Ooh! That’s rough
By EW & JP Mitchell
At shows we’re often asked ‘where do you get your rough? Now I ask you, if you had a source of good cheap rough, would you tell me? The answer we give is truthful ‘wherever we can find it’. Tumbling and cabochon cutting (cabbing) you can quite literally pick it up rough for free along most beaches. Particularly those on the east coast, where you can find a good range of quartz and quartzites, jaspers and even agate, jet and amber.
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Stones from a beach and elsewhere are good where colour is of prime importance, some can even be faceted. Walk along by the wet shingle facing the light and as well as picking those you like, look about two paces ahead, translucent stones such as carnelian glow. Cabbing has the advantage that both the free and commercial material are readily available as slabs or pieces. Small, thin and or fragile material can be bonded to a suitable backing. For example the thick plasticine like resin mixes used for plumbing can also be used to support turquoise.
International gem dealing is mostly in US dollars, but buying on the internet is easy with Paypal and Visa. Unless you buy in quantities of 100gms or more at say $150 (£100) and upwards you pay for selection. By the piece or in small amounts the equivalent of three or more times as much. If you use an auction site such as Ebay; look at all pictures very critically, and read the description and conditions of sale carefully. When buying a parcel, of which at least 10% can be expected to be good; or a piece, where the cost +postage still make the sale attractive, compared to a dealers price it’s OK. You need individual stones to be at least 3-4cts to cut stones of 5mm and upwards. Otherwise I think the American expression leaverite (leave ’er right there) applies.
Agood rule of thumb; in purchasing is that a $1 US is a £1 UK by the time postage, VAT and so on is added. If you pass the VAT threshold currently (£15/$24 US) you pay cost + postage+ VAT. Then the post office will charge £8 for collecting it.
As you read the magazine you likely go to shows, so let’s start there. Now to select from a heap of rough is what the Americans term cherry picking. You can do this at shows without the usual mark up in price that buying by the piece would attract. Most varieties of quartz and a good variety of more exotic stones can be found.
If you see it, buy it! I’m still kicking myself as, at a recent show I saw some nice, large, clean (free from flaws) phenacite crystals. I’ll get some cash I thought, then got distracted and forgot. By the time I remembered they were sold.
To begin searching, the tools you need are simple. The one between your ears (billions of Giga thingies), which will hopefully remind you to bring your glasses! Abusiness card with clear printing or a piece of white card, with black X’s on it. A bright white light source such as an LED torch; though often the lights on a stand can be used. A loupe is helpful, more so as you become accustomed to using it.
Lemon quartz, this does occur naturally but usually is the result of radiation (low level) or heating. Stones in a heap will appear better coloured than when separated Cabochons have the advantage that quite thin material can be used. They need a thickness of about 1/4 the final width of a cut stone. High colour not clarity is wanted. . For faceting select first for clarity and a surface fairly free from indentations or bumps. Now look at the size and shape. For faceting a truncated octahedron is best giving about a 45% yield (size of finished stone) but apart from diamonds and fluorite you don’t get a lot of these.
Ball shaped (soccer or rugby) gives a fair yield though only about 25%.The thinnest dimension is again a limiting factor as for faceted stones the height is about 3/4 of the width. Place your choice on the card, in good light, for faceting you want stones that appear like these, with nice clear X’s. These will cut a bright stone.
If the X looks blurred these stones when cut will be well coloured but sleepy (turbid); and are more suitable as cabochon material. See pictures overleaf.
Grinding or sawing leaves a frosted surface. It’s usually done to cut out flaws. With any rough stone If it is wetted it becomes clear and any internal features can be seen. The picture to the right shows a dry stone after wetting. Most dealers don’t mind this if you use clean water; but are less than happy with spit, not very effective, and baby oil, very effective but mucky to use.
Most quartz varieties don’t do sleepy, they do zoning. Pictured are amethyst, smokey quartz and, though not quartz, sapphire, to show this effect.
The direction in which zoning disappears, and in which most crystals show their best and clearest colour is called the C axis; hold a pencil vertically the lead represents the C axis of the crystal. Tourmaline is an exception it often has very distinct colour zones and a fuzzy C axis; so it’s usually cut perpendicular to the C axis. It a nasty trap for the unwary; the C axis does not always pass light so round or oval stones don’t work out. Whatever its shape colour or clarity hold it up to the light and rotate it if at some point it appears dark the C axis is partly or fully closed. A good dealer will always note whether the C is clear or not.
Some crystals are noticeably plechroic, that is, depending on the direction in which they are viewed different colours are seen. This is not colour change! Tanzanite after heating is blue and purple before blue, violet and orange even green. Iolite sometimes sold as tanzanite is blue (just like tanzanite) and water clear and sometimes yellowish. Sapphire is often blue and green.
Recently via the internet, I bought some ‘tanzanite’, the pictures showed nice blue stones. These were expected to be, opaque, but pretty and saleable pieces.
I got tanzanite blue pieces which when rotated were almost clear. The stones were iolite, good pieces worth far more than the expected tanzanite. Did a cheater fail to prosper? Or was it just ignorance? Still lucky for me.
All stones appear to change colour when viewed in daylight or artificial light; if you can view them under both. Iolite is often sold as having ‘colour change’ which it doesn’t have.
Alexandrite is the classic, ‘an emerald by day and a ruby by night’, also rare and expensive.
The best alexandrite mine, it’s said, is old Russian jewellery. Garnet and sapphire can also both show a marked colour change. All these phenomena are really demonstrating the fact that daylight, fluorescent and incandescent light have very different colour spectrums.
Colour change is often used to maximise the price of rough material. Even with man made rough satisfy yourself that it has a good colour change before you buy.
Pictured (overleaf bottom of page) is man made ‘alexandrite’. It has a nice colour change but not green to red, like the real MacKoyski. It is man made corundum (sapphire) alexandrite is chrysoberyl, not yet, as far as I know, man made.
Back to cherry picking, using the torch or the stall lights hold the stone so it is brightly lit but the light does not shine directly into your eyes. This should make any included object show up. Roll the stone between your fingers and look for any internal flaws such as fractures, veils or bubbles (spherical) and or inclusions; such as voids or any opaque objects.
Aveil is a partly re-grown fracture; a rainbow flash means diffraction in this case caused by the small gap produced by a fracture.
Bubbles are characteristic of glass so are often an indication of ‘man made’. Moldavite (only green in nature), obsidian (usually black or brown, sorry no blue, this is manufactured glass) and tektites (black or brown and almost opaque) are all natural glass and do have included bubbles.
It helps to see the prices at which online dealers are selling here’s a brief dealer list.
Color-wright.com A good range of natural and man made stones.
Neweragems.com A good range of natural stones.
Online dealers such as these sell good material, but not cheaply. They not only have their reputation to consider but will be here tomorrow. Most are both helpful and generous with their time and advice.
Try, for example, John Bailey’s rough evaluation article(s) on http://facetingacademy.com
So there you have it money, or time, or both.
By EW & JP Mitchell. Rough Rock, Cut Stones & Jewellery sold in aid of the Children’s Society (Reg. Charity 221124).
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