Lapidary Technology Through the Ages: Laps and Polish

Justin K Prim
Oct 7, 2018 · 20 min read

written by Justin K Prim with contributions by Jon Rolfe, Gearloose Lapidary, LLC and Thomas Smith, Adamas Instrument Corporation

Originally Published in the US Faceters Guild Newsletter, September 2018

Whether we are competition cutters, hobbyists, or professional gemstone faceters, there is one thing that ties us all together and that’s our usage of lapidary cutting and polishing wheels, known as laps, and the various compounds we put on the laps to cut and polish a gemstone.

The idea for this article came about during my research on the colored stone faceting machines of history. Every time I would find a new illustration it would be accompanied with a description of how the machine was used and what laps were used with it. I was fascinated to discover that the early lapidary technology was not as different to our current tools as I would have imagined.

The Beginning

History remembers Flemish diamond cutter Lodewyk van Bercken as the inventor of the horizontal diamond wheel (or scaif in diamond cutting terminology) in 1476. Under close scrutiny though, it seems that Lodewyk might have been mistitled because we have two illustrated representations of early faceting machines in manuscripts of the era. Henri Arnaut, one of the most learned and well known medical astrologers of his century, left us an incredibly detailed drawing of one of these machines in 1439. In a German manuscript called the Codex Latinus Monacensis, 40 years before Bercken, we see a crude drawing of the same kind of machine, so it seems likely that Lodewyk van Bercken was not actually the “father of faceting” that we were lead to believe.

from the Treatise of Henri Arnaut de Zwolle, Netherlands, 1439

This technical drawing tells us that the instrument was used to “polish precious stones, the fragments of which are well-suited for medical use.” (Arnaut, 1439, p. 136) It doesn’t say much about the laps but luckily in the Codex Latinus Monacensis, we learn that “it requires three polishing disks, the first is lead, the second is tin, the third is copper.” (CLM 197, 1430, pg. 48) This is incredible to me because, though I don’t have a lead lap in my collection, I do have a tin and a copper lap that get regular use in my machine. It seems that in 588 years, technology hasn’t changed too much. Let’s delve deeper and see what we find.

Developments in Prague

from the Gemmarum et Lapidum, Anselmi Boetii de Boodt, Prague, 1609

De Boodt tell us that Through a rope, the wooden wheel moves a tin wheel, on which water mixed with emery powder is sprinkled.” (Boodt, 1609, pg. 38) We not only see a continued use of tin but we also get an idea of one of the abrasives they were using to cut and polish colored stones.

Emery, which we see most often referred to in old lapidary manuscripts by its Greek name “smuris” means “to smooth” or “to polish.” Mineralogical analysis reveals that sapphire, ruby, and emery are very nearly the same substance. The sapphire contains 92% alumina, the rest being silica and iron oxide. The ruby contains 90% alumina and common corundum contains 91% alumina. Emery contains 86% alumina, thus very close to the other three and having, like them, only two other components besides alumina. Emery has been written about for its abrasive properties since Pliny the Elder, 2000 years ago. Emery is an effective abrasive because its extremely hard particles wear away the protuberant parts of the stone more rapidly than they themselves wear away. Emery would have been slower to use to use than diamond powder, but more readily available and much cheaper.

A hunder years later, in one of the earliest compiled encyclopedias, the Dictionary of Arts and Sciences in 1728, we learn that “The oriental ruby, sapphire, and topaz are cut on a copper wheel with diamond dust, tempered with olive oil, and are polished on another copper wheel with tripoli and water. The hyacinth, emerald, amethyst, garnets, agates, and other stones are cut on a leaden wheel with smalt (emery) and water, and polished on a tin wheel with tripoli. Turquoise, girasol and opal, are cut and polished on a wooden wheel with tripoli also.” (DAS, 1728)

Tripoli Powder and Emery Powder

Now we see that not only are they using their spinning wheels with diamond and emery powder but also with a new abrasive called tripoli or “rotten stone.” Tripoli is a fine powdered porous rock used as a polishing abrasive. It is usually weathered limestone mixed with silica. Tripoli particles are rounded rather than sharp, making it a milder abrasive. Tripoli comes from various places including Brittany, in France, and Derbyshire, in England, whose residents refer to it as “rotten stone.” Tripoli also comes in different forms. “Hard rotten stone” occurs in detached nodular lumps, dispersed through large rock debris of limestone. The soft rotten stone occurs as a kind of spongy earth, either coating the more hardened variety or deposited in considerable quantities under the debris of limestone rock. Rotten stone is produced by the disintegration of a particular variety of limestone, probably a black marble. (PMSDUK, 1843, pg. 270)

Millstones

Sandstone Cutting Wheels in Idar-Oberstein. Photos by Justin K Prim

These type of cutting mills were pioneered for cutting agate and quartz. The wheels used no grit, only the friction of the spinning sandstone wheel against the stone. After the introduction of electricity in 1891, they developed smaller sandstone wheels against which they could free-hand facet stones. For polishing, they had a small wooden spinning wheel on which they would wet and brush on a home-made polishing powder, that included ingredients such as powdered slate or aluminum oxide. Each cutter had his own special recipe. They continued to cut stones like this until the 1870’s when Bohemian technology came to Germany and Idar-Oberstein adopted the hand-cranked machine technology similar to the rest of Europe.

The Sandstone Cutting Millstone and Wooden Polishing Wheel of Idar-Oberstein. Photos by Justin K Prim
from Familiar Lessons on Mineralogy and Geology, John Mawe, London, 1821

Industrial Revolution

“It is necessary to prepare a new polishing mill by scraping it with a knife, or rather holding the edge of the knife lightly upon the face of the mill, and turn it gently round both ways, which gives it a rough surface, and causes it to hold the rotten stone better. [The stone] should be washed and applied to the wood mill with flour emery, or fine sand and water, before it is polished on the pewter mill; after which, and finally, the cloth or list mill may be resorted to, which will heighten the polish, if necessary. There is another mill of copper or iron to be used with coarse emery, which will slit marble and soft substances (milk may be used instead of water). These are the mills generally used, but to render this apparatus more complete and amusing, three others are added- one is covered with cloth, and is intended to be used with putty of Tin and a little water. The mill covered with list [selvedge fabric] should be used with putty and water; it is useful in polishing substances with uneven surfaces. The plain wood mill may be used with sand or fine emery and water; it is applicable to various purposes, marble, spars, gypsum, or shells. It is necessary to state that the mills should be kept in nice order, clean, and separate from each other, as the smallest particle of emery would spoil the polishing mill.” (Mawe, 1821, pg. 103)

For a book written almost 200 years ago, the technology and techniques seem very modern, from the large selection of lap materials to the tip about keeping your laps clean. We can see that a lot has changed between the 1600’s and the 1800’s. We must also consider that modern crystallography studies really bloomed in the late 1700’s and early 1800’s, so this new understanding of crystal growth and crystal systems would have helped cutters to improve their craft and increase their ability to cut stones.

from Turning and Manipulation, Charles Holtzapffel, London, 1864

Later on in the century, we learn from Charles Holzapffel in his book Turning and Manipulation that Notwithstanding the apparent expensive of the diamond power, it is very generally employed… and although for this and some of the softer stones, emery, or in some cases even sand, might be successfully employed, the diamond powder is almost exclusively used, as it is found to the most economical, when the time occupied in the cutting is taken into account. The diamond powder cuts more rapidly than emery and it’s very much more enduring. Many lapidaries employ the same lead mill, both for roughing and smoothing the surface of the stones; some lapidaries however employ two benches for these purposes so that the work may be taken from the roughing mill to the smoothing mill, with out the loss of the time incurred in crushing the coarse emery quite fine, but when one bench only is used for the roughing and smoothing, the same lap is used to serve both purposes.” (Holtzapffel, 1864, pg. 1306)

Modern cutters can see how much work a lapidary from the 1860’s might have had to go through in order to cut and polish on the same machine. Considering that the faceting machine of the mid 1800’s would have been a large piece of furniture, it must have been quite an expensive novelty to have two machines. We definitely aren’t talking about hobbyists here. Anyone who could afford two of the costly machines would have definitely needed to make a good income from cutting to pay for their investment.

from the Encyclopedia Brittanica, 1875

Modern Era

from Gem Cutters Craft, Leopold Claremont, London, 1906

Coming into the 1900’s I found one last book entry that was helpful. From G.F. Herbert Smith, we learn that “In recent years the artificially prepared carborundum, silicide of carbon corresponding to the formula CSi, which is harder that corundum, has come into vogue for grinding purposes. To efface the scratches left by the abrasive agent and to impart a brilliant polish to the facets, material of less hardness, such as putty-powder, pumice, or rouge, is employed; in all cases the lubricant is water. The grinding laps are made of copper, gun-metal, or lead; and pewter or wooden laps, the latter sometimes faced with cloth or leather are used for polishing. As a general rule, the harder the stone the greater the speed of the lap.” (Smith, 1912, pg. 105)

In the 1930’s, manufacturers discovered how to plate diamonds onto laps and industrial flat-lapping starts to develop. This is important because from here on out, the technological advances of the industrial manufacturing industry would trickle its innovations into the realm of gem cutting in America and throughout the world. The introduction of plated laps meant that gem cutters no longer had to go through the effort of grinding diamond powder to their desired level of fineness and then mix it with oil and apply it to the lap. They could simply put the lap on the machine and start cutting. The downside of this was that the lap had a much shorter life; whereas the old copper or tin laps might last decades or lifetimes, the plated lap could wear down in months or years depending on how much it was used.

This problem was solved twenty years later with the introduction of diamond sintered laps. A patent search leads me to believe that the first sintered metal bond diamond wheels were invented in 1954 by Paul Blackmer and their introduction into the lapidary community gave cutters a new, long lasting choice for cutting laps. Now instead of months, a sintered lap which has a high amount of diamond infused all the way through the metal of the lap, could be used for decades. The tradeoff was that a sintered lap was much more expensive than a plated lap, making it potentially too costly for a hobbyist but a great investment for cutting factories.

Members of GE’s early 1950s Project Superpressure team. Courtesy of the H. Tracy Hall Foundation

Another important innovation in 1954 was when GE discovered how to synthesize diamonds for the first time. In a belt press, they made the first synthetic mono crystalline diamond. The ability to synthesize diamonds would change the cutting industry forever by providing an abundant and cost-efficient source of diamond powder.

The final breakthrough of 1954 was the creation of the ceramic lap. Invented at the Crane Packing Company by Don Berry and Don Hurst, the technology was developed in order to flat-lap cast iron seals for vacuum pipes. These seals have all kinds of industrial applications including nuclear power plants. They need the iron seals to be perfectly flat so that nothing (such as nuclear radiation) could leak out of them. This technology eventually found its way into the world of gem cutting: In 1973, David Miller and Leonard Thiel started using recycled ceramic computer hard disks to make ceramic laps for gemstone polishing. Ceramic laps are made of a mixture of aluminum oxide and ball clay and some cutters like them because they can cut a really nice, optically flat facet. The downside is that the facet edges are so incredibly sharp (even down to 100x magnification) that they can easily chip.

In the early 1970’s, another development in abrasives occurred when Dupont, an explosives company, thought “What if we take graphite and put it in a steel tube and blow it up?” To their surprise, the explosive process fused the carbon molecules together and they created the first polycrystalline diamond. As an abrasive, the advantage of polycrystalline diamond is that is has no cleavage planes so it doesn’t disintegrate as easily and it retains its particle size longer, so it lasts longer on the lap. Since it has no sharp edges, it rolls and polishes more easily. It wasn’t until the 21st century that polycrystalline diamond (PCD) started to be regularly used in the lapidary field.

Monocrystalline and Polycrystalline Diamond Powder Photos courtesy of Beijing Grish Hitech Co., Ltd and OFTechAbrasives

As we approach the end of the 20th century, into our story enters our celebrity innovators, Jon Rolfe (Gearloose) and Thomas Smith (Adamas Facet). Both of these guys have been cutting stones since their childhoods and both have extensive backgrounds in the sciences and mathematics.

Jon was a material scientist who was making his own lapidary materials to supplement his faceting hobby. After years of making laps with the historical materials that this article has already covered, he started to dream up new ideas for alloys that would improve the ability to cut and polish stones. He came up with BATT formula in 1997. He sent a few prototype laps to friends and cutters on the US Faceters Guild message board. The reaction to the lap was dramatic and Jon had to start working nights and weekends to meet the demands for his new lap. By lucky synchronicity, 1997 was also the year that the US Environmental Protection Agency decided to classify lead metal as a reportable toxic waste. Suddenly no lap makers wanted to mess with the metals used to make cutting laps because they contained a percentage of lead. Jon, who is an avid proponent of using environmentally safe materials had already designed his BATT lap to be lead free, so when other large manufacturers were pulling back from the lapidary industry, Gearloose was able to jump in and fill the gap with a brand new product. When I spoke to Jon he told me that in 20 years he sold 13,748 BATT laps worldwide, so I think we can all agree that his innovative tin alloy lap has had an effect on cutters and cutting culture around the world.

2000s and Beyond

During his research and experimentation, he discovered polycrystalline diamond (PCD). Around 1982, he called up Dupont, the only producer of the PCD and ordered a sample. He really liked how well it worked for gem cutting and he wanted to start using it to make new products. Unfortunately, PCD was very expensive and they only sold it in large quantities. Thomas was able to get smaller quantities from a distributor, so he started making his own cutting compounds with it. He continued to experiment and try new things, drawing upon both his scientific and diamond cutting backgrounds.

Let us fast forward to 2012. Thomas has just returned from a hiatus from the gem cutting world. He hears about Gearloose and gives Jon a call out of the blue. He tells Jon that he has the “magic bullet for quartz.” They agree to sign a non-disclosure agreement together and then the brainstorming sessions begin. Jon and Thomas on their own are incredible innovators and they understand the physics of cutting and polishing in a way that most people never will. Thomas’ innovations combined with Jon’s background and the fact that he owned a lap factory a few miles from his New England home meant that lots of new possibilities were suddenly available to the both of them. The meeting of Jon and Thomas was something of a cosmic trigger for the world of gem cutting and the innovations that followed are nothing short of spectacular.

Thomas’ first idea was using a proprietary Zirconium Oxide compound as a superior way of polishing quartz. This idea lead to the creation the Creamway lap and Zirconium Battstick and then later, the Skyway Lap.

After that, they developed a new type of ceramic composite lap called the Matrix. The Matrix is the most complex surface ever used for gem cutting. Jon explained to me that surface complexity is important in the calculation of friction, the management of the fluid film, and in determining how much energy is transferred to the polishing particles. All these tiny interactions happen between the nearly non-existent space between the lap and the stone. Jon told me that the complexity of its surface means that the Matrix is essentially a 10” lap ground into an 8” circle!

Micro-photos showing the complex structure of the surface of the BATT, BA5T, and Darkside Laps. Photos courtesy of Gearloose, Ltd.

Around this time, a few customers were asking Jon to make wax laps for polishing very soft stones. Instead of making creating a lap of wax,Thomas came up with a better solution which ended up being the Lightside lap. It’s a soft polishing wheel for stones with a hardness of 1–5 mohs that has become popular with specialty gem cutters.

At some point in their innovative frenzy, Thomas revealed his idea of using polycrystalline diamonds instead of monocrystalline diamonds to improve the speed and quality of the polish on stones. Jon quickly incorporated PCD into his existing diamond Diasticks and created a truly modern and hi-tech kind of polish agent.

A few years later, Jon would redesign his Diasticks again. He knew that Diamonds love oil and oxides love water and he wanted to exploit these facts and create the perfect hybrid polishing stick. After a long period of experimentation, he was able to create a new type of polishing compound that works for oil and water, which means that he is now able to just sell one type of polishing compound stick to all cutters that he calls the Pandemonium stick.

Our final innovation happened in 2017 when Adamas Facet debuted a new type of tribochemical polish. This new compound uses diamond powder or oxides plus either an alkaline or acid additive depending on which type of stone you are polishing. When you mix the base polish with the additive, the chemicals react together and chemically activate to create a slurry that speeds up polishing time and improves the surface finish quality of the stone.

Conclusion

As a new cutter coming into the trade in the 21st century, the choices can be a little confusing. In America, Gearloose products have become an industry standard for cutting and polishing laps, while overseas in Asia, the old technology still reigns supreme. In Thailand and Sri Lanka, two of the major cutting countries in the world, it’s very common to see people cutting on inexpensive diamond plated laps and then polishing on thick, locally made copper laps. I’ve seen the copper laps prepared by scratching them with the edge of an old plated topper lap and then applying the diamond powder/coconut oil mixture with a finger.

Bunter Machine with Dual Cutting and Polishing Wheels. Photo by Justin K Prim

In the European cutting cities, we see various techniques employed for cutting jewelry and watch stones. In Geneva, the Swiss-made Bunter machine uses a heavy duty sintered diamond lap for cutting and then a thick copper or tin lap is used for polishing. In Idar-Oberstein, lap technology has improved since the water-wheel powered millstones of olden times. In the workshop I visited in 2017, I saw many machines using sintered cutting laps and copper laps for polishing. In France, hand cranked machines with big 20" copper laps for hard stones and tin laps for softer stones have been used since the 1800’s and are still used today though electric machines sit right beside them with diamond sintered laps for cutting.

Diamond sintered cutting lap and copper polishing lap in Idar-Oberstein in 2017. Photo by Justin K Prim

What can we expect from the future of gem cutting? Will these new materials eventually eliminate the old ones? Will future innovations supersede the best tools that we have today? From my research and experience, I think it’s safe to say that the old and the new ways will continue to co-exist for a long time. Exporting American-made innovations has proved to be much more expensive than buying a locally made traditional copper and tin laps, so I think the gem industry will make do with what it can get the easiest and cheapest. For those that strive for the most pristine polish or the easiest cutting experience, Jon and Thomas have assured me that they are still dreaming up exciting ideas for new materials and advanced composites that will make cutting and polishing faster, easier, and more Earth-friendly.

Acknowledgements

References

Baynes, T.S. (1875)“Lapidary” Encyclopedia Britannica, London

Boodt, AB (1609) Gemmarum et Lapidum

Codex Latinus Monacensis 197, Bayerische Staatsbibliothek München, Clm 197, I. fol 23v (1430)

Chambers, E. (1728) “Lapidary” Dictionary of Arts and Sciences, London

Google Patent Search: https://patents.google.com/patent/US2828197

Holtzapffel, C. (1864) Turning and Manipulation, Holtzapffel & Co, London

Mawe, J. (1813) A Treatise on Diamonds and Precious Stones

Mawe, J. (1821) Familiar Lessons on Mineralogy and Geology

Broughman, F.R.S. (1843) Penny Magazine of the Society for the Diffusion of Useful Knowledge, Vol. 12, Charles Knight & Company, London

Schulz, W.G. (2004) First Diamond Synthesis: 50 Years Later, A Murky Picture Of Who Deserves Credit, Chemical & Engineering News

Smith, G.F. H., (1912) Gemstones and their Distinctive Characters, Methuen, London

About the Author

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Justin K Prim

The collected written works of Justin K Prim : Travel Adventurer / Gemologist / Musician / Author of The Heart of Merlin

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Justin K Prim

The collected written works of Justin K Prim : Travel Adventurer / Gemologist / Musician / Author of The Heart of Merlin