Perfect Cut For Your Gemstone

Cutting and Polishing gemstones

The shine given to the surface of a stone -either by rubbing it with grit or powder, or against another stone – is its polish. It can also be said that polishing is the systematically progressive reduction in the size of scratches until they are invisible to the naked eye. Polishing of a gemstone is done by the use of very finely powdered abrasives such as corundum powder, tripoli, pumice, putty powder, etc. Each gem material requires special treatment to obtain the best results. It is here that most of the trade secrets apply. In general, the polishing powder should not be quite as hard as the material to be polished, else it may grind rather than polish. The material should be used with water or oil to give it a creamy consistency. Dark- colored gemstones and those that are translucent or opaque, for instance opal and turquoise, are often polished rather than faceted, as they are organic gems. Opal, being a softer rock require treatment more like that accorded cut glass, and soft abrasive powders, such as pumice, suffice to polish them.

They may be polished as beads or as flat pieces to be used in inlay work, or cut en cabochon with a smooth, rounded surface and usually a highly polished domed top and flat base. Gems which are transparent are normally faceted, a method which shows the optical properties of the stone’s interior to its best advantage by maximizing reflected light which is perceived by the viewer as sparkle. There are many commonly used shapes for faceted stones. For example, a rough diamond crystal is fashioned into a brilliant-cut. This is the most popular cut for this stone because it maximizes the gem’s naturally strong light dispersion. The craftsman, or lapidary, who cuts the stone aims to show its best features, taking into account its colour, clarity, and weight. The facets must be cut at the proper angles, which varies depending on the optical properties of the gem. If the angles are too steep or too shallow, the light will pass through and not be reflected back toward the viewer. There are several stages in the cutting of a gemstone, each of which may be carried out by a different expert.

Cut Types

Cabochon Cut

Cabochons is the earliest form of gem cutting forms. Cobochon cut gemstone usually have a flat base and a round, curved, convex dome like top which can be oval, coushion or round in shape. The stones that are cut in cobochon cut are Turquoise, Lapis Lazuli, Coral, Star Sapphire, Moonstone and Opal. The cabochon cut does not give much brilliance as compared to other cuts.

Brilliant Cut

The brilliant-cut is the most popular for diamonds, and for many other stones, particularly colourless ones. The brilliant cut gives the most complete return of light out through the front ensuring brilliance and fire. Round cut is the most common shape in brilliant cut. Other shapes include oval brilliant cut (43 to 57 facets), pear shaped pendeloque (58 facet) and the boat shaped marquise or navette (58 facet).

Step cuts

A step cut is obtainedby cutting a stone with several series of rectangular facets one above the other parallel to the edges in the manner of a pyramid with its top chopped off. The base and table are square with triangular facets. Fine step cut stones can be very brilliant. Emerald, Quartz Tourmalite and Amethysts are a few gems that are commonly cut in Step cuts. The Emerald cut (50 facets) is an example of Step cut and has rows of facets that resemble a staircase and usually are four-sided.

Mixed cuts

Mixed cuts consists of a brilliant cut top and a step cut back. Sapphires, Rubies and other transparent colored stones are frequently cut in this style.

Buff Top cut is an example of Mixed cuts which mixes a Faceted cut with a Non-Faceted cut. tops of colored stones are polished with a smooth unfaceted, slightly convex surface, the back being facetted in either the brilliant or the step arrangement. This results in a gem with the typical domed top of a Cabochon and a faceted pavilion. This cut shows good brilliance. Rhodite, Cubic Zirconia, Quartz and Amethyst are some of the stones that are cut in buff style.

Princess cut

Princess cut (76 facets), maximizes a gem’s luster. Princess cut is a square version of the Round Brilliant cut with numerous sparkling facets. The crown of the stone in a princess cut is usually very thin and due to the heavy depth and extra facets, they more brilliant and sparkly and make excellent diamonds for engagement rings. Diamonds and other transparent light colored stones are cut in this style.

Briolette Cut

A briolette cut stone is a drop shaped stone covered with numerous facets that corners to a pointed end. The more facets the stone has, the more brilliance it has. Briolette cut is an ancient cut style and can be found in many antique Victorian jewels and also in the Royal crown jewels. Many transparent colored stones are cut in this manner including diamonds, rubies, emeralds, garnets, aquamarines and sapphires.

Fancy cuts

Fancy shapes like triangles, ovals, pear shaped, kite-shaped, heart shaped, lozenge-shaped, pentagonal, hexagonal, rhomboids, parallelograms, rhomboids, octagons etc. require a lot of work. It requires a lot of expertise on part of the cutter of obtaining such shapes. Recent advances in cutting technology have produced a breathtaking range of innovative new shapes like flowers, clover leaves, stars etc.