David Turner - Geology and Mineralogy of Gemstones

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Carol Frost, Chair, Publications Committee

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The right of David Turner and Lee A. Groat to be identified as the authors of this work has been asserted in accordance with law.

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Library of Congress Cataloging‐in‐Publication Data

Names: Turner, David, 1981– author. | Groat, Lee Andrew, 1959– author.

Title: Geology and mineralogy of gemstones / David Turner, Lee A. Groat.

Description: First edition. | Hoboken, NJ : Wiley ; Washington, D.C. : American Geophysical Union, 2021. | Series: AGU advanced textbooks | Includes bibliographical references and index.

Identifiers: LCCN 2020027427 (print) | LCCN 2020027428 (ebook) | ISBN 9781119299851 (paperback) | ISBN 9781119299882 (adobe pdf) | ISBN 9781119299875 (epub)

Subjects: LCSH: Precious stones.

Classification: LCC QE392 .G76 2021 (print) | LCC QE392 (ebook) | DDC 553.8–dc23

LC record available at https://lccn.loc.gov/2020027427LC ebook record available at https://lccn.loc.gov/2020027428

Cover Design: Wiley

Cover Image: Cobalt‐blue spinel from southwestern Baffin Island, Nunavut, Canada; © Lee A. Groat

Earth Science departments at universities across North America are diversifying their academic offerings for entry level science courses. Among topics that are catching on are the mineralogy and geology of gem materials. This textbook aims to support these courses. At the same time, the geological settings that give rise to gemstone deposits are as unique and fascinating as those for precious and base metal deposits. Gemstones also have captivating connections to our cultural history, from the well‐celebrated diamond deposits of South Africa to the lesser known occurrences of semiprecious gemstones that are dotted across every continent. The interdisciplinary aspect of gemstone deposits provides wonderful natural laboratories to better understand the Earth's processes and how human civilization has exploited the Earth's natural resources for its beautiful treasures. However, with this comes a need to consider the economic, political, social, environmental, health, and ethical impacts of extracting precious stones whether by large‐scale, small‐scale artisanal, or illegal mining operations. Earth's human population continues to grow and urbanize, and to increase its consumption of nonrenewable resources such as gemstones, so the human, environmental, and ethical implications of these practices are more important now than ever.

This book is designed for undergraduate learners and satisfies the needs of both lower level introductory courses and upper level geoscience curricula. It is intended to include basic concepts of geology in the context of a low‐to‐mid level understanding of gem deposits. It also includes some fundamentals of mineralogy in order to put the understanding of physical properties of gems in context.

It is not intended as a replacement for an “Introduction to Mineralogy” textbook, but does include sections of sufficient depth of knowledge for an upper level “Mineralogy and Geology of Gemstones” course. It is also not intended to replace a “Determinative Gemology” reference book, but briefly covers common tools and the properties they measure/exploit. The references at the end of each chapter should also allow students and instructors to easily access the original “raw” scientific information for further study, either for personal interest, as stepping stones for semester capstone projects, or for inspiration to undertake scientific research into the geological world of gemstone deposits.

The book is divided into two parts. Part I contains content focused on developing base mineralogical and geological knowledge while Part II provides details of the gemstones themselves and their geological settings. Lower‐level learners can focus on introductory material (and be exposed to greater details) while upper‐level learners can jump into the greater details of subsequent chapters (and also be able to fall back on more basic knowledge). Midlevel or keen lower‐level learners should be able to make use of the entire book to scaffold their learning. Topics include the geological settings of diamond and the big three colored gemstones (emerald, ruby, sapphire) as well as a collection of other gemstones such as spinel, ammolite and jade, but excludes some topics like synthetic materials and coral.

This volume aims to include an abundance of up‐to‐date scientific findings, but as the progress of research marches forward it will be inevitably somewhat out of date upon printing. Notification of significant omissions, errors, and new science will always be appreciated, as will be suggestions for new content and ways in which the book has been successfully used!

The book benefited greatly from constructive reviews by Fernando Corfu (University of Oslo), Matthew Field (AMEC Environment & Infrastructure UK Limited), Ian T. Graham (University of New South Wales), Stefanos Karampelas (DANAT, Bahrain Institute for Pearls & Gemstones), Aaron Palke (Gemological Institute of America), Lin Sutherland (Australian Museum), Kimberly Tait (Royal Ontario Museum), and one anonymous reviewer. All errors and omissions are, of course, the responsibility of the authors.

In order to understand the world of gemstones and their geological origins, we first need to build a foundation by learning about some mineralogy concepts. Mineralogy, in its most basic definition, is a branch of science concerned with the study of minerals. Though seemingly a fairly narrow topic, mineralogy reaches far into a number of other disciplines from medicine (e.g., effects of mineral fibers on lungs) to ceramics (e.g., firing of clay‐based pottery) and the origins of the Earth itself (e.g., mineral inclusions trapped in diamonds). This book focuses on understanding the geological origin of gemstones, most of which are natural materials known as minerals and are found within rocks. Before deciphering their origins, we must understand gemstones as minerals.