Describing Gemstones

Gemstones can be divided into groups based on how they are formed. The most common groups are minerals, human-made gemstones, rocks, organic materials, or amorphous materials.The mineral groups are further divided into mineral families. For example, all the gemstones that have silica (SiO2) as a building block are silicate gemstones.

Gemologists, or people who specialize in the study of gems are concerned with the identification, quality, and cut of gemstones. Lapidary is the craft of working with stone, especially gemstones. Lapidarists are the people responsible for the setting of the cutting of the gems. Jewelers are people who set the stones so people can wear the gems in a bracelet, ring, earring, or necklace.

Lapidarists work with gemstones in several different ways.The simplest method is called tumbling. The gemstone is put in a revolving barrel with sand. This rounds off the gemstone’s corners and polishes it to a bright shine. Gemstones can also be cut. The cutting style used for a particular gem is mainly determined by the optical properties of that gem. The simplest type of cut is known as a cabochon. The gem is cut with a flat bottom and a curved top. Gems with color like agate, hematite, and malachite are best suited for this style.

Cabochons emphasis the color texture, and are usually cut with a diamond coated saw blade. Gemstones can also be shaped by faceting. In this style, the gemstone is cut so that it has a large number of flat faces, or facets. Faceting takes advantage of cleavage, the natural planes of weakness in minerals. For example, an uncut diamond is difficult to cut, since it is one of the hardest substances known. A lapidarist has to take into account the different natural cleavage planes to assist in cutting the diamond. An uncut diamond is not pretty to wear. But a correctly faceted diamond can make a rainbow of every ray of light. A jeweler adds value to a faceted gem by setting it in an appealing ring or bracelet.

Faceting is the most complicated kind of cut, and creates the most valuable gemstones. The gemstone can be
faceted in such a way that it sparkles. Patience is also important to fashion the various shapes shown. The cut faces of a gemstone have different names. The top of the gemstone is called the crown and the bottom is called the pavilion. The widest part of the gemstone is its girdle. The facets on the crown and pavilion have different names, depending on where they are located.

Softer gems emphasize the surface of the gem, not the internal play of light. These gems are carved by an artist to create their beauty. Designs or words can be engraved into the surface of the gemstone. The design is dependant on the artist. Jade is an example of a gemstone that can be carved. It is usually the mineral jadeite or nephrite that is used to produce the characteristic green color. Jade is especially used to create decorative pendants. A cameo is actually from a mollusk shell. Certain shells (especially conch type shells) have two different colored layers. The artist carves an image in one layer and the other layer is the background. Different types shells have different colors. Carvers work with a carving tool called a bullino, introduced by Italian carvers several hundred years ago, or small dental drills, to grind away the outside shell.