Category: minerals

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australasia climate geology minerals

Drought in South Australia creates soil problems

Dr Paul Shand (Australia) In South Australia, the staff of the Commonwealth Scientific and Industrial Research Organisation (CSIRO) Land and Water have recently shown that the River Murray, adjacent wetlands and the Lower Lakes (Alexandrina and Albert) close to the Murray Mouth are being seriously impacted by a combination of low water levels and the presence of acid sulfate soils (ASS). The Lower Lakes and the floodplains below lock 1 at Blanchetown are undergoing their first drought since the introduction of barrages more than 50 years ago. Lakes, such as Lake Bonney and Lake Yatco, as well as several wetlands formed by the River Murray, are being isolated as one option to generate water savings and help mitigate drought-related problems in the Murray-Darling Basin. Field observations and chemical analysis confirm the occurrence of both sulphuric materials (pH <4) and sulphidic materials (high sulphide concentrations and pH >4) in a range of ASS subtypes (Fig. 1). Fig. 1. Acid Sulphate Soil with sulfuric material near Swanport adjacent to the Murray River. In addition, some areas contain ‘monosulphidic black ooze’, that causes rapid oxygen depletion of lake and drainage waters when the ooze is mixed with oxygenated waters during disturbance (Fig. 2). Fig. 2. extensive cracking and accumulation of white and yellow Na-Mg-Fe-Al-sulphate-rich minerals or salt efflorescences. Unpleasant smells (‘rotten eggs’), as a result of rotting vegetable matter and the release of gases, have been experienced in these areas of exposed soils when water levels are extremely low or the lakes have … Read More

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Geology Museums of Britain: Portland Museum, Dorset

Jon Trevelyan(UK) Fig. 1. A huge Titanites giganteus adorns the doorway. I visited this little museum a while ago while on a Geologists’ Association field trip. I have passed it several time and always loved the large Titanites giganteus above the door (Fig. 1) of this picturesque cottage (Fig. 2). As a result, I had always wanted to visit, but more particularly I want to see the famous fossil turtle (Fig. 3) that is exhibited there. Fig. 2. One of the two seventeenth century cottages making up the museum. Fig. 3. The lovely fossil turtle at the museum. In fact, Portland Museum is a lovely example of a local museum containing (among other things, geology (Fig. 4), in this case, tucked away in a beautiful part of the ‘island’ in two seventeenth century cottages, near Rufus Castle and the popular Church Ope Cove. Fig. 4. Some of the geological exhibits at the museum. The Isle of Portland in Dorset represents the most southerly point of the Jurassic, which is a UNESCO designated World Heritage Site and famous for its geology, fossils and geomorphology. It is joined to the mainland by the equally famous Chesil Beach but has always been regarded (not least by its inhabitants)as separate from the mainland, and this is reflected in the museum’s collection. That is, Portland Museum does not just contain geology and palaeontology; its exhibits also reflect the Isle’s history and people. Portland Museum was founded in 1930 by Dr Marie Stopes, renowned for her … Read More

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geology minerals north america

A new Park County gem discovery: Tarryall fire agate

By Steven Wade Veatch Exceptional specimens of iridescent fire agate have recently been found in Park County in the USA, close to Tarryall Creek and near the Tarryall Reservoir. Fire agate is a variety of chalcedony (pronounced kal SED’ uh nee), a form of microcrystalline or cryptocrystalline (crystals too small to be seen without high magnification) quartz (SiO2). It contains inclusions of iron oxide (limonite) that produce an iridescent effect or ‘fire’. Chalcedony is generally formed near the surface of the Earth, where temperatures and pressures are low. The Tarryall fire agate has a botryoidal (grape-like) growth form. The agate is also layered: it contains thin layers of plate-like crystals of iron oxide in various planes. When light travels through these thin layers, the planes produce the iridescent colour play of red, gold and green. Fig. 1. Good fire agates are impressive in their rich and dramatic colour play. They form in cavities and cracks in the country rock from low temperature, silica-rich waters, in a way similar to how black opal forms. Lee Magginetti specimen. Photo date June, 2007, © by S. W. Veatch. The fire agate specimens were found as seams in granite near the Tarryall Creek. This  is a tributary of the South Platte River, approximately 25 miles (40km) long, in Park County, central Colorado. It drains a portion of north and central South Park, an intermontane grassland south-west of Denver. Tarryall Creek runs in several forks along the continental divide in the Pike National Forest and … Read More

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geology minerals north america volcanoes

That Arizona hot spot might be a volcanic field

Deborah Painter Let’s see, when I say “Arizona hot spots”, what might come to mind for many people are the restaurants, nightclubs and sports events in Phoenix (the US state’s largest city), the Grand Canyon of the Colorado River, attracting visitors from around the world, Tombstone (the infamous “town too tough to die”, where the equally infamous 1881 gunfight at the OK Corral took place), and any portion of the desert in the daytime during August. But how many people think of the many volcanoes in Arizona USA, part of a volcanic field that is likely not finished erupting? Arizona, USA has seven young (Quaternary Period) volcanic fields. The three youngest fields are the San Francisco, Uinkaret and Pinacate volcanic fields. The first two of these young fields are on the Colorado Plateau of northern Arizona; the Pinacate Field is much farther south on the Arizona-Mexico border. The San Francisco Field is the focus of this article. It is situated near Flagstaff and Williams in northern Arizona (Fig. 1). It extends approximately 5,0002km from Williams to the Little Colorado River. There are slightly over 600 cones. The field was active as recently as 932 BP (Before Present), with the eruption that formed Sunset Crater at Sunset Crater Volcano National Monument. Fig. 1. The San Francisco Volcanic Field. (Credits: United States Geological Survey/Wikimedia Commons.) The spectacular San Francisco Peaks within this field are originally a single stratovolcano that experienced deep erosion (Fig. 2). Mount Elden near Flagstaff is a large volcanic … Read More

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england geology historical / biographies minerals mining

German Miners in Cumbria

By Jean Tyler One fine Summer’s day in 1564, a group of men on horseback made their way westward from Carlisle along the rough road to Keswick. One of their number rode with the covered wagon that contained clothing, personal chattels and the tools of their trade – mining. These men came from Germany and were the finest miners and smelters in the world. They were here in England at the request of the English Crown and their job was to extract the rich, glowing copper from the mineral veins of Lakeland. So begins the story of mining in this country. The first group of ten men arrived in Keswick in 1564 and were easily accommodated in local lodgings. What a flurry of excitement this must have caused in this little town that consisted of no more than one muddy street with a few squalid yards running off it. At that time, the housing was of timber and wattle daub construction with bracken-thatched roofing. Behind the houses ran strips of land with middens, pigsties and more very basic housing – buildings that were little more than hovels. The arrival of the Germans created a flutter amongst the local girls who were soon vying with each other for the attention of these small, tough men from overseas. Unhappily, some of the inhabitants were suspicious of the foreign strangers who were set to earn good money doing a proper job and violent confrontation eventually resulted in one of the incomers, Leonard Stoulz, … Read More

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africa / middle east europe geology historical / biographies minerals south america

Building stones of the Ancient World

By Ken Brooks (UK) Local stone was an essential element in the development of early civilisations, as its availability and quality determined the building styles that they created. The effective working and use of stone as a building material was a skill acquired by man at an early stage of history in many different regions of the world. Today, we can identify their methods of working stone by studying the buildings, quarries and the tools that have survived them. Egypt For thousands of years, the River Nile has carved its way through areas of sandstone, granite and limestone on its 750-mile journey through Egypt to the Mediterranean. From very early times, and even to the present day, the Egyptians have built their homes with bricks made from mud – an abundant raw material along the banks of the River Nile. It was around 5,000 years ago, as organised religion became established, that they began to use locally available stone to construct temples and pyramids. Between 2590BC and 2500BC, the ancient Egyptians built three huge pyramids on the Giza plateau (near present-day Cairo). Fig. 1. The pyramids at Giza. The bedrock in this area is a nummulitic limestone dating from the Eocene period, 34 to 55mya. It is an interesting thought that some of the largest man-made structures on earth were constructed from the fossil remains of tiny organisms (foraminifera). Work on a pyramid began with the extraction of limestone blocks at a nearby quarry. The only tools the Egyptians had … Read More

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BOOK REVIEWS climate england fossils geology minerals mining palaeontology volcanoes

Lake District: Landscape and Geology, by Ian Francis, Stuart Holmes and Bruce Yardley

I recently reviewed another of the guides in Crowood Press’s excellent “Landscape and Geology” guides, which was undoubtedly a great read. And this one is equally good, with great, full colour pictures, maps and diagrams, and easy to read text, with descriptions of interesting walks and what can be seen on them.That is, there are easy-to-understand explanations of how the rocks formed and how the geology affects the landscape, and there is also an n exploration of the long human story of the landscapes.

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Iceland: Classic Geology in Europe (3rd edition), by Thor Thordarson and Ármann Höskuldsson

reviewed the 2nd edition of this guide a while ago and, as I said then, Iceland seems to set the hearts of certain geologists racing and, reading this field guide and that previous incarnation, it is abundantly clear why. Iceland’s fascinating geology is clearly set out in this concise and authoritative book. The island, astride the Mid-Atlantic Ridge, is a ‘natural laboratory’ where the earth sciences can be watched in real-time. Rifting of the crust, volcanic eruptions and glacial activity are among a host of processes and features that can be observed in this fascinating land.

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Book review: Isle of Wight: Landscape and Geology, by John Downes

This is another guide in the excellent “Landscape and Geology” series of local geological guides published by The Crowood Press. And this is as good as the others. Admittedly, it has a wonderful subject matter, because the Isle of Wight is a geological gem with its 110km long coastline displaying a range of rocks dating from Lower Cretaceous to Oligocene age. I know from personal experience that many of its sands and clays contain collectable fossil bivalves and gastropods, and its famous dinosaur footprints attract attention from both geologists and tourists, with always the possibility of finding a bone or two.

extra-terrestrial geology minerals space

Meteorites: A primer

Dr Kendal Martyn Meteorites have long held fascination for me – that is, they aren’t from this planet. Added “glamour” has come from recent suggestions that at least one meteorite impact on earth could be responsible for mass-extinction events, the largest “smoking gun” in evolutionary selection. Also, meteorites are the … Read More

BOOK REVIEWS england geology minerals mining museums, societies urban, art, anthropology

Book review: Minerals of the English Midlands, by Roy E Starkey

Goodness me! This is a massive work (432 pages) – but written with enthusiasm from the heart, with authoritative text, lovely photos throughout, fascinating anecdotes and history, with detailed geological descriptions of all the relevant counties. Now, I’m no expert on minerals, which fall well outside the scope of my interests. However, I cannot praise this book too much.

BOOK REVIEWS geology minerals volcanoes

Book review: Introducing Geophysics, by Peter Styles

Notwithstanding the somewhat daunting use of the word “geophysics” in the title, this is another great book in Dunedin’s Introducing Earth and Environmental Sciences series of guides. In fact, In fact, the only real way to understand the Earth, in all its large and slow-moving immensity, is to study its physics and that means using the classical disciplines of heat, gravity, magnetism, electricity, vibrations and waves. That is, everything we know about the deep Earth has been learnt from geophysics.

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Book review: The Chalk of the South Downs of Sussex and Hampshire and the North Downs of Kent (Geologists’ Association Guide No 74) (vols 1 and 2), by Rory N Mortimore

I have to admit, I was beginning to wonder where Prof Rory Mortimore’s update of his excellent Chalk of Sussex and Kent was. And now I know. It wasn’t a second edition he was working on, but this magnificent magnum opus in two volumes covering a vastly greater area than that other guide. And the wait was more than worthwhile. The thoroughness, writing quality, content and publication standards are superb.

geology minerals

Quartz is more than silicon dioxide

Dr Kendal Martyn (UK) This article describes several processes producing the shape of crystals. Such processes are illustrated in the most common mineral from the Earth’s surface, quartz. Quartz or “simple” silicon dioxide, is made up of interlocking atoms of silicon and oxygen, arranged into various symmetrical structures depending on … Read More

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Book review: The Peak District: Landscape and Geology, by Tony Waltham

The Crowood Press are really developing a nice little series of books on the landscape and geology of select regions of the British Isles, and Tony Waltham’s addition to the series about the Peak District is well worth a read. This new one follows the same format as the others – beautiful, full colour photos and diagrams, a fascinating chapter on each of the important geological and geomorphological aspects of the area (including buildings and industry), and an author who knows his stuff and can write it down with an easy and authoritative style.