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November-December 2009

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Media Reviews: November/December 2009

La Fluorita: Un Siglo de Minería en Asturias (The Fluorite: A Century of Mining in Asturias), by M. Gutiérrez Claverol, C. Luque Cabal, J. R. García Álvarez, and L. M. Rodríguez Terente. Published by the authors, Oviedo, Spain. 565 pages; 2009; 75€ (padded hardcover). In Spanish.

After many years of data research, interviews with miners and mining companies, visits to old and new mining works, and searches in the historical Asturian archives and other mining-related Spanish institutions, we have in our hands this wonderful book written by four enthusiastic lovers of Asturian mineralogy and mining history.

At 3.2 kilograms, this is not a pocket-sized book nor is it a compendium of photographs of Asturian fluorspar. It is much more: The book is almost encyclopedic in content, designed to satisfy the scientific curiosity of the mineral collector, the future mining engineer or geologist, the historian, and, I dare add, the most distinguished teacher.

Chapters highlight the mineral wealth of Asturia with full-color graphics, data tables, and geological diagrams, together with aerial images that show clearly mining demarcations. The book contains more than five hundred photographs depicting all varieties of fluorite, calcite, dolomite and other associated minerals, as well as many valuable historical documents. Also included are maps and photographs of miners, the installation of mining equipment, and scenery showing the area's beauty.

The book is divided into seven chapters. The first presents a detailed introduction to the economic importance of the exploitation of fluorite worldwide, then in Spain, and finally, in more detail, in the Asturias region. The second chapter provides a historical framework for the mines, beginning with purely scientific quotes from the nineteenth century about the Asturias lands and their fluorite ores, to a chronology of early fluorspar mining in the twentieth century. The chapter ends with a tour of the most important mining companies that were established, flourished, and gradually disappeared through changing economic and social times. It also gives the status of active operations and future plans for new areas currently being explored.

The third chapter, titled “Geological Framework of the Fluorite,” immerses readers first in the area's structural geological features and the formation of the different mining sites. It also covers all aspects of fluorite mineralogy: paragenesis, crystallographic diversity, inclusions, color zoning, and possible genetic models.

The next three chapters tell about the mining districts of La Collada (Chapter 4), Caravia-Berbes (Chapter 5), and Villabona-Arlós (Chapter 6), all located in the Permian- Triassic basement rocks. Common to all chapters are historical notes and anecdotes, the geology of the district, and the minerals to be found. The various mines and deposits are described in detail and accompanied by incredible photographs of specimens of scientific interest; precise locations are given for each (finally!). The chapters each conclude with a discussion of the economy and the workers' way of life. Included are localities with such well-known names as Veneros Sur and Mina Josefa in the district of La Collada; La Cabaña, Cuetu l'Aspa, Mina Jaimina, and Mina Emilio in the Caravia-Berbes district; and Minas de Villabona, Mina Moscona, and Mina Cucona in the Villabona-Arlós district.

The seventh chapter is a compilation of considerable information about other mines located in the Paleozoic limestone substrate that, because they are smaller and located in rugged mountain areas, have not contributed to the history of Asturian fluorite. The book is complemented by an extensive bibliography and an interesting glossary of mining and geology terms. This is an essential book for mineral lovers, especially for fluorite collectors. Asturian fluorite has finally been given its due place in a worldwide context, and individual specimens are finally given their correct localities.

Joan Rosell
Barcelona, Catalonia, Spain

Pegmatites by David London. The Canadian Mineralogist, Special Publication 10. 347 pages; 2008; $125.00 (hardbound, with accompanying CD-ROM).

Pegmatites are very special deposits of rock, of that there is no dispute. To a mineral collector, pegmatites are special for their beautiful gem crystals; to a mineralogist, for their exotic rare minerals; to a petrologist, for their unusual textures; to a geochemist, for their distinctive and evolving chemical signatures; to a geologist, for their relationships to plate-tectonic environments; and to a miner, for their hidden riches that can only be unlocked if he can decipher their enigmatic riddles. Just as pegmatites have something to intrigue the collector, scientist, and miner alike, so too this book has much to offer each in his quest to better understand these wonderful deposits.

Pegmatites is organized into two parts of nine chapters each. Part I, titled simply “Geology,” provides an excellent review of our current understanding of pegmatites. If you are unsure what a pegmatite is, you will certainly know by the time you finish Chapter 1, and your curiosity will be whetted to know more about these fascinating deposits. Chapter 2 takes a brief look at some of the diverse theories that have been proposed to explain pegmatite formation and looks in greater depth at the seminal work of Richard H. Jahns, especially his pursuit of experimental studies culminating in a 1969 paper with C. Wayne Burnham that, in a sense, revolutionized our understanding of the formation of pegmatites.

Chapter 3, “Anatomy and Classification,” is particularly illuminating, as it places both pegmatite structure and chemistry into geological context. Of particular note, and given special attention here, is the work of Petr Černý and his group at the University of Manitoba. Their chemical classification of rare-element granitic pegmatites into LCT and NYF families has added greatly to our understanding of pegmatites.

Chapter 4 provides an overview of pegmatite mineralogy. It is by far the longest chapter in Part I, but, even so, it is far from exhaustive. My own favorites, the secondary phosphates, are barely mentioned, but that is understandable considering their relative rarity and the fact that they provide relatively little insight into the petrogenesis of pegmatite bodies. The minerals and mineral groups that are covered in this chapter span a broad spectrum but, in general, are those that are most common and/or that provide important insights into pegmatite formation. The final four chapters of Part I discuss the transition from granite to pegmatite, common granitic pegmatites, rare-element pegmatites, miarolitic (gem-pocket) pegmatites, and nongranite pegmatites. All five chapters use well-chosen examples of specific pegmatites and pegmatite districts to illustrate the principles discussed.

Part I, in general, is very well illustrated with well-chosen images and diagrams. The numerous specimen images, mostly taken by David London of specimens in his own collection, can be best described as utilitarian rather than artistic, but they do their job well. Considering that the term pegmatite relates more to texture than to mineralogy or composition, it is not surprising that Part I also includes many images of distinctive and instructive pegmatite textures, and these serve well in illustrating the descriptions and discussions in the text. The diagrams in Part I are similarly effective in this regard.

Part II of the book, titled “Origins,” has a very different flavor and takes a very different tack. Here, London delves into the tough questions concerning pegmatite genesis, applying the results of his own extensive and insightful experimental research. The concepts and theories developed in the chapters of Part II are not for the casual page-turner. The illustrations are mostly diagrams, and, although London has done an excellent job of keeping these as straightforward as possible and explaining them well, many require concentration and careful study.

Although most mineral collectors will find Part I a more enjoyable “read,” those willing to invest the effort to work their way through the nine chapters of Part II will come away with insights that the pegmatite giants of decades past could not have dreamed of. The revolutionary Jahns-Burnham model, largely accepted for the last half-century, held that pegmatites form when granitic melts become water saturated, resulting in the exsolution of immiscible aqueous and silicate fluids. Instead, London's research supports a process involving rapid, nonequilibrium crystallization from relatively low-temperature melts enriched in fluxes and incompatible elements. To fully appreciate the implications of this theory and how it can be applied to the understanding of the origins of pegmatites and many of their unusual features, as the saying goes, “You'll have to read the book.”

Anthony R. Kampf
Natural History Museum of
Los Angeles County (California)

Paleozoic Fossils by B. L. Stinchcomb. Schiffer Publishing, 4880 Lower Valley Rd., Atglen, PA 19310; 160 pages; 2008; $29.95 (softbound).

Bruce Stinchcomb's Paleozoic Fossils is a richly illustrated photo atlas of common and not-so-common fossils of Cambrian to Permian age. The book appears to be targeted at fossil collectors and rockhounds, but professional paleontologists may also find it a useful teaching reference. Some of my geology majors have already expressed enthusiastic interest in obtaining a copy. The work does not pretend to be comprehensive (how could any reference even come close, considering the subject is the entire Paleozoic?) and admits to a bias toward readily obtainable retail specimens and fossils collected from North America and the midcontinental United States in particular.

The book has nine chapters. The first covers the basic concepts of fossils, geologic time, plate tectonics, and sedimentary deposits. It also includes short discussions about fossil collecting, rock shops, and fossil retail values. Many of the illustrated specimens have estimated retail values. I do not particularly like encouraging the general public to perceive fossils as objects of commerce; however, my own teaching collection includes many specimens obtained in the open market. And Stinchcomb does remind collectors about the importance of rare fossils being considered scientifically first. It is refreshing to read the emphasis on differentiating paleontology from archaeology. Stinchcomb also implies that government entities really do not know what they are doing in trying to establish blanket no-fossil-collecting rules (I agree).

The remaining eight chapters are devoted to each Paleozoic period. How do seven geologic periods receive eight chapters? Two chapters are devoted to the Ordovician—one for the Lower Ordovician by itself, the other for the Middle and Upper Ordovician. A separate Lower Ordovician chapter is not justified, despite the stated rationale. It would make more sense to have one chapter for the Lower and Middle Cambrian and another for the Upper Cambrian.

The fossils illustrated in each chapter are a wonderful mix of the common, less glamorous (but still fascinating) forms, and the unusual. Some moderately obscure groups (to the average collector) are also present. Invertebrate, vertebrate, plant, bacterial, and trace fossils are all given a fair amount of attention. Not unexpectedly, the majority of fossils in the book are invertebrates. Each fossil photograph has a separate, fairly informative caption that includes identification, age, stratigraphy, location, and estimated retail value. The captions also have brief comments about morphology, behavior, host rock, or higher-level classification.

Some aspects of the book are bothersome. Usage of geosyncline terminology in modern literature, even aimed at nonprofessional geologists, is unfortunate and unnecessary, as is the term fucoid. It would have been helpful to have locality information for every field photograph. Almost all of the photographs have high to very high contrast, which occasionally obscures features of the depicted fossil. The orange, red, and turquoise background colors for many of the illustrated specimens are visually distracting—either black or gray would have been preferable. Misspellings of genus names, place names, stratigraphic names, geologic time terms, and even nonscientific words are moderately common. That, along with some punctuation and capitalization errors, and a couple of upside-down photos indicate the work could have used a more careful round of editing. Some of the fossil identifications are wrong, some of the higher-level classification assignments are outdated (for example, Brooksella has been shown to be a sponge, and Chancelloria is not a sponge), and other errors have crept in (e.g., conulariid skeletons were indeed originally composed of calcium phosphate).

It was delightful to see the Brooksella star cobbles (I just like those!), the crinoid holdfast-encrusted hardground, the healed bite marks on trilobites (they are indeed not infrequent in some units), the Cambrian “monoplacophorans,” the Missouri crinoid calyx internal molds, the Scyphocrinus loboliths/floats, and many other intriguing specimens. I am partial to soft-bodied fossils, and they make it into this book, but only those from readily accessible deposits such as Mazon Creek and some Silurian lagerstätten.

Despite the flaws, the diversity of fossil groups depicted in this book is impressive. It gives a fairly decent overview of the Paleozoic fossil record (although few brachiopods are shown). I recommend this book to casual and serious fossil collectors, to geology students, and perhaps to geology educators as well.

James St. John
Ohio State University—Newark Campus

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