How are gemstones cut?

The craft and science of cutting and polishing gemstones is known as lapidary. Lapidary comes from the Latin words meaning ‘of and related to stones’. The beginning of the art of cutting gems was probably as simple as rubbing two rocks together to smooth one with the other, which is exactly the way they are cut and polished today, with the added refinement of precision equipment and various man made abrasives.

Primitive lapidary was used to smooth and carve the bright or colorful pebbles and stones that could be found in stream beds and on hillsides as well as the ‘organic’ gems including jet, ivory, amber, shell, bone, coral, bone, teeth and antlers. These softer stones and organics could be scraped or carved with a sharp flint rock and sanded smooth with (you guessed it) sand. Progressively finer finishes could be obtained as more polishing materials were discovered, such as iron oxide from iron ores.

As early as 3000 BC softer gems such as turquoise, malachite, lapis lazuli, and the organic gems were being fashioned into ornaments and gems. Jade, agate and other harder gems were being worked by 1100 BC. The Roman era brought the discovery of emery (ground sharp grained corundum) and the ability to carve or polish virtually any gem was made possible. Diamond point tools and resin/emery saws and wheels were in use in India by 100 AD and lapidary science was in full swing around the known world.

Modern technique is virtually the same process as has been used for thousands of years updated with only improved equipment and the use of graded diamond abrasives and man made polishing compounds.

The basic steps for cutting and polishing gems are:

Sawing or chipping = Preform
Grinding = Shaping
Sanding = Smoothing
Polishing = Final Finish

Gems may also be tumbled, drilled or carved. Stones that are polished into smooth shapes with a domed or rounded top are called ‘cabochon cut’ or ‘cabochons’ and stones with many flat faces are called ‘faceted’.

The actual science of diamond cutting is a latecomer to the lapidary field, only developed a few hundred years ago and only perfected during the 18th century producing the ‘ideal’ cut. The earliest attempts at diamond cutting, because of its extreme hardness, were merely to smooth the natural crystal faces or carve inscriptions into the diamond surface using another sharp diamond crystal as a tool. Today diamonds are sawed using diamond impregnated bronze discs and sliced and drilled with lasers.

The steps in cutting a diamond are:

Sawing and cleaving = Preform
Bruting = Shaping
Blocking = Initial main facets
Brillianteeering = Final Facets

The development of diamond cutting also precipitated the high degree of artistic faceting of all transparent gemstones to bring out their maximum beauty. Today there is a booming trend in unique gemstone cuts that use faceting, carving, concave faceting, laser cutting, ultrasonic carving and combinations of these techniques.

Why doesn't my white gold stay white?

White gold, being an alloy made up of primarily pure gold which of course has it's unique deep yellow color, is often found to be a very pale yellow color instead of true white. This lightening of pure gold's deep color is accomplished by adding metals that contribute to the alloys overall ability to reflect light of all wavelengths thus making it appear "white". The variation in color of different types of white gold alloys stem from the base metals chosen to do the alloying and the percentage of each used in the composition. The various alloys are designed to provide good working qualities during manufacturing as well as the desired color and can all vary somewhat as to the degree of 'whiteness'.
As a result of this variation and the apparent light 'yellowness' to some alloys, white gold jewelry is commonly given a final electroplated finish with rhodium. Rhodium is a precious white metal considered to be a part of the 'platinum group metals' along with osmium, iridium, ruthenium, and palladium. Some of these metals are candidates to be used as alloy metals for white gold along with nickel and silver.
It is the 'rhodium plated' finish that wears away sooner or later on white gold jewelry and allows the color of the actual gold alloy to show through and lets the jewelry take on a yellowish hue. Combined with the scuffing and scratching of normal wear a white gold piece can start to look very dingy. A good polishing to remove scuffing and a fresh rhodium plated finish will give the article a like-new appearance. This plating can last quite some time but ultimately depends on the amount of wear and tear the piece receives. Since most jewelers will charge for this refinishing service due to the high price of rhodium, a couple of times a year should be limit for this type maintenance as excessive polishing will wear out the jewelry prematurely.
There is one more scenario for the 'white gold' that turns colors and that is that it is in fact a yellow gold alloy article that has just been plated white to give it the appearance of white gold. Since it is not white to start with, this type of jewelry will discolor quite rapidly. If the color change was the owners choice they'll have to deal with the constant upkeep of the appearance. If the item was misrepresented as white gold by a seller they buyer may have recourse for a return or replacement of the jewelry.