An acclaimed international collection of earth science articles and book reviews on palaeontology, geology, minerals and more
This is an ambitious little field guide, which aims to allow amateurs to identify basic rocks and rock formations, for the first time, in a systematic way., as it says: “… using only careful observation, a magnifying glass, a pocket knife – and a bit of patience”.
Stephen Moreton (UK) Our journey around Ireland concludes in Ulster. This comprises Northern Ireland, which is part of the UK, and the counties of Cavan, Donegal and Monaghan, which are part of the Republic of Ireland. As geology is no respecter of politics, the national border is ignored here. I … Read More
Helen Gould UK) What are meteorites? Lumps of rock left over from the formation of the solar system or “chipped off” planets during major impacts can become trapped in the Earth’s gravitational field and fall as meteorites. The three main types are iron, stony and stony-iron. All of these are … Read More
Stephen Moreton (UK) In the first two articles of this series, we looked at Leinster and Munster. Continuing in a clockwise fashion brings us to Connaught. Some of Ireland’s oldest rocks are to be found here, forming the Ox Mountains. The rugged and mountainous west is dominated by metamorphic rocks … Read More
Stephen Moreton (UK) In the second part of our tour of Ireland, we head for Munster, which occupies the southwest corner of the island. Geologically, the rocks are mostly inland Carboniferous shales and limestones, with Devonian sandstones forming the coastal peninsulas. All host mineral localities of note. Starting in County … Read More
Stephen Moreton (UK) The island of Ireland has much to offer the mineral collector, but is relatively unknown to most. This may in part be due to a lack of published information, although, for years, the troubles in the north also served to deter visitors for many years. This series … Read More
Helen Gould (UK) Following on from my articles on plate tectonics and the rock cycle, the tables below will hopefully be useful as an aide-mémoire to identify rock samples on your field trips. Further reading Introducing Metamorphism, by Ian Sanders, Dunedin Academic Press Ltd, Edinburgh (2018), 148 pages (Paperback), ISBN: … Read More
Helen Gould (UK) In Plate tectonics (Part 3): The rock cycle, I presented an overview of the relationship between the rock cycle and plate tectonics, and then went on to look more closely at igneous rocks. This time, I want to discuss sedimentary and metamorphic rocks, and review the occurrence … Read More
Helen Gould (UK) What is the rock cycle? Usually, the first thing that budding geologists learn about rocks is that there are three kinds: igneous, sedimentary and metamorphic. These three major kinds are divided up into many different types of rock. For example, marble, slate and metaquartzite are all metamorphic … Read More
Helen Gould (UK) As we saw last time (Plate tectonics (Part 1): What are they?), the Earth is a pretty dynamic place, with tectonic plates moving about on the surface, driven by convection cells in the upper mantle. But producing a workable theory, which combined most of the observations of … Read More
Helen Gould (UK) What does “plate tectonics” really mean? The Earth’s surface bears about 20 plates, which are able, over millions of years, to move about on layers beneath the crust. Some of the surfaces of these plates consist of continental crust, some of oceanic crust, some both (Fig. 1). … Read More
Jon Trevelyan (UK) If Yorkshire really is ‘God’s Own County’, then clearly the Almighty is an enthusiastic geologist. Just how lucky is the Yorkshire man who, on the same day, can see some of the best and most varied geology in the world, set out in glorious coastal and mountain … Read More
Richard M Haw (UK) Blue John is a unique variety of blue-purple banded fluorite. Hydrocarbons or oils have been deposited on some of the crystal surfaces while the mineral was forming. These oil layers are partly responsible for giving the stone an alternate blue and white banding, best seen when … Read More
Stephen K Donovan (The Netherlands) The city of Amsterdam in the Netherlands is surrounded by a great defensive earthwork on its landward side, the Stelling van Amsterdam (= Defence Line of Amsterdam), along which are a series of forts and batteries (Figs. 1A-E and 2). This major structure was built … Read More
Philip Dunkerly (UK) In A geological model for the alluvial gold environment (Part 1), the first part of this article, I discussed how alluvial gold is found and suggested a geological model for alluvial gold deposits. (Readers are recommended to have another look at that part to remind them of … Read More
Philip Dunkerly (UK) Mankind almost certainly first found gold when a yellow, glint from the bottom of a stream bed attracted the attention of one of our ancestors in pre- historic Africa. Ever since, the allure of gold – its colour, improbable density, malleability and scarceness – meant it has … Read More
Stephen K Donovan (The Netherlands) Stop 1. Waterford District, near Codrington Agricultural Station (approx. 59º 36’ 8” W 13º 6’ 49” N; Fig. 1) The area considered in the final part of this guide is outlined in A field guide to Barbados (Part 1): Introduction (Donovan & Harper, 2010, fig. … Read More
Stephen K Donovan (The Netherlands) Stop 1. Chalky Mount (approximately 59º 33’ 15” W 13º 13’ 55” N; Fig. 1) The area considered in this part of the guide is outlined in Donovan & Harper (2010, fig. 1d) and Figs. 1 and 2. As with other articles in this series, … Read More
Stephen K Donovan (The Netherlands) The area considered in this part of the guide is outlined in Donovan & Harper (2010, fig. 1C) and Fig. 1 of this article. As in other articles in this series, the starting point is Bridgetown. Stop 1: The Barbados Museum The Barbados Museum and … Read More
Stephen K Donovan (The Netherlands) Stop 1: Arawak Cement Quarry The area considered in this part of the guide is outlined in Donovan & Harper (2010, Fig. 1b) and Fig. 1. As with other articles in this series, the starting point is Bridgetown. Drive north from the Bridgetown area on … Read More
Stephen K Donovan (The Netherlands) and David AT Harper (Denmark) Introduction This article is the second part of a field guide to Barbados, the first part of which is A field guide to Barbados (Part 1): Introduction. The areas visited by different the excursions outlined in Parts 2 to 6 … Read More
P W Forster (UK) I have many years of experience collecting and cutting agates. It was my wife who originally had an enthusiasm for these beautiful semi-precious stones and it was because of her enthusiasm that I developed an interest that has now become an obsessive hobby for the both … Read More
Stephen K Donovan (The Netherlands) This is the first of six articles that will introduce the geology of the Antillean island of Barbados. It is an expanded and more detailed guide derived from two earlier publications (Donovan & Harper, 2005, 2009). The structure of the guide will include a summary … Read More
Mugdha Chimote (India) The term ‘Quaternary’ is derived from the Latin word “Quaternarius” (meaning “four”, such that the Quaternary is “the fourth great epoch of geological time” in the now-abandoned system of dividing geological time). It refers to the most recent period of the Earth’s history, covering a span of … Read More
Mugdha Chimote (India) The Deccan Traps occupy approximately 25% of the total of peninsular India, that is, the triangular shaped landscape of southern India. They traverse the states of Maharashtra, Karnataka, Madhya Pradesh, and Gujarat. The Deccan Traps are currently believed to occupy about 500,000km2 of northwest peninsular India. It … Read More
Mugdha Chimote (India) Introduction Sandwiched between the Arabian Sea to the west and the vast Indian subcontinent to the east, the Western Ghats, a haven for trekkers and travellers, are a 1,600km long range of mountains along western edge of Deccan Plateau. Also known as “Great Escarpments of India”, the … Read More
Deborah Painter (USA) “Look over there!” I exclaimed as I stood on the grounds of a manufacturing plant and stared across the tracks of the Atchison, Topeka and Santa Fe Railroad to the east of the plant. I was pointing at several mountains a few kilometres in the distance. “That … Read More
Dr Robert Sturm (Austria) The mineral zircon (more correctly, orthosilicate zircon or ZrSiO4) is an important accessory mineral in various rocks of the earth’s crust, but most of all of igneous rocks with the mineral composition of granite. An accessory mineral is a mineral comprising less than about 10% of … Read More
Robert Sturm The Isle of Skye is a part of the Inner Hebrides in the north-west of Scotland. It has a total area of 174,000 hectares and has an irregularly shaped coastline that is typical of the British Isles. Since the early nineteenth century, the island has become a centre … Read More
Robert Sturm (Austria) During the last few decades, the interest of diverse geosciences has increasingly focussed on the examination of so-called ‘shear zones’, because the displacements between two lithological blocks represent natural ‘laboratories’, within which the phenomena of mineral alteration and deformation are clearly shown for the purposes of scientific … Read More
