It is said that gem cutting artisans exist since several millennia before Christ. It all started with rudimentary tools to modern machines the artisans of today use. Here we will learn some of the favorite techniques used by the artisans of today and some of the most fashionable forms.
According to Wikipedia, a lapidary is an artist or artisan who forms stone, minerals, or gemstones into decorative items. It is the work of cutting or polishing precious gemstones. Most lapidaries specialize in working on particular stones and are sensitive to such characteristics as depth of color, hardness, and the effects of light when viewed from various angles or axes. The word lapidary comes from the Latin lapis that means stone.
It is said that the earliest known lapidary work likely occurred during the Stone Age. As people created tools from stone, they realized that some geological materials were harder than others. Another documented example of what can be considered as “lapidary art” came in the form of drilling stone and rock. The earliest roots of drilling roots, a lapidary method, dates back to approximately one million years ago.
Neolithic men were the first who created the first jewelry. They would bore a small hole through the Lapis Lazuli and string the pebbles of blue with a thread. Historians believe the link between lapis lazuli and human beliefs dates back over 6,500 years. Ancient civilizations, including Egyptian, Mesopotamian, Chinese, Roman and Greek, valued highly this stone.
Jewelry served as a status symbol in Mesopotamia as it always has everywhere else, but it also played a significant role in how the Mesopotamian civilization functioned
Another ancient civilization that developed cutting and jewelry fashioning methods for lapis lazuli, turquoise and amethyst were the early Egyptians.
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By the early 1st millennium the lapidary arts were quite developed in the Indian subcontinent.
A distinct unpleasant smell is caused mainly by the sulphur content of the stone when lapis lazuli is cut. It is said that experienced cutters can tell the intenseness of the stones blue color by the smell.
In this post you will find
Lapidary Techniques
Sawing
Normally a thin circular blade made mostly of steel and copper is used to saw through a piece of lapis. The blade is also coated along the outer edge with diamond grit, allowing it to literally scratch its way through the lapis stone.
Grinding
The grinding wheels are studded with diamonds and this gives it the necessary hardness to cut away the lapis stones. These wheels are used to shape the stones to a rough shape.
Sanding
Here, much finer abrasives are used. The sanding wheel, used appropriately allows the artisan to remove any scratches left by coarser abrasives during grinding. It establishes the final shape of the stone prior to polishing.
Lapping
It is very similar to grinding and sanding, except that it is performed on one side of a rotating flat disk known as a lap.
Drilling
A small rotating rod or tube with a diamond tip is used to drill through lapis. A prehistoric from of drilling Lapis Lazuli like the bow drill is still used on the streets of Kabul.
Tumbling
A process in which the stone is turned on a slow speed in a rotating barrel for extended periods. This gradually smooths and polishes the stone into very attractive shapes. Use Chrome oxide when tumbling lapis lazuli. Group your tumbles by hardness.
Most modern lapidary work is done using motorized equipment. Gemstone material that has not been extensively cut and polished is referred to generally as rough. Rough material that has been lightly hammered to knock off brittle, fractured material is said to have been cobbed.
Fashioned Cutting Forms
Cabochon
Cabochon cutting or cabbing is the most popular form of gem cutting. Although a fair amount of skill, almost anyone can master this technique. Rough material for cabbing can be found or purchased inexpensively. At the beginning a lot people practice with any stone they trade or find and as they gain experience, they move on to more valuable materials like turquoise or lapis lazuli.
You can cab on a faceting machine, but you can´t facet on a cabbing machine. Something to keep in mind if you are a beginning lapidary student and budgeting your equipment costs.
Faceted Stones
A faceting machine usually employs a motor that turns a lap, a water supply, an adjustable handpiece with index gears and a protractor, and an adjustable mast or platform to hold the handpiece assembly.
Beads and Spheres
Spheres are initially sawed into cubes or dodecahedrons and then ground to shape between two pipes or rotating concave cutters, allowing the stone to rotate freely in any direction to form a perfect spherical shape.
Inlays
A Lapis Lazuli is cut to fit and glued into a hollow recess in another material and then the top ground and polished flush with the surrounding material.
Intarsias and Mosaics
Small pieces of lapis of different shades are fit together and the top cut and polished.
Sculptures
Gemstones can be carved, like other materials, into almost any form, limited only by the talents of the sculptor. Carving is accomplished with a variety of diamond-impregnated steel bits, saws, and grindstones.
Polishing
When polishing, Lapis Lazuli must be handled with care because of its modest hardness and not subject it to much pressure. Polishing can be used for ultra fine shaping.
After a gemstone is sawed and ground to the desired shape and sanded to remove rough marks left by coarser grits, it is usually polished to a mirror-like finish to aid light reflection from the surface of the stone (or refraction through the stone, in the case of transparent materials).
Incredible results are gained polishing a Lapis Lazuli stone.
Polishing Agents
Very fine grades of diamond (50,000 to 100,000 mesh) can be used to polish a wide variety of materials, but other polishing agents work well in many instances. Usually, these polishing agents are metal oxides such as aluminum oxide (alumina), cerium oxide, tin oxide, chromium oxide, ferric oxide (jeweler’s rouge), or silicon dioxide (tripoli). Different stones are often very inconsistent in their ease of polishing, particularly in the case of faceted stones, so gemcutters are often very inventive in trying new combinations of polishing agents and polishing surfaces, often tin, tin-lead, lead, leather, felt, pellon, wood, or lucite laps for flat surfaces such as facets.
When polishing lapis, polishing agents are used. Usually chrome oxide o alumina are used. A small felt wheel damp used with the agent is the best way to polish lapis.
Rounded surfaces, such as on cabochons, are often polished on felt, leather, cork, cloth, or wood. Polishing removes small quantities of stone and can be used, especially when faceting small stones, to do ultrafine shaping of the stone.
One important factor when working with lapis is that the pyrite inclusions are much harder then the rest of the stone. Pyrite makes this stone more vulnerable to fractures.
When you hold a piece of jewelry made of lapis lazuli, don´t forget that an artist transformed a stone from the heart of a mountain into the celestial jewel you have in your hands…
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