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Opinion: What science can tell us about the ‘world’s largest sapphire’

Anonymous — Wed, 06 Jan 2016 14:31:13 +0000

̽��ֱ��“Star of Adam”, recently found in a mine in Sri Lanka, is believed to be the biggest sapphire ever discovered. It weighs in at over 1,404 carats, that’s around 280g or just under ten ounces. But what do we know about the formation of this remarkable gemstone – and how could it grow so huge?

Sapphire is a bright blue gem mineral and a form of corundum (aluminium oxide), the hard gritty stuff used as an abrasive in emery paper. It is incredibly hard – a fact important in understanding its occurrence in places like the Sri Lankan mines.

Sapphire is a type of “dirty” corundum. If you add just a trace of iron and titanium to the mixture of aluminium and oxygen from which the corundum is growing, it forms as sapphire. (If you add chromium to the corundum as it grows then you will get a ruby – Sri Lanka is also famous for its rubies).

̽��ֱ��Star of Adam sapphire is an example of a “star sapphire”. When you look at it it appears to have a six-pointed star inside, which shines out from the gem and is due to reflections of light from tiny whisker-like crystals of rutile (a titanium-dioxide mineral) that were trapped within the sapphire crystal as it grew.

Ancient river sediments

̽��ֱ��stone was found in the Ratnapura mines in the south of the country, about 100km south-east of the capital, Colombo. Ratnapura is Singhalese for “gem town” and Sri Lanka has been known for its gem deposits for more than 2,000 years. It seems likely that Sinbad’s “Valley of Gems” in the Tales of the Arabian Nights is a reference to the Ratnapura area. In 1292, Marco Polo wrote: “ ̽��ֱ��Island of Ceylon is, for its size, the finest island in the world, and from its streams come rubies, sapphires, topaz, amethyst and garnet."

Ratnapura gem mine. hassage/Flickr, CC BY-SA

̽��ֱ��gems of Ratnapura are found in ancient river sediments – old river beds that are now covered with more layers of mud and sand in an area that is largely given over to paddy fields. ̽��ֱ��hard gem minerals, sapphires, rubies, spinels and garnets, were long ago weathered and eroded from the nearby highlands. Because of their hardness they survived as large pebbles and crystals, eroded out of the rocks where they first formed, and transported down the rivers which acted like a natural panning system. River-borne (alluvial) gold and diamonds are often sorted and concentrated in river sands by similar processes, elsewhere on the globe.

On their journey along the river the softer rocks from the highlands would have been worn down into mud and fine sand, but the harder minerals survive better, and retain their size and often their shape. ̽��ֱ��average annual rainfall for the island is more than 2,000mm, and the tropical weather means that the erosion and weathering of the highland mountains is even more accelerated.

Ratnapura is in the “wet zone” of the island. Its gem-bearing gravels have yielded a number of historic gemstones, possibly including a 400-carat red spinel given to Catherine the Great of Russia, and a giant oval-cut spinel, known as the “Black Prince Ruby” (it was mistakenly identified as a ruby), which features in the British Queen’s imperial state crown.

̽��ֱ��Star of Adam sapphire would originally have been created within rocks and granites of the Sri Lankan highlands. ̽��ֱ��granites, which form when molten magma cools and becomes solid, have been dated as almost two billion years old, and were subsequently squeezed and re-worked in a massive mountain-building episode due to tectonic churning of the Earth’s crust that happened more than 500m years ago.

Temperatures and pressures deep within the roots of these mountains would have reached more than 900˚C and over 9,000 atmospheres pressure during this event. ̽��ֱ��sapphire could have formed either within the granite, as part of a rock type called a pegmatite, or within the younger rock created by pressurisation and heating.

In either case the temperatures and pressures would have changed only very slowly over millions and millions of years, and this is how the crystal was able to grow so big. Once formed, the mountains that it sat within would have been eroded and uplifted, and so it was brought to the surface, picked out of the rock by the forces of rain and weathering, and transported down river to the gem sands of Ratnapura. Today it sits in the hands of a private owner.

Simon Redfern, Professor in Earth Sciences, ̽��ֱ�� of Cambridge

This article was originally published on ̽��ֱ��Conversation. Read the original article.

̽��ֱ��opinions expressed in this article are those of the individual author(s) and do not represent the views of the ̽��ֱ�� of Cambridge.

Simon Redfern (Department of Earth Sciences) discusses how the "Star of Adam" sapphire was formed in the highlands of Sri Lanka.

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̽��ֱ��Star of Adam

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Six steps to a better material world

ns480 — Wed, 30 Nov 2011 15:58:59 +0000

A six-part manifesto for drastically reducing a fifth of the world’s carbon emissions, caused by the production of materials like aluminium and steel, has been released online.

̽��ֱ��list is at the core of a new study by a team of eight researchers, who spent three years working with industry and manufacturers to find out how our demand for vital materials such as metals, concrete and paper can be made more sustainable in the future.

Their findings are being published as a book, Sustainable Materials With Both Eyes Open, which can be read for free online at: https://www.uselessgroup.org/publications/book/chapters. In an effort to communicate their ideas as widely as possible, the group has also broken new musical territory by releasing an album of songs about them.

Samples from the 12-track recording “With both eyes open”, which purports to be “the first album written for the 300 million people worldwide who convert metal ores into finished buildings, vehicles and goods”, can be found on the website as well, and the album is now available from Amazon. There Are No Silver Bullets by ̽��ֱ�� of Cambridge

At heart, the research has a deeply serious message. Most of what we use on a day-to-day basis depends on producing energy intensive materials – metals, ceramics and polymers. At the start of the 20^th century, global production of these materials was virtually nothing. Now we make 10 times our own bodyweight of steel, aluminium, cement, plastics and paper every year, for every person alive, and it costs us a fifth of all the world’s energy to do so.

This brings with it a number of problems, such as associated land stress and demand for water. ̽��ֱ��most pressing issue, however, is that materials production involves burning fossil fuels and putting CO2 into the atmosphere.

̽��ֱ��team of eight researchers, all from the Department of Engineering at the ̽��ֱ�� of Cambridge, set out to find ways to make materials production more sustainable in a way that will have a real impact on the Intergovernmental Panel on Climate Change’s target to reduce greenhouse gas emissions to 50-85% of 1990 levels by 2050.

This is easier said than done: “Energy intensive industry is already highly motivated to reduce its energy consumption because energy purchasing is about one third of its costs,” Dr Julian Allwood, who led the research team and specialises in low carbon materials research, says. “Overall, it doesn’t have many further efficiency options left, and we also have to face the fact that demand for these materials is growing, and likely to double if unchecked.”

“We wanted to consider whether we could cut emissions by reducing the amount of stuff produced in the first place. Every aspect of our lives today depends on materials like steel and aluminium. If we want a sustainable future, we need to reduce the impact of producing them, and our biggest option for achieving this is to reduce our thirst for new material.”

̽��ֱ��book identifies a raft of options for reducing our demand for materials production, most of which have received very little attention. Although the study looks individually at cement, plastic and paper, at its heart is a list of six steps which could make huge changes to the carbon footprints of the aluminium and steel industries. In summary these are as follows:

Use less metal by design. ̽��ֱ��researchers argue that we use more material than we need in areas such as construction, car manufacturing, and the production of food cans.
Reduce yield losses. Some industries waste a large fraction of the material they originally receive due to “off-cuts”. ̽��ֱ��book suggests several ways of refining processes to limit this effect.
Divert manufacturing scrap. Does scrap metal really need to be scrapped? ̽��ֱ��researchers argue that in many cases it could be given to other companies or remoulded at room temperatures instead.
Re-use old components rather than recycle them. Car dismantlers are already doing this, but other industries could be doing it more, with re-use of steel in construction looking particularly attractive.
Extend the lives of products. Goodbye, in-built obsolescence – we could and should be refining products to extend their life-cycles.
Reduce final demand. Could we make a difference individually by using less stuff? ̽��ֱ��answer is unquestionably yes – but whether we are prepared to is a different matter. ̽��ֱ��researchers found no evidence that we would be any less happy if we did, however.

Overall, the impact of making all or a number of these changes could be huge. By optimising steel beams for buildings, for example, the researchers reckon we could cut the emissions caused by producing these beams by about 30%. Similarly, taking a series of measures to reduce yield losses would lead to an estimated 16% reduction of CO2 emissions in the steel industry, and 7% in the aluminium industry.

Allwood and his team are now focusing not just on releasing their findings, but on encouraging manufacturers and other companies to develop real-life case-studies that show these changes can be made to the way our materials are produced. For example, the researchers are already working with a supermarket chain on the construction of a new outlet made entirely from old materials (point 5).

“ ̽��ֱ��aim now is to get this connected to policy,” he adds. My job is really to try to trigger demonstrations of how these ideas could work. I think that everyone has a fear of something that has never been tried before. If we can provide examples that people can copy, then it greatly reduces the barrier that stops governments and companies from implementing these ideas and helping them to spread.”

Every year we make 10 times our own bodyweight of steel, aluminium, cement, plastics and paper, for every person alive, using a fifth of all the world’s energy supply to do so. Now researchers are releasing a manifesto to change that and help cut carbon emissions. And they’ve also released an album of songs to go with it.

Every aspect of our lives today depends on materials like steel and aluminium. If we want a sustainable future, we need to reduce the impact of producing them.

Julian Allwood

Joost J Baker Ijmuiden from Flickr

Scrap-metal

Material Manifesto - Six things we could do to make the future of materials use more sustainable

1. Use less metal by design

̽��ֱ��study argues that we could make big savings by optimising the design of metal components. ̽��ֱ��materials used by industry are often designed in a regular shape to make production easier and more efficient. But this means that they often use more material than they have to. For example, the metal “I” beams used in most steel frame buildings are produced to standardised specifications, rather than for specific tasks.

̽��ֱ��researchers calculate that if we can optimise the beam designs to suit their use, we could make weight savings of up to 30% - with a similar reduction in the emissions caused by production. Similar techniques could be applied to the production of components for cars, the “rebar” used to reinforce concrete, and steel cans for food storage. One simple tweak would be to change regulations. “Pretty much everything in a building is over-designed out of fear for safety,” Allwood says. “All national building regulations in the UK are written with a minimum level of steel. If we instead gave firms a target level, we would be able to stop people over-specifying without compromising safety.”

2. Reduce yield losses

At least 25% of liquid steel and 40% of liquid aluminium never makes it into products. Instead, it is cut off as scrap in manufacturing. One extreme example is the aluminium wing skin used for aeroplanes – 90% of the metal produced in this process ends up as “swarf”, or aluminium scrap.

̽��ֱ��researchers found that this is often the result of habit, rather than necessity. Simply designing more components with tessellating or near-tessellating shapes would make a big difference. Clothing manufacturers have, for example, actually derived the algorithms needed to make sure that rolls of fabric are used to maximum effect. Manufacturers could do the same thing with the metal they receive. ̽��ֱ��team calculated that reducing yield losses through this and other techniques would cut CO2 emissions by about 16% in the steel industry, and 7% in the aluminium industry.

3. Divert manufacturing scrap

Scrap metal is usually sent for recycling, which means melting it (an energy-intensive process). In fact, it could just be used elsewhere. For example, most steel scrap comes from “blanking skeletons” – the remains of sheets of steel after shapes have been cut out of them. About 60 megatons of steel are scrapped on this basis every year. ̽��ֱ��study says that we could effectively reduce scrap steel by half if these skeletons instead went to the manufacturers of smaller components, who can use what’s left.

Alumnium swarf cannot be cut in the same way, but it can be compressed and welded at room temperature. ̽��ֱ��researchers have been developing a technique to create new components by swarf-extrusion – squeezing aluminium through a die, and creating solid-bonded swarf that can be re-used.

4. Re-use old components before recycling at all

Old components are often recycled when they could instead be re-used directly. Car dismantlers are an example of good practice, breaking up damaged or old vehicles and re-using the components. But steel in construction remains the biggest potential asset and although the beams from dismantled buildings are usually recycled, they could often instead be used again straight away. “When you take a building down, the steel girder is totally reusable,” Allwood says. “All you need to do is unbolt it and clean it – because steel doesn’t degrade in use. Re-use means we can avoid all the energy of melting, casting and re-rolling old steel.”

5. Extend the lives of products

Most demand for products in developed economies isn’t to expand the overall stock, but to replace existing items. Fridges are a good example – we still need them but in the UK we destroy, every year, 33% more fridges than we make cars. ̽��ֱ��researchers advocate modifying products rather than replacing them wholesale, and urging manufacturers to develop adaptable designs that would help this process. This requires a change in thinking and an end to planned obsolescence.

Is this an economically convincing argument? Allwood reckons so: “If we can purchase a standard new fridge for around £200, expecting it to last 10 years but guaranteed for only three, we’re unlikely to agree to pay £2,000 for a fridge with a 100 year guarantee. However, we might agree to pay £40 a year indefinitely for a fridge that would always be maintained and upgraded to the latest standards. And if that’s the case, we can offer the supplier double their income over a much longer period, compared with a single purchase with no commitment.”

6. Reduce final demand

̽��ֱ��fall-back option that no policy-maker would ever condone, except in times of war. Yet it remains the case that we could be living with less stuff overall. In the UK, for example, we each spend 225 hours per year in the car. We have 28 million licensed cars with, on average, four seats in each. There are 60 million people. So each car seat is, on average, in use for 2% of the year. We could reduce our overall stock to 7 million cars with ease.

This is, of course, scuppered by the convenience factor of having a car when we need it. But the researchers looked into recent studies of happiness and well-being and found that there is little reason to believe that we would be less happy than we are now if we took measures such as this. Indeed, with only 7 million cars in the UK, we would all be £1,000 a year better off on average and our journeys would be a good deal quicker and less stressful. We may not want to make these changes to our convenient lifestyles, but that is not to say that we couldn’t do it if we needed to.

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