I am a faceter.  I check gemstone listings on eBay fairly often.  Occasionally I see statements that are untrue.  I am writing this guide to provide correct information.

Myth 1

Most of faceted gemstones are machine-cut.  Only a small number of exceptional stones are hand-cut.

or

Hand-faceted stones are more valuable than machine-faceted stones.

Truth: All the gemstones are hand-cut.  There is no such machine like you throw in a rough stone and after a while a faceted stone pops out.  I have heard that an automated faceting machine is being developed, but it is far from a practical use.

Technically each facet is made by grinding, sanding and polishing a rough stone on a flat round file (or disc with polishing compounds) that turns around like a vinyl record.  They are called laps.  The rough stone is attached to a small stick called a dop. It is seated in a faceting head. 

There are only three factors to make a facet: 1) what angle to the dop to cut, 2) which side of the stone to cut and 3) how much to cut off. 

A modern faceting machine exactly controls the three factors with a faceting head (see the drawing below).  Nowadays, with computer-generated precision cutting diagrams, accurate combination of these three factors produces crisp and vibrant gemstones we have never seen before.  These are gemstones of the new generation based on mathematics (angles) and physics (optical properties of minerals).  You may not often see stones cut in this manner.  But if you pay attention to cut details, you can easily spot them. 

Old types of faceting machines do not have a faceting head so you cut a stone by holding the dop freehand guessing the angles, sides and depth, or using a jam-peg (a wooden block with holes cut in different angles) that holds a dop.  These are the methods used by the early faceters.  But they are basically how overseas cutting houses are still doing.  These are common stones you find on eBay and jewelry stores.

But regardless of a new or old machine, you have to sweep the rough stone over the lap by hand to cut.

Basic Function of a Modern Faceting Machine

Faceting Head

Myth 2

Scratches and nicks on a facet can be easily re-polished by a capable faceter.

Truth: Even for a capable faceter, it is difficult to fix those problems unless the stone is entirely re-cut.  To re-polish, the problem facet has to be aligned precisely parallel to the lap.  It is nearly impossible if once the stone gets off the dop.  Also re-polishing takes off some of the stone.  It makes surrounding meet points off, creating another problem.  Or if the blemishes are simply smoothed with a hand-held polishing gadget (imagine something like a dental drill), those facets are not flat any more.  

Normally the recovery rate of re-cutting is 50-60% or less by weight.  Weight is a cubic function of dimension.  Let's say you had a scratched gemstone with a 10-mm diameter and had the stone re-cut.  Suppose it became a 8.5-mm stone.  The final weight of this stone is roughly 60% of the original weight (0.85 x 0.85 x 0.85 = 0.614).  This is considered a good recovery.

• I know only a couple of  faceters who can re-cut a stone with >80% recovery.

If you know the stone you are interested has scratches and nicks in a highly visible area, by all means, avoid it.  Such a purchase is logical only when the stone is very high quality except for the blemish and priced so that the re-cutting cost and stone loss are allowable. 

Myth 3

The Round Brilliant cut is one of the most difficult cut designs.

Truth:  It is one of the easiest cut designs.  Many faceting instructors even use it for the first design to teach.  It is one of the most beautiful cut designs nonetheless.

The cutting difficulty roughly correlates with the number of angle and mast height changes.  The Round Brilliant cut requires only 7 changes.  For example the oval cut shown here requires 22 changes, and is much more difficult to cut.  The difficulty is also dependent on the number of facets. The Round Brilliant has 57 facets plus 16 girdle facets.  The oval shown here has 73 facets plus 16 girdle facets.

Round Brilliant (left) and Oval Brilliant (right)

The Round Brilliant cut is often used in diamond.  Some people mistakenly call it "Diamond Cut".  But this design can be used in any other gemstones with minor angle adjustment. 

Myth 4

You can get incredibly great deals on trendy hot gemstones on eBay.

Truth: You get only what you paid for. 

I consider Paraiba tourmaline, chrome tourmaline, tsavorite, spessartine, Mali garnet etc. as trendy gemstones.  High quality roughs for these gemstones are very expensive.  To cut a 1-carat stone, you need a 3 to 5-carat rough.  For example, a good tsavorite rough costs easily $100/carat.  So the rough alone costs at least $300.  Even if some sellers can get the rough at cheaper wholesale prices, why can they sell a 1-carat tsavorite starting $0.99?  Something does not add up.   

In the Tucson gem show, which is one of the biggest gem shows in the world and sets the gem trend, there are only a handful of faceted Mali garnet over 1 carat in size.  They are sold at several hundred dollars per carat wholesale.  On eBay I see faceted Mali garnets more than 1 carat start at $5 without reserve.  Why don't they sell them at the Tucson gem show or through established routes so that they can make 100 times more money?  Something does not add up.

My experience and common sense tell me the followings:

• Those sellers are not giving away those gemstones at those prices.

• They are still making money.  They have to make a living.

• To make money, the cost of roughs and cutting must be lower than the prices.

• The qualities of cheap roughs are terrible.  Miners and rough dealers don't sell high quality roughs at give-away prices.  There is high demand for quality roughs for them to make money.

• Low quality materials produce low quality finished stones.

• Those stones must be treated in some way to look better than what they really are.  For more information on treated gemstones, click to take a look at my another guide: A Quick Guide to Colored Gemstone Treatments

• Or the genuineness of the stones is questionable.

Suppose there was a stone whose market price is $100-200/carat, and you got it for $90/carat.  You might have gotten a good deal.  But if you got it for $5/carat, I doubt the quality and/or genuineness of the stone.  There is a reason for the cheap price. 

I urge you to do your homework, when you buy a gemstone on eBay.  Research on the market price and what to look for.  You can buy many junks for the price of one good gem.  But junks are junks.  That is not a good deal.

This guide is supposed to be a supplement to my another guide: How to Find Precision-Cut Gemstones on eBay.

This guide is updated from time to time, when more information becomes available.  If you learned something new and useful from this guide, please click "yes" below.  Thank you!!