Since the 18th century, many stone cutting factories have been established in the Jura region. It is one of the French cradles of the lapidary professions. In 1917, Dalloz was created in order to preserve this heritage, threatened by the war. It is thus with the lapidary that our history began…
What is the lapidary industry?
The lapidary industry includes all the processes used to shape a stone (most often natural and synthetic gems). The goal is to enhance each gem value by playing with shape, the number of facets and angles of the facets.
The cut determines the quality of stones as well as its color. An ideal cut maximizes the brilliance of a gem, giving it the best possible shine.
Stone cutting is the skill of the lapidary; an exceptional profession requiring great know-how.
What are the ways to cut?
The cutting process is done in 4 main steps.
- Once the rough is extracted for fine stones, or created for synthetic stones, it is cut into several pieces: this is the sawing. It is used to eliminate the defects of constitution (inclusions, impurities …).
Depending on their crystallization, some gems such as diamond and topaz are cleaved. The cleavage aims to cut the stone along its axes of crystallization in order to obtain two distinct parts, like sawing.
- The stone is then cut, gradually revealing the desired final shape. Diamond saws or other chipping machines are used to achieve this result.
- The third step is to give the gem its final shape. The lapidary performs symmetry work to make facets appear (faceting) or give the stone a cabochon shape or other.
- Finally, the gem is polished, thus reinforcing its brilliance.
These steps can be done either manually or with the help of automated machines.
Manual or machine cutting?
This choice can be guided by rough prices, the quantity of gems to be cut or customer requirements in terms of cutting precision. The lapidary’s expertise also consists of a refined analysis of the material, which enables him to decide on the cutting process to be used. Depending on the characteristics of the rough (friability, inclusions, impurities), the lapidary may favor hand cutting.
Generally speaking, machine cutting is used in major lapidary industries, whereas hand cutting is preferred in craft industry.
Hand carving is the traditional method of stone cutting, requiring the skill of the lapidary.
Manual faceting machines are more or less elaborate. The simplest are polishing discs used to shape the stone “by eye”, giving it right angles. The more complex ones allow angles for facets to be displayed and can have symmetry marks, allowing greater precision when cutting.
Over the years, technologies have improved to offer automated systems capable of replacing human work.
The cutting stations can be automated by means of programs defining the actions to be performed on the material (sawing, polishing, etc.). In this category, the cutting can be mechanical but also LASER or water jet under high pressure. In addition, mechanical arms can be used to move the stones on the different cutting stations.
Automated cutting is fast, practical for mass production and guarantees a good calibration of the stones. It will always require human verification to determine possible design or material defects. This is where quality control comes in.
Once the work of the lapidary or automated machines has been completed, the final stones are sent to the jewelry workshops, ready to be set on jewelry or to be used as ornaments of any kind.