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Book Review “Mont-Saint Hilaire: History, Geology, Mineralogy”

SP14

SP14Mont Saint-Hilaire: History, Geology, Mineralogy by L. Horváth, R. A. Gault, E. Pfenninger-Horváth, and G. Poirier; editor: R. F. Martin.

644 pages; 2019; CDN $125 plus $12 shipping in Canada; US $125 outside Canada plus shipping ($20 USA, $28 overseas) (hardbound).

This is a long-awaited book. Mont Saint-Hilaire is one of the world’s top mineral localities and ranks first in mineral diversity. A widely referenced 1990 article on Mont Saint-Hilaire by two of the present authors, Horváth and Gault, described 245 species from the locality (see Mineralogical Record 21:284–392). With the publication of Mont Saint-Hilaire: History, Geology, Mineralogy, the list now stands at an extraordinary 437 species. Equally remarkable, Mont Saint-Hilaire is the type or cotype locality for 69 species. It has also produced thousands of mineral specimens that reside in institutional and private collections worldwide, from best-of-species to the uncommon and rare. It might be noted here that although the locality is universally referred to as Mont Saint Hilaire, often abbreviated as MSH, the actual locality is basically the quarry that occupies only about 3 percent of the area of the mountain.

The book opens with a preamble by Robert F. Martin, editor of this and other volumes in the Special Publication series of The Canadian Mineralogist. In an introduction the authors note that although the mountain has been designated as a Biosphere Reserve of world importance by UNESCO, its geological and mineralogical importance has not been recognized outside the geoscience community. The introduction Media Reviews Volume 95, March/April 2020 189 continues with an outline of the book and acknowledgments of the many individuals who had in some way contributed to it.

The “History” section (16 pages) begins with a geographical and historical account of Mont Saint-Hilaire and the surrounding region, followed by an overview of early geological and mineralogical investigations, with biographical sketches of the principals involved. Here “early” refers to before 1954 when quarrying began. A history of the quarry operations follows. Of special interest to mineral collectors and curators is a map showing the chronological and spatial evolution of the present quarry with the various quarry names that appear in the literature and on mineral labels. The section concludes with the story of what may be called the modern era of scientific investigations and mineral collecting beginning in the early 1960s. The first part is an overview of the institutions and researchers involved in the investigations and their contributions to the mineralogy and geology of the mountain. The second part is a who’s who of mineral collectors who have made significant contributions through their discoveries and documentation. The history section is well illustrated with photos of scientists, collectors, and the quarry.

Geology is the key to the mineral diversity of Mont Saint- Hilaire. The “Geology” section (30 pages) begins with an overview of the regional geology focusing on the Monteregian Hills petrographic province, which consists of eleven major alkaline igneous complexes in the form of plutons. Before turning to Mont Saint-Hilaire, brief descriptions are given of the other plutons and the associated sills and dikes that are well known to mineral collectors as the locales of the Francon and Demix-Varennes quarries. A discussion of the geology of the mountain follows. Geology is commonly subject to changing interpretations, and here, as in much of this section, the authors provide a historical perspective. The final subsection is devoted to the geology of the Poudrette quarry (now called Carrière Mont St-Hilaire) and a detailed description of the geologic micro-environments or modes of occurrence in which the minerals occur.

Some changes from previous classifications may be noted. “Sodalitolite segregations” replaces “sodalite xenolith,” “granite” is added as a minor but significant micro-environment, and “pegmatites” are subdivided into “carbonate pegmatites” and “alkaline or nepheline syenite pegmatites.” Two of the mineralogically more diverse pegmatites, the “yofortierite pegmatite” and the better known “Poudrette pegmatite,” are singled out for separate descriptions. The minerals found in each microenvironment are listed.

The “Geology” section is enhanced by colored geological maps of Mont Saint-Hilaire and of the Poudrette quarry as well as by a three-dimensional perspective diagram of the southern part of the quarry showing the location of various rock types, some geologic features, and the numbered quarry benches or levels later referred to in the mineral descriptions.

Authors of Mont Saint-Hilaire at the VIP reception to celebrate the book launch, 7 November 2019, at the Canadian Museum of Nature in Ottawa, Ontario, Canada. From left: Robert Martin, Robert Gault, Glenn Poirier, Elsa Pfenninger-Horváth, and László Horváth. Photo by Reni Barlow, courtesy Canadian Museum of Nature

For most readers the centerpiece of the book will be the “Mineralogy” section (476 pages). It begins with remarks about the mineral diversity of Mont Saint- Hilaire and about the six appendices that complement the mineral descriptions (more about the appendices later in this review). A summary of the instrumental methods used for the mineral identifications and chemical analyses in the book, and the institutions and people involved follow.

The mineral descriptions (430 pages) are in alphabetical order by species; also included in the listing are mineral groups or supergroups that have special relevance to the mineralogy of Mont Saint-Hilaire. Thus, under polylithionite the reader is directed to the mica group wherein the micas are listed and described, again in alphabetical order, together with a table of chemical analyses. Dimorphs such as epididymite and eudidymite, or related species such as ancylite-(Ce) and calcioancylite-(Ce), are also described together. This arrangement facilitates a comparison of similar species. Also in the alphabetical listing are some mineral names that are no longer valid but that appear on older Mont Saint-Hilaire lists and labels.

The individual mineral descriptions vary in length from a few lines to several pages, with longer accounts mainly for type species, rarer species, and species yielding fine-quality specimens for mineral collectors and museums. Each entry begins with the name of the mineral or group in large font, with the names of type species highlighted in red. This is followed by the chemical formula, and for type species, the crystal system, space group, and unit-cell dimensions. The name of the group or supergroup to which a mineral belongs is given in the mineral description that follows.

The descriptions variously start with an account of the mineral’s first discovery, documentation, and identification at Mont Saint-Hilaire, and for rarer minerals occurring in other alkaline complexes, information on the type-mineral locality and description, and other occurrences. Then we find details of the mode(s) of occurrence for each species, associated minerals, and for some species the year and location in the quarry of significant finds. There are also interesting accounts of major discoveries and the collectors involved. Finally, the paramount question for mineral collectors: What does the mineral look like? The information provided includes general appearance, crystal habits and forms, twinning if any, properties such as color, luster, cleavage, and response to ultraviolet radiation, and rarity. The mineral descriptions are accompanied by crystal drawings, photographs (593), selected X-ray diffraction and other crystallographic data, and results of electron-microprobe analyses (359 analyses, many done especially for the book).

The “Mineralogy” section ends with notes on the organic coatings that may cover the minerals, an annotated list of the minerals in the unknown (UK) series, a compilation of gemstones cut from Mont Saint-Hilaire minerals, and a compilation of pseudomorphs. Since about 1965 a UK number has been assigned to minerals that could not be readily identified; the list now stands at 127. Most have now been identified as known species, new species, or mixtures. Thirty-six have been partially or fully characterized chemically and structurally and may represent new species. Since the publication of this book, UK77 (kodamaite), UK95, and UK124 have been approved as new species by the IMA CNMNC.

Although Mont Saint-Hilaire is not normally thought of as a gemstone locality, faceted gemstones have been cut from 29 species. For pseudomorph collectors there is a list of the 50 minerals known to form pseudomorphs, accompanied by a photo gallery.

The book ends with an exhaustive bibliography (1,107 references), a general index and appendices, and a note about the authors. The ten appendices contain much useful information. Here we find lists of Mont Saint-Hilaire minerals by chemical classification, in alphabetical order, by relative rarity for each micro-environment, and those that are either enriched in rare metals or in which they are structurally essential constituents. Fluorescence and phosphorescence are particularly useful aids in the identification of Mont Saint-Hilaire minerals, and another appendix provides their response under three wavelengths of ultraviolet radiation. Other appendices list Mont Saint-Hilaire type-species in the chronological order of their description, with the year of discovery and persons or institutions credited for their discovery, the authors of type-species descriptions, and the photographers whose photos appear in the book. A brief glossary of geological and mineralogical terms is also provided.

This profusely illustrated book is printed on glossy A4 (210 × 297-mm) paper with a Smyth-sewn case binding. This allows pages to open wide and lay flat, a real convenience for a book that weighs 2.3 kilograms. The layout is spacious, with the text either full-page or in two columns. For a 644-page book, there are very few errors.

Mont Saint-Hilaire: History, Geology, Mineralogy is the culmination of many years of meticulous documentation and research. It is unlikely that it will ever be surpassed as the authoritative mineralogy of the locality. It is a must-have book for anyone interested in the minerals of Mont Saint-Hilaire and deserves a place in every serious mineral collector’s library. Many of the minerals are described for the first time, which should motivate mineral collectors and mineral museum curators to look more closely at Mont Saint-Hilaire specimens for the presence of new and rare species. (I know that I will.) And mineralogists conducting research on alkaline rocks will find the book to be a valuable source of information on the composition of minerals and other data. I highly recommend this book.

Dr. Peter Tarassoff
Redpath Museum, McGill University
Montreal, Quebec, Canada

This book review was published in “Rocks & Minerals” Volume 95, March/April 2020