from Familiar Lessons on Mineralogy and Geology, John Mawe, London, 1821

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 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

As we come into an era closer to our own, I felt I needed some help because there were more innovations in the 1900’s 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.

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.