Under the right conditions, over millions of years, geological activity can form extremely striking and amazing minerals. Once they have formed, these rare giants can be destroyed by the very forces that created them. Few survive, and even fewer are discovered and collected undamaged. This book is a comprehensive illustrated guide to 260 outstanding examples of gems and minerals from the collection of the Royal Ontario Museum. When Theophrastus described 16 minerals in his textbook De lapidibus, around 300 BCE, he laid the foundation for the science of mineralogy. Advances in the 20th century, particularly the use of X-ray crystallography, now allow the crystal structure of most minerals to be described at the atomic level. The informative introduction of Gems & Minerals explains some of this science, providing definitions of many of the book's technical terms. The book then describes each mineral, accompanied by a photograph. The mineral's chemical and physical properties are identified, as well as how it was formed and where it can be found. Gems & Minerals contains more than 400 photographs and focuses on the beauty of the mineral kingdom. It contains many images of spectacular crystals and gems as well as magnificent manufactured objects made from gold, silver and gemstones. Historical background, the origin of the mineral's name and interesting lesser known facts complete this guide to a fascinating aspect of the natural world around us.