Australian
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Teacher’s notes

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This clip shows the processes of cutting and polishing raw opals. It opens with Mark Jackson presenting a rough opal to his father, Stuart, an opal cutter and licensed valuer. Stuart examines and values the opal at $500 in its raw state. He explains that cutting and polishing it will either diminish or increase its value, depending on the quantity of impurities that are revealed. Stuart grinds dirt off and shapes the piece. He estimates that it is worth about $1,400 wholesale and if cut into two stones could be worth about $2,000.

Educational value points

• The activities explored in this clip, which take place in the town of Coober Pedy, offer an example of making an income through ‘adding value’ to a product. Stuart Jackson estimates that Mark’s opal, worth $500 in its raw state, could increase in value five-fold through cutting and polishing but, if a cut and polish reveals weaknesses, the value could diminish to about $250. Thus, the process of value adding also runs the risk of diminishing the value of the product.

• Given an opal’s impurities, it takes skill to cut and fully reveal gemstones from the raw material. Water is used to reduce the risk of burning or cracking the opal. Coarse to fine diamond grinding wheels remove sand spots and saw marks. Finally, the shaped stone is polished, again using water, with cerium oxide on a felt wheel.

• This clip demonstrates common techniques used by documentary makers to convey information through personal interest, characters and a story. This particular narrative attracts interest due to the personal connection between Mark and his father, and the intrigue in finding out how much Mark’s raw opal will be worth once it is cut, ground and polished. At the same time viewers learn about aspects of opal cutting and polishing.

• Opal is a mineral, an amorphous hydrated form of silica (silicon dioxide), not as solid as quartz but of a similar hardness to glass. It varies in colour, and is often milky white. Its iridescence accounts for its appeal as a gemstone. The value of opals depends on their colour, pattern, soundness and size. Precious opal has more colour than common opal. About 90 per cent of all opal found is common opal, also known as potch.

• Coober Pedy is a major opal-mining centre, 850 km north-west of Adelaide, South Australia. In 1920 the Stuart Range Opal Field, named after explorer John McDouall Stuart (1815–66), was renamed Coober Pedy, an anglicised version of kupa piti, meaning ‘white man in a hole’ in the language of the Antakarinja, traditional owners of the land.

• As well as being a centre for opal production Coober Pedy is famous for its underground homes, which miners have built or converted from old mines to escape from the extreme heat of the day and the cold of the night.

• Australia accounts for 95 per cent of production of the world’s precious opal and the main mined deposits are at Lightning Ridge and White Cliffs in New South Wales, in central Queensland, and at Mintabie, Andamooka and Coober Pedy in SA. Opal is the official gemstone of SA, where the activities shown in the documentary are located. Opal was made the official gemstone of the Commonwealth of Australia in 1993.

Father and Son Mark and Stuart Jackson work in their opal workshop.
Narrator This is Mark’s dad, Stuart Jackson, a licenced valuer and expert opal cutter.
Stuart Jackson Oh, lovely! Yeah, very nice.
Mark Jackson That’s about five pennyweight that piece.
Stuart five pennyweight. I was gonna say probably about 2 grand an ounce, so quarter of an ounce, so calculates to about $500 a piece.
Mark You reckon we would get more if we clean it up?
Stuart Well, it may not. It may not increase the value. You might find a whole heap of sand in there, and dirt. It doesn’t…it looks fairly clean but with opal you just never know.
Mark It’s a lucky dip.
Stuart It’s a luck dip – exactly. So hopefully, judging by the nice bar in here, it’s going to increase probably five-fold, just by cleaning it up, so from $500 piece we’re hopefully looking at a $2,500 piece, but there’s no guaranteees. If it goes the other way, it might end up at $250.
Mark We’ll take the risk.
Stuart Take the risk? OK, let’s have a bit of a clean then.
Mark Let’s go.
Mark places the stone in a polishing machine.
Stuart Nice bar. You can see it’s just starting to come up a little bit now. It’s still got a film of potch over the top. Yeah, a little bit of dirt coming in this side, but that’s OK. Yeah, might just slice that off. Yeah, starting to kick in now a bit, isn’t it? Not too much off here. Yeah, you can see it really coming up now.
They examine the stone.
Mark Beautiful colour. Can’t wait to polish.
Stuart No, we’ll get a shine on it.
Mark So how much you reckon per carat?
Stuart Oh, she’s gonna go 140, mate, 135, 140 a carat. It’s very nice. It’s actually starting to really pick up now. I mean, I’ve only faced it. Once we start getting a bit of the crap out of the way, we’re looking about a ten…nine to ten carat stone wholesaling at about 140. That’s $1,400 from a $500 piece.
Mark Beautiful.
Stuart Minimum. That’s the wholesale price.
Mark Better cut the rest of the opal off.
Stuart I think it’s definitely worthwhile. There’s still two stones out of here, so if we get, say, 1,400 bucks for that one, there’s still that one – another $300 or $400 there, so we should clear about 2 grand out of that one piece.
Mark Fantastic.