A Garnet for Gaukler

Hand-faceting a stone in 14th century style for a Master's replica project.

The finished stone

An octagonal, simply faceted rhodolite garnet, cut by hand

Master Gaukler's complete brooch

Gilded silver with pearls, rubies, sapphires, and my garnet

For more information on the complete object, see Gaukler's post about the piece.

I have a particular fondness for the Colmar Treasure; a collection of coins and jewelry from the mid 14th century discovered hidden in a wall in the town of Colmar, France. Abandoned by a Jewish family before they were killed under the suspicion of spreading the Black Death, it was unearthed by construction workers in 1863 and eventually came to be housed in the Musée de Cluny. It’s an illustration of the growth and success of the family, as the items range from very plain rings with glass gems, to a gorgeously elaborate gilded and begemmed brooch that is the centerpiece of the collection.

I’ve made replicas and recreations of several different pieces from the Treasure, half a dozen rings and a somewhat simpler version of the brooch. As I developed the brooch project in particular, I became acquainted with Master Gaukler; we spent many hours discussing 14th Century jewelry and techniques at his stall at Pennsic. I learned a great many things that I could improve if I ever reattempted the brooch, and got access to a wealth of additional research materials for my lapidary undertakings. And since I specialize primarily in stone cutting, we agreed to partner in the future if he ever needed a specific gem for any of his projects.

Well, last fall he informed me that he was working on his own recreation of the classic brooch and needed a center stone. The cabochons and pearls were simple enough to source, but the center stone is a very old style of faceting that would be extremely difficult to find commercially. However, it was the perfect occasion for me to attempt a more historic style of gemcutting. I happily took up the challenge and the opportunity to contribute to such a project.

The Brooch itself: design and details

The brooch features mostly irregular cabochons of ruby and sapphire, each somewhat cloudy with inclusions and set in what Jack Ogden's "Jewelry Technology in the Ancient and Medieval World" describes as "pie-crust" settings. These cabochons are accentuated with pearls pinned onto the backing.

The centerpiece, however, is a deep red garnet of high clarity, simply faceted, and held in a claw setting. Originally, I (and the gallery book from the Met!) had entertained whether this was a post period replacement from some time in the ~100 years that the brooch was held in private collector hands. However, additional research into other contemporary pieces has presented me enough occurrences of similar work that I no longer believe it was a post period replacement, just a style that was only beginning to be used. By the 15th Century, stones cut in similar ways were rampant, and this piece might just have been ahead of its time.

Image Source: The Met Museum

Brief gemstone terminology interlude

Each feature of a faceted gemstone has a specific name that will make discussion of the design more straightforward. For the unfamiliar, they are:

Table - the large flat facet on the top of a gemstone.
Crown - facets that make up the upper half of a gemstone
Girdle - the "belt" of facets that divides the gemstone into halves.
- At this point in history, the girdle often is not specifically cut but instead follows the natural outlines of the stone. See the irregular garnets and sapphires in the brooch's cabochons. If the girdle is geometric, it's often because the rough crystal had existing flat edges.
Pavilion - facets that make up the bottom half of a gemstone.
Culet - a single flat facet on the bottom of the pavilion.
- Not commonly seen in modern gemstones, this is thought to be done to reduce the likelihood of breaking off the otherwise sharp point.

Detail shot of the Colmar central garnet. Three key features observable here:

soft rounding on the upper edges of the girdle facets, implying no crown facets and only a single large table. This is likely a result of an existing large flat portion on the original rough.
clear facet edges in the pavilion, especially in the bottom left of the image, suggest a single tier of pavilion facets: one facet per side of the octagonal girdle outline
texture visible in center of the stone suggests a large culet, which might even be the original rough surface of the uncut stone.

While examples of truly faceted stones are rare in the 14th Century, some contemporary examples do exist. Here, we see a similarly cut sapphire in the crown of 14th-Century Princess Blanche of Lancaster, recorded in the inventory of Richard II in 1398. The outline follows the natural shape of the sapphire crystal, which can grow in this octagonal tablet shape.

Looking in the bottom left of this gem, we can see one tier of crown facets leading into a very large table. Especially on the left-most edge, a pavilion facet is visible similarly to the single tier of pavilion in the Colmar brooch. Finally, the reflections don't indicate that the pavilion facets converge to a single point, indicating a somewhat large culet.

Also, note the similarity in setting to the Colmar gem. It was this object in particular that has led me to rescind my suspicion of the Colmar garnet being a postperiod replacement, as it contains multiple tablet cut sapphires mounted this way.

Source: "Crowns in the treasure of Richard II". The Institute of Historical Research and Royal Holloway, University of London, 2007.

Tools and Methods

Actual depictions of faceting equipment prior to the 1600s are very few and far between. I have found no images of any faceting equipment that are actually dated within the 14th Century itself, the earliest being the mid-1400s.

However, the principles of the faceting machines described for most of the period are fairly consistent: A lapidary turns a hand crank which drives a metal disc, upon which abrasive medium is sprinkled. Water or oils are used for lubrication, and gemstones are pressed against these discs by hand to achive shaping and polishing actions.

Image Source: Volmar's Das Steinbuch (1489), digital redrawing by Justin Prim

Modern Tooling, Identical Function

While eventually I do have plans to build my own version of a 16th-century hand-cranked lapidary bench, at this moment I have not done so.

Instead, I will be using my modern UltraTec V5 for this project. I won't be using all of it, though.

A significant portion of the modern complexity is contained in the mast, the black upright portion of the tool on the right side. It consists of the precision adjustment tools for controlling angle, rotational index, and depth of cut.

Without those, it's essentially nothing more than an electrically driven version of the Steinbuch illustration: a disc-shaped cutting lap, powered by a small motor in the housing, plus a water feed for lubrication.

Image Source: UltraTec Website

Cutting and Polishing Media

In terms of cutting media, I am also skewing more modernly on this project. The main cutting was done on the left lap, a sintered bronze material imbedded with 600-grit diamond powder. Polishing used the right lap, pure copper with 8,000 grit diamond paste. While diamonds were used as a cutting abrasive, the regularity and fineness that I have access to is certainly far greater than they could imagine.

Theophilus' On Divers Arts (1122) describes gems being shaped and smoothed on sandstone, with polish coming from ceramic powder and oil on a lead plate, with final buffing using ceramic powder on leather.

Later, we see the sandstone replaced by emery powder, with laps made of copper, tin and lead used in various combinations, all mounted on various horizontally-rotating platforms similar to the prior machines. Eventually, by the 1600s, we see frequent mentions of diamond dust used for cutting as well.

Sources:

Codex Latinus Monacensis 197, 1430
Gemmarum et Lapidum, Anselmi Boetii de Boodt, Prague, 1609
"Des principes de l'architecture, de la sculpture, de la peinture, et des autres arts qui en dépendent: avec un dictionnaire des termes propres à chacun de ces arts," Félibien, André, 1697

Work-holding Methods

Both Theophilus and Félibien describe using adhesives to secure gemstones to some kind of handle to make the gemstone easier to manipulate during cutting. Theophilus specifies using chaser's pitch and a wooden rod, while Félibien recommends something akin to resin for the same purpose. In modern lapidary arts, the traditional material is a stiff hard wax, and the process is called "dopping".

I prefer using a modern resin superglue, which I can set up and position the gemstone freely and then set the resin nearly instantly with a UV light. I benefit from being able to freely reposition the stone and also have the speed of setting, but the principle is the same. Instead of a wooden rod, I mounted the gemstone of the brass dop sticks I use with my UltraTec. The black stick is a Delrin rod that is bored to accept the dop.

This gives me a longer handle to work with and also lets me remove the gemstone by heating the brass dop in an alcohol burner to soften the glue when the stone is finished.

Initial Shaping

To begin, I used the 600-grit lap and a slow drip of water. Initial cuts were made while holding the stone parallel to the dop and cutting the largest square I could out of the original oval shape of the stone. This helps me maximize yield.

Next, I used the corners of the square as references and carefully ground them away until I had the desired octagon shape. This completed what would be the girdle of the finished stone.

To place the pavilion facets, I braced my hand at an approximate 45° angle and cut them down until they met the girdle. Each time I removed the stone from the lap to check progress, I stopped the lap and placed the facet back down flat, making sure to re-find the face I had been cutting, then turned the lap back on. This helped me minimize miscutting, though that did happen a lot.

Once the pavilion was completed, I held the dop perpendicular to the lap and gently cut the culet down until I had about the right proportion I observed in the original stone.

As someone used to being able to specify very precise angles and immediately return to them over and over, this extra care required was a challenge. It did, however, connect me to the cutting process in a way I had never been before. You really get the sense of how this was a craft that would take years of practice to develop the physical sense of where you were cutting instead of using external measurement tools. It was a fascinating sensation, honestly.

Polishing and Adjustments

I did the polishing of the stone on the copper lap charged with 8,000 grit diamond paste. The principle was the same as cutting: on a stationary lap, position the facet in contact with the lap, then turn it on slowly and hold the stone steady while sweeping it back and forth. To check my progress, I stopped the lap from spinning and wiped it with a cotton cloth before restarting the process. I started with the girdle, holding the dop parallel to the lap as before.

After the first pavilion facet, I actually found it easier to remove the gemstone from the dop and hold the stone directly with my fingers. Since my geometry was already set, the longer handle interfered with my ability to do the more important job of making sure I was precisely returning to existing facets. I got that feedback far more easily when holding the gemstone itself.

The culet was polished by holding the stone to the lap with my finger, then I flipped it over to polish the flat table facet the same way. I did end up re-dopping the stone to round the edges of the table to create the soft pseudo-crown facets. These were done entirely on the 8,000 grit lap since the amount of material removal was so small.

Afterwards, I cleaned any residue from the gem with alcohol, and it was finished!

Unexpected Insights: Why the hand crank?

I have wondered for some time why, in both De Boodt and Félibien's texts, hand-cranked lapidary wheels are shown in the same workshop as treadle-powered engraving machines. Why, I wondered, were the lapidary wheels not powered in a way to allow the artists to use both hands? Clearly the technology was known, and even used by the same people!

This experiment showed me what I suspect is the answer: Control.

To accurately register a facet onto the lap, the lap must be stationary. I discovered that when I turned on my electric motor, it "jumped" to a minimum speed and sometimes caused me to lose the facet (as can be seen by the bright triangle reflection in the above image).

A treadle powered tool would have a similar initial jerk before a smooth speed can be achieved, which would inevitably lead to frustrating errors. A hand-powered wheel could both be used for smooth and continuous cutting, or very slow, very gentle motion that could be perfectly matched to the needs of the cutter as the cut progressed.

This kind of physical discovery that makes no sense to someone only observing, but becomes immediately apparent to anyone trying to actually do the craft, is probably the most enjoyable aspect of all my lapidary research.

Finished Gemstone and Comparison to Extant

Overall I'm extremely pleased with the final outcome! I think the finished product is as similar as I could possibly have achieved, at least with my limitation of never actually having seen the extant piece. There are a few assumptions I made about the shape of the stone, which someday I hope to be able to validate in person.

The experiment was also a rousing success in terms of practical insight to what the cutting process might have been like for medieval artisans. While I do intend to continue to remove modern conveniences from the process and get closer to the original methods of work, I am content with this as the current level of authenticity.

My deep gratitude to Master Gaukler for the collaboration offer! It was an honor and a pleasure to be a part of this project, and I look forward to more in the future!

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