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one man and his tumbler
Prior to becoming immersed into the extended world of stone polishing and lapidary I’m afraid I was guilty of a little snigger when I heard of folk spending weeks tumble polishing stones.
Not a complete novice to the tumbler having left many items of jewellery to rotate overnight but stones are a different matter.
After seeing a 2nd hand tumbler for sale, a rare thing being of the two barrel variety and not a common educational aimed device that can appear a little work shy. My tumbler had also hardly been used, perhaps the realisation of how long the process can take or a room not far enough away as the incessant tumble sounds began to fray nerves.
Having the tumbler and all the grits and powders in one go is just too much temptation to not start immediately. Barely able to read the instructions consecutively I was suddenly on my knees scrambling around looking for rough, I was not going to make that newbie mistake of tossing a handful of rough in just to get going, only realising later they had a mixture of harnesses and there seemed only to be a couple of stones left and a lot of grit!
No I was just going to get the nearest rough I could find, that turned out to be fluorite, predominately blue, put by sometime ago when I thought I could sell it to proper lapidarists, assured that it was from a batch used by overseas cutters. Selling to local lapidarists is a tricky art but? I digress… In went the stone, oh yes not too full, cover in water not less than 2/3 not more than 3/4 (why isn’t there a line!) and how much 80 grit, I don’t had a tablespoon to measure, I could get one but that would take valuable minutes rushing to the kitchen, time I could ill afford to spare. Yes that looks enough, perhaps just a little more oops..
How did I unfasten the end of the barrel, where did the rubber ring go and locking nut, having several barrels helped here. Then switch it on, oh that’s a bit loud, out into the garage, well that’s it I’ll check later, hmm I’m sure it’s ok to leave on unattended, a few hours later I peeked through the window – all looked good.
First thing in the morning, no change, after a visit to the office, yep that sounds like its doing it, this went on for a few days, after 4 I was supposed to examine and recharge with grit unless the stones looked in good shape, which they did.
Out into the garden hose , plastic tubs wash then off hold up to the light, wow I may have potential here, off to get a rag, taking a second glance at the stones (now sun dried) they looked like more work was need. Onto stage 2, get everything clean, stones water, 220 grit this time, not another week well here goes.
A week later, the next stage was to repeat the last one arggh… but I did check them before time, knowing that disturbing the ‘rotating’ could delay tumbling for a few hours whilst the contents find the optimum position within.
Finally the polish, and a smaller barrel because somewhere along the line they’d all shrunk, what I’ve yet to mention is that I had chosen or the first rough I had found was fluorite and I looked it up for some advice, well I did have a few weeks to wait.
Everyone mentioned how tricky fluorite was and had different even bizarre methods or tips for tumble polishing it. Here’s an appropriate time to mention that whilst the internet is a wonderful resource for some many reasons, very little information is edited, checked for authenticity and outright truth. Luckily (ahem) I just went with intuition. After a couple of checks I felt a certain apprehension, convinced that the stones were reducing in size but the actual appearance wasn’t improving I decided to stop!
Not sure whether to be pleased with my initial efforts, no fanfare sounded as I held up the freshly washed stones to the light, but I think they looked good. So did the wealth of folk I tried to thrust them in front of at any opportunity. Always having some stones in my pocket I spent several days feeling like a tumbler myself. Finally after compliments from the actual supplier of said stones who also commented on the difficulty of polishing said fluorite I accepted that I’d done a good job or was that just beginners luck!
Now what other rough do I have?
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Plucking some rough from the ever growing piles is no doubt fun at times but also an increasing weight to bear, creating a space just shouts louder for more finds & purchases to fill, this green and yellow agate called loudest, perhaps gaining in popularity,
it seems to have adopted the name of the mythical singer orpheus from the (same region) Rhodope Mountains Bulgaria which was first given to the mineral Hinsdalite, nevertheless this agate is found with celadonite(silicates of manganese, iron, potassium)
and brown, yellow jaspers, with it occasional clear or dendritic areas it can produce wonderful landscapes.
by Ron Willis
I am the proud owner of an Australian Robilt faceting machine, which I bought from a friend who
never really got started - that was in 1970. Since then I have suffered humiliation, frustration,
hopelessness, personal damage and insufferable anger. Not one perfect gem has come off that
machine since it has been in my possession.
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lapidary in ancient egypt
Beautiful gemstone artefacts span the history of Ancient Egypt. However, surprisingly little is known of Egyptian lapidaries and their work.
Experiments by an engineer called Denys Stocks showed that the copper and bronze chisels of the time could only effectively cut soft stones without causing damage to the tool.
Gemstone material can also be damaged by pounding with hard rocks or meteoric iron, so it has been difficult for Egyptologists to work out how semi-precious stones (such as those found in the jewellery of Tutankhamun) were shaped.
However, a discovery that an ancient lapidary wheel was first used in Mesopotamia (modern Iraq) around 1750-1595 BC suggests the Ancient Egyptians may too have used lapidary wheels. I put some Egyptian objects under a microscope to try and find out.
Microscopic Examination of Egyptian Objects Under the microscope, stones shaped by hand look different to those shaped on a wheel. Hand abraded stone appears as a mass of lines of various thicknesses, some going in different directions, along with the presence of pits.
Wheel abraded stone appears as sharply defined, parallel lines in a single direction.
An amethyst cabochon from an Egyptian ring under a microscope showed characteristics of stone which had been abraded away by hand. These included a mass of lines of various thicknesses going in different directions, along with the presence of pits.
However, a lapis lazuli beetle from an Egyptian gold bracelet (shown above right) suggested a strong probability that the stone was worked against a wheel. Tool marks made by wheel and those made by saw (cut more deeply into the stone) can appear similar. However, the location of the marks
on the beetle’s domed and polished wing case and their feint appearance indicate wheel rather than saw markings.
Looking at the object under the microscope also revealed that the craftsman had not fully flattened off the beetle’s base – perhaps because it would be disguised by its adhesive/gold setting.
Examination of turquoise and lapis lazuli in an Egyptian bird pendant (shown below) indicates that the gemstone has been sawn to size. A wheel may have been employed in shaping the stone or used against the stone surface to make saw marks less visible.
The dates of this jewellery suggest a strong likelihood that a lapidary wheel was used by Ancient Egyptian craftsmen by at least around 1400-1308 BC. The wheel is likely to have been driven by a bow (ancient tomb paintings show jewellery workers using bow drills). The Ancient Egyptians had early knowledge of wheel technology and access to all the raw materials for making and operating lapidary wheels. These included beech and cork woods, copper, leather, cloth and beeswax. They also shared technologies with Mesopotamia at this time.
Abrasive grits such as sand and garnets
(plentiful in Egypt and harder than quartz) are well known as effective abrasives in modern lapidary. Other stones such as flint and agate are also likely to have been used for abrasive purposes.
Under the Microscope :
Looking at semi-precious stone objects under a microscope gives a fascinating insight into the work of Egyptian lapidaries.
A small carnelian cat forming part of a gold ring was shown to be at the high end of craftsmanship and highly polished.
Looking at the carnelian under a microscope shows that leather is likely to have been used in the polishing process and that the base has probably been worked on a flat lapping wheel. A hand tool has been used to carve the cat as well as an Egyptian sign (known as an ankh) under the base of the carnelian block on which the cat stands.
The carnelian in the area behind the cat’s front legs may have been drilled out with a bow drill and it is highly likely that a file has been used to work the area. The worker does not appear to have been able to reach inside the area to polish it.
Due to the high level of polish on objects such as this, modern lapidaries suggest that diamond as an abrasive formed part of the polishing process. However, there is a complete lack of evidence for precious gemstones (such as diamonds, rubies and sapphires) in Ancient Egypt at the time this jewellery was made.
The Ancient Egyptians traded with Afghanistan for lapis lazuli from the fourth millennium BC. However, trade between India and Afghanistan was known long before this (as far back as the sixth millennium BC).
It seems possible that India’s diamond bearing source rocks may have been obtained by panning rather than mining, so may have entered Egypt via the Afghanistan trading route. Ancient Egyptians seem to have preferred colour rather than ‘sparkle’ in their gemstone objects and their semi-precious stones were unfacetted. This may account for the absence of diamond objects in early Ancient Egypt and support a view by an Egyptologist called Flinders Petrie in 1884 that diamond was used as a tool rather than ornament.
Other Lapidary Tools
It is highly likely that Ancient Egyptian lapidaries adopted a system of sand panning, extracting minerals to create stone working abrasives. Early Egyptian stone working tools probably had multiple functions. A bow drill for instance, can be used for drilling, to hold stone whilst it is ground or to form part of a tool to hold a gemstone cutting wheel.
The bow can also be transformed into a saw by stringing copper wire across the bow, charging it with abrasive and working the tool back and forth against a gemstone. As well as the likelihood that a file was used in Egyptian lapidary, a flint point used with abrasive makes an effective tool for sketching designs on semi-precious material.
Acknowledgements: With special thanks to master gem cutters Debbie Goldsmith and Peter Martin. Thanks to the following for contributing to my research : Peter Hurst (North West lapidary and Mineral Society), Graham Scarr and Dave Black (Peak District Lapidary and Mineral Society), Martin Stolworthy (Norfolk Mineral and Lapidary Society), Tony Mitchell (Medway Fossil and Mineral Society) and David Whipp. Thanks also to Sidcup Lapidary and Mineral Society, Elsie Hansford, David Bryant, Egyptologist Suzanne Lax-Bojtos and the Department of Ancient Egypt and the Sudan at the British Museum.
About Andrea Whytock:
I am interested in ancient civilizations, minerals and gemstone working. The information in this article is taken from my Master’s Degree dissertation: ‘Getting Stoned in the New Kingdom: An Exploration of Ancient Egyptian Lapidary Practices’ which I completed in 2012.
HOW TO CUT TOURMALINE
Tourmaline is to me a truly fascinating gemstone. I am attracted by the wide range of colours in which it occurs and by its property of dichroism which can lead to even greater variety within the same stone. Don't worry about the term dichroism if this is new to you. Any gem crystal that is dichroic has a structure which absorbs light differently depending on which way it passes through. This property is only
significant optically from a cutters point of view. A piece of tourmaline without obvious physical problems will cut and polish well in any direction, but looking at how the light is behaving gives us some choices as to how the finished stone will appear.