FACETIPS - AN ‘EPIDOTE’ ANECDOTE

November 24, 2019
Duncan Miller

A few years ago, faceting friends of mine in Durban bought some green gem quality material sold as epidote or possibly peridot. It was nice clear green, and some pieces of rough still adhered to a matrix, "dug out of the ground right in front" of the vendor from Moçambique. The cutting and polishing was easy, apparently working like tanzanite. But the surface of the polished stone degraded quite rapidly, developing hazy spots, so samples were sent to me for identification.

The specific gravity measured by hydrostatic weighing was 3,55. It was quite soft, with a Mohs’s hardness of about 5, and had perfect cleavage, forming faces at 90° to each other. This indicated that it probably was cubic, so it could not be epidote, or peridot. Between crossed polars it was isotropic, which figured with its being cubic, but the cleavage meant it wasn’t glass. Under magnification, it contained swarms of fine, round bubbles. This was a puzzle. So I polished a face to measure the refractive index, which was 1,73.

This combination of properties indicated synthetic periclase (MgO). Webster’s Gems notes that it has been marketed under the trade name of Lavernite. So what about the matrix specimen? A closer look at that showed some nice little brown cubic crystals lining vugs in cleaved green masses. Another piece had an opaque, vesicular brown matrix, probably also periclase but with higher iron content. The vendor had lied.

 
A piece of synthetic periclase (MgO) sold as natural faceting rough. The front and side faces are cleavage faces at 90° to each other. The top face is a saw cut. The sample is 15 mm long.

 

A ‘matrix’ specimen of synthetic periclase, with small brown cubic crystals lining vugs in the green periclase ‘matrix’. The field of view is 25 mm wide.

 

FACETIP – POLISHING REALLY TROUBLESOME FACETS

October 25, 2019

Duncan Miller

Polishing soft gem materials, Mohs’s hardness 5 and less, and facets near the cleavage of some harder materials can be very difficult with commonly used polishing laps. Some years ago, Gearloose Lapidary (www.gearloose.co) introduced the Lightside™ lap, intended specifically for polishing soft materials. It is a ‘reduced-friction’ composite lap, used with diamond or oxide slurry to produce flat facets without significant edge rounding. It is described as a ‘durable, p...


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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 ...


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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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