What is a Cabochon ?
This is a question I often get from people who return from gem mining.
A cabochon has a domed top surface, continuously smooth and shiny with a flat bottom surface. The most common shape is oval but, cabochons can be cut into any shape - oval, square, round, triangle, cushion, etc.
Opaque or Translucent gemstones with vivid or bright pleasing colors are best finished into cabochons, as it is better suited for the beauty and characteristics of the stone.
- Think about jelly beans -
If gemstones looks like colored jelly beans than they are cabochon-grade rough gemstones, candidates to be cut into cabochon finished gemstones.
Cobbing and Trimming are common methods to reduce large pieces of gemstones into smaller, more useful sized pieces.
What is Cobbing ?
Cobbing gemstones is a method of breaking large stones into smaller pieces. When a rough gem has visible internal cracks the most logical method for cobbing is to break the stone along these natural cracks in order to conserve the largest possible pieces. The objective of cobbing is to divide the stone into the largest pieces that can be made free from significant cracks or inclusions.
When no cracks are visible and when the stone is too it can be broken or sawed into pieces. Gem rough is cobbed to make suitable sized pieces to match the finished size desired.
Nippers can quite efficiently when a stone can fit between the nipper claws. For larger stones a trim saw can be used. I use a pair of tile nipper purchased at Lowes. The kind used to break ceramic flooring tile. Another way to cob gemstones is to place the stone against a sharp chisel point and then strike the gem with pick hammer. I do not use this method.
What is Trimming ?
Trimming gems is a method of reducing a gemstone into usable pieces ready to be fashioned into a finished gemstone. Trimming is often performed with a wet saw but, can also be done by cobbing. I use a trim saw to slice large pieces into smaller sizes in order to isolate a block or slab of gem grade material. Cobbing and Trimming go hand in hand. These are two terms that are often used for essentially the same purpose.
Fabricate 3-stone Cabochon Ring
These are the steps for cutting cabochons for a ring. The the pieces I started with were a banded agate cabochon, Emerald rough, 14K gold ring with pear shaped precious Opal.
I purchase 14K gold settings for oval cabochons, purchase large banded agate stone, re-cut the banded agate to smaller size, cut the emerald rough, re-cut the opal to smaller oval shape.
These are the Goldsmithing and jewelry making steps. Remove the pear shape setting from the ring band; re-size the ring band; solder the three individual oval settings together to make the three stone head; solder the 3-stone head onto the band.
Prong set cabochon stones were glued in with water clear epoxy in combination with securing the prongs to hold the stones.
Mixed Parcel - Cabs & Faceted
These rough gemstones were mined in North Carolina. My client brought them to me to cut and make into finished jewelry. I cut the black stone and low grade green emerald into oval shaped cabochons and faceted the small yellow Citrine. Then I made one 14K gold and two sterling silver bezel pendants to set the cabs and a sterling silver treble clef for the faceted stone.
Star Sapphire Cabochon Ring
A client handed me this very large star sapphire gold ring with a seven cluster illusion head (diamonds already removed). I re-sized the ring, removed the original head, cut the star sapphire to a smaller size, hand-made a yellow gold bezel and soldered it into the ring. Neat look, I made this ring for a local Kentucky client.