Opal: fiery SiO2
 Sulfur dioxide is one of the simplest and most abundant building blocks in the Earth's crust. It forms some of the most beautiful and well-known minerals and gemstones: rock crystal, agate, amethyst, citrine, chalcedony, carnelian, and many others. However, in its hydrous form, opal, it can surpass all other gemstones in the world in preciousness and rarity. The legendary play of colors in precious opal and the rich variety of this gemstone are unique in the mineral kingdom.
 This extra Lapis describes the locations where opals are found, their play of color, their formation, and their value. Experts from Europe and Australia, the promised land of opals, contributed to this edition.

 Contents :
 The World Map of Opals: Revision of a 1977 map known worldwide in the opal community / Opal, the Colorful Harlequin: An Introduction to Opal, its Deposits, and its Significance (Eduard Gübelin) / Why Opals Spark Fire: A Brief Excursion into Optics: The Physics of Opal's Play of Color (Max Weibel) / Concise Opal Encyclopedia: Locations and Technical Terms (Paul Downing, Karl Fischer, Maximilian Glas, Peter Huber, Rudolf Mende, Barrie O'Leary, Manfred Szykora, Klaus Thalheim, and Joachim Zang) / Separate Chapters on Denmark, Honduras, Indonesia, Mali, Saxony, Slovakia, Turkey, and the USA / Australia: Opal in Australia: The Formation of Opal Deposits (Jack Townsend, Ministry of Mines, Eastwood, South Africa) / New Ideas about Australia: Thoughts on the Formation of Precious Opals (Len Cram, Lightning Ridge, New South Wales) / Queensland: "Home of the Boulder" (Wilson Cooper and Barry J. Neville, Ministry of Mines, Brisbane QLD)/Sparkling Bones: Precious Opal Plesiosaurs in White Cliffs (Alex Ritchie, Australian Museum Sydney)/Shimmering Shells: Precious Opal Fossils from Australia's Cretaceous (Brigitte Szykora, Munich)/Mexico: The "No. 2" in the World Ranking: Current Report on Mexico's Opals (Jürgen Schütz, Kirschweiler)/Henry Hope's Opal: Did Hope Own Montezuma's Opal? (John S. White, Stewartstown PA)/Brazil: Bamburro, the Great Find: Current Report on the Piaui Opals (Jochen Knigge, Lampertheim)/Pedro II/Kirschweiler: "The Opal Village". The Opal Story of Kirschweiler (Klaus-Eberhard Wild, Idar-Oberstein)/What Does a Harlequin Cost? Interview with Jürgen Schütz of the Emil Weis company, Kirschweiler, on the evaluation of precious opals/The language of precious opals: nomenclature and classification (Jürgen Schütz, Kirschweiler, and Manfred Szykora, Munich)/Composite opals: doublets, triplets, mosaics. Introduction to "composite opals" (Karl Fischer, Starnberg)/Syntheses and imitations: overview of the most important products (Manfred Szykora), Munich/Precious opal in Lapis: Important opal articles in previous issues of the magazine Lapis: an ideal complement to this opal issue

 With cover, 100 pages in lapis format (21 x 30 cm). Published: 1996