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 teacher. Things get a lot more difficult when you want to facet non-standard, soft, or easily cleavable stones. For the past few months I have tackled various soft gem materials. This required learning some new skills. I had to practise and perfect hybrid dopping using wax and cyanoacrylate glue with a necessary accelerator to ensure the glue set. Faceting soft, and easily cleaved materials requires using sharp, fine diamond grit laps. Some very soft materials, like cerussite, tend to bind to the finest laps, so a compromise is necessary. The steepest learning curve was in polishing. Directional cutting and polishing were mandatory because of their differential susceptibility to cleave, chip and scratch. Polishing direction and pressure had to change for just about every facet. For such stones, patience and a responsive polishing technique are as important as choice of lap and polishing medium.

 

Cerussite 75,42 ct; 18 mm
Rhodochrosite 2,84 ct; 8 mm
 

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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WHO CUT THAT STONE, OR WHAT IS A GEM CUTTER WORTH?

May 24, 2019
Duncan Miller

The photograph here is of a magnificent 164,11 ct spodumene (variety kunzite) in the collection of the Smithsonian Institution, USA (https://geogallery.si.edu/10002906/spodumene-var-kunzite).


The accompanying text credits the mine at which it was found (in 2010 at the Oceanview Mine in Pala, California), the funds with which it was acquired (Tiffany & Co. Foundation endowment in 2012), and the photographer (Greg Polley). So who cut this stone? This is like acknowledging the ar...


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FACETIPS A simple Emerald Cut

May 9, 2019

Duncan Miller

The Emerald Cut is not a meetpoint design so cutting stones with repeatable proportions and facet widths involves guesswork. The following sequence for cutting pavilion and crown avoids most of the guesswork and enables you to cut pairs or sets of matched stones. This sequence is modified from FACET DESIGN Vol. 4 by Robert Long & Norman Steel, in turn based partly on FACETING FOR AMATEURS by Glenn & Martha Vargas. This example uses 5° steps for the three pavilion tiers, but you ...


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WHAT IS A PSEUDOMORPH, AN EPIMORPH OR A PARAMORPH?

May 9, 2019

According to https://en.wikipedia.org/wiki/Pseudomorph:

In mineralogy, a pseudomorph is a mineral or mineral compound that appears in an atypical form (crystal system), resulting from a substitution process in which the appearance and dimensions remain constant, but the original mineral is replaced by another. The name literally means "false form". Terminology for pseudomorphs is "replacer after original", as in brookite after rutile.

paramorph (also called allomorph) is a mineral chan...


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