Lapidary HQ

How Gemstones Go From Lumps Of Rock To The Sparkling Gems We Love

When precious stones are found in mines, they don't look half as dazzling as they should look. Gems are finely cut, shaped and polished to give it that mesmerizing stunning and impressive look. The method of cutting the stone is known as gem cutting or lapidary. This process was started in the early 1300s in Venice. Later in the 1400s this method was used in Paris and Bruges. There are four basic styles of gem cutting, namely tumbling, faceting and carving. The precious stones should be cut so well that they mirror and reflect the light that falls on them. If the gem has not been cut or polished well, it destroys the beauty and the shine of the stone. For example, an alluring diamond, if not polished and cut well, will not be as valuable, rich or worthy compared to a well polished diamond.

The gem cutter or a lapidary, also known as lapidarist begins the process of lapidary by sawing the gem. The gem from the mine is first cleaned with oil or water, to remove the residues present on the stone. The stone is then sawed with a thin circular blade. One can use different sizes of blades, depending on the size of the stone. Sawing helps remove all the debris and chunks of mud stuck to the stone. The second step is grinding the stone.

Grinding is usually done with silicon carbide wheels or diamond-impregnated wheels, which is used to give shape to the gemstone to a desired rough form, called a preform. The third step is sanding which removes the scratches and dents caused by grinding. Sanding is a very delicate fine process, which is similar to grinding. If the stone needs to be flat at one end, then the stone goes through a process called lapping.

Laps are made of iron or steel, to flatten one side of the stone. Then stone is then polished, to create a mirror like effect. Polishing makes the stone so clear and dazzling that it shines. Polishing agents like tin oxide, aluminum oxide, ferric oxide and so on are used. Cloth, leather, wood, can also be used for polishing. The next process is cabochon. The gem is smoothly rounded and polished on top, and either flattened or slightly rounded on the bottom. This is usually done to opaque or transparent stone.

Transparent stones are also faceted. The stone is flattened at on the sides symmetrically and the entire surface is polished thoroughly, making it shine. The stone is then dopped on a metal dopstick, and later sanded and polished on a lap. Water or any liquid is used to clean the stone. A well faceted stone acts like a mirror, reflecting the light that falls on it, thus making it shine.

Gregg Hall is an author living in Navarre Florida. Find more about this as well as diamond jewelry at gemstoneanddiamondjewelry.com

Cutting Stone - The Lapidary Artist, Part Two

While a good eye is needed to select a nice piece of rough, talent and artistry are required to produce a finished cabochon suitable for adornment. This is where the lapidary’s skill really shines. It is also the most fun. Taking a dull piece of rock and turning it into a shiny thing of beauty is very satisfying. There are many different ways this can be achieved. However, they all involve grinding and polishing.

As a child, this author would sit for hours, rubbing a pretty rock back and forth on the concrete walkway in the backyard of her family home. Well, it probably only seemed like hours. Now she has a much faster and easier way of achieving a polished stone.

As mentioned before, it all boils down to grinding on the pre-trimmed slab and then polishing it. The methods are as varied as are the lapidaries themselves. But they all begin with a coarse grit and work their way to finer and finer grits.

Some lapidaries prefer to use sanding/grinding belts. These are impregnated with silicon carbide. For the most part, these belts are mounted to a wheel that is turned by a motor. Water is supplied, either as a drip or in a reservoir, as a coolant and lubricant.

Others will use a combination of solid silicon carbide wheels and belts. A drawback to the solid silicon carbide wheels is that, if you are not careful to move the cabochon around on the grinding surface, you will get dips in the wheel and these must be ground out (or dressed) periodically. A diamond T-bar dressing tool is required for this. Even if you are careful, periodic dressing is required. The belts wear out quickly and must be replaced quite often. However, some lapidaries consider this to be the most economical.

This author prefers to use a machine fitted with diamond impregnated wheels. The initial cost is greater, but they last much longer and never need to be dressed. She has tried the method mentioned above and finds that diamond cuts faster and requires less water, which is much less messy.

Some lapidaries prefer to use “laps”. These are flat discs, the best of which are diamond. They spin around as would an old-fashioned long playing vinyl record. These laps are mostly used by lapidaries who facet gemstones, but some “cabbers” find them easier to use.

All the preparation, selecting the rough material, cutting it into a slab, trimming it to the rough shape and selecting your method of grinding and polishing, all lead up to the moment when the lapidary gets in front of their grinding/polishing machine and starts to cut the stone. For this author, this is the most anticipated moment.

Her grinding/polishing machine has six wheels. The coarsest wheel is used to refine the pre-trimmed shape and remove the deepest scratches. The next wheel is used to further refine the shape and start to remove more of the scratches. The first two wheels are hard wheels; there is no give to them. The third wheel is a little resilient and generally more pressure is applied to this and the subsequent wheels.

Sufficient time must be spent at each stage to remove the scratches. The whole point of moving from coarse to fine grit, is to move from big scratches to very small scratches and finally to no scratches. The cabochon should be dried and inspected before moving on to the next wheel. If you do not spend enough time at each stage, it is a waste of your time. You will get to the end and still have visible scratches on your cabochon. Then you must determine how bad the scratches are and back track the appropriate number of steps.

Some materials will naturally take a better shine than others. So some lapidaries will finish up with a polishing compound applied to a buffing wheel. This author uses a hard felt buffing wheel first, and then a soft muslin buff. Any buffing compound residue must be washed away.

It is very exciting to come to the end of all this, dry your cabochon, and look at it in the sunlight. If you have done everything right, you will have taken a dull piece of rock, with pale colors, and turned it into a vibrant and shiny work of art.

Occasionally, this author will have visitors to her studio. Some will ask if they might try grinding and polishing a stone. Their delight at the process and happiness with the result is always a source of great joy for her.

About the Author - syzygyjewelry.com

Cutting Stone - The Lapidary Artist - Part One

All rocks have beauty within them. It takes an experienced lapidary to bring it out. A lapidary is someone who takes rough stone, rock, or minerals and cuts and polishes them so that they may be added to jewelry or simply kept for display. Some lapidaries carve stone into fanciful or representational shapes. Others will take materials like agate, onyx or fluorite and shape it into useful items like bowls, vases and plates.

For a lapidary who makes primarily cabochons (a cabochon, or cab, is flat on the back side and either domed or slightly domed on the top with a high polish), it all begins with saws. Actually, it all begins with the rock. However, we are not talking about rock hounding today.

After acquiring a piece of rock, it must be cut into slabs. If the piece of rock is quite large, the lapidary will have to begin with a slab saw. A slab saw typically consist primarily of a disc shaped blade with a diamond coated rim, a motor, and a reservoir to hold the coolant/lubricant. The coolant/lubricant can be either water or oil. Water is a lot less messy and typically only commercial cutting houses will use oils. The largest slab saw this author has ever seen stands about eight feet tall. It is a diamond blade drag saw and was built to cut large petrified wood stumps.

Depending on the size of the finished cabochon and the material being used, the slabs will be cut to varying thicknesses. If the lapidary wants a very high dome on the finished cabochon, the slab will need to be fairly thick. Also, softer materials produce more waste when cutting and polishing and therefore, need to start out thicker.

A trim saw is a smaller version of a slab saw. These are most commonly cooled and lubricated with water. If the rock is small enough, a trim saw may be used in place of a slab saw. Trim saw blades most often are four inches, six inches, eight inches or ten inches in diameter. A four inch diameter blade will slice through a rock that is less than two inches deep.

When the lapidary has the slab that she wants, primarily the trim saw is then used to trim the slab as closely to the finished shape as possible. Some lapidaries produce calibrated shapes. These are usually traced onto the stone with a template. The most common shape found as calibrated cabochons is oval. However, square and round shapes are also produced.

They will be made to a strict set of size requirements. This is usually expressed in millimeters: 12mm x 10mm, 30mm x 20mm, for example. These are primarily made for purposes of competition. They are judged on best use of the material, size, perfection of shape and polish. Most commercially available calibrated cabochons are made by machine and the final polish is achieved in a tumble polisher.

This author finds free-form cabochons to be most pleasing. They also present the biggest challenge for working into jewelry. It is possible to purchase mountings for the calibrated shapes, but not so for the free-form shapes. Mountings for the free-forms must be fabricated from scratch. Your piece of artisan jewelry has had a great deal of time put into it by the time it has found its way to your neck or wrist.

Once the slab has been trimmed to a rough shape, then the real fun begins. The lapidary then grinds and polishes the stone. This is where the lapidary's skill really shines.

About the Author - syzygyjewelry.com