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Nature's Treasures: Minerals and Gems - report
Flett Lecture Theatre, Natural History Museum, London
Sunday, 7th December 2008.
There was a wide range of talks, with subjects from 20 nm-sized microbes and how they are used (Karen Hudson-Edwards ) to Yucca Mountain (Andy Rankin, talking about fluid inclusions and their use in the assessment of the mineralogical aspects of the site), and from Roy Gill’s “neural dumps” (he was talking about colour in minerals), to Chris Stanley’s threat to sing a song about the Periodic Table of the Elements. Jeff Harris gave a talk on “Smashing Diamonds” wherein he professed his preference for smashing up diamonds so he can study them better, than cutting them up to make jewellery out of them), and Jack Ogden combined mineralogy and gemmology nicely in his talk on the history of how precious and semi-precious stones have been used for thousands of years as personal adornments. Brian Jackson took us on a tour of agates, where he got up close and personal with some very beautiful specimens, and spoke about the origins of some of the weird and wonderful shadings and patterns in a variety of samples, including many from Scotland. Brian also gave away a large batch of agates in the exhibition afterwards – thanks Brian! Kathryn Goodenough gave a fascinating talk about the work being done by the British Geological Survey in Africa, in particular work in Madagascar to map a number of economic deposits and to help local scientists to use GIS methods to help manage the data available. Adrian Finch spoke about luminescence as an analytical tool in mineralogy and Bob Symes talked about responsible mineral collecting.
Abstracts (with downloadable slide sets)
Dr Roy Gill, formerly of the University of Edinburgh
Crystallization in the cosmos results in minerals occupying an independent niche somewhere between planets and quarks. This overview presentation explores the phenomenal breadth and depth of knowledge concerning the growth, symmetry, colour and chemistry of nature's exquisite crystal forms and examines how electromagnetic radiation helps us to unravel a mineral's deepest secrets.
Minerals, Gems and the Ancient World
Attractive minerals have been used as 'gems' in personal ornaments since the Stone Age. This presentation will look at the early days of gem use, the varieties of minerals so used and the factors that influenced their trade and working. The simple ornaments of the Stone Age developed into the far more sophisticated jewels of ancient Egyptian and the Near Eastern Civilizations and then, with the opening up of the trade between East and West following Alexander the Great's conquests and the availability of new materials and technology, the modem gem trade was born. Although the general evolution of gem use in antiquity is quite well known, the various factors that influenced this evolution, such as abrasive availability, have often been largely ignored.
Diamonds (2 Mb)
Marvelling at the beauty of a cut diamond is one thing, but to break a diamond to understand how some parts of the interior of the Earth work is something really special. This talk will show that diamond formation occurs not in isolation, but accompanied by specific mineralogies which may become encapsulated and thereafter protected from further change by a very robust and chemically inert parent. Mineral inclusions in diamonds are usually no more than 100 μm (0.1mm) in longest dimension and have morphologies which have been imposed by the diamond. The mineralogy indicates two principal upper mantle growth environments, referred to as peridotitic (olivine, orthopyroxene, pyrope garnet, diopsidic clinopyroxene and sulphides) and eclogitic (almandine garnet, omphacitic clinopyroxene and sulphides). Diamond formation takes place over a depth range of about 500kms (starting at 150km), so that some diamonds with very specific inclusions which are distinct from those mentioned above, grew in the lower mantle. From the chemistry of the majority of the inclusions and for both principal environments, formation temperatures average 11500C with determined pressures (1σ) ranging from 5.3 ± 0.8 GPa (1GPa ≈ 10km of vertical depth). From radioactive elements in some silicate and sulphide inclusions the genesis ages indicate that no diamond is younger than 990Ma and some are as old as 3600 Ma, which is 80% of the age of the Earth. In this research the broken diamond is very important as it provides information not only about carbon isotopic (δ13C) signatures, but also about the levels and aggregation states of nitrogen, diamonds’ commonest molecular impurity. These results can be then linked to the characteristics of the mineralogy of the inclusions. Not a bad scientific return for smashing diamonds.
Fluid and Solid inclusions in Minerals and
Gems; guides to their origin
Perfect crystals are unknown in nature. Defects range from the atomic scale to gross imperfections such as depressions and cavities on the macroscopic scale. Usually, these cavities are sealed over during a period of later growth trapping tiny portions of mineralising fluids (and co-precipitated solids) from the geological past . These fossil droplets provide important information on the physical and chemical conditions prevailing mineral growth from these ancient mineralising fluids.
The presentation will illustrate the splendour and beauty of fluid inclusions and illustrate their usefulness with particular reference to recent research on the origin and authenticity of “ancient” Crystal Skulls and gem rubies.
Mapping and mineral exploration in Africa
The British Geological Survey may be best known for producing geological maps of the UK, but also has an international reputation for mapping in developing countries. In these areas, geological maps underpin some of the fundamentals needed for development, such as the search for mineral and water resources. In recent years, BGS has worked in a number of countries in Africa, including Madagascar, Mozambique, Ghana, Mauritania and Morocco. Many of these countries are relatively poor, but they have a wealth of mineral resources which could provide a basis for economic development.
BGS carries out a whole range of work in African countries, in partnership with local geological surveys and universities. Mapping almost always starts with remotely sensed information such as satellite images or aeromagnetic maps. In large-scale mapping projects, where poor exposure and difficult access often make traditional geological mapping very difficult, remotely sensed data provide excellent background information. Bedrock mapping is typically accompanied by stream sediment analysis, indicating hotspots of key minerals such as gold which can then be investigated in more detail. This talk will illustrate some of the work that BGS has been doing in Africa, showing just how ‘nature’s treasures’ can be discovered in some very remote places.
'Environmental’ Minerals: Bacteria, Fungi, Worms, Toxins and the
Human Body (2.7 Mb)
'Environmental’ minerals are
exciting because they are the solid expression of the dynamic
interaction of water and life at the Earth’s surface. Bacteria,
for example, can cause minerals to precipitate within their cell
walls, or act as substrates. Fungi can deteriorate building
materials, forming secondary minerals as a consequence.
Earthworms ingest sediment and excrete clay minerals. Toxic
elements can be removed from waters and soils by their
incorporation into minerals, and these processes are often
helped by organisms. Even human teeth, bones and for some,
kidney stones, are examples of environmental biominerals.
Industrial applications of Minerals
The talk will cover those applications involving what are generally termed industrial minerals and rocks, gemstones and metals, but not fossil fuels. Minerals form the basis of life as we know it; they are integral to our history and our culture. From providing sources of essential elements and vitamins to lending shelter and protection from weather and enemies, from clay for pots to metals for weaponry used in hunting and defence, humankind has needed and utilized minerals for many thousands of years. In the industrial age, producers have had a seemingly unending capacity for creating and developing products of use to man derived from minerals and rocks. Industrial applications for minerals are constantly growing as our technological requirements expand. Everyday objects that the general public takes for granted can contain unexpected metals or mineral derivatives that have been utilized for a specific purpose depending on a specific property. To take a mobile phone as an example, roughly 50% is plastic, 15% glass and ceramics, 15% copper and 20% a cocktail of the following: C, Au, Ag, Ni, Cd, As, Pb, Hg, Mn, Li, Zn, Sb, Be, Bi, In, Nb, Ta, Sn, Co, Pt, Ir, Re, Pd, Rh, Ru, Cr.
Minerals in the field: where to find them, and
how to collect responsibly (4.6 Mb)
The mineralogical sciences have more than kept apace with the use of and application of today's sophisticated analytical techniques, thus providing further understanding of the geochemistry, structure and environments of mineral formation. However, as for the other natural sciences, it is the collection of natural mineral specimens that provides the fundamental starting blocks of study.
Responsible collecting by informed amateur and professional mineralogists continues to advance our science and the understanding of the geological environment. Most major ore-fields have an extensive literature, but smaller pockets of unusual mineralization have perhaps only a single reference or note. Using such literature, geological maps and their interpretation, and to a great extent, local knowledge, interesting and important pockets of mineralization may be discovered and provide new scientific information. Using examples from the British Isles of varied geological environments, this talk will focus on a few areas of mineralization whether they be primary or secondary in origin, which have provided, in past and recent years, a stimulus to scientific mineralogical investigations.
Agates are probably the most common gemstones on Earth. They have been used to create ornaments for around 7000 years. The volcanic rocks of Scotland host agates which have been used to create traditional Scottish pebble jewellery. The formation of agates is of scientific interest. They are made from silicon dioxide in the form of the mineral quartz but, despite their simple chemistry, the mechanisms that bring about the variety of colours and structures is still not fully understood.
Mineral Luminescence: the Brilliance of Imperfections
Many minerals emit light (‘luminesce’) when hit by incident energy. For example, shining ultra-violet radiation onto minerals (‘fluorescence’) is widely used by amateur mineralogists as a diagnostic tool and the results are often spectacular. However there are many forms of irradiation, including electrons, x-rays and ions.
Luminescence encodes information about how real minerals differ from idealised perceptions of chemistry and structure. No mineral is truly ‘perfect’ and by varying the irradiation, mineralogists are gaining insights into the types of defects in real minerals. This talk reviews some of the important breakthroughs that have occurred in understanding minerals from luminescence.
Minerals are – quite literally – brilliant.