Cabochoning of Gemstones and Opal

 

The North Brisbane Lapidary Club is very well set up for cabachoning, having several grinding machines, including two of the most advance machines available with diamond wheels, and separate sanding and polishing units allowing several people to be working at different stages of cutting and polishing all at the same time.

The art of cabachoning is a good starting point for anyone wanting to learn lapidary. It allows a beginner to get a feel for a variety of stones that will have differing hardness and texture, and require varying amounts of effort to achieve a good finished product, at the same time learning to use and respect the machinery, being guided through the whole process by experienced instructors.

The knowledge and skill gained through cabachoning is invaluable when advancing to faceting, where the stones are generally more expensive, the process is a lot more complex and easier to make mistakes, and the equipment is far more sensitive and expensive.

In cabachoning the process starts with selection of material, which may be a solid piece of rock or a “slab”.

A slab is simply a flat piece of stone that has been cut from a solid piece of rock.

Starting with a solid piece, an instructor will help the beginner in deciding where and in which direction to cut a slab from the rock. N.B.L.C. has several diamond bladed saws, of varying size, to cut slabs from the rock.

From the slab a smaller piece is cut to suit the size and shape chosen for the finished stone.

This is then ground to the chosen shape and domed, on the wet grinders.

A series of progressively finer wet sanding discs smooth the surface and removes all scratches ready for polishing using a leather or felt buff.

This process is basically the same for the vast majority of stones, with only a few exceptions.

Opals, for example, require more specialized knowledge and techniques to bring out the full potential of each stone. Often the best colour in an opal will be found in a thin vein, and may be more brilliant in one particular direction. It is also a relatively soft stone and can easily be ruined with a heavy hand. Being a very valuable stone, it is important to get it right when cutting opal.

N.B.L.C. runs regular specialised opal cutting courses, run by members with years of opal cutting experience.

One great advantage of being a member of a North Brisbane Lapidary Club is, no matter what stone you wish to cut, chances are one of our members will have already cut one and are always willing to share what they have learnt.