Ruel A Macaraeg (USA) In recent years, a number of ammonite pendants, similar to the one in Fig. 1, have been offered by tribal art dealers. As scientific objects, they offer the interest all fossils – a chance to study the tangible remains of ancient life. Being among the more abundant of fossil types, ammonites normally wouldn’t excite major paleontological interest. However, the relatively unexplored locality from which these ammonites come, and the unfamiliar use to which they are put, call for a closer look. Fig. 1. Ammonite pendant. They are reportedly from the Dani – a people from the central highlands of Irian Jaya (the western, Indonesian half of New Guinea) – and the methods and materials used in their construction support this attribution. Surrounded by steep mountains on all sides, these highlands were largely isolated from the outside world until the 1930s, when passing airmen spotted densely clustered villages and cultivated fields in the river valleys. Anthropologists were quick to realise the importance of this enduring Neolithic culture, and among the works published on the Dani were the book Gardens of War and its accompanying film Dead Birds (Gardner & Heider 1968), which remain classic studies of social violence. These investigations emphasised the ritualised nature of Dani warfare, during which the normally unadorned men would dress in elaborate costumes decorated with cassowary feathers, boar tusks and bailer shells. Scholarly interest soon translated into artistic interest and tribal collectors began turning their attention to Dani ornaments, which now appear … Read More
Steven Wade Veatch (USA) Blue John stone is the name given to banded fluorite found in the Castleton area of Derbyshire in England (Ollernshaw, 1964). It has been prized for centuries. Chemically, it is a calcium fluoride (CaF2) and occurs in distinct bands of different colours: blue, white, purple and yellow. The colour banding is thought to be from periodic changes in the composition of the mineralising solution and the physical conditions during its formation (Mackenzie and Green, 1971). The name of this distinctive material is thought to have come from the French “bleu et jaune”, referring to its blue and yellow colours. Blue John is mined from only two places – Treak Cliff Cavern and Blue John Cavern in Castleton. It occurs either in veins up to 7.5cm thick or as nodules in a limestone unit found inside natural caverns beneath a hill west of Castleton. The caverns are now tourist attractions, where visitors can go on underground tours (British Council, 2008). Castleton is an excellent example of a quintessential English town. A beautiful stream quietly flows through this picturesque community of quaint tea shops, inviting pubs, charming cottages and old stone houses. Peveril Castle is a short walk up the hillside. Fig. 1. Located in limestone, deep witihin the Treak Cliff and Blue John Caverns, Blue John has been mined for its beautiful colours for centuries. (D Veatch specimen, photo by S Veatch.) Blue John was first discovered about 2,000 years ago when the Romans mined lead and … Read More
Stephen K Donovan (The Netherlands) My writings on urban geology are normally centred in the area around my home in Noord Holland, but sometimes I am lucky enough to travel. A personal wish that I have had since I was a teenager was to see and, if possible, board a dreadnought battleship. This whim was finally satisfied in March 2014, when I visited the last surviving dreadnought from World War I, the USN Texas, preserved at the San Jacinto Battleground State Historic Site, near Houston (Fig. 1A). What I had not realised was the battleship is interred adjacent to the site of the Battle of San Jacinto, where a rag-tag army of insurgents, following defeat at the Alamo and Goliad, decisively defeated the Mexican army in under 20 minutes in April 1836, thereby winning independence from Mexico for Texas. Fig. 1. Two breathtaking exhibits at the San Jacinto Battleground State Historic Site, near Houston, Texas. (A) The dreadnought battleship, USN Texas, commissioned in 1914 and a veteran of two world wars. (B) The San Jacinto Monument, built in 1936 from Cordova Cream Shellstone and the tallest memorial stone column. The San Jacinto Museum of History is in the base. The Battle of San Jacinto is commemorated by a towering monument (Fig. 1B), which is the tallest memorial stone column, about 175m, and some 4.5m taller than the much better known Washington Monument in Washington DC. The San Jacinto Monument is visible over a wide area of this flat coastal plane … Read More
The Geologists’ Association have extended their excellent series of geological guides by producing what some people (including me) would think at first was a slightly self-indulgent couple of volumes on ‘Devonshire Marbles’.
Rosalind Jones (France) “Time and tide wait for no man” and “truth is often stranger than fiction.” Both these sayings apply to Scotland, especially Argyll with its islands at ‘the edge of the world’. Here, historic stones – some truly associated with destiny, others more dubiously linked by legend – fascinate and abound. Fig. 1. Perched erratic, Ben Hogh, CollColl and Tiree, to the northwest of Mull and Iona, are non-identical ‘twins’. Coll is rugged and rocky; Tiree is low, fertile and flat. However, in common with islands of the Outer Hebrides, both have pure white strands of calcareous sand made chiefly from maerl, backed by sand dunes of flower strewn machair (a low-lying grassy plain found on some of the northwest coastlines of Ireland and Scotland, in particular, the Outer Hebrides). Individually, they have their own strange, legendary stones – glacial erratics that have drawn myth to themselves and one which ‘rings’ its own warning today. Fig. 2. Sand dunes and white maerl sandy beach, Isle of Coll.Maerl is formed when Atlantic Ocean currents force upwards dissolved mineral that nourishes the marine organisms of the Hebridean fringe. From this rich cold water, calcium carbonate is extracted, not only by invertebrates to make their shells, but also by the calcareous red algae, Phymatolithon and Lithothamnion coralloides, collectively known as ‘maerl’. Found at depths of between 10m and 18m, living maerl beds produce small granules between 2mm and 10mm in size that accumulate in beds and which grow at 1mm a year. Sorted by currents and eventually washed landwards … Read More
Charles Underwood (UK) Fossil sites are generally the result of happy coincidence. It may be that this is the result of natural processes, when the sea or a river has eroded into cliffs of fossil bearing rocks. It could also be the result of human activity, where a quarry opened up for commercial reasons also happens to contain fossil-rich layers. However, it is rare for a fossil site to be made specifically for access to the fossils; and, when this does happen, access is usually restricted. However, there are exceptions. One of these is in the great Moroccan phosphate fields. Fig. 1. Meadows of spring flowers conceal the fossil-rich rock just below the surface. Strip mining for mineral phosphates is massive business in Morocco, providing the raw material for a vast proportion of the world’s phosphate fertiliser. Near the town of Khouribga, vast spoil heaps extend across the horizon and give an indication of the scale of the rock extraction going on behind them. These phosphate-bearing rocks are famous for their fossil content, and the cream and tan fossils from them can be seen for sale the world over. Unfortunately, access to the mines is very difficult and so, most of the time, collectors will have to satisfy themselves with what they can buy from dealers. While, purchasing specimens allows access to some really impressive finds, inevitably the fossils are out of context so their age is uncertain, and small and otherwise ‘unsellable’ fossils cannot be obtained. As some layers … Read More
Stephen K Donovan (The Netherlands) Building stones may tell us something or nothing about the geology of the local area. As Ted Nield (2014) recently highlighted in his book, Underlands, stones used in Britain today are rarely local. Once upon a time, local stone would have been derived from a nearby quarry. Now, stones are commonly imported from overseas. If that is the case in the British Isles, then pity the poor geologist in the Netherlands, where genuine exposures of rock only occur in the south, in the province of Limburg, and mainly consist of Upper Cretaceous chalks and limestones. In consequence, ornamental and facing stones on buildings are almost invariably imported. I mainly have eyes for the imported Upper Palaeozoic limestones, probably mainly Carboniferous, but potentially including some from the Devonian. These rocks are common (van Roekel, 2007), but I also pay attention when I spy a beautiful granite, in the broadest sense, which are common on the fronts of banks and used even more extensive to clad offices. This article is about two such granites (out of many) cladding buildings in Noord Holland, which have particularly caught my eye. For a general mineralogical reference, I recommend Deer et al (1966). A faulted granite in Hoofddorp This site is close to the limestone street art in Siriusdreef (described by Donovan, 2014; and see also Fig. 1) and is an easy walk from Hoofddorp railway station or bus stops on the #300 express bus route. The building in question (there … Read More
Steven Wade Veatch (USA) Quartz (SiO2) is a common mineral found in all three classes of rocks (igneous, metamorphic and sedimentary), in many environments and in a range of colours. However, rose and blue quartz are less common than some of the other varieties. This article discussed these two extraordinary minerals. Rose quartz Rose quartz has a pale pink to rose-red colour, thought to be caused by trace amounts of titanium, which absorbs all colours except pink. In a laboratory experiment, samples of rose quartz from several localities were carefully dissolved in acid. The remaining insoluble residue consisted of thin microscopic fibres, which may also be responsible for the colour of rose quartz. Well-formed rose quartz crystals are rarely found in nature, but when they are, they are generally found in massive chunks associated with pegmatites (Fig. 1). Fig. 1. This large rose quartz specimen was found at the Devil’s Hole Mine (owned by Tezaks), about a mile from the town of Cotopaxi, Colorado. (Photo © 2007 A Schaak.) The term pegmatite refers to exceptionally coarse-grained crystalline granite. Since rose quartz is cloudy, it is not popular as a faceted gem, but it is commonly made into cabochons (Fig. 2), rounded into beads for necklaces or carved into various objects. Fig, 2. A cabochon pendant from the same rose quartz near Cotopaxi. (Photo © 2007 A Schaak.) It has been named as South Dakota’s official state mineral. Here, rock hounds have a good chance of finding specimens ranging from shades … Read More
Trevor Devon (UK) Eleven members of the Hastings and District Geological Society (HDGS) assembled in front of the Canterbury Law Courts on a fine Sunday morning in June 2010 to meet up with our guide for the day, Geoff Downer. Geoff had previously given a talk to HDGS in the spring on the building stones of St Augustine’s Abbey and clearly had a great passion for this subject (he calls it a “hobby”). The day was spent on a gentle walk around the eastern part of Canterbury, largely taking in St Martin’s Church, St Augustine’s Abbey and Canterbury Cathedral. Geoff provided a fascinating commentary on the geology, history, archaeology and architecture of the area, and stopped at appropriate sites to explore and identify the building stones more fully. Given that Canterbury had been an important major Roman town, and given its subsequent ecclesiastical history from Saxon to Norman and medieval times, there was no shortage of material to see. After a brief introduction to the geology of the Ouse Valley, we took a short walk to look at the thirteenth century Conduit House (Fig. 1), a well-preserved example of medieval water technology that was used to collect groundwater from the natural springs of the surrounding hills and gravity feed it down to St Augustine’s Abbey using lead pipes. The reservoir and tunnels are constructed of all sorts of stone, using some reclaimed material from the nearby city and the structure would originally have borne a circular roof. From this fascinating … Read More
Bob Williams (UK) Chert and flint are crystalline (perhaps more accurately described as microcrystalline) forms of rock that man has made use of from Stone Age times. The crystals consist of a microcrystalline form of silica, more commonly known as quartz (silicon dioxide). Flint is the better-known form of this substance and is commonly found as very hard concretions in deposits of chalk. It is so hard that, when the chalk is eroded, the flint remains in an almost undamaged state. Fig. 1. The Clactonian culture ‘handaxe’ tool, which was the first tool we found at Southend beach. When fractured, flint and chert nodules disintegrate to produce conchoidal, glass-like breaks, and this creates sharp edges capable of inflicting physical damage. When controlled, this damage can be put to practical use and early species of man (Homo erectus, H habilis, H neanderthalensis and early H sapiens) recognised this fact and put it to good use in their everyday lives. During the Ice Ages, spreading ice sheets eroded many millions of flint nodules from chalk deposits and spread them all over the UK. When the ice melted during warmer interglacial periods, the nodules were deposited wherever they happened to have been transported to. Such flint nodules are referred to as “derived” nodules. Early man came to recognise them and collected them to make use of their physical properties. In this way, the first stone tools appeared and, as skill levels developed in their manufacture, they became more and more sophisticated in form. … Read More
Stephen K Donovan (The Netherlands) A misconception shared by many non-palaeontologists is that fossils are rare. For example, when governments pass legislation to protect their fossil heritage, they are stopping the export of complete and well-preserved specimens, such as those of Mesozoic dinosaurs, hominids and Ice Age mammoths. There can be little argument that protecting their prehistoric heritage is responsible. Yet, these same politicians will support, for example, the export of cement. This may seem unrelated, but, of course, limestone is rich in fossils, most particularly invertebrates (Bathurst, 1971), and is an essential component of cement. These fossils are not dinosaurs or mammoths, admittedly, but they are fossils nonetheless. Legislation needs careful wording to ensure that exporting cement is not an illegal activity. Fig. 1. Imported rocks used in raised flowerbeds and paving at Amsterdam Zuid (=south) railway station, the Netherlands. (A) General view. The grey stone is Carboniferous limestone; the pink stone is gneiss. The Wagamama restaurant is to the left of the photographer. (B) Detail of the upper surface of limestone on a raised flower bed. The fossils are dominantly fragments of crinoid and a colonial tabulate coral (Michelinia? sp.) is seen towards the bottom of the page and a section through a productid brachiopod(?) is right of the coin. The coin is €2, about 25mm in diameter.The Netherlands is an exporter of cement from the Upper Cretaceous limestone quarries in Limburg, in the far south of the country (Felder and Bosch, 2000) and therefore trades fossils in … Read More
Stephen K Donovan (The Netherlands) My late wife, Dr Trina MacGillivray, was a geomorphologist. She loved the Netherlands and the Dutch landscape, but more than once made astute comparisons with the scenery of other northern European countries. The Dutch landscape, if it has a fault, is too organised, too well arranged and too manicured. Woe betide the blade of grass that dare step out of line. Trina’s observations extended to Belgium. If travelling to Brussels by train, it is immediately obvious when you have crossed the border because the landscape relaxes. It is not unruly or untidy, but, unlike the Netherlands, it does not need to maintain a near-geometric precision. Trina liked her trips to Belgium, too. These memories were revived on a recent bus ride from Leiden to Hoofddorp, near Amsterdam Schiphol International Airport. It was a grey, overcast day – the sort of dreary weather that the Netherlands does too well and too often. Even before we had left Leiden, the regular geometry of the town impressed itself on me. But then there was something in the central reservation that caught my eye – a cluster of irregularly rounded boulders of various lithologies (Fig. 1E, F). It occurred to me then that such clusters of boulders were not so unusual in the Dutch landscape, breaking up the geometry in unusual ways (Figs. 1 to 3), yet were undoubtedly man-made. Fig. 1. Boulders in Leiden, 4 February 2015. (A) The boulder garden, a favourite of all children who like … Read More
Back here in the United States, the blockbuster movie Jurassic World still plays in theatres, while presidential candidates hit the campaign trail. This confluence of events reminds me of a crazy idea I had back in 1992, a couple years after Michael Crichton published his novel. This tongue-in-cheek essay explores the idea to its full absurdity.
It won’t come as any surprise to a reader of this magazine, but might to the vast majority of the UK population (and probably anyone reading this elsewhere), but this country is a great place to find dinosaurs.
Growing up, I collected and purchased trilobite fossils for my own personal collection, to learn about and understand prehistoric life. They were to me, and still are, a fascinating group of fossils to examine and wonder about how the myriad of different forms evolved.
This fascinating book looks at the professional interaction over more than 30 years between a respected husband and wife team of US palaeontologists working for most of their professional lives in Australia (Prof Pat Vickers-Rich and Tom Rich) and a freelance artist (Peter Trusler), as he tries to interpret their work and bring to life ancient organisms and environments.
Normally, I wouldn’t be interested in semi-precious stones and other pretty things. Personally, I prefer grubbing around in the dirt, perhaps for those far more beautiful, elusive and perfectly formed Cretaceous terebratulids or Silurian trilobites. However, some semi-precious stones have the advantage of also providing a tangible link to the ancient history of life.
I like the GA guides. They are excellent resources for amateurs and professional geologists alike and I frequently browse mine, planning geological trips I will probably never take, because I live in geological unexciting London.