KYAWTHUITE, THE RAREST MINERAL, FOR NOW…

September 25, 2019

Duncan Miller


Reproduced by courtesy of the Natural History Museum of Los Angeles County

Every year, the International Mineralogical Association approves the names of many newly discovered minerals (http://nrmima.nrm.se//recentmin.htm). The requirements are stringent, involving analytical descriptions of both the chemistry and physical structure of any candidate new mineral. Most of these are microscropic and not display-worthy. But every now and then, a new mineral is discovered that not only is macroscopic but also of gem quality. Brazilianite is a well-known example, first thought to be chrysoberyl but later recognised as a completely new mineral species. Taaffeite, originally discovered as a cut gem looking similar to spinel, is another example.

In 2015, kyawthuite, with the composition Bi3+Sb5+O4, was approved by the IMA on the basis of a type specimen consisting of a single faceted gemstone of 1,61 carats (http://minerals.caltech.edu/manuscripts/2017/Kyawthuite/index.html). It was found as a waterworn crystal in alluvium at Mogok Township, Myanmar – a region renowned for its varied gemstones. Now the cut gemstone is in the collections of the Mineral Sciences Department, Natural History Museum of Los Angeles County, USA (https://www.mindat.org/min-46909.html).

As far as I can determine, for now this faceted gem is the only known specimen of kyawthuite, making it not only the rarest mineral but also the rarest gemstone. If mineralogical and gemmological history is anything to go by, this situation is not likely to last long. Either the name will be discredited by another study showing that it is structurally and chemically too similar to a known mineral species to warrant another name – as happened fairly recently to the former ‘marshallsussmanite’ from the Kalahari Manganese Field, now synonymous with schizolite – or more mineral specimens will be found, and perhaps more gems.




The photographs of kyawthuite are all reproduced courtesy of the Natural History Museum of Los Angeles County
 

Madagascar - the Road to Hell-Ville

September 25, 2019

Mandy Freeman

With a sense of excitement and anticipation of the mineral treasures Madagascar offers, we boarded Air Madagascar on 1st July this year (okay, 4 hours late, but at least on the same day). Our trip was part rock-hunting (obligatory in the Freeman household), and part island-holiday. Boy, were we in for a surprise…

We arrived in Antananarivo, capital of Madagascar where our adventures in a hired 4x4 with driver began. Tana, as it is known, has several stone markets where you...


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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 th...


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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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