Since the beginning of civilization, humans have always used crystals as jewelry. Carnelian and rock crystal beads dating from around 6000 B.C. have been excavated in Iraq. During 2500 B.C. a gemstone trade flourished in Rome, Egypt, Greece, and China. Diamonds gained popularity in India from 800 B.C. and were cherished as talismans.
Throughout history, various technologies evolved around the world to polish, cut, and drill stones. It is believed by 1000 BC, the art of faceting stones were already quite advanced in the Indian subcontinent.
Crystal jewelry normally consists of stones that are very hard on the Mohs scale (7 and above), and this means to refine and polish them requires the right tools and skill. Crystal cutting is a distinctive art of engineering and art, and has to be carried out with a lot of precision by experienced and skilled artisans.
What are the terms used in crystal jewelry cutting? Let’s explore the commonly used terms.
Faceting: The faceting process is also called Lapidary. It involves creating small flat, polished surfaces on a gemstone to enhance its reflective character. What about carving? Faceting and carving are different terms with an overlap of meanings. Carving is a specialized technique by itself. But as time goes on, the difference between faceting and carving of a gemstone is diminishing with the emergence of new designs and techniques of cutting.
Durability: The stone must be robust so as to sustain mounting at the time of fixing. Especially the stones that are going to be used for rings and cufflinks – to resist physical stress and knocks, resistance to chemicals, and the ability handle daily wear and tear.
Hardness: The ability of the gemstone to resist scratching. Usually a hardness of 7 or higher on the Mohs scale is preferred for rings and jewelry.
Cleavage: Defined as the characteristic of the gemstone to split when struck with a blow. Obviously, the lower the cleavage, the higher the desirability of the stone.
Color: Color is very important and is a result of other trace mineral inclusions. Transparency is also a highly desired trait; opacity is not. Hence, gemstones must be transparent and exhibit a clearly defined color. The refractive index of the stone is important.
Birefringence: This means the double refraction of light as it goes through a crystal, which then manifests as an optical difference in the refractive index of the light.
Dispersion: This means the ability of the gemstone to disperse white light into a spectrum of rainbow colors. Depending on quality of the stone, the rate of dispersion varies. It is usually high in diamonds and zircons.
Common terminologies in lapidary:
Crown: The top section of the stone, just above the girdle.
Pavilion: The bottom section of the stone, just below the girdle.
Girdle: A fine line that divides the stone into a top and bottom section.
Table: A large area on the crown section of the stone.
Culet: The flat bottom section of the stone.
Star: The area around the edge of the table area.
Critical Angle: The angle at which maximum light can be reflected back into the stone. It is directly proportional to the stone’s refractive index.
Culet Angle: The angle at which the culet facet is trimmed.
Crown Angle: The angle at which crown facets are trimmed.
Dopping: Placing a stone on a dop stick in order to facet it.
Dop stick: A metallic rod that holds the rough stone whilst it is being processed for cutting.
Index Gear: With a whole lot of teeth at its outer rim, index gears are used to rotate the stone during cutting. Index gears are available in different numbered variants; i.e. 80 Index Gear, 96 Index Gear, 120 Index Wheel, 77 Tooth Wheel, and 32 Tooth Wheel.
Epoxy joint: Epoxy here means an adhesive, and an epoxy joint means the joints glued with the help of an adhesive (epoxy).
Facet head: Part of a faceting machine, and the most complex part of it. It serves to hold the stone at the correct mounted position, at the right angle, and also rotates it while the facets are cut into the stone.
The Basic Faceting Process in 14 Steps
Once the machines are set up and various parameters are defined, the faceting process kicks off. These are the general, basic steps.
- Determine the stone that needs to be faceted.
- Contemplate on the type of cut to be undertaken using a rough geometry.
- Prepare a diagram and modify the angles for the stone.
- Before choosing the table, analyse the stone well to consider any factors before the cutting process.
- Hold the stone firmly with the dop stick.
- Affix the dop stick onto the facet machine head to lock it well in place. Set the desired angle to cut and begin with carving the outside shape of the stone.
- After cutting the first Pavilion facet, raise the head of the facet. Re-index it well and start cutting again.
- For each index position, repeat the same process.
- Using a sandstone wheel, start the smoothing process to give a more refined design and pattern to the crystal pieces; getting rid of the rough cuts.
- Move the stone from the pavilion dop stick to the culet dop stick. The tip of this pavilion dop is inserted in the cavity, filled with epoxy, and is pressed for 5 minutes to make it firm.
- Once the second Epoxy joint is hardened, separate the dop sticks.
- Put the dop stick back into the Facet Head while realigning the correct index.
- Cut the crown mains well to move to the next stage of polishing.
- After engraving is completed, the stone needs to be polished and glossed. The piece is glazed ensuring its clarity is distinctly maintained. The polishing is done on the buffer wheels manually. The lesser quality pieces are glossed by soaking them in hydro-fluoric acid.
After polishing is completed, the gemstone is removed from the dop stick and cleaned to obtain a refined crystal stone, ready for evaluation/classification based on its carat value.