̽��ֱ�� of Cambridge - mineral

Rare mineral discovered in plants for first time

Anonymous — Mon, 05 Mar 2018 13:58:12 +0000

Scientists at Sainsbury Laboratory Cambridge ̽��ֱ�� have found that the mineral vaterite, a form (polymorph) of calcium carbonate, is a dominant component of the protective silvery-white crust that forms on the leaves of a number of alpine plants, which are part of the Garden’s national collection of European Saxifraga species.

Naturally occurring vaterite is rarely found on Earth. Small amounts of vaterite crystals have been found in some sea and freshwater crustaceans, bird eggs, the inner ears of salmon, meteorites and rocks. This is the first time that the rare and unstable mineral has been found in such a large quantity and the first time it has been found to be associated with plants.

̽��ֱ��discovery was made through a ̽��ֱ�� of Cambridge collaboration between the Sainsbury Laboratory Cambridge ̽��ֱ�� microscopy facility and Cambridge ̽��ֱ�� Botanic Garden, as part of an ongoing research project that is probing the inner workings of plants in the Garden using new microscopy technologies. ̽��ֱ��research findings have been published in the latest edition of Flora.

̽��ֱ��laboratory’s Microscopy Core Facility Manager, Dr Raymond Wightman, said vaterite was of interest to the pharmaceutical industry: “Biochemists are working to synthetically manufacture vaterite as it has potential for use in drug delivery, but it is not easy to make. Vaterite has special properties that make it a potentially superior carrier for medications due to its high loading capacity, high uptake by cells and its solubility properties that enable it to deliver a sustained and targeted release of therapeutic medicines to patients. For instance, vaterite nanoparticles loaded with anti-cancer drugs appear to offload the drug slowly only at sites of cancers and therefore limit the negative side-effects of the drug.”

Other potential uses of vaterite include improving the cements used in orthopaedic surgery and as an industrial application improving the quality of papers for inkjet printing by reducing the lateral spread of ink.

Dr Wightman said vaterite was often associated with outer space and had been detected in planetary objects in the Solar System and meteorites: “Vaterite is not very stable in the Earth’s humid atmosphere as it often reverts to more common forms of calcium carbonate, such as calcite. This makes it even more remarkable that we have found vaterite in such large quantities on the surface of plant leaves.”

Botanic Garden Alpine and Woodland Supervisor, Paul Aston, and colleague Simon Wallis, are pioneering studies into the cellular-level structures of these alpine plants with Dr Wightman. Mr Wallis, who is also Chairman of the international Saxifrage Society, said: “We started by sampling as wide a range of saxifrage species as possible from our collection. ̽��ֱ��microscope analysis of the plant material came up with the exciting discovery that some plants were exuding vaterite from “chalk glands” (hydathodes) on the margins of their leaves.

"We then noticed a pattern emerging. ̽��ֱ��plants producing vaterite were from the section of Saxifraga called Porphyrion. Further to this, it appears that although many species in this section produced vaterite along with calcite, there was at least one species, Saxifraga sempervivum, that was producing pure vaterite.”

Dr Wightman said two new pieces of equipment at the microscopy facility were being used to reveal the inner workings of the plants and uncovering cellular structures never before described: “Our cryo-scanning electron microscope allows us to view, in great detail, cells and plant tissues in their “native” fully hydrated state by freezing samples quickly and maintaining cold under a vacuum for electron microscopy.

"We are also using a Raman microscope to identify and map molecules. In this case, the microscope not only identified signatures corresponding to calcium carbonate as forming the crust, but was also able to differentiate between the calcite and vaterite forms when it was present as a mixture while still attached to the leaf surface.”

So why do these species produce a calcium carbonate crystal crust and why are some crusts calcite and others vaterite?

̽��ֱ��Cambridge ̽��ֱ�� Botanic Garden team is hoping to answer this question through further analysis of the leaf anatomy of the Saxifraga group. They suspect that vaterite may be present on more plant species, but that the unstable mineral is being converted to calcite when exposed to wind and rain. This may also be the reason why some plants have both vaterite and calcite present at the same time.

̽��ֱ��microscopy research has also turned up some novel cell structures. Mr Aston added: “As well as producing vaterite, Saxifraga scardica has a special tissue surrounding the leaf edge that appears to deflect light from the edge into the leaf. ̽��ֱ��cells appear to be producing novel cell wall structures to achieve this deflection. This may be to help the plant to collect more light, particularly if it is growing in partly shaded environments.”

̽��ֱ��team believes the novel cell wall structures of Saxifrages could one day help inform the manufacture of new bio-inspired optical devices and photonic structures for industry such as communication cables and fibre optics.

Mr Aston said these initial discoveries were just the start: “We expect that there may be other plants that also produce vaterite and have special leaf anatomies that have evolved in harsh environments like alpine regions. ̽��ֱ��next species we will be looking to study is Saxifraga lolaensis, which has super tiny leaves with an organisation of cell types not seen in a leaf before, and which we think will reveal more fascinating secrets about the complexity of plants.”

There is a risk that some of these tiny but amazing alpine plants could potentially disappear due to climate change, damage from alpine recreation sports and over-collecting. There is still much to learn about these plants, but the collaborative work of the Sainsbury Laboratory and Cambridge ̽��ֱ�� Botanic Garden team is revealing fascinating insights into leaf anatomy and biochemistry as well as demonstrating the potential for Saxifrages to supply a new range of biomaterials.

Story by Kathy Grube, Communications Manager, Sainsbury Laboratory.

A rare mineral with potential industrial and medical applications has been discovered on alpine plants at Cambridge ̽��ֱ�� Botanic Garden.

Biochemists are working to synthetically manufacture vaterite as it has potential for use in drug delivery, but it is not easy to make

Raymond Wightman

Paul Aston

Saxifraga sempervivum, an alpine plant species discovered to produce "pure vaterite".

̽��ֱ��text in this work is licensed under a Creative Commons Attribution 4.0 International License. For image use please see separate credits above.

Yes

Going underground: Cambridge digs into the history of geology with landmark exhibition

sjr81 — Fri, 24 Nov 2017 00:01:00 +0000

Uncovering how the ground beneath our feet was mapped for the first time – and revealing some of the controversies and tragedies geology brought to the surface of intellectual debate, Landscapes Below opens to the public on Friday, November 24, at Cambridge ̽��ֱ�� Library.

Featuring the biggest-ever object (1.9mx1.6m) to go on display at the Library: George Bellas Greenough’s 1819 A Geological Map of England and Wales (the first map produced by the Geological Society of London), as well as a visually stunning collection of maps from the earliest days of geology – the exhibition explores how these new subterranean visions of the British landscape influenced our understanding of the Earth. All the maps belonging to the library are going on display for the first time.

“I think the maps are beautiful objects, tell fascinating stories and frame geology in a new light,” said exhibition curator Allison Ksiazkiewicz. “This was a new take on nature and a new way of thinking about the landscape for those interested in nature.

“We show how the early pioneers of this new science wrestled with the ideas of a visual vocabulary – and how for the first time people were encouraged to think about the secretive world beneath their feet.”

As well as maps, Landscapes Below also brings together an extraordinary collection of fossils, artworks and a collection of 154 diamonds, on loan from the Sedgwick Museum of Earth Sciences. Displayed together for the first time, the diamonds were collected, arranged, and produced by Jacques Louis, Comte de Bournon who later became the Keeper of the Royal Mineral Collection for King Louis XVIII.

Another important exhibit on display for the first time is the first edition of George Cuvier and Alexandre Brongniart’s Researches on the Fossil Bones of Quadrupeds (1811), on loan from Trinity College. It examined the geology of the Paris Basin and revolutionised what was considered ‘young’ in geological terms.

Artists were also keen to accurately depict the geological landscape. After surviving Captain Cook’s ill-fated third voyage of discovery, artist, John Webber returned to England and travelled around the country painting landscapes and geological formations, as seen in Landscape of Rocks in Derbyshire. Christopher Packe’s A New Philosophico-Chorographical Chart of East-Kent (1743), on loan from the Geological Society of London, is a remarkable, engraved map that draws on early modern medicine in the interpretation of the surrounding landscape.

“ ̽��ֱ��objects we’re putting on display show the many different applications of geological knowledge,” added Ksiazkiewicz. “Whether it’s a map showing the coal fields of Lancashire in the 1830s – or revealing how this new science was used for economic and military reasons.”

In many ways, the landscapes the earliest geologists worked among became battlegrounds as a scientific old guard – loyal to the established pursuits of mineralogy and chemistry – opposed a new generation of scientists intent on using the fossil record in the study of the Earth’s age and formation.

Exhibitions Officer Chris Burgess said: “Maps were central to the development of geology but disagreement between its leading figures was common. Maps of the period did not just show new knowledge but represented visible arguments about how that knowledge should be recorded.”

̽��ֱ��exhibition also includes objects from those with rather tragic histories, including William Smith – whose famous 1815 Geological Map of England has been described as the ‘Magna Carta of geology’. Despite publishing the world’s first geological map (which is still used as the basis of such maps today), Smith was shunned by the scientific community for many years, became a bankrupt, and ended up in debtors’ prison.

John MacCulloch, who produced the Geological Map of Scotland, did not live to see his work published after his honeymoon carriage overturned and killed him at the age of 61. He spent 15 summers surveying Scotland, after convincing the Board of Ordnance to sponsor the project. There was some dispute about how MacCulloch calculated his mileage and spent the funds, and the Ordnance only paid for six summers’ worth of work. Five summers were paid for by the Treasury and four from his own pocket.

Added Ksiazkiewicz: “Not only do these maps and objects represent years of work by individuals looking to develop a new science of the Earth, they stir the imagination. You can imagine yourself walking across the landscape and absorbing all that comes with it – views, antiquities, fossils, and vegetation. And weather, there’s always weather.”

Landscapes Below runs from November 25, 2017 to March 29, 2018 at Cambridge ̽��ֱ�� Library’s Milstein Exhibition Centre. Admission is free. Opening times are Mon-Fri 9am-6pm and Saturday 9am-16.30pm. Closed Sundays.

A box full of diamonds, volcanic rock from Mount Vesuvius, and the geology guide that Darwin packed for his epic voyage on the Beagle will go on display in Cambridge this week as part of the first major exhibition to celebrate geological map-making.

We show how for the first time people were encouraged to think about the secretive world beneath their feet.

Allison Ksiazkiewicz

Cambridge ̽��ֱ�� Library

A Treatise on Diamonds and Precious Stones, 1813, by John Mawe

̽��ֱ��text in this work is licensed under a Creative Commons Attribution 4.0 International License. For image use please see separate credits above.

Yes

Licence type:

Attribution-Noncommercial-ShareAlike

Fingerprinting rare earth elements from the air

lw355 — Fri, 01 Jul 2016 09:00:00 +0000

Next time you use your mobile phone, spare a moment for the tiny yet vital ingredients that make this and many other technologies possible – the rare earth elements (REEs).

Used in computers, fibre optic cables, aircraft components and even the anti-counterfeiting system in euro notes, these materials are crucial for an estimated £3 trillion worth of industries, with demand set to increase over the coming decades.

Currently, more than 95% of the global demand for the REEs is met by a single mine in China. ̽��ֱ��security of the future supply of these 17 critical metals, which include neodymium, europium, terbium, dysprosium and yttrium, is a major concern for European governments, and the identification of potential REE resources outside China is seen as a high priority.

Over the past year, Drs Sally Gibson, Teal Riley and David Neave have been working together through a ̽��ֱ�� of Cambridge–BAS Joint Innovation Project (see panel) on a remote sensing technique that could aid the identification of REEs in rocks anywhere in the world. ̽��ֱ��project brings together expertise in remote sensing, geochemistry and mineralogy from both institutes to take advantage of the properties that make the metals so special.

“Despite their name, the rare earth elements are not particularly rare and are as abundant in the Earth’s crust as elements such as copper and tin,” explains Riley from BAS. “However, to be extractable in an economic way, they need to be concentrated into veins or sediments.” It’s the identification of these concentrations that is critical for the future security of supply. REEs all have an atomic structure that causes them to react to photons of light through a series of electronic transitions. This gives them the magnetic and electrical properties for which they are prized in plasma TVs, wind turbines and electric car batteries. And it also means that for every photon of light they absorb, they reflect other photons in a unique way – it is this property that the researchers have latched onto as a means of tracking them down.

“ ̽��ֱ��light they reflect is so specific that it’s like a fingerprint, one that we can capture using sensors that pick up light emissions,” explains Gibson, from Cambridge’s Department of Earth Sciences. “ ̽��ֱ��difficulty, however, is that in naturally occurring rocks and minerals, the rare earth element emission spectra are mixed up with those of other elements. It’s like looking at overlapping fingerprints – the challenge was to work out how to tease these spectral fingerprints apart.”

Gibson has over 20 years’ experience investigating how REEs are generated during the melting of the Earth’s mantle. “Collective understanding of the geological make-up of the world is now good enough that we know where to look for these rocks – at sites of a certain type of past tectonic activity – but even then it’s difficult to find them.”

Riley is the head of the Geological Mapping Group at BAS – his job is to “map the unmapped” areas of the polar region to understand the geological evolution of the continent. Much of his work depends on being able to develop new ways of interrogating satellite- and aircraft-based remote sensing data. “It became a frustration that we could collect data and say generally what was on the ground but that we couldn’t define individual fingerprints, and so we developed the analytical tools to do this.”

Gibson and Neave gathered rocks containing REE-bearing minerals from around the world – sourced from mining companies, museum collections and universities. One such source was the Harker Collection housed in the ̽��ֱ��’s Sedgwick Museum of Earth Sciences. This collection contains specimens of minerals and rocks rich in REEs that were collected decades previously by geologists who were unaware of their economic importance.

Neave analysed the emission spectrum of each rock and related this to its gross and microscopic composition. From this information he began to untangle the individual fingerprints, resulting in what the researchers believe is the most comprehensive ‘spectral database’ of REEs in their natural state – in rocks.

̽��ֱ��next goal is to use this spectral database as a reference source to track down deposits from the air. “Although data from aircraft is now good enough to be analysed in this way, we are waiting for new satellite missions such as the German Environmental Mapping and Analysis Program (EnMAP) to be launched in the next few years,” explains Riley. ̽��ֱ��plan would then be to carry out reconnaissance sweeps of the most likely terrains and explore the possibility of mining these areas. “Our hope is that this research will help to create an internationally unique and competitive capability to map these surprisingly common – yet difficult to find – materials,” adds Gibson.

Vital to many modern technologies yet mined in few places, the ‘rare earth elements’ are in fact not that rare – they are just difficult to find in concentrations that make them economic to mine. Researchers from Cambridge ̽��ֱ�� and the British Antarctic Survey (BAS) are investigating whether the remarkable properties of these materials can be used to track them down from the air.

̽��ֱ��light they reflect is so specific that it’s like a fingerprint, one that we can capture using sensors that pick up light emissions

Sally Gibson

Aurora Cambridge

̽��ֱ��search for rare earth elements is one of a host of ongoing projects between the ̽��ֱ�� and BAS. Like these, a new centre – Aurora Cambridge – will reflect the ethos that innovation developed for the Antarctic is transferable to a global setting.

Aurora Cambridge aims to generate new research and entrepreneurial activity focused on climate change and challenging environments through academic, business and policy partnerships. It will be located at BAS in Cambridge and has been funded by the National Environment Research Council with support from the ̽��ֱ��.

̽��ֱ��building is due to open in 2017; however, 27 ̽��ֱ�� of Cambridge–BAS Joint Innovation Projects are already under way with funding from the Higher Education Funding Council for England – including the development of mapping technologies for rare earth elements led by Drs Sally Gibson and Teal Riley.

Other projects include research on cold-adapted enzymes with potential applications in the biotech industries, remote sensing for conservation of seabirds and marine mammals, and the measurement of coastal vulnerability through sea-level rise. Many involve external industrial partners and other research institutions as well as researchers from BAS and 12 ̽��ֱ�� departments.

“ ̽��ֱ��collaborative projects demonstrate not only the importance of research technology to the Antarctic but also their transferability beyond its shores to a global setting,” explains BAS Director of Innovation Dr Beatrix Schlarb-Ridley. “ ̽��ֱ��SPECTRO-ICE project, for instance, has brought scientists at BAS who are concerned with monitoring the atmosphere above the ice cap together with physicists and mathematicians who are working hard to avoid seeing the atmosphere in their study of the stars – both use similar techniques and need to operate advanced instruments at difficult locations.”

“This is just the beginning,” says BAS Director Professor Jane Francis. “ ̽��ֱ��new innovation centre will help us to extend the range of fruitful partnerships with academia, business, policy makers and the third sector to create tangible benefits for society.”

www.bas.ac.uk/aurora-cambridge

̽��ֱ��text in this work is licensed under a Creative Commons Attribution 4.0 International License. For image use please see separate credits above.

Yes

Opinion: Harder than diamond: have scientists really found something tougher than nature’s invincible material?

Anonymous — Tue, 19 Jan 2016 14:00:25 +0000

Ask most people what the hardest material on Earth is and they will probably answer “diamond”. Its name comes from the Greek word ἀδάμας (adámas) meaning “unbreakable” or “invincible” and is from where we get the word “adamant”. Diamond’s hardness gives it incredible cutting abilities that – along with its beauty – have kept it in high demand for thousands of years.

Modern scientists have spent decades looking for cheaper, harder and more practical alternatives and every few years the news heralds the creation of a new “world’s hardest material”. But are any of these challengers really up to scratch?

Despite its unique allure, diamond is simply a special form, or “allotrope”, of carbon. There are several allotropes in the carbon family including carbon nanotubes, amorphous carbon, diamond and graphite. All are made up of carbon atoms, but the types of atomic bonds between them differ which gives rise to different material structures and properties.

̽��ֱ��outermost shell of each carbon atom has four electrons. In diamond, these electrons are shared with four other carbon atoms to form very strong chemical bonds resulting in an extremely rigid tetrahedral crystal. It is this simple, tightly-bonded arrangement that makes diamond one of the hardest substances on Earth.

How hard?

Vickers test anvil. R Tanaka, CC BY

Hardness is an important property of materials and often determines what they can be used for, but it is also quite difficult to define. For minerals, scratch hardness is a measure of how resistant it is to being scratched by another mineral.

There are several ways of measuring hardness but typically an instrument is used to make a dent in the material’s surface. ̽��ֱ��ratio between the surface area of the indentation and the force used to make it produces a hardness value. ̽��ֱ��harder the material, the larger the value. ̽��ֱ��Vickers hardness test uses a square-based pyramid diamond tip to make the indent.

Mild steel has a Vickers hardness value of around 9 GPa while diamond has a Vickers hardness value of around 70 – 100 GPa. Diamond’s resistance against wear is legendary and today 70% of the world’s natural diamonds are found in wear-resistant coatings for tools used in cutting, drilling and grinding, or as additives to abrasives.

̽��ֱ��problem with diamond is that, while it may be very hard, it is also surprisingly unstable. When diamond is heated above 800℃ in air its chemical properties change, affecting its strength and enabling it to react with iron, which makes it unsuitable for machining steel.

These limits on its use have led to a growing focus on developing new, chemically-stable, superhard materials as a replacement. Better wear-resistant coatings allow industrial tools to last longer between replacing worn parts and reduce the need for potentially environmentally-hazardous coolants. Scientists have so far managed to come up with several potential rivals to diamond.

Boron nitride

Microscopic BN crystal. NIMSoffice/Wikimedia Commons

̽��ֱ��synthetic material boron nitride, first produced in 1957, is similar to carbon in that it has several allotropes. In its cubic form (c-BN) it shares the same crystalline structure as diamond, but instead of carbon atoms is made up of alternately-bonded atoms of boron and nitrogen. c-BN is chemically and thermally stable, and is commonly used today as a superhard machine tool coating in the automotive and aerospace industries.

But cubic boron nitride is still, at best, just the world’s second hardest material with a Vickers hardness of around 50 GPa. Its hexagonal form (w-BN) was initially reported to be even harder but these results were based upon theoretical simulations that predicted an indentation strength 18% higher than diamond. Unfortunately w-BN is extremely rare in nature and difficult to produce in sufficient quantities to properly test this claim by experiment.

Synthetic diamond

Synthetic diamond closeup. Instytut Fizyki Uniwersytet Kazimierza Wielkiego, CC BY

Synthetic diamond has also been around since the 1950s and is often reported to be harder than natural diamond because of its different crystal structure. It can be produced by applying high pressure and temperature to graphite to force its structure to rearrange into the tetrahedral diamond, but this is slow and expensive. Another method is to effectively build it up with carbon atoms taken from heated hydrocarbon gases but the types of substrate material you can use are limited.

Producing diamonds synthetically creates stones that are polycrystalline and made up of aggregates of much smaller crystallites or “grains” ranging from a few microns down to several nanometers in size. This contrasts with the large monocrystals of most natural diamonds used for jewellery. ̽��ֱ��smaller the grain size, the more grain boundaries and the harder the material. Recent research on some synthetic diamond has shown it to have a Vickers hardness of up to 200 GPa.

Q-carbon

Q-Carbon closeup. North Carolina State ̽��ֱ��

More recently, researchers at North Carolina State ̽��ֱ�� created what they described as a new form of carbon, distinct from other allotropes, and reported to be harder than diamond. This new form was made by heating non-crystalline carbon with a high-powered fast laser pulse to 3,700 °C then quickly cooling or “quenching” it – hence the name “Q-carbon” – to form micron-sized diamonds.

̽��ֱ��scientists found Q-carbon to be 60% harder than diamond-like carbon (a type of amorphous carbon with similar properties to diamond). This has led them to expect Q-carbon to be harder than diamond itself, although this still remains to be proven experimentally. Q-carbon also has the unusual properties of being magnetic and glowing when exposed to light. But so far it’s main use has been as an intermediate step in producing tiny synthetic diamond particles at room temperature and pressure. These nanodiamonds are too small for jewellery but ideal as a cheap coating material for cutting and polishing tools.

Paul Coxon, Postdoctoral research associate, ̽��ֱ�� 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.

Paul Coxon (Department of Materials Science and Metallurgy) discusses the materials that have each been heralded as the new “world’s hardest material”.

Judy van der Velden

Diamonds

̽��ֱ��text in this work is licensed under a Creative Commons Attribution 4.0 International License. For image use please see separate credits above.

Yes

Licence type:

Attribution-Noncommercial-ShareAlike

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.

BBC

̽��ֱ��Star of Adam

̽��ֱ��text in this work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License. Images, including our videos, are Copyright © ̽��ֱ�� of Cambridge and licensors/contributors as identified. All rights reserved. We make our image and video content available in a number of ways – as here, on our main website under its Terms and conditions, and on a range of channels including social media that permit your use and sharing of our content under their respective Terms.

For image use please see separate credits above.

Yes

Licence type:

Attribution

Chemistry curbs spreading of carbon dioxide

gm349 — Fri, 06 May 2011 10:59:18 +0000

̽��ֱ��findings may have implications for carbon sequestration in saline aquifers – one of the many methods being explored to mitigate rising CO2 levels in the atmosphere.

Depending on the strength of the reaction between dissolved CO2 and porous rock, the new research shows that distinct scenarios of CO2 transport may occur in deep saline rock formations.

Jeanne Andres, a Schlumberger Foundation PhD researcher at the Department of Chemical Engineering and Biotechnology at the ̽��ֱ�� of Cambridge, said: “If one knows the physical properties of the aquifer, one can now calculate the movement of CO2 across it, and when it will begin to mix with the brine. In theory, one can manipulate the strength of reactions, thereby engineering the movement of CO2 – keeping it in one area or moving it to another within the aquifer - to enhance its storage underground.”

With weak reactions, the CO2 will spread from the top throughout the depth of the aquifer, but with stronger reactions, the CO2 remains near the top of the reservoir, leaving the deeper part inactive.

̽��ֱ��strength of these reactions can vary significantly among deep saline reservoirs - rock formations possess a wide range of chemical reaction rates depending on the mineralogy (e.g. calcite, dolomite, etc) as well as other factors such as temperature and pressure,. With the new insight this research provides, it would now be feasible to consider creating and injecting compounds which could alter the strength of reactions in the aquifer.

To arrive at their conclusions, the researchers established that the basic interaction between fluid flow and the rate of chemical reactions (chemical kinetics) in a deep porous medium is governed by a single dimensionless number, which measures the rate of diffusion and reaction compared to that of the natural mixing of fluids (convection).

As applied to the storage of CO2 underground, the scientists demonstrate how this new parameter controls CO2 flow and mixing in briny porous rock. Through numerical simulations, the researchers found that above this parameter’s critical value, reaction stabilizes the CO2 system and convection no longer occurs. Below the parameter’s critical value, stronger reactions result in longer delays in the onset of convective mixing throughout the reservoir.

For systems with similar convective mixing strengths, stronger reactions, indicated by rising values of the new parameter, can increase the minimum rate at which pure, lighter CO2 dissolves into the brine, enhancing storage and reducing the risk of leakage.

Dr Silvana Cardoso, Reader in the Department and project leader, said: “This research shows how rigorous mathematical analysis coupled with strong physical understanding can help us grasp the complex interactions of flow and reaction in a carbon reservoir. Such knowledge will be valuable in guiding future approaches to carbon storage.”

̽��ֱ��paper ‘Onset of convection in a porous medium in the presence of chemical reaction’ was published in the journal Physical Review E.

̽��ֱ��presence of even a simple chemical reaction can delay or prevent the spreading of stored carbon dioxide in underground aquifers, new research from the ̽��ֱ�� of Cambridge has revealed.

In theory, one can manipulate the strength of reactions, thereby engineering the movement of CO2 – keeping it in one area or moving it to another within the aquifer - to enhance its storage underground.

Jeanne Andres

Jeanne Therese H. Andres

CO2 fingers - Strong chemical reactions between dissolved carbon dioxide and porous rock (top) may stop CO2 fingers from spreading from the top throughout an aquifer’s depth, in contrast to systems with no reaction (bottom).

This work is licensed under a Creative Commons Licence. If you use this content on your site please link back to this page.

Yes