Information

 

 

 

What is the difference between a custom cut and commercially cut gemstone?

 

Custom cut gems are cut for performance and commercially cut gems are cut for profit.

When we select a piece of rough to cut there are several things that need to be considered before one can start cutting.

Orientation of the rough-; this not only ensures that the finished product will be of the best possible clarity it also gives us an indication as to the design that will best suite the specific piece of rough and with certain types of gemstones the axis on which it is cut also determines the colour.

Next, regardless if we know what the rough is supposed to be we take an RI reading, this gives us the refractive index of the specific material and we are able to adjust all the relevant angles to ensure maximum light return. A perfectly cut gem will reflect all the light back through the crown (top) thus ensuring maximum brilliance and scintillation.

Many people have not had the opportunity to see a gem cut properly. Once you do the difference is very apparent. Most often this cutting is done on jamb peg faceting machines or totally freehand as in the video. While this style of cutting is very fast, it is not  accurate at all. In larger cutting houses, the work is done on an assembly line type process, where one worker will only dop stones, then pass them to the next that shapes them, then passed to another cutter who polishes. The workers are paid by the number of pieces they produce and the weight. To maintain the maximum weight they will cut stones with angles below the critical angle for the stone. This causes the stone to "window" as light escapes out of the bottom.

But windowing is just part of the story. Most commercially cut stones are not symmetrical, the facets don't meet correctly at sharp intersections, the girdles are not polished, and the polish used is not very fine

A commercially cut Gemstone is typical of the diagram and pictures below. If you examine a commercially cut gem you will normally find that the pavilion (bottom) is bellied. The reason for this is weight retention and less wastage equates to a larger gem and higher profit. This negatively affects everything a custom gem cutter strives for. In addition to this you will also find that facets do not align because many of them are cut freehand

See diagrams and pictures below:

In Fig A we see a picture of a commercially cut gemstone, the purple lines on the diagram to the left indicate what happens to the light return on a gem that is cut incorrectly. As you will see in this photograph it is very apparent when you compare it to the photograph in Fig B which is the same gem that has been re-cut. Note the purple lines indicating light return in Fig B where the angles have been optimized for the specific gem type. This near 100% light return is totally impossible to achieve when accurate machinery is not used.

 

Fig A
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Fig B
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As you will see in the following video there can be no degree of accuracy in commercial cutting facilities such as this one.

 

 

The pictures below are of one of our machines. It is accurate, reliable and repeatable,  it is a necessity to have this degree of accuracy when cutting computer aided designs created with Gem Cad. This degree of accuracy is also required to ensure that the gem is cut at the correct angles specific to the gem type. If you look at the video of the commercial cutters you will note that it is totally impossible for them to cut anything at the correct angles and this is not possible in a commercial environment such as the one in the video.

 

Click on Image to Enlarge

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How does our pricing system work?

You may notice that our prices do not conform to general pricing structure for gems. This is because we do not price the gems on market related values, our rough is obtained from many different sources, and sometimes we get it for a song and other times at a much higher price. We take the purchase price of the rough and any costs incurred in obtaining the rough that will constitute the base price of the gem, it is then a matter of how much labour went into cutting the masterpiece and that will determine the final price.

 

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