no books or computer programs containing designs, for cutters to follow. Designs are kept secret by the cutters as well as any techniques they might have developed. A cutter must develop his own designs, by trial and error, then adapt them to the different types of gemstones.

In Australia Jim is one of the few, if not the only person that cuts concave faceted stones for commercial sale.  If you get a piece of jewellery, featuring concave faceted stone/s, then you really are getting something which is unique. He is constantly trying out new ideas for stone designs and if you are a jewellery designer with an idea for a particular shape do not hesitate to contact him, as he loves a challenge. As part of the development of this site we plan to show available designs with a short description, sorry no cutting instructions.