Gems have always been manipulated and worked in a way to enhance their beauty, color and shine. The machining of gems is an ancient craft, and the greatest masters in this field were Indians and Egyptians. Basic grinding techniques include grinding and polishing.
Grinding is one of the basic treatments of gems. Its purpose is to highlight the refraction of light and enhance the glitter of gem.
In the past, an irregular grinding was used, in which the gems were only roughly grinded and did not have a symmetrical shape as they do today. There was little loss of raw material during this grinding. Today it is used only in industrial processing of less valuable precious stones (obsidian, hematite, quartz).
With transparent stones, smooth surfaces, so-called "facets", are sharpened symmetrically to enhance their shine and glitter.
The most famous and most commonly used cut is the so-called "brilliant" cut, which is used for diamonds and other transparent gems. The facets on this cut are ground so that the rays of light are reflected as much as possible from the bottom of the stone. This brush gives the most accentuated shine, colour and beautiful brilliance.
Opaque coloured gems are most often ground into rounded shapes, so-called lenses. These gems can also be adorned with ornaments.
The gem cutter must be well aware of their physical properties - hardness, cleavage, plexroism - working with them and using them correctly.
Polishing was used as the very first method of processing gems. It was wiping one stone over another, like in rotating drums where the stones were mutually polishing one another with a coarse abrasive and water. For further upkeep, different abrasive pastes and powders were used. Now to polish the surfaces of gems, we use polishing discs with polishing pastes.
Some gems have an intriguing inner drawing that is enhanced by cutting the gem and cutting the surfaces to a high gloss at both ends. Cutting is mainly used in agate, jasper and similar stones.
Cutting discs are used for cutting - the best are diamonds. A coolant (water or some other emulsion) must be poured into the cut, otherwise it may crack the stone.
Engravings can be made with gems. Intaglios or plastic carvings can be made from the precious stone, the so-called "camel". The intaglio uses mainly transparent stones (e.g. quartz); for the others, the most suitable are multi-colored stones with a layered structure (e.g. agate or onyx).
Plastic grinding, which involves cutting, grinding and engraving the gem, is a widely used machining technique. This produces small sculptures and haberdashery.
Gemstoneartist.com. (2016). How Gems Are Cut - The Gemstone Artist The Gemstone Artist. [Online] Available at: http://gemstoneartist.com/gemstone-articles/how-gems-are-cut/ [Accessed 8 Dec. 2016].