This manual is meant to be a general guide to beginning faceting, Remember that the information in this manual is general and that there are a lot of ways (techniques) to get the same job done, In this manual I will outline the cutting methods that I use and the ones that work best for me. theadvice that I can giveyou – is to learn the basic infromation in this manual.As you get some cutting experience, you will gradually find what works best for you. Don’t be afraid to do some experimenting and try other techniques. What you find works best for you will depend on many things – your personality, machine you use, the type of stones you cut, and so on. As you learn how to cut, you willalso find that some stones, even though they are the same type, cut differently from eash other, so what you did last time may not work. Experimentation is a good way to help solve problems you may run across.
Stone Design Basics:
There are a few terms for describing a faceted stone or a faceting design, These terms are genral and, depeneding on where you are, they might have slightly different meanings. Also, depending on how complicated the design is, the terms may not apply to all of the design. At the right is a design
for a standered round brilliant note the names of the facets and like a wedding cake at the tiers (layers of facets like a wedding cake at the same angle around the stone) meet each other (point to point) to form the top (crown) and bottom (pavilion) of the stone, joined by the girdle (vertical). Notice the dimensions in the side view. Most stones should be divided into roughly thirds, 35% of the total depth of the stone should be the crown with the pavilion about 60% of the stone. The table should around 50% of the total width of the stone. These figures are averages and, depending on the design, they could be quite different. The facet names apply generally to almost all shapes (square, oval, rectabgle,) of stones, as long as they are in the same position. Meetpoints are points where two or more facets meet. most of the time in cutting a stone involves mahing facets meet, getting them to line up. On some stones (commercially cut in particular) the girdle facets are not cut. its just rounded, this saves a lot cutting time. You will also notice that the facets usually don’t meet. I cut girdles, I think it adds to the stone finished look.
A Few Other Common Types:
A few types of cuts (facets) are very common as you can see the names are usually descriptive of the cut. I listed these basic types because you may hear them talked about, but there are hundreds of other designs (although the types of facets are pretty much the same) and I don’t have time to go into them in this text. I recommend that you do some reading to familiarize yourself with them.
“c” axis It is easier than it sounds, the “c” axis runs perpendicular 90 to the crystal growth. it is generally the direction in the crystal that has the best color. You often must know where the “c” axis is to orient for cutting. If any (quartz has none).
A flat plane along which some crystals can be split. Basically it is a weak spot (direction) in the crystal growth. A crytal with perfect cleavage is weak and breaks (cleaves) easly with slight pressure (Topaz). These types of crystal must be oeiented so that cutting forces(and facets) are not placed on a clavage planes. Some crystals have imperfect cleavage in several directions (sapolite). So it’s important that youy know the type of materil you are cutting and it’s cleavage, if any (quartz has none)
Critical angle (C.A.)
In faceting the critical angle is the angle below which light entering a material (stone) is no longer reflected back up through the crown of the stone. Foe example, the critical angle for quartz is about 40.5 if the pavilion of the stone is cut below this angle the light will go straight through the bottom of the stone instead of reflecting up through the crown like it should. When this happen the stone loses brilliance and sparkle, causing the stone to look dead. The refractive index (R.I.) of a material is what determines the critical angle. The higher the R.I. of the material the lower the critical angle. for examply, the R.I. of Quartz is 1.54 the critical angle is 40.49, the R.I. of Diamound is 2.41 and the critial angle is 24.62. The higher the R.I. of a material, the more light reflection and brilliance it has (the light tends to bounce around traped inside of the stone causind dispersion). look at a Diamound next to a piece of Amethyst sometime and see the ( big ) difference.
History of Facetted Gemstones
Facetted Gemstones made their appearance in European jewelry during the late 13th and early 14th centuries. With the advent of the horizontally turning cutting-wheel in the late 1400s came the possibility of designing and repeating elaborately conceived geometric faceting schemes, thereby controlling and enhancing the light coming from within the stone.
Starting with the burgeoning Renaissance gem-cutting trade in Bruges, to Venice, Florence and eventually the whole of Europe, the management of light became the central theme in gem cutting. During the same period, Flemish painters, such as Jan Van Eyck (c. 1390-1441) also took up the obsession with light and reflection in their artwork. Using the laws of optics as a guiding force, the exterior shape and facet scheme of a cut gemstone would now be preordained by the refractive and reflective properties of the mineral itself.