Seventh largest diamond ever found discovered in Botswana.

The Lucara Diamond Company has announced discovering what is believed to be the seventh largest diamond ever found at its Karowe Mine in eastern Botswana, in a press release issued on 8 August 2023. The diamond is described as weighing 1080.1 carats (216.02 g), and to measure 82.2 x 42.8 x 34.2 mm. Importantly, the gemstone is reported to be a Type IIa top white diamond, which is to say a diamond with almost no impurities, a type of diamond which make up only about 1-2% of all diamonds discovered, and which are correspondingly more valuable than other diamonds of similar size. 

The new Lucara diamond. Lucara Diamonds.

The largest diamond ever found is the Sergio Diamond, found at Lençóis in Bahia State Brazil, in 1895, by Sérgio Borges de Carvalho, after whom it is named, which weighed 3167 carat (633.4 g). Surprisingly, the Sergio Diamond was not found within a diamond mine, but on the surface. The Sergio Diamond was a carbonado, a type of diamond with a black colour, a micro-porous structure, and a high graphite and amorphous carbon content, as well as frequently containing inclusions of other minerals or metals. Notably, some of the inclusions found in carbonado diamonds are extremely rare on Earth, and they have very low proportions of the isotope carbon¹³ compared to other diamonds, as well as radioactive inclusions, again not found in other diamonds. All caronado diamonds subjected to uranium-lead isotope dating have been found to be about 3 billion years old, and almost all carbonado diamonds come from two locations, Brazil and the Central African Republic. This has led to speculation that these diamonds are derived from an extra-terrestrial body which impacted the Earth in the distant past, although no hypothesis as to how such a body could have formed has ever gained widespread acceptance. Because of their hardness, carbonado diamonds were widely sought for use in drill bits in the nineteenth century, although they have been replaced by more modern materials today. Despite its exceptional size (most carbonado diamonds are smaller than a pea), the Sergio Diamond was sold for £6400 in London in September 1895, then broken up to make diamond drill bits.

An engraving of the Sergio Diamond published in Popular Science Monthly in 1906. Wikimedia Commons.

The second largest diamond ever discovered, and the largest gemstone-quality diamond, was rhe Cullinan Diamond found at Cullinan in what is now Gauteng Province, South Africa, in April 1905, which weighed 3106 carat (621.2 g) when it was found. The Cullinan Diamond was purchased by Louis Botha, the Prime Minister of the Transvaal Colony, and given to the British King Edward VII, who had it cut into nine large gemstones and a number of smaller fragments known as 'The Brilliants'. The largest of these cut stones, known as Cullinan I or the Star of Africa, has a mass of 530.4 carat, and is mounted on the Sceptre with Cross, part of the British Crown Jewels, which is carried by the monarch at their coronation.

(Left) The uncut Cullinan Diamond in 1908. (Right) The Star of Africa Diamond in the Sceptre wirh Cross in 1919. Wikimedia Commons.

The third largest diamond ever found is the Sewelô Diamond, recovered at Lucara's Karowe Diamond Mine in Botswana in April 2019, which weighs 1758 carats (352 g). This was the largest diamond ever found in Botswana, and its name was chosen by a competition organised by Lucara, meaning 'rare find' in Setswana. The Sewelô Diamond was purchased by the French fashion house Louis Vuitton, with the intention of having it cut into smaller gems.

The Sewelô Diamond. The diamond has a black crust formed of pitted carbon, but is gemstone quality beneath. Lucara Diamonds.

The fourth largest diamond ever discovered is an unnamed diamond found at Lucara's Karowe Mine in June 2021. This diamond had a mass of 1174.76 carats, and measuring 77 x 55 x 33 mm. This gem is considered to be of variable quality, although with a significant proportion of high quality diamond.

An unnamed diamond found at Karowe Mine in June 2021. Lucara Diamonds.

The fifth largest diamond ever discovered was the Lesedi De Rona Diamond, found at the Karowe Mine in November 2015. Like the new diamond, this was a Type IIa top white diamond, and has a mass of 1111 carat (222.2 g) when it was found. At that time, it was the largest diamond ever found in Botswana, and the third largest diamond ever found, prompting Lucara Mining to organise a national competition in Botswana to chose a name. The winning name, Lesedi De Rona, translates as 'Our Light' in Setswana, and was chosen by Thembani Moitlhobogi of Mmadikola. The diamond was purchased by the London-based jeweller Graff, and cut to form one large diamond, the 302.37 carat Graff Lesedi De Rona Diamond, and 66 smaller gemstones.

The uncut Lesedi De Rona Diamond in 2015. Lucara Diamonds.

The sixth largest diamond ever discovered was found at the Debswana-owned Jwaneng Mine in southern Botswana in June 2021, and had a mass of 1098 carat (219.6 g), measuring 73 x 52 x 27 mm. 

The unnamed diamond found at Debswana's Jwaneng Mine in southern Botswana in June 2021. Reuters.

Thus, the new diamond is the seventh largest diamond ever discovered, the sixth largest gemstone quality diamond ever discovered, the sixth largest diamond ever found in Africa, the fifth largest diamond ever found in Botswana, the fourth largest diamond extracted from the Karowe Mine, and one of only seven diamonds ever found with a mass of greater than 1000 carat. 

That five of these seven diamonds have been found in Botswana, and four of them from a single mine, since 2015 is not a coincidence. but marks the introduction of new technology pioneered at the Karowe Mine. Modern mines typically use crushing machinery to extract diamonds from their parent rock, but this is generally thought to break up a significant proportion of larger diamonds. The Karowe Mine uses X-ray fluorescence technology to scan ore before it passes into the crushing equipment, thus allowing for the machinery to be stopped and particularly large diamonds to be recovered. 

Flow chart showing the processing and sorting of diamonds at the Karowe Mine. Lucara Diamonds.

See also...

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Royal Canadian Mounted Police investigate after rare Ammonite stolen from Alberta mine.

The Royal Canadian Mounted Police is mounting an investigation after two men were seen stealing a rare Ammonite from a mine in Lethbridge in southwestern Alberta on Thursday 18 July 2019.  Ammonites are extremely common fossils in Mesozoic marine deposits, and are not generally considered to be particularly valuable, however the Late Cretaceous shales at Lethbridge produces large Ammonite fossils comprised of a mineral called Ammolite, which is valued as a gemstone by jewelry makers, and has resulted in Lethbridge becoming home to what is probably the world's only commercial Ammonite mine. The specimen was seen being removed in broad daylight by workers at the other end of the open pit mine, but the thieves managed to escape before the miners could reach them. It has an estimated value of about Canada $50 000 (about US$38 250).

An Ammolite Ammonite from the Lethbridge Ammonite Mine. Minedat.

Ammonites are almost ubiquitous fossils in Mesozoic Marine deposits, and as such have been used extensively in interpreting and dating these deposits. They were free-swimming Cephalopods, related to modern Octopus, Squid, Cuttlefish and Nautiloids, and like many other Molluscs are thought to have had shells comprised primarily of aragonite, a form of calcium carbonate less stable than the more widely found calcite (the primary mineral in limestone and marble). Aragonite has a sheen not present in calcite (it is the primary mineral in nacre, or mother of pearl), but because it is unstable most fossils of Ammonites (and other originally aragonitic shells) are generally recrystalised as calcite. The Lethbridge Ammonites, however, are still comprised primarily of aragonite, but have absorbed a number of metal ions from their environment, including : aluminium; barium; chromium; copper; iron; magnesium; manganese; strontium; titanium; and vanadium.This gives the fossils both a distinctive sheen and a unique colouration, which is marketed as the gemstone Ammolite.

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Generating free oxygen in the atmosphere of exoplanets without the presence of life.

In the past two decades over a thousand planets have been found orbiting stars other than our own, many of which appear to be small rocky planets in the habitable zones of their stars (i.e. the zone in which such a planet might host liquid water, thought to be an essential precursor for life). The Transiting Exoplanet Survey Satellite, due for launch in 2017, is intended to look for Earth-like planets around nearby stars. To do this it will look for biomarkers, chemical signs thought to be indicative of life, in the atmospheres of any planets that it finds. One of the most obvious such biomarkers to look for would be molecular oxygen (O₂) which makes up 20% of the atmosphere on Earth, and which is thought to be entirely produced by the actions of photosynthetic Bacteria, Algae and Plants.

However in order to be sure that such biomarkers are genuine signs of life, scientists need to be confident that they could not be formed in other, abiotic ways. Oxygen, for example, can also be formed by photodissociation of water molecules (H₂O) by ultraviolet light, and therefore could potentially make up a high proportion of the atmosphere of planets that receive high amounts of such radiation. Large amounts of ultraviolet light are also though to be extremely harmful to life, so that such planets could probably be ruled out of any search for life quite easily, but the potential remains that free oxygen could be produced in other, less easily detectable ways.

An artist's impression of the planned Transiting Exoplanet Survey Satellite. NASA.

In a paper published in the journal Nature Scientific Reports on 10 September 2015, Norio Narita of the Astrobiology Center at the National Institutes ofNatural Sciences in Tokyo, the National Astronomical Observatory of Japan and the Graduate University for Advanced Studies, Takafumi Enomoto and Shigeyuki Masaoka of the Graduate University for Advanced Studies and the Institute for Molecular Science, and Nobuhiko Kusakabe, also of the National Astronomical Observatory of Japan describe a process by which rocky planets could potentially develop atmospheres containing substantial levels of oxygen without photosynthetic organisms or exposure to high levels of ultraviolet radiation.

Narita et al. observe that the mineral titania (a form of titanium dioxide, TiO₂), can act as a catalyst for the photodissociation of water molecules by light at near-ultraviolet wavelengths (280-400nm). They further note that the mineral appears to be common in the universe, having been detected in dust outflows around giant stars and supernovas as well as on the Moon and other bodies in the Solar System. Substantial amounts of exposed titania on the surface of a planet with water in its atmosphere could potentially lead to a build-up of molecular oxygen in the atmosphere of the planet.

 SEM image of the surface of a grain of titania. Tong et al. (2015).

Narita et al. calculate that were the Earth's surface to be covered by titania, and that levels of near-ultraviolet radiation measured at the Hateruma Observatory between 2000 and 2014 are typical for Earth over a longer period then the level of oxygen seen in our atmosphere could be produced in about 20 000 years, and the all the water in the Earth's oceans could potentially be photodissociated within 20 000 000 years, though they calculate that the amount of exposed titania at the Earth's surface is actually less than 250 km².

From these calculations Narita et al. conclude that it would be possible for an Earth-like planet orbiting a Sun-like star to develop levels of molecular oxygen in its atmosphere similar to those seen on Earth through the catalytic action of titania without the presence of any form of life.

Next Narita et al. examined the possibility of the titania process creating oxygen-rich atmospheres around Earth-like planets orbiting non-Sun-like stars. They modelled Earth-like planets around a series of hypothetical stars; an M6 Red Dwarf star with an effective surface temperature of 3000K (compared to 5778K for the Sun), a radius 15% of that of the Sun, a luminosity 0.09% of the Sun's and an Earth-like planet orbiting at a distance of 0.03 AU (3% of the distance at which the Earth orbits the Sun); an M0 Red Dwarf with an effective surface temperature of 3800K, a radius 50% of that of the Sun, a luminosity 7.2% of that of the Sun and an Earth-like planet orbiting at a distance of 0.27 AU; a K2 Orange Dwarf Star with an effective surface temperature of 5000, a radius 73% of the Sun's, a luminosity 33% of the Sun's and an Earth-like planet orbiting at 0.58 AU; and an F6 Yellow-white Dwarf star with an effective surface temperature of 6300K, a radius 150% of the Sun's, a luminosity three times that of the Sun and an Earth-like planet orbiting at a distance of 1.73 AU. In each case they found that an oxygen-rich atmosphere could potentially be created by the titania catalyzed photolysis of water.

Narita et al. caution that the formation of oxygen by the photolysis of water will not automatically lead to the development of an oxygen-rich atmosphere. On Earth photosynthetic organisms are thought to have produced oxygen for millions of years before it began to build up in the atmosphere, as free oxygen reacted with a variety of substances present on the Earth's surface, most notably iron, and only once these oxidisable substances had been used up beginning to accumulate in the atmosphere, and as similar reactive substances are likely to be present on any alien world, then titania would need be present at the surface of the planet and suitable near-ultraviolet radiation reach that surface, for long enough for all such reactions to occur before oxygen began to accumulate in the atmosphere.

See also...

Determining the Habitable Zone of 70 Virginis.                                                                         70 Viriginis is a G-type Yellow Dwarf Star about 59 light years from Earth in the constellation of Virgo. It is calculated to have a mass 109% of that of the Sun, but radius 194% of the Sun’s, and a lower temperature, 5393K, compared to 5778K for the Sun, from which it is calculated to be somewhat older, approximately 7.77 billion years (compared to about 5.0 for the Sun)...

How alien moons could produce false signs of life.                                                               In the past two decades over a thousand planets have been discovered orbiting stars other than our own...

 

Kepler 186f: an Earth-sized planet in the habitable zone of a Red Dwarf star.                One of the key objectives in the search for planets orbiting other stars has been to locate planets in the habitable zones of such stars, i.e. planets on which liquid water could potentially exist. A number of planets with habitable zone orbits have been described...

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Hydrated silicate minerals in the Mariner Valley, Mars.

Hydrated minerals (minerals containing water) are considered to be evidence of the former presence of liquid water on Mars. They have been observed at a number of locations on the planet, and seem to have been formed in a number of phases, with the oldest, Noachian, deposits (thought to be approximately 4100 to 3700 million years ago) frequently containing hydrated phyllosilicates, younger, Hesperian deposits (from about 2700 million years ago to between 3200 and 2000 million years ago) containing hydrated sulphates and the youngest, Amazonian, deposits (anything younger than Hesperian) containing hydrated ferric oxides. A variety of hydrated minerals have previously been detected in the Valles Marineris (Mariner Valley), the largest canyon system on Mars, where the central portion contains extensive hydrated sulphate deposits, and hydrated clays, silicates and iron minerals have also been observed.

In a paper published in the journal Geophysical Research Letters on 30 December 2014, Catherine Weitz of the Planetary Science Institute, Janice Bishop of the SETI Institute, Leslie Baker of the Department of Geological Sciences at the University of Idaho and Daniel Berman, also of the Planetary Science Institute describe the discovery of iron rich allophane or opal deposits (hydrated silicates) in the Coprates Chasma region of the central Valles Marineris.

(Top) Mars Orbiter Laser Altimeter topography overlain on Thermal Emission Imaging System (THEMIS) daytime infrared mosaic of central Valles Marineris, including Melas, Coprates, and Eos chasmata. The yellow rectangle indicates the location of the bottom left figure. (Bottom left) Portion of HRSC image H0438_0000_ND4 showing Coprates Chasma. The yellow rectangle identifies the location of study region and bottom right figure. (Bottom Right) Portion of CTX image P18_008141_1647 with CRISM spectral parameters derived from image HRL0000A8F6 overlain in colour (red is olivine index, green is band depth at 1.9 μm, and blue is doublet between 2.2 and 2.3 μm). The Fe-rich allophane/opal deposits are outlined in yellow, whereas blue lines outline smectite exposures. Weitz et al. (2014).

Allophane and opal are semi-amorphous hydrated aluminium silicates, which generally form as weathering products of volcanic rocks on Earth. They are considered to be quite unstable, particularly in their high-iron forms, which tend to break down into iron rich clays. While chemical weathering processes on Mars are thought to be slower than on Earth, it is still unlikely that these minerals could have persisted at the surface for very long periods of time, suggesting that they have either been formed recently (in geological terms) by the action of water, or have been recently exposed by active geological movements, either of which would be a significant discovery.

Expanded views of the areas outlined by black boxes in the bottom right image above. (b and c) Hydrated nanophase Fe-rich allophane/opal corresponds to materials within yellow outlines. Portion of HiRISE images ESP_033010_1645 and PSP_008141_1645. (d) Channel containing Fe-rich allophane/opal (red arrows). Portion of HiRISE image PSP_008141_1645. (e) Example of smectites along the wall rock. Weitz et al. (2014).

The Coprates Chasma region is interpreted as a graben structure, which is to say an area where rock movements have drawn two areas of planetary crust apart, resulting in thinning of the crust in the central area, which in turn tends to lead to subsidence and slumping. The allophane/opal deposits are exposed on an area of slumping (landslips) thought to be in the region of 50-100 million years old. It is unclear if these minerals predated this slumping, and have been exposed by it, thereby potentially representing a greater reserve buried beneath the surface, or whether they are younger material that has formed at the surface as the result of the weathering of other minerals exposed by the slumping.

HiRISE DTMperspective view at 2X vertical exaggeration with CRISM spectral parameters overlain in colour (red is olivine index, green is band depth at 1.9 μm, and blue is doublet between 2.2 and 2.3 μm). The red arrows identify the eastern Fe-rich allophane/opal deposit (whitish blue), which extends across 940m in elevation, whereas the green arrows identify exposures of smectites within the wall rock (yellow-light green). HiRISE stereo pair images PSP_008141_1645 and PSP_007785_1645 were used to make the DTM. Weitz et al. (2014).

See also…

Interpreting landslide deposits in the Mariner Valley, Mars.

Landslides on Mars typically have much greater runout distances than those on Earth, due to the planets lower gravity and thinner atmosphere. This can lead to areas of layered deposits from different landslides quite distant from the source, particularly within the larger canyons on Mars. Since it is possible to produce approximate ages for such deposits based upon the number of impact...

Ice in Martian impact craters.

The surface of Mars has been observed continuously by the Mars Orbiter Camera from 1997 to 2006 and the Mars Reconnaissance Orbiter since 2006. During the time that these observations have been occurring around 200 new impact craters have been observed on the surface of the planet; most of them in dusty areas, where they are easily detected due to the dark blast patterns that surround fresh impacts in these...

Examining an Ordovician Stromatolite with a tool to look for life on Mars.

The potential of there being life on Mars has been a stalwart of popular fiction for over a century, though to date no signs of actual life have been discovered. Recent discoveries of geological structures on Mars that indicate the presence of large bodies of open water in the early history of the planet. This new understanding of the planet makes the search for evidence of ancient life on Mars a more realistic...

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What Hayabusa brought back from 25143 (Itokawa).

In November 2005, the Japan Space Agency's probe Hayabusa touched down on the near Earth asteroid 25143 (Itokawa) in order to collect samples. The probe landed in the Muses Sea are of the asteroid, and was due to fire a projectile into the surface in order to dislodge material from the surface for collection. In the event this projectile did not fire, but the probe was able to collect a small number of mineral grains floating above the surface, of the asteroid, which has negligible gravity. This material was returned to Earth for analysis in June 2010.

Close up image of taken from Hayabusa. A & B indicate possible recent impact sites. Circles represent possible hydrological sinks. Arrows point to areas of talus (rubble). Curved lines indicate possible debris flow. Japan Space Agency.

25143 (Itokawa) is a 558 m long, 288 m diameter asteroid with a 556 day period (year) on an orbit that crosses that of the Earth. It is roughly bean-shaped and has a surface covered in rubble; in fact it may be rubble all the way through. The asteroid rotates on its axis every 12 hours, and has a gravity of about a millionth of the Earth's (though this varies from place to place, dependent on the local density of the asteroid). 25143 (Itokawa) has a number of areas on the surface that appear to be hydrological sinks.

These hydrological sinks are surprising in on an asteroid, which is not somewhere we would expect to find water, but are attributed to the former presence of ice. It is thought that the asteroid may have formed further out in the solar system, where chunks of ice (not necessarily water ice) were incorporated into its makeup. At some point it was shifted onto its current orbit, where it passes closer to the sun. This caused the asteroid to heat up, and the ice to sublimate (turn directly from a solid to a gas) in a similar way to material evaporating from the surface of a comet. After this happened the loose rocky material covering the new void subsided forming a sinkhole.

The orbit of 25143 (Itokawa). Bellatrix Astronomical Observatory.

On 27 February 2012 a paper was published in the Proceedings of the National Academy of Sciences, by a group of scientists lead by Eizo Nakamura of the The Pheasant Memorial Laboratory for Geochemistry and Cosmochemistry at the Institute for Study of the Earth’s Interior at Okayama University, detailing the results of a study of five mineral grains brought back from 25143 (Itokawa) by Hayabusa, and the deductions made from these studies.

The grains were made of the minerals olivine, pyroxene, diopside and plagioclase, all common in igneous rocks from the Earth and the Moon, with small inclusions of other common minerals. They ranged in size from 30 × 40 μm to 90× 110 μm, and all were covered in tiny pits, apparently impact craters caused by the action of tiny grains 10-20 nm across. This is interesting as these may not have originated from 25143 (Itokawa), or a similar asteroid. In the Solar System objects larger than 5 μm tend to fall towards the sun, whereas those smaller tend to be carried outwards by the solar winds.

Scanning Electron Microscope images of an olivine grain from 25143 (Itokawa). (A) Detail of part of the grain as shown in inset. F1, F2 & F3 represent fracture plains (the plains along which a mineral will split). C, D & E are areas of magnification. (B) Back Scattered Electron Microscope image of (A) showing mineral textures; Ol is olivine, Pl is plagioclase. (C, D & E) Detail of (A) showing craters made by tiny impacts. These are 100-200 nm across, implying impactors 10-20 nm across. From Nakamura et al. (2012).

While the minerals from which 25143 (Itokawa) are made are not unusual they do tell us something about the history of the asteroid. The minerals present would generally form at a temperature of about 900°C, far hotter than the temperature likely to be reached during the formation of a 300 m radius asteroid. From this Nakamura et al. conclude that 25143 (Itokawa) was formed as part of a larger body, from which it has become separated at some point.

See also The composition of Comet C/2009 P1, The composition of Comet 10P/Tempel 2, Asteroid 2012 BX34 to pass within 59 000 km of Earth, The dust-tail of Asteroid P/2010 A2 and Fragments of Mars found in Morocco.

Geology Today to hold online Minerals and Fossils Event.

Geology Today is published by Wiley Blackwell on behalf of the Geological Society of London (the UK's main professional body for geologists) and the Geologists' Association (the UK's main non-professional geological organization). It contains articles about current developments in the geological sciences written by experts for the general reader, as well as news about the geological community, and regular features on fossils, minerals etc.

From 5-16 March 2012 Geology Today is hosting an online Minerals and Fossils Explained event, which will enable students & members of the public to participate in a geosciences conference, without having to travel (scientific conferences within easy distance are a once in a lifetime event and not to be missed; the Palaeontological Association held one a mile from where I was living two years ago - and I spent the entire two weeks in bed with Swine Flu). The event will feature online discussions on common & interesting fossil groups hosted by experts in the field.

5 March will see an opening session, followed by online discussions on Taphonomy (the study of fossilization processes) and Fossil Lagerstätten (exceptionally well preserved and plentiful fossil deposits), followed by discussions on three particularly famous fossil assemblages; the Ediacaran Biota (well preserved, but enigmatic Precambrian Fossils that may, or may not, represent the earliest multicellular animals in the fossil record), the Burgess Shale (exceptionally well preserved Early Cambrian fossils from British Columbia, with many soft bodied animals) and the Lady Burn Starfish Beds, a site in Southeast Scotland noted for exceptionally well preserved Ordovician invertebrates, particularly trilobites and echinoderms. On the mineral side there will be discussions on alpha-quartz (or to the layman, quartz), Opel, Alkali Feldspar and Plagioclase Feldspar.

Echinoderm from the Lady Burn Starfish Beds. Huntarian Museum and Art Gallery.

7 March will see discussions on notable groups of Palaeozoic Invertebrates; Trilobites, Graptolites, Brachiopods, Crinoids and Eurypterids (water scorpions), and on the mineral side Olivine Group minerals, Amphiboles, Micas, Garnets and Kyanite.

Olivine, (Mg,Fe)₂SiO₄. School of Ocean and Earth Science, University of Southampton.

9 March will see discussions on prominent groups of Mesozoic Invertebrates; Belemnites, Nautiloids, Bivalves, Rudists (a group of reef-forming bivalves that went extinct at the end of the Cretaceous) and Sea Urchins. On the mineral side there will be discussions on Calcite, Dolomite, Baryite, Gypsum and Fluorite.

A preserved Late Cretaceous Rudist Bivalve Reef, near Isona in Spain. Paul Harnik, National Evolutionary Synthesis Center.

12 March will see discussions on Cenozoic Invertebrates, namely; Gastropods, Barnacles, Bryozoans, Benthic Forminifera and the Palaeontology of Amber. On the mineral side there will be discussions on Hematite, Galena, Sphalerite, Pyrite, Azurite and Malachite.

Malachite with Azurite crystals. Muséum national d'Histoire naturelle.

14 March will see discussions on Vertebrate groups, notably Anaspid (Jawless) Fish, Ichthyosaurs, Therapod Dinosaurs, Azhdarchid pterosaurs and Saber-toothed Cats. The mineral side will see discussions on naturally occurring pure elements, Graphite (carbon), Copper, Silver, Sulphur and Gold.

The event will close on 16 March.

The experts hosting the discussions will be:

Peter Doyle, palaeontologist and geologist, of University College London and the Department of Earth and Environmental Sciences at the University of Greenwich, the Editor in Chief of Geology Today and Lethaia, and a prolific author in the geosciences field.

Duncan Pirrie, mineralogist and geologist, of the Cambourne School of Mines at the University of Exeter, and deputy editor of Geology Today.

Craig Barrie, mineralogist and geochemist, of the Mineralogical Society of the UK and Ireland and a member of the editorial board at Geology Today.

Howard Falcon-Lang, palaeobotonist and palaeontologist, of Royal Holloway, University of London and the University of Munster, a member of the editorial board at Geology Today and science writer for BBC News Online.

Jamie Pringle, geophysicist and sedimentary geologist, of the Keele University and a member of the editorial board at Geology Today.

Colin Prosser, geologist and palaeontologist, of Natural England and a member of the editorial board at Geology Today.

Jon Radley, geologist, of Warwickshire Museum and the School of Geography, Earth and Environmental Sciences at the University of Birmingham and a member of the editorial board at Geology Today.

Hugh Rollinson, mineralogist, petrologist and geochemist, of the University of Derby and a member of the editorial board at Geology Today.

You can sign up for the event here.