Lapidary Technology Through the Ages: Laps and Polish

The Beginning

The story of the flat lap is essentially the story of faceting. Before the invention of the horizontally spinning flat wheel, all stones were cut on round water-wheel powered cutting mills or rubbed against a flat, stationary abrasive surface and were almost always cut as domed cabochons. This all changed in the early 1400s, when the artistic revolution of the Renaissance kicked off in Europe and technology and its associated ideas started to transform.

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.

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

Our next stop in history is Prague. In 1575, Rudolph II sets up his court in Bohemia which ends up being a very important place, not only for gem cutting, but for science, the arts, and philosophy. Rudolph was very interested in the new thinking of the time, and the Renaissance thinkers had some big ideas. One of the important families that he was able to persuade to live at his court was the famous gem cutting dynasty from Italy, the Miseronis. He invited Dionysio Miseroni to run his gem cutting and jewelry workshop. Bohemia had just begun to mine its famous garnets, so there was plenty of work to do. We learn from the Codex Latinus Monacensis that the master cutters in Venice were using the hand-cranked faceting machine that we saw above, so it's likely that a descendent of this faceting technology came with the Miseronis from Italy. By the time it arrives in Prague, it looks very different than it did in 1439. We have a manuscript from 1609 by Anselmus Boetius de Boodt, a teacher, astronomer, and alchemist, who was Rudolf's personal physician and also in charge of Rudolph's cabinet of minerals.

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. It 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 than diamond powder, but more readily available and much cheaper.

A hundred 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)

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." It 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

I have to take a moment to speak about what was going on in Germany at this time. The major cutting center of Germany is Idar-Oberstein, and they held on to ancient stone cutting practices for longer than anyone else in Europe. Idar-Oberstein started cutting stones on waterwheel-powered cutting mills towards the end of the 1200s. The work was hard and slow and back breaking. Before the existence of a flat spinning wheel impregnated with diamond powder, there was sandstone. Giant sandstone wheels were turned by the force of a running river. Sandstone, an organic abrasive made of quartz grains held together in a natural cement, was probably the earliest abrasive in history. For reference, sandstone is a 6-7 on the Mohs scale of hardness, whereas emery is between 6 and 9, depending on its specific mixture of corundum, spinel, and other minerals.

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 1870s when Bohemian technology came to Germany and Idar-Oberstein adopted the hand-cranked machine technology similar to the rest of Europe.

Industrial Revolution

The coming of the French Revolution and the Industrial Revolution brought a lot of changes for the lapidary trade and for lapidary technology. We see a lot of improvements in the cutting machines and in the cuts of gems. John Mawe provides us a great illustration of a portable faceting machine, and on the left, we see a pile of laps, or mills as they were called at the time.

In the accompanying text, we discover what they were used for:

Polishing is performed by a mill made of pewter. Whilst the left hand is employed turning, the right applies the stone to the surface of the mill, which is charged with emery, and kept constant wet by brush. When the surface is sufficiently worn down, the lead mill may be displaced and the polishing mill erected; it must be charged with rotten stone or tripoli with a little water. A feather from the mouth supplies oil. (Mawe, 1813)

A few years later, Mawe released another book with even more information on laps of the time:

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 1600s and the 1800s. We must also consider that modern crystallography studies really bloomed in the late 1700s and early 1800s, 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.

Later on in the century, we learn from Charles Holtzapffel in his book Turning and Manipulation that

Notwithstanding the apparent expensive of the diamond powder, 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 1860s might have had to go through in order to cut and polish on the same machine. Considering that the faceting machine of the mid 1800s 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.

Modern Era

As we come into an era closer to our own, I felt I needed some help because there were more innovations in the 1900s than in the previous 400 years of lapidary history. I was lucky enough to be able to call upon Jon Rolfe and Thomas Smith, very much the leaders of innovation in the faceting industry today, to help me piece together the tale of the 20th century.

Coming into the 1900s, 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 than 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 1930s, 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.

Twenty years later, the introduction of diamond sintered laps solved this problem. A patent search leads me to believe that Paul Blackmer invented the first sintered metal bond diamond wheels in 1954, 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.

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 monocrystalline 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 1970s, 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 it 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.

As we approach the end of the 20th century, into our story enter 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

Thomas Smith had a natural propensity for math and sciences and began faceting colored stones, and later diamonds, after he finished college. In the early 1980s, dissatisfied with the technology available at the time, he started to experiment with homemade polishing compounds. He talked with other hobbyist cutters to get ideas about what people were using to polish gems and what they liked and disliked.

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 of 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 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!

Around this time, a few customers were asking Jon to make wax laps for polishing very soft stones. Instead of 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 we entered the 20th century, the world of gem cutting technology made very few innovations since its inception in the early 1400s. Essentially, the lapidary would take a piece of metal of varying hardness (lead, tin, or copper) and apply oil or water mixed with an abrasive (diamond powder, emery powder, or an oxide) in order to cut and polish the gemstone. This was the only method of cutting stones for 500 years. As the industry developed new methods of creating abrasives, the gem cutting community adopted diamond embedded laps and diamond sintered laps which, for a time, completely replaced the old techniques of cutting in the West. Then as the 21st century arrived, with the help of innovators like Gearloose, Adamas, and a handful of others, a smorgasbord of new products arrived to compete with and eventually replace the old technologies.

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.

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 for polishing.

In Idar-Oberstein, lap technology has improved since the water-wheel powered millstones of olden times. When I visited a workshop there in 2017, I saw many machines using sintered cutting laps and copper laps for polishing. In France, lapidaries have used hand-cranked machines with big 20″ copper laps for hard stones and tin laps for softer stones since the 1800s and still use them today, though electric machines sit right beside them with diamond sintered laps for cutting.

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 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

Special thanks to Jon Rolfe (Gearloose Lapidary, LLC), Thomas Smith (Adamas Instrument Corporation), and Sébastien Hourrègue, who provided crucial information to the author during the writing of this article.

This article, with contributions by Jon Rolfe and Thomas Smith, was originally published in the US Faceters Guild Newsletter, September 2018, and has appeared on Medium.com.

The International Gem Society would like to thank Mr. Prim for giving us permission to post his article here.

References

Arnaut, H. (1439) Treatise of Henri Arnaut de Zwolle, Bibliothèque nationale de France, Paris (ms. 7295, for 137, Manuskript Arnold)

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