My New Toy

August 25, 2019

by Duncan Miller

A few months ago I bought an Imahashi faceting machine, Faceting Unit Model FAC-8C, the earlier of two models. This one dates from 1970, co-incident with when I started faceting. Sometime during the 1970s my father owned one briefly, but I took no notice of it then. Now it intrigued me, because it is a platform machine, unlike the more familiar mast machines. Platform machines have several attractive features. You can lift the entire handpiece free of the machine to inspect the stone, and the smaller quill assembly is more stable when cutting low angle crown facets. This model Imahashi also has an ingenious system of replaceable cams that allow you to preform ovals, marquise and pear-shaped stones to specific length/width ratios. Not only that, but the mechanical cam system enables you to set the angle for any one tier of facets, say the crown mains, only once; then as you work your way around the index settings the angles are adjusted automatically for the rest of the facets of that tier. This facilitates and speeds up the production of standardised brilliant cuts in these low-symmetry shapes. So far I haven’t used the cam system, but cut a standard round brilliant in smoky quartz, just to get a feel for the machine. This model Imahashi doesn’t have a cheater and the dops are not keyed, so alignment after transfer and polishing can be tricky.

A later model, FAC-8P, doesn’t have the cam assembly, but it does have a cheater. This was developed in response to requirements of professional cutters who wanted greater flexibility in the indexing, especially for re-cutting gemstones. Justin Prim has documented the history of these developments and how they revolutionised gem cutting in Sri Lanka (https://medium.com/justin-k-prim/the-mo ... 94a5a504c3). Justin is a faceting historian and has described the operation of various other faceting machines in his World of Faceting Machines YouTube videos:

https://www.gemologyonline.com/Forum/phpBB2/viewtopic.php?f=8&t=24388&sid=d26b305d3cd54942497e079f0cf95fcf.


Imahashi faceting machine FAC-8C


Head of the Imahashi machine with the stainless steel cam system to cut an oval


Imahashi handpiece sitting on the platform


Smoky quartz, 15 mm, cut on my ‘new’ machine
 

Return to Tubussis reveals Surprise

August 25, 2019

by Mandy Freeman

During one of the excursions arranged at the 2019 Gemboree, a group of enthusiasts decided to split from the main convoy to return to Tubussis to spend a little more time looking at what this tiny village has to offer. The Green Dragon Mine is located near to Tubussis, and the area is known for good quality demantoid or green garnets. One of the vendors had laid out tables, which due to time constraints, the convoy missed on the first visit, and some very nice aquamarine spe...


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Rocking the Richtersveld 2019

August 25, 2019

‘Oh, oh, oh,
matchbox full of diamonds
pocket full of rain
I'm as happy as a hotel in the springtime
when the flowers bloom again’

David Kramer’s song about the Richtersveld starts on the road to Lekkersing: “O ja, vanaand stap ek alleen op die pad na lekka sing.”

It came bubbling into my brain the night we were briefed that we would be on the road to Lekkersing the next morning, deep in the Richtersveld, deep in diamond country, and it all seemed to make a new kind of sense. We w...


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FACETIPS

July 24, 2019

By Duncan Miller

How to teach yourself faceting, in three easy steps:

1.      Acquire a faceting machine. https://facetorsguild.com.au/About-Faceting-Machines

2.      Learn to facet. https://www.gemsociety.org/article/lapidary-fundamentals-gemstone-faceting/

3.      Become an expert. https://www.youtube.com/watch?v=oD6ZlNmtwmM&list=PLFIMjYf_BtnvaVZNQkHJ4ieF-v1fqPgqu&index=2

These are good introductory lessons for those starting out faceting, and perhaps don’t have access to a mentor or ...


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Southern African Lapidary Stones to watch out for: Botswana Agates

June 25, 2019


Willie Visser has had this Botswana agate for a number of years. Recently he decided it was time that he took the plunge to cut it, and he was amazed to find it was the most beautiful agate he had ever owned. He has called it “The Mona Visa”.

By coincidence it is exactly 10 years since he cut open another special agate and found a fish.
...
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Zultanite - A relatively new gemstone from Turkey

June 24, 2019

By Peter Rosewarne

My wife and I recently visited Istanbul for a few days on our way to Venice and beyond. An 11-hour non-stop flight on Turkish Airways from Cape Town International Airport got us there. Impressions of Istanbul were favourable; interesting, friendly, good food, clean and safe. We stayed in the Old City and did a lot of walking and had an obligatory tourist boat ride along the Bosphorus (East meets West). We visited the Grand Bazaar, the largest covered bazaar in the World with...

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Tanzanite

June 24, 2019
Duncan Miller

A tanzanite was re-cut last month by Duncan. The original stone was very lop-sided, with a shallow pavilion on one side, so there was considerable weight loss. The girdle is deliberately thick to retain weight and keep the finished stone over 5 ct.

 
14,6 × 11,1 × 7,3 mm; 8,67 ct before re-cutting



12,5 × 10,5 × 6,7 mm; 5,39 ct after re-cutting


...
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HYBRID DOPPING WITH WAX AND CYANOACRYLATE GLUE

June 24, 2019

Duncan Miller

Initial dopping requires a flat surface on your rough. Prepare a flat dop with a blob of hot wax on it and in the transfer fixture push this against another flat dop face to form a layer of wax a few millimetres thick. You can build this up with several layers if the stone you are going to cut is very heat sensitive. Clean the flat on your rough with alcohol. When the wax is cold, apply a small drop of cyanoacrylate glue (CA), position the rough on the dop quickly, and let the gl...


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Ye Olde English Spar Boxes – a Hobby Revived!

June 24, 2019
Lesley Andrews

During the nineteenth and early twentieth centuries a popular pastime among the mining population of Northern England was the construction of spar boxes. These were used to decorate their homes, and also to sell to make some extra money. Spar boxes were made up of various crystals (spar is the old name for a crystalline mineral) which were collected by the miners working in the lead and iron mines of the north Pennines and Lakeland areas.

My first encounter with spar boxes in 200...


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Rhodochrosites

May 24, 2019

Duncan Miller





These are the rhodochrosites (presumably from Hotazel) that I have been faceting, on and off, for the past two months. The ‘pink’ stones (on the left) are 0,65 ct; 0,68 ct; 1,46 ct; and 0,96 ct.  The ‘red’ stones (on the right) are 1,39 ct; 1,66 ct; and 1,71 ct. The rough was acquired more than twenty years ago as a small batch of broken and half-finished stones. A recent article about faceted rhodochrosite in The Journal of Gemmology inspired me to try to resurrect them...


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