Duncan Miller

After several years, or after many years, a gem cutter lands up with a junk box. Mine contains disappointing stones abandoned in disgust and partly-worked stones that came over the years with various faceting machines and batches of rough. As a lock-down project I decided to see what I could make from the contents of the faceting junk box. (There are another two – one with cabochons and another with broken synthetics. You never know, you know…)

To make it something of a ...

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 ...

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...

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...

By Duncan Miller

(This is a follow-up to a previous article on faceting quartz, to be found with other faceting articles on the club’s website http://ctminsoc.org.za/articles/category/Faceting.) 

Every faceter knows quartz, those great big glassy-looking chunks that seem to cry out to be turned into doorknobs. Or pretty, golden ‘citrine’ that can cut brilliant yellow stones. Or glowing, dark purple amethyst with seductive blue flashes, dreamy rose quartz, or rutilated quartz with geom...

By Duncan Miller

Topaz is a rather under-rated gemstone. This perhaps it due to the fact that pure, colourless topaz is relatively plentiful. Much of it is irradiated and then heat-treated to produce various intensities of bright blue. Natural blue topaz tends to be much paler, although dark blue stones do occur naturally. These are rare and hence more valuable. Natural topaz occurs in a wide variety of colours, including light green, yellow, orange and pink. The famous orangey-pink topaz fr...

By Duncan Miller

I started faceting in pre-GemCad days and found cutting ovals very laborious. I would cut the girdles by eye, using various oval templates, and placed the brilliant-style facets by eye too. Producing matching pairs was very trying. The advent of meetpoint faceting and GemCad overcame all these difficulties. Now there are lots of designs for ovals that are meetpoint, requiring no preform, with the girdle outline evolving out of the cutting sequence. You can access some of the...

By Duncan Miller

This was another jeweller’s request. The setter had broken one of a matching pair of blue-green stones, destined for earrings, bought by the client in India as emeralds. They were apatite; but nevertheless the broken stone had to be replaced to fit the already-made setting. Fortunately I had just one piece of blue-green apatite that matched the colour. In order to produce a stone of the same size and proportion I had to replicate the oval precisely. I could have slapped fa...

By Duncan Miller

Here is a quick and easy oval with a standard 1:1.30 proportion. It has a fully conical pavilion, so you can spin a conical preform, stopping just short of producing a point. This means you don’t have to change angles and mast height when cutting the sixteen pavilion facets, which saves time and avoids mistakes. This is a fully meet-point design that doesn’t require a preform, so it would be good for a beginner’s first oval. It doesn’t work well in quartz or beryl, s...

By Duncan Miller

Here are two stones that Duncan Miller cut recently from rough he bought two months ago at Open Day. The yellow citrine (from Johann de Jongh) has only 58 facets, is 22 mm wide and weighs 37 ct. The design is ‘Xephyr’ by Arya Akhavan (yes, with an ‘X’). The light green fluorite (rough from Rob Smith), is the first one he has ever cut. It has even fewer facets, only 36, is 15,5 mm wide and weighs 16,2 ct. The design is slightly modified from ‘Six Shooter’ by the late Jeff Graham.  ...

 A magnificent 63 carat sphalerite from Aliva in Spain (http://gem-sphalerite.com/) cut by Duncan Miller. The design is Marco Voltolini’s “Superstarfish Dome 80”.

 A unique type of blue-green garnet has entered the gem market. The garnets reportedly come from a deposit near the border of Tanzania and Kenya. GIA’s Carlsbad laboratory obtained a small parcel of blue-green rough material and two faceted stones for examination. Unlike traditional blue-green garnets that exhibit a colo...

“Eye of the Storm” a faceting design created by Robert W. Strickland on 12^th September 2017, in honour of those who suffered loss in the Caribbean hurricanes of 2017.

This design was first published in the United States Faceters’ Guild newsletter of September 2017.

When photographed directly into the centre of the culet, all the crown facets go dark, and the only light is in the “eye”, but viewed from other angles, the stone ...

Duncan Miller

A polariscope consists essentially of two polaroid filters, or a source of plane polarised light and one polaroid filter. The source of polarised light can be a white computer screen or even the sky, viewed at 90 degrees to the Sun. For the filter, or analyser, you can use a sheet of polaroid, or a lens from a cheap pair of 3D movie spectacles.

Let’s start with a white computer flat screen. Even an older cell phone screen without a plastic cover produces plane polarised ligh...

Duncan Miller

During the 1974/75 university holidays I was fortunate to work for Sid Pieters in Windhoek for several months. It was a wonderful experience, including seeing some of the most famous mineral specimens then coming out of Tsumeb, but also to encounter some very special gem materials. Through Sid Pieters’s generosity I returned home to Cape Town with a few small fragments of jeremejevite from the original Namibian occurrence at Cape Cross and some pieces of cuprite from Onganja t...

Duncan Miller

Inclusions in gemstones often are seen as just a nuisance by faceters, who find themselves urged to buy only ‘clean’ rough. I suppose it is a matter of taste, but inclusions that do not detract from the visual appearance of a gemstone can aid in proving its authenticity. And some inclusions definitely enhance the value and appearance of certain gems. A visible ‘horse tail’ inclusion of asbestos fibres in Russian demantoid is perhaps the most famous example of desirable ...

Duncan Miller

Synthetics are a wonderful source of relatively inexpensive faceting rough, in a wide array of colours, some of them not available at all in natural stones. On the whole, synthetic gem rough is predictable in its behaviour and also enables the cutter to explore quirky cuts in larger sizes than would be affordable in natural rough. And increasingly jewellers are setting well-cut synthetics in precious metal jewellery. So dive in, and enjoy yourself.

The most commonly available ...

Duncan Miller

Duncan Miller

Many faceters recommend that beginners start with aquamarine. It usually presents no problems in faceting or polishing, is relatively easy to obtain, and in lighter colour it is not overwhelmingly expensive. Aquamarine is the blue or blue-green gem variety of the mineral beryl, an aluminium beryllium silicate. It occurs in elongated hexagonal barrel-shaped crystals. It is dichroic, with the most intense colour when viewed along the length, the so-called c-axis. This is a pity, ...

Duncan Miller

This is the first of an intended series of articles on faceting and polishing a variety of gemstones. I am beginning with quartz because that is what most people start faceting when they first take up the hobby. Quartz rough is inexpensive and readily available in a wide range of colours. It is not necessarily the easiest material to polish, but if a particular stone behaves badly it is no great loss to set it aside to be tackled at a later date. You should try to select rough ...

I cut off the end of a damaged Goboboseb quartz crystal because it had a deep purple central inclusion at the one end, which I thought would make an interesting stone to facet.

 But then I noticed that the end of the remaining piece had regular purple stripes radiating from the centre to the points of the hexagonal crystal. So I cut off another section of the crystal to the depth I hoped I would need for cutting a gem.

I first tried to find the middle of the purple star shape, and marked s...

By Duncan Miller

If you are going to facet, you need to learn something about mineralogy because you need to know what stones you should obtain, how their characteristics affect their behaviour while you are cutting and polishing them, and how they affect the optical properties of your finished gemstone. The easiest material for beginners to cut and polish is common red garnet. It presents no problem with cleavage or orientation for colour, and generally behaves itself well during ‘cutting...