Lapidary – Finally, A Use For Those Rocks In Your Head!

Lapidary is the process of turning rocks into lovely gemstones. By the way, sorry about the rocks in your head comment, I guess they are more likely marbles! Either way, you can become a rock polisher. Confusing but true, the term lapidary describes the process, the person who does it and the place where the work is done.

Mother nature has been doing this for billions of years. Polishing stones in river beds and other places where water wears away rock. Humans have been shining rocks for a much shorter period of time. By 5,000 years ago, Mesopotamians where carving and polishing stones using grinding tools making flat and rounded shapes. Since then the technical aspects of this hobby have changed to make it much easier than rubbing two rocks together till they shine.

There are four main categories of gem cutting and polishing. These are faceted, lapped, cabochon and tumbled. Faceted stones have many flat surfaces oriented precisely around the stone in such a way to reflect and refract light bringing out its total beauty. Lapped stones are polished perfectly flat. Cabochons have smooth rounded surfaces which many times are arbitrary in shape. Tumbled stones are polished but irregular in shape. Each of these uses a completely different process.


The simplest of these processes is tumbling. It also requires the least amount of equipment, a tumbling machine and various grades of grinding grit and polish. The tumbling machine consists of a tumbling drum, an electric motor and a frame with rollers. One of the rollers is connected to the motor via a belt which when the drum is set onto the rollers, will rotate the drum at about 60 RPM. During operation the stones to be polished are placed inside the drum with an abrasive grit and water. The rotation of the drum causes the stones to rub against each other and with the help of the abrasive grit wear them smooth.

The polishing process is carried out in three to four stages stepping from coarse 80 or 100 grit, a period of 400 to 600 grit, a fine polish step and last of all a short period of soap solution for cleaning the stones to a fine luster. Tumblers come in many sizes from two pounds on up to 12 pounds. Select the size that best fits your needs.

From the finished tumbled stones you can make pendants, key ring dangles and just polished rocks for decorations. I use these as starting material for my electroformed pendants. See my page on electroforming.


When most people think of lapidary, making cabochons is usually what they think of. Cutting and polishing cabochons is the next easiest and least technical of the remaining three. There is however the investment in some equipment such as a trim saw, wet grinding and sanding and polishing equipment. But, with this added startup cost comes much greater versatility in preparing and polishing gemstones.

You will need about eight foot of bench space to set up your lapidary equipment. These include the trim saw, a couple of wet grinding/sanding arbors and final polishing arbor. With this shop you will be able to purchase slabbed rock and turn them into finished cabochons. The only gemstones you will not be able to polish include ruby, sapphire and diamonds as these are too hard to be handled with your new equipment. If your desire is to begin with chunks of rock, say your a rock hound, you simply need to add a slab saw to the list of equipment.

The cabochon making process begins by taking a slab of gemstone rock and marking out the cuts you want to make to bring out as much of the rocks natural beauty as possible. Normally you will use a template with various size circles and ovals on it to mark the target areas. Use the template like a small window and picture in your mind how the finished product will look. Think about rock grain orientation, imperfections, and color differences when picking the parts to save. It is kind of like composing a picture with your camera. Also, you may find it helpful to wet the stone surface with water as it will brighten the colors and other features of the rock surface. When you are ready, take a hard pencil and mark on the side to be polished, the area you want to cut out.

So, the next step is to use your diamond blade trim saw to cut out and trim off any extra rock not within the marked area that will eventually be the finished cabochon. Remember, that the diamond blade must be run with water on it or it will overheat and wipe the diamonds off the blade. When you have finished trimming give the blank a good rinse with water to remove any wet stone particles.

Next step is to put a handle on our cabochon blank. This is done with a short piece of wooden dowel, three to four inches long and some dop (Rhymes with top) wax. Dop wax comes in various sized slabs which you will break off some pieces and put into a metal cup and heat gently until soft. When softened sufficiently insert your wooden dowel and spin the dowel with your fingers. You want a nice blob on the end of the dowel. With the cabochon blank dry push the end of the dop wax laden dowel onto the back side of the cabochon blank. Then using your fingers press the dop wax onto the stone surface flaring it out to cover nearly all of the back side of the blank. If you are working a large cabochon use a larger diameter dowel as it will be more comfortable to hold onto. If your doing a really tiny shape then a small diameter dowel is called for. If you have any problems with the dop wax sticking you can warm the stone surface as well. This usually cures the problem.

During the next step you will use a coarse, 220 grit grinding wheel to shape your cabochon down to the line you made on the stone face when using the template. Again, make sure you have a small amount of water running onto the stone to prevent overheating of the grinding wheel and your stone. After you have finished the grinding give the stone a good rinse under the faucet to prevent any stray grit particles from getting onto your sanding drum which is next in the lapidary process.

The next stage in our lapidary project is to begin the final shaping, usually with a 320 grit wet sandpaper on a rubber sanding drum. Remember to turn on the water sufficient to keep the sandpaper wet and washed off as you are working with the stone. Before I forget, it is advisable to not put the waste water from the cutting and sanding process into your sewer drain. The heavy rock sludge will quickly plug everything. Since some stones have a bit of limestone in them, it can pretty quickly solidify this sludge that will seem like concrete when you are trying to remove it. Instead, you can catch the water and sludge in a bucket and put in the trash or spread these solids in your garden or yard. Volume wise they don't amount to much.

Now we are getting down to the final steps. Remember to always give your cabochon a good rinse before moving to the next step. Next we move to another rubber sanding drum with a 500 to 600 grit sanding belt on it. This will take us to a near finished product. In each sanding stage keep working the stone surface on the sandpaper until there is no evidence of spots rougher than any others. I know this seems kind of vague, but as soon as you have done a couple you will see the difference.

Finally we have made it to the polishing step. It is absolutely critical that no rouge grit particles get from anywhere in the process onto the leather polishing disk. If it happens you may have to discard the leather disk and start with a new one. These disks are run moist but not with water running on them like we did with the previous stages. Usually for cabochon polishing you will use Tripoli (a fine grained silicon powder) and/or cerium oxide. If you use both, get separate polishing disks for each. Once you have the high gloss shine, give the stone a good soap and water wash and admire you finished cabochon.

Last step is to remove the dop stick and wax. Using a small knife slide it along the rock/wax surface and pop the wax off. Remember to recycle the wax and dop dowels as they can be reused over and over again.

Lapped and Faceted Lapidary Processes

Since these lapidary techniques are more advanced and typically not meant for the lapidary hobbyist, I will not get into them more than I have already.

Rock Hardness

Rock hardness is determined by comparing them to the Moh's scale of hardness. This is a one to ten scale with one being the softness and ten the hardest. Here is the scale:

Diamond 10

Corundum 9

Topaz 8

Quartz 7

Feldspar 6

Apatite 5

Fluorite 4

Calcite 3

Gypsum 2

Talc 1

Some of the common gemstones you may work with compare as follows:

Agate 7

Amethyst 7

Carnelian 7

Emerald 7.5 to 8

Garnet 7 to 7.5

Lapus Lazuli 5.5

Malachite 3.5 to 4

Moonstone 6

Opal 5 to 6.5

Tigers eye 7

Turquoise 5 to 6

Since most of the grinding wheels and sanding belts have a form or corundum on them as cutting surfaces, you can see why some stones will not work up well without moving up to diamond cutting and polishing equipment. They are just too hard.

Home Business Opportunity

So, can you turn lapidary into a money making hobby? The answer is yes you can. A number of years ago I purchased all of the equipment and a bunch of turquoise slab material and after work and weekends made up cabochons which I sold to a variety of jewelry makers. If this is your goal, I recommend checking out how you might sell you product. There is always ebay and where you will find such items currently for sale. As usual, some stones sell better than others.

Another reason to get into lapidary is if you make, or want to make jewelry. Lapidary perfectly complements a jewelry making hobby and together make an even better money making opportunity.

Other descriptors include hobby ideas, craft ideas, find a hobby and fun hobbies.

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