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Geological expedition along the southwest coast of Scotland

Dr Robert Sturm (Austria) Compared to the geological architecture of other European countries not exceeding a total area of 100,000km², the geology of Scotland is characterised by an unusual diversity of geological features. Due to its tectono-metamorphic complexity Scotland attracted numerous earth scientists in the eighteenth and nineteenth centuries, whose main aim was the development of theories about, on the one hand, rock formation and, on the other, metamorphic alteration of initial lithologies. Besides being the preferred target of foreign scientists, the country has also produced its own important figures in the history of geological research. In this context, James Hutton – the “father of modern geology”, after whom, for example, ‘Hutton’s Unconformity’ at Siccar Point in Berwickshire is named – has to be mentioned, but also Hugh Miller and Archibald Geikie provided valuable contributions to the enlightenment of various geological problems. Fig. 1. Geological subdivision of Scotland into four main units. Returning to the geology of Scotland, it is possible to subdivide the country into four main geological and geographical units. The Southern Uplands, which extend south of the Southern Uplands Fault, are mainly composed of sedimentary rocks dating back to the Silurian and the Devonian. The Central Lowlands or Midland Valley, which border the Southern Uplands Fault on the north, represent a rift zone that chiefly comprises Palaeozoic rocks of both sedimentary and volcanic origin. North and west of the Highland Boundary Fault lies the Highlands and Islands, which, due to their geological diversity, can be further subdivided … Read More

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Guide to minerals: Amethyst

Steven Marquez (USA) Amethyst is the violet to purple variety of quartz. It is often associated with albite and orthoclase in pegmatites. Fine specimens of amethyst can be classified as semiprecious gemstones. This specimen was found in Cripple Creek Colorado, as a near surface deposit on the David Leighton gold mine, owned by Steven Wade Veatch across from the hardware and grocery store on Teller County 1. The short, stubby amethyst crystals formed gas pockets in a hot, welded ash deposit that once covered the landscape of Cripple Creek. Amethyst is also mined in great quantities from the state of Minas Gerais in Brazil. A deep purple amethyst is commonly found in Uruguay. The colour purple is a royal colour, which is why amethyst is often used in jewellery for kings and queens. It was highly valued by Egyptians and the ancient Greeks believed that it protected against intoxication. Amethyst is the birthstone for February. Fig. 2. Note the faint crosswise striations on the surface of the amethyst crystal. This is one of the diagnostic features of quartz. The specimen is from the Steven Veatch collection. Photo by Steven Marquez. Facts on fileChemical formula: SiO2Composition: silicon dioxide; the colour is caused by iron or manganese impuritiesColour: purple, greasy lustreStreak: whiteHardness: 7Crystal system: hexagonalTransparency: transparent to translucentSpecific gravity: 2.65Lustre: vitreousCleavage: noneFracture: conchoidalTenacity: brittleGroup: silicates, tectosilicatesHaiku Brilliant purple Never ceasing to amaze Glowing like the stars About the author Fig. 2. Steven Marquez, seen working on the curation and cataloguing of the … Read More

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Book review: Introducing Mineralogy, by John Mason

I have been fortunate enough to review for this magazine a large number of books from the Dunedin series of guides introducing aspects of the different sciences, especially the earth sciences. And Introducing Mineralogy continues the high standard set by its predecessors. It is slightly larger than some of the other guides in the series, but is still beautifully illustrated, nicely written and very informative.

Book review: Guides to: The Jurassic Coast; The Lake District; and Cornwall, by Robert Westwood

These three guides by Robert Westwood are in the same simple format. All are local geological guides to specific areas of the UK and all are illustrated by lovely full colour photographs. They all contain simple, introductory geological introductions for the uninitiated, and then more detailed expositions of what makes the regions so special.

Book review: Amber: Tears of the Gods, by Neil D L Clark

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.

Book review: Fossils in Amber: Remarkable snapshots of prehistoric forest life, by David Penney and David Green

Here at Deposits, we like our amber and this certainly isn’t the first book on the subject I have reviewed. In fact, over the years, we have published many articles on the fossilised sap and its inclusions, and have just finished publishing a short, two-article series by the authors of this excellent little publication.