(Nodule: Open one and you never know what you may find)
Where is this colourful place? ……and the colours are correct. Clue: it is in this country and the scale of the picture is deceiving. The place is enormous…….
Email me the answer or see me at the AGS evening meeting. Open to all. A fossil for the first correct answer.
The answer was: Powys Mountain in Anglesey, the site of an enormous copper mine which has been mined for its ores since the Bronze Age. A fascinating place and worth a visit.
Mike Howgate from the AGS visited the site last year and recognised it immediately. He was duly award a rare fossilised shell which I hope will take pride of place in his collection……..
Another puzzling photograph to be shown soon……
Picture by RF
SYNOPSIS OF RECENT TALKS
Tuesday 13th June 2107
“Internal Features of Gemstones” by Pat Daly from Gem-A
Pat explained that inclusions and flaws found in almost all gemstones can be observed using a gemmological microscope with an angled lighting option or even using a standard 10x loupe.
The inclusions would assist in determining if the stone was genuine, synthetic or had been heat treated to enhance the colour and even from which locality.
A ‘Horsetail’ inclusion (as in the plant) in a demantoid garnet would prove that the stone was genuine, as this particular flaw is impossible to reproduce in an artificial garnet.
Similarly, fissures or ‘feathers’ can occur in emeralds and this is expected and proves it is a natural stone.
Synthetic rubies can contain bubbles which would not be expected if the stone was of good natural quality, as for instance in a Star Ruby. A glass filling technique is used abroad to fill fractures in rubies, Pat’s advice was to be careful who you buy from!
Diamonds can contain pyrope and olivine crystals and some diamonds can even contain a diamond crystal as an inclusion.
Moldavite, a tektite from a meteor impact has complicated inclusions, folded and refolded from the impact but these would not be evident if it was synthetic.
Almost any translucent stone can be examined under a gemmological microscope and its internal structure studied. For instance, hematite in quartz, moss agates, small cauliflower-like hematite growths in Jasper, fire agates with irradesence and even inclusions in Baltic amber, including detail down to the hairs on the trapped insects. Finally, rutile in quartz will show up as reddish needles with the stones being polished to show them off for the best effect.
Pat showed numerous photographs of Gemstones with various inclusions to illustrate his interesting talk. – 34 Members attended.
Tuesday 9th May 2107
“Chromite, Tungsten & Iron: Mineral deposits and mines in Portugal” by Lesley Dunlop from Northumbria University.
Leslie’s interest in the minerals of Portugal followed on from her earlier studies of deposits in Devon and Cornwall.
With a geological map of Portugal she pointed out how the rocks are older in the North, being pre-Cambrian and Silurian but younger towards the South of the country. An Ophiolite complex near the northern Braganca district hosts chromite deposits in its ultrabasic rocks and has hundreds of disused shafts and adits from mining which continued up until the 1950’s. A photograph showed an example with black flecks of chromite in a metamorphic rock which would have been derived from a depleted mantle source.
Travelling South, the Panasqueria granites are associated with the Tungsten and Tin deposits, the former being very important since the 1930’s and still being mined today, mainly for heating and lighting elements, machine tools and as a high temperature alloy. The Romans originally mined the tin deposits which were found in veins above the granite in the country rock. Wolframite is the Tungsten ore and Cassiterite the Tin ore.
The Iberian pyrite zone in Southern Portugal is primarily worked for iron but gold, silver and copper are also found. Pegmatite is a primary source of Lithium which is mined in central and southern Portugal and becoming increasingly important with the interest in electric vehicles powered by Lithium–iron cells. It has a similar composition to granite but can contain much larger crystals of feldspar and quartz, as Lesley illustrated with some excellent photographs.
Aside from the minerals in the country, Estremoz and Borba in the South have huge marble quarries, worked vertically in open cast pits and have lifts large enough to hoist lorries to and from the quarry floor.
Lesley mentioned many other places of interest, including the Lisbon coastline, Ordovician quartzite ridges, mine tailing or waste tips, Mouros museum (although closed) and also of course mentioned the great climate and the dodgy roads!
Tuesday 11th April 2017
“Sandstone Fantasies of Jordan” by Dr. Tony Waltham of Geophotos.
Tony explained that he and his wife had visited Jordon many times over a number of years and although he called it ‘boring Jordon’ because of its scrubby, flat, desert areas, the wonderful World Heritage Site of Wadi Rum, the Nabataean capital of Petra with its elaborate sandstone mausoleums plus its geology made up for it.
The country itself is almost landlocked, being surrounded by Saudi Arabia, Syria and Israel and only having one connection with the Red Sea at the Gulf of Aqaba. The Dead Sea is an important tourist resort and is 400 metres below sea level. A slide of Tony’s wife floating around reading illustrated how the sea is around ten times saltier than most oceans and also shrinking, due to the siphoning off of its water source for agriculture.
Wadi Rum near Aqaba is a rocky and desert environment with canyons cut deep into the sandstone and granite rock. The Nabataeans carved images of humans and animals into the rocks forming the valleys when they inhabited the area around 300BC. Modern Bedouins live in tents and houses nearby and drive four wheel all terrain vehicles for transporting the many tourists around the area, a complete contrast to when Tony first visited in the 1980’s.
He mentioned Black Iris’s growing wild, phosphate mines, dolerite dykes in granite, volcanic plugs, showed images of huge landslides caused by flash flooding, tall pinnacle’s of Cambrian sandstone with bedding and most impressively, some wonderful pictures of the Nabataean ‘Treasury’ and ‘Monastery’, elaborate, temple like sandstone buildings carved into the rock at Petra. Along with hundreds of other smaller buildings cut into the rock, they were all originally built as mausoleums, for interning their dead and are fairly small inside. The sunlight showed up the incredible colour banding in the rock and also ‘Liesegang’ rings in the sandstone roofs inside some of the tombs, caused by precipitation during the formation of the sedimentary rock.
Tony’s talk was superbly illustrated with his own photographs and fluctuated somewhere between being a travel talk and a geological lecture. He was very enthusiastic and made it a very interesting and educational evening.
Penny Badham from the AGS bought in some wonderful rocks collected from the area during a visit in 1994 and also one of her well executed watercolours of the ‘Treasury’. See below….
Tuesday March 14th 2017
“Stones said to have fallen from the clouds” – Prof.Paul Henderson. UCL.
From the earliest recorded meteorite fall in 1492 through to the 1800’s the idea that meteors may have originated from space was not well received. Sceptics put forward theories that volcanoes, subterranean gases, debris from hurricanes and many other ideas were much more likely. The theory they were from volcanoes on the Moon or a sign from God were also accepted. It was not until a major fall in Siena in 1794, witnessed by locals and European visitors that scientific investigations were carried out, papers and books written by academics and the study of meteors really began to develop. The Wold meteorite in Yorkshire of 1795 and a further large fall in France in 1803 helped to convince most that the meteorites did fall from the sky, but much further away than previously ever imagined. Now we understand that most of these extra-terrestrial rocks originate from the asteroid belt between Jupiter and Mars, can be microscopic dust or over 1000meters in diameter, as in the K/T event.
The last recorded fall in Britain was in 1991, in Mr Arthur Pettifor’s back garden in Glatton, Cambridgeshire. So keep looking………
Paul Henderson gave this interesting talk to 32 attentive AGS members, along with some fascinating slides and facts. Julia, Doug, Mike and C.D. bought along the related objects shown below and we thank them very much.
Tuesday 10th January 2017 – Synopsis
‘IGUANODON’ by Dr. Chris Duffin, Scientific Associate at the Natural History Museum.
Gideon Mantell was a famous geologist and paleontologist in the 1800’s and a passionate collector of fossils. With his wife Mary he was credited with finding the very first Iguanodon tooth in Tilgate Quarry, Sussex in 1822. Whether he found it, his wife or possible a quarry worker was never really established. The name was conceived due its similarity to an Iguana tooth, although considerable larger.
Further finds and a bone assemblage discovered in Maidstone Kent in 1834 enabled Mantell to make the first attempt at a reconstruction. He made one well-known error by placing the (then unknown) modified thumb on the nose to resemble a horn. This is still depicted in Richard Owens reconstruction in concrete and steel in Crystal Palace Park. (see ‘Gallery’ page of the website)
The discovery of much better specimens in later years revealed that the horn was actually a modified thumb.
Before that was established Gideon Mantell suffered a carriage accident in 1841, resulting in a spinal deformity and death in 1852 from an opium overdose. His deformed spine was removed and pickled and stored at the Royal College of Surgeons. Unfortunately it was thrown away in the 1960’s …….
In 1878 the remains of 38 fossil Iguanodon’s were found in a coalmine at Bernissart in Belgium at a depth of over a 1000 feet. It was established that they lived around 125mya during the early Cretaceous. The assembly of 36 females and 2 smaller males have given rise to many theories on their deaths and also where and how they lived. Were they drowned in a gorge during a massive flood? Did they all die inhaling noxious fumes? Or was it similar to a modern elephants graveyard?
Whatever, the number of complete skeletons enabled Louis Dollo, a French born paleontologist to establish the position of the modified thumb with certainty. Along with four other fingers it would have been a slashing weapon and used for defense. He also established that the teeth, which met at a steep angle, gave a parallel bite and were suitable for grinding leaves and foliage, as an Ornithischian herbivore. Their pubis bone faced backwards at an angle allowing for a larger digestive tract. These huge animals would have measured up to 13 metres long, weighed over 3 tons and been bipedal although capable of walking on all four limbs.
9 of Dollo’s reconstructions are still on show in Brussels.
Chris gave a fascinating talk on a topical subject to around 38 AGS members, introducing all the Victorian personalities involved in the early discoveries with lots of slides and detail.
Some specimens bought in by Eric Freeman and displayed for the talk.
Tuesday 13th December 2016 – Synopsis
“Our Heritage – Stone Tools and Rock Art” Bob Maurer from Harrow & Hillingdon Geological Society.
Bob brought along some wonderful examples of horn, flint and sandstone Palaeolithic tools. (see photos) The latter type he found several years ago in a cave in South Africa and has been dated to 700,000 years old. Two other examples were attempts to fashion flint-cutting tools himself during a two-day ‘Flint Knapping’ course. He was determined to discover the skills and intricacies required to produce a Stone Age tool.
The talk guided us through the early attempts 2.5 mya to fashion stone tools (Oldowan), through to later more sophisticated tools and weapons.
Around 1.7mya ago during the lower Palaeolithic man began to improve on basic cutting tools by fashioning stones with many more cutting edges and sophistication. More advanced primitive people of 700,000ya were quite capable of removing hides in one piece, dismembering the carcass and cooking the meat, as well as being fully clothed in animal skins. Evidence of tanning processes to soften the skins have also been found.
Bob illustrated the talk with a number of slides of cave paintings in Libya, depicting Bovid and Aurochs which were introduced to North Africa around 15,000 to 20,000ya, during the Africa Humid Period. Altamira Caves in Spain date from the same period and show Palaeolithic herds of European bison and bulls. With sea levels much lower it was possible that man migrated down through Italy into Sicily and into Africa. Rock art in the Akkakus Mountains of Libya show wide horned Bovid herds and in the Libyan Museum tethered and harnessed animals. Man is depicted with Caucasian features and wearing dress like kilts.
Other similar cave paintings show dogs hunting gazelle, humans with head ornaments and war scenes while others show stylised dance scenes with muscle and movement depicted. The colours were mainly red and were made from iron oxides, such as hematite or ochre ground up and mixed with animal fat and blood etc.
Bob also described the oldest musical instrument ever found, a long, thin flute- like instrument with five finger holes found in Hohle Fels cave in Germany, made from a wing bone of a Griffon vulture and dated at 40,000 years old.
An interesting lecture with plenty of colour slides to illustrate the talk and actual stone tools to examine.
Tuesday 8th November 2016 – Synopsis.
‘Carbonado-Diamonds From Space’ by Prof. Hilary Downs, Birkbeck University London.
Not your average diamond, but micro diamonds found in Carbonado rocks in alluvial deposits of West Africa and Brazil. They can range from 1um to 200um in size but mostly are nearer 10um and are used mainly in industrial processes. Previous opinion was that they had originated from deep within the earth, but recent theories suggest they may have arrived on the Earth’s surface by impact with a comet, asteroid or some other carbon rich object.
They are not polycrystalline or mono-crystalline diamonds as recovered from Kimberlite pipes but were shown in electron microscope images to be cube-like crystals. When tested they were approximately 3 Ga (3 billion) years old. Some rocks had a glassy crust and shock features as well as radiation damage and metal inclusions, all indicative of an impact from space. They contained VERY rare Nitride minerals, some not normally seen even in meteors and there were other hollow needle like crystals of unknown minerals. Evidently there are no carbon planets in our solar system, therefore it has been suggested that they may have originated from outside our solar system, although this has now been discounted as unlikely. More likely a Titan-like moon impact created high temperatures in a carbon rich atmosphere, thereby causing ‘plasma’ to form which then condensed to produce Carbonado, similar to chemical vapour deposition. This would explain the porosity, crystal morphology and the nitride metals, but it is only a hypothesis………..so watch this space.
Tuesday 11th October 2106 – Synopsis
‘Mesozoic Marine Reptile Renaissance Part Two’ Dr. Mark Evans, Leicester Arts & Museums Service.
The Mesozoic Marine Reptile Renaissance Part Two: Sauropterygians
Following on from the talk last year on the recent increase on our understanding of ichthyosaurs and their relatives, the talk focused on the sauropterygians. This was the longest lived group of Mesozoic marine reptiles ranging from the Olenekian (Early Triassic) all the way to the end of the Cretaceous and included the plesiosaurians of the Jurassic and Cretaceous. Recent years have seen a flood of new taxa from the Triassic of China. Some of these are similar to European taxa from the Germanic Basin and the Alps demonstrating interchange between the western and eastern areas of the Tethys Ocean. Among the new discoveries are members of a newly recognised enigmatic group, the Saurosphargidae, which may well be the sister group of the sauropterygians proper. The durophagous placodonts, the earliest diverging sauropterygian group, is also represented in China. Together with European material these new finds have improved our understanding of the evolution and palaeobiology of this somewhat overlooked group. Renaissance is also happening closer to home in the study of the Jurassic plesiosaurians of the UK. Dr.Evans summarised ongoing work on early Jurassic rhomaleosaurid plesiosaurian specimens, including those from the Leicester collections, which indicated that their diversity was higher than previously thought. He also described the skull of a giant pliosaurid plesiosaurian discovered in recent years in Dorset. The whole talk was illustrated with some wonderful coloured, life-like reconstructions of the marine reptiles.
Tuesday 13th September 2016 – Synopsis
“Virtual Fossils – Soft Bodied Sensations from the Silurian” by Prof. Derek Siveter from the Oxford University Museum.
Derek’s hobby of Palaeontology many years ago turned into a career spanning more than forty years. His talk concentrated on the Silurian period (around 425my.) and the remarkable fossil finds in Herefordshire Konservat-Lagerstatte. These are worms, molluscs, brachiopods and arthropods, plus others, entombed in nodules and beautifully preserved. (see photo) They occur as calcite in-fills inside the nodules and were encased in clay almost immediately after burial, which helped preserve them. The nodules themselves were discovered in a volcanic ash layer from where the calcium helped to produce calcium carbonate which replaced the soft tissues of the animal. The fossils are very small, just a few millimetres usually and cannot be ‘prepared’ or removed from the the surrounding matrix by normal methods. Instead, they are ground down in 20µ increments (20 thousandths of one millimetre), then photographed, then ground down again, photographed and so on until the fossil is destroyed (!) The photographs are then downloaded into a ‘Spiers’ software program which reconstructs the slices into a 3-D image or ‘Virtual Fossil’. The enlarged coloured images can then be studied in detail, including all the soft parts, and also turned into models of the animals. Derek gave a fascinating talk and showed us numerous wonderful photographs.
My photo of fossil with permission.
For more info on this subject click on the link: www.shropshiregeology.org.uk and look at the suggested reading topics.
Tuesday 12th July 2016 – Synopsis
John Pearce – ’30 years collecting with the Sussex Mineral and Lapidary Society’
John has been around the UK and the world in his quest to find the ultimate mineral. Field trips to The Isle of Sheppey, Wells in Somerset, Cumbria, Skye, Namibia, Lanzarote, New Jersey, Bulgaria, Ireland, India and the Faroe Islands, to name a few! He has paddled around with Wellington boots full of water, abseiled down cliffs, crawled through tunnels, scrabbled around quarries and been down several mines and one time found so many specimens he had to ship them home by sea; seriously. Wulfenite, Barite, Stilbite, Azurite, Peridotite, Zeolites, Galena, Gold, Samsonite, Chabazite are a just a few of the beautiful minerals that John has found over the years. The descriptions of the trips and the photographs of some of his beautiful finds made it a fascinating talk.
TUESDAY 14th June 2106 – Synopsis