Whether you are a rockhound, gem and mineral collector, jewelry maker or simply someone who appreciates a beautiful gemstone, you are sure to encounter the field of lapidary. Have you ever wondered how to shape, smooth and polish gemstones or semi precious stones? In a nutshell, that’s what lapidary is. It’s the process of shaping and putting a nice finish on a stone.
Although some lapidary processes require high levels of technical skill, expertise and the use of complex equipment, there is almost no barrier to entry for the beginner. Getting started in lapidary does not necessarily require a workshop full of fancy equipment. A lot can be achieved with a minimal amount of tooling.
Let’s take a look at some basic lapidary techniques and equipment available to beginners. The fundamental principal of progressing through a series of increasingly finer abrasives applies to all of these processes yet each process employs a unique set of tools and equipment.
Polishing stones in a tumbler
Tumbling can be thought of as a way to mimic nature breaking down stone through erosion. Have you been to a rocky beach or walked through a dry riverbed and observed that the stones in these places are rounded and smooth? These stones have been naturally tumbled smooth.
If you have never made this observation, now is a great time to take a hike and go look at some lovely, smooth river rock.
Over time, water flowing through the river channel forcefully agitates the stones causing their sharp edges to wear down. The same thing happens on the beach with repetitive pounding of the waves.
And this is also what goes on inside the barrel of a tumbler except we get to add a little twist to speed up the smoothing process. By combining the rough gemstones with hard abrasive grit and mechanically shaking or rolling them around in the tumbler we re-create the action of the beach or the river on a human scale instead of waiting for a geologic eternity.
One thing the river hasn’t figured out yet is how to polish the rocks after they’ve been tumbled smooth. But we humans are clever and we follow the basic principles of lapidary. We know that by changing out the abrasive periodically to progress through grits from coarse to extremely fine, we can put a polish on those stones high enough to see our own reflection.
Tumblers are great for beginners because they are mechanically simple and require virtually no dexterity or finesse. Just load up the tumbler, close the lid and away you go. Depending on the stone material and the type of tumbler used, it can take many weeks to polish start to finish. Patience is a key ingredient for tumbling. But once the tumbler is loaded and started it does all the hard work automatically and you can pay attention to other things. There’s no sound quite like the soothing rumble of a tumbler gently rolling in the background.
There are two types of tumblers to choose from, rotary tumblers and vibratory tumblers.
A rotary tumbler has a cylindrical barrel that rolls horizontally on a drive shaft. It tumbles the rocks inside the same way that clothing gets tumbled in a clothes dryer.
We now carry a line of rotary tumblers from Covington. Take a look in our shop and you’re sure to find the right model for you.
A vibratory tumbler comprises a hopper attached to a vibrating mechanism which rapidly shakes the hopper and it’s contents.
Generally, rotary tumblers are better at taking rough stones down to a smoother, more rounded shape. They take longer than vibratory tumblers which work much faster for polishing but are not ideal for achieving rounded shapes. A beginner might start out with a rotary tumbler to get some hands on experience. Then, by adding a vibratory tumbler later they can enjoy the best both tools have to offer.
Cabochon cutting on a cabbing machine
For some beginners, the patience it takes to wait for a batch of stones to finish tumbling would be agonizing. Fortunately, there are other lapidary activities that take less time.
Within the field of lapidary, cutting and polishing cabochons on a cabbing machine is the ultimate form of instant gratification. A nice cabochon can literally be made in under an hour and a beginner can take to it right away.
Typically, a cabbing machine has an array of six grinding and polishing wheels arranged next to each other on a long shaft. The shaft may be directly attached to a motor or it may be mounted on bearings and attached to a belt and pulley drive. The abrasive surface is on the cylindrical perimeter of the wheels.
Each wheel on the shaft employs a different mesh size abrasive and the wheels progress incrementally from coarse for shaping to medium for smoothing to fine and extra fine for polishing. A water drip system or splashing system keeps the wheels wet and a shroud catches water flung from the wheels as they spin.
The coarse grinding wheels are often metal with diamond grit either sintered or electroplated to the grinding surface. The fine abrasive wheels are often composite materials with some cushion and the grit is bonded to the grinding/polishing surface with resin. Sometimes a leather disk charged with polishing compound such as cerium oxide is mounted on the end of the machine for a final buffing finish.
The 6″ Cab King available in our shop is a great cabochon machine to get started in cabbing. Watch out, it’s so much fun you may never want to stop!
Paired nicely with a cabbing machine is a trim saw for cutting out cabochon blanks. Trim saws are small, wet operated diamond saws with a table to support a thin stone slab. The saw blades are usually in the range of 6” to 10” in diameter and are meant to be operated freehand.
With no other tools but a cabbing machine, a trim saw, some dop sticks and dop wax, a beginner can learn how to turn a slab of stone into a finished cabochon in one sitting.
And Covington makes a combination unit that includes the saw, grinding and polishing wheels all in one machine. It’s a great way to save space and comes with everything you need to get started. Go for the diamond model. It’s available in our shop.
Carving gemstones with a flex shaft tool
It takes a lot of talent and practice to carve a fancy intaglio or intricate shapes into a gemstone. However with some persistence, carving basic, free form organic shapes and curves is doable for a beginner. And, this really can be an inexpensive and space saving way to get a start in lapidary.
Flex shaft rotary tools
A Foredom flex shaft tool or a Dremel tool with a flex shaft attachment, along with a handful of bits, burrs and a water drip system is the basic set up for lapidary carving. The work should be kept wet while carving to keep the burrs and the stone from overheating and also to prevent generating dust. To keep things wet the work is done under the stream of the drip system or alternatively dipped frequently into water.
Carving is done freehand with the flex shaft handle in one hand and the stone in the other. A dop stick attached to the stone can also be helpful for holding on to the work. Coarse shaping happens first with coarse grit diamond burrs followed by smoothing with finer grit burrs. Pre-polishing and polishing is achieved using buffing wheels and shaped felt or wooden bits charged with the appropriate polishing compound.
The only limits to the shapes that can be made by carving are from the materials. Some materials are more brittle than others limiting the carver to simpler shapes. Some materials are more forgiving and invite more adventurous designs.
Cutting and faceting on a flat lap machine
A beginner can graduate to more advanced faceting by learning the basics with a flat lap machine (also just called a flat lap) on which simple faceted shapes such as pyramids, cubes and crystal forms can be cut freehand. Cabochons can also be effectively cut and polished on a flat lap.
Flat lap machines
The grinding and polishing surface of a flat lap is on the planar side of a disc-shaped wheel (called a lap disc or just lap) which rotates on a spindle. Some flat laps are oriented at an angle for ergonomics and others are horizontal like a record player. As with other lapidary equipment, a water drip system keeps the grinding surface wet and a shroud with a catchment system keeps the water contained.
To progress through the series of abrasives, the coarse lap must be removed from the spindle and changed out for the next finer lap. To save time, some people use a magnetic backed lap disc that grips a steel platen on the machine making it easy to swap them out.
Worth mentioning here are faceting machines even though they are more advanced, more expensive and not usually where a beginner would start out. However, some mechanically minded beginners would naturally take to mechanized faceting techniques after learning basic flat lap techniques.
Fundamentally, a faceting machine is a flat lap machine that incorporates a mechanical arm with an indexing dop stick holder. This arm, attached to the machine body, accurately guides the gemstone to contact the lapping surface at various angles in relation to the machine platen.
What makes a faceting machine an option for a beginner? Any manual move that can be made on a flat lap machine can also be done on a faceting machine. It can be operated freehand without using the mechanical arm. In this way, the beginner can learn the basics and then advance without acquiring more equipment.