For both cabs and faceted gems, the top is called the crown. The widest part of the gem, the part that defines its outline, is called the girdle. Viewed from the side, the girdle is usually fairly thin. The bottom of a faceted gem is called the pavilion. The largest facets are called mains. There are both pavilion mains and crown mains. The large, horizontal facet on the top, the one that acts as a window into the interior of the gem, is called the table facet. Adjoining the girdle are the break facets. Their purpose is to scatter light, creating more scintillation. There are both crown and pavilion break facets. The top rows of facets, those next to the table, are called star facets. Along with the other crown facets, they serve to control the entry and exit of light from the gem. The pavilion facets are designed to reflect the light back to the viewer.
Cutting and Polishing
- There are four basic styles of gem cutting: tumbling, cabochon, faceting and carving.
- Tumbling:- The simplest form of gem cutting is tumbling. This is where the rough material is put in a revolving barrel with abrasives. Progressively finer abrasives are used until a polish is obtained. It is easy; takes a minimum of equipment and the results are sensational!
- Cabochon:- Cutting cabochonis probably the most common form of gem cutting. Cabs are gems that are cut with a flat bottom and a curved or domed top. If you can envision an opal or a piece of turquoise, you are looking at a cab.
- Faceting:- The purpose of faceting is to bring out the brilliance of a gem. That is where the light entering the stone is reflected off the bottom facets and returned to the viewer.
- Carving:- Carving is the most challenging of the lapidary arts and there are very few recognized experts in the field. To be successful, one must have a distinctive artistic sense and a thorough understanding of the principles of lapidary. Unlike working in wood or metal, the materials present define limits as to what can be done. There are several types of carving. One of the best known is cameo. These are usually cut from sea shells or agates, but they can be carved from almost any material. Often cabochons are carved. If the design is cut into the top, it is called an intaglio, or a relief carving. If the design is carved on the back, it is a reverse intaglio. Some carvings are not designed to be used in jewelry; they are cut simply for their beauty. These are classed as stand-alone carvings.