And this updated edition contains a host of new findings on “Gemstones for Collectors,” additional gems in the “Table of Constants,” and the “double fraction” figures that experts have long wanted—a very special new feature.All the gemstones are treated in their many variations: more than 1,500 full-color photos showcase each precious and semiprecious stone in both its rough, natural, and its polished and cut renditions. Each entry offers complete information on the gemstone’s formation, structure, physical properties, and characteristics, along with the best methods of working, cutting, and polishing it. There are even full treatments of lesser-known gems, from andalusite to vesuvian, and a special section is devoted to rocks as precious stones, including alabaster, onyx, obsidian, and fossils. Organic gem materials are also covered, such as coral, ivory, amber, and pearl. Charts and tables help collectors identify unknown gemstones and check for genuineness.

    

    Gives a rational exposition of the principles used in the interpretation of isotopic data and shows how such interpretations apply to the solution of geological problems. Current with references up to 1985, chapters in this edition have been revised, and new chapters on Sm-Nd, Lu-Hf, Re-Os, and K-Ca decay schemes and cosmogenic radionuclides have been added. Data summaries and references have been expanded. Also includes problems for student study and abundant line drawings with explanatory captions.

    Volume I takes the account from prehistoric times through the mid-1880s, with emphasis on the park's exploration and its trouble-filled early years under federal management. Volume II covers the years of military administration of the park and the more recent developments under the National Park Service.