When precious stones are found in mines, they havent undergone rock polishing and don’t look half as dazzling as they should look. Gems are finely cut, shaped and are then put through some rigorous rock polishing to give it that mesmerizing stunning and impressive look. The method of cutting the stone is known as gem cutting or lapidary. This process was started in the early 1300s in Venice. Later in the 1400s this method was used in Paris and Bruges. There are four basic styles of gem cutting, namely tumbling, faceting and carving. The precious stones should be cut so well that they mirror and reflect the light that falls on them. If the gem has not been cut or the rock polishing has not been done well, it destroys the beauty and the shine of the stone. For example, an alluring diamond, if the rock polishing and cut has not be done well, it will not be as valuable, rich or worthy compared to a well polished diamond.
The gem cutter or a lapidary, also known as lapidarist begins the process of lapidary by sawing the gem. The gem from the mine is first cleaned with oil or water, to remove the residues present on the stone. The stone is then sawed with a thin circular blade. One can use different sizes of blades, depending on the size of the stone. Sawing helps remove all the debris and chunks of mud stuck to the stone. The second step is grinding the stone.
Grinding is usually done with silicon carbide wheels or diamond-impregnated wheels, which is used to give shape to the gemstone to a desired rough form, called a preform. The third step is sanding which removes the scratches and dents caused by grinding. Sanding is a very delicate fine process, which is similar to grinding. If the stone needs to be flat at one end, then the stone goes through a process called lapping.
Laps are made of iron or steel, to flatten one side of the stone. Then the rock polishing takes place, to create a mirror like effect. Polishing the rock makes the stone so clear and dazzling that it shines. Rock polishing agents like tin oxide, aluminum oxide, ferric oxide and so on are used. Cloth, leather, wood, can also be used for rock polishing. The next process is cabochon. The gem is smoothly rounded and polished on top, and either flattened or slightly rounded on the bottom. This is usually done to opaque or transparent stone.
Transparent stones are also faceted. The stone is flattened at on the sides symmetrically and the entire surface undergoes an intensive rock polishing, making it shine. The stone is then dopped on a metal dopstick, and later sanded and polished on a lap. Water or any liquid is used to clean the stone. A well faceted stone acts like a mirror, reflecting the light that falls on it, thus making it shine.
February 26th, 2009 at 4:22 am
Great post - This completely answered my question, keep it up!
October 9th, 2009 at 11:53 am
living in costa rica, i am finding quite a few beautiful stone that are either quarts like or some sort of agate. they are very heavy and glasslike of a finish and beautiful colors. reds mustard yellows, and green with mixed quarts veins. i would like to start slicing and polishing these but dont know how to start. any help?
January 11th, 2010 at 5:05 pm
This is a great post regarding rock polishing!
June 21st, 2010 at 4:54 pm
I tried my hand at faceting once at my local lapidary club. It was interesting but I just didn’t have the patience for it. Also, my stone kept falling off the dop stick (I think that was what it was called in the faceting process too, not just regular rock grinding but I can’t remember now).
Interesting article. Thanks. Lapidary work is fun.
July 19th, 2010 at 11:23 am
Great articles on rock polishing and well, lapidary in general - I’ve subscribed to your RSS, please keep them coming!