synthetic corundum.7, gems

Recently a number of stones have appeared on the market that were thought to be reconstructed ruby. Although the exact process used for the commercial production of synthetic corundum has been known for many years, the degree to which synthetic material may overlap in appearance the reconstructed stone is given little attention in present text books. In fact, little information has been published concerning the exact method used to produce reconstructed ruby.

gems, history of gemology, history of mineralogy, Arabic mineralogy, history of science, Egypt, Rome, Greek science, astronomy

On its first publication in 1952, Augustine to Galileo was widely welcomed as having ‘removed for ever any excuse there may have been for ignorance of medieval scientific thought’. The book has since become a standard work, and the second (revised and enlarged) edition is now reissued with further corrections. Medieval scientific thought is deceptive both in its similarities to and in its differences from modern science. It was a series of actions in the great adventure of philosophical reformation that separates the classical world from our own. In the course of that adventure, as at all times in the history of science, one system of scientific thought gave place to another not merely because new facts were discovered, but more significantly because men began to ask new questions, to look at long-familiar evidence in a new way. Not only the origins but the nature of modern science can scarcely be understood without a knowledge of the period covered by this book. Dr. Crombie begins with an account of the remains of those Greek scientific conceptions found in the West after the fall of Rome, and of the new ideas about the natural world introduced with Christianity. He then traces the process of the recovery of Greek science from Byzantium and Islam, the assimilation of the new knowledge in the Latin West, the parallel development of technology, and the new conception of experimental science that was formed in the thirteenth and fourteenth centuries. The shifts in scientific thinking in the later Middle Ages emerge as a product of the empiricism of technology married to the methods of rational abstraction of mathematics and philosophy. These shifts prepared the ground for the final revolution brought about by Galileo and his contemporaries. A consideration of their work brings the author to his conclusion. Dr. Crombie is one of the most outstanding historians of science, and is University Lecturer in the History of Science at Oxford.

synthetic spinel, gems

synthetic corundum.7, gems

corundum, sapphire, Australia.12, gems

gems, jade, jadeite, fei cui, Mesoamerica, Mexico, Guatemala, Costa Rica, Mayans, Olmecs, Aztecs, archaeology, history, archaeogemology, Pre-Columbian jade; Costa Rica; Maya; exchange; iconography, lapidary

Two important studies in Maya archaeology form the foundation of this book: A Study of Maya Art: Its Subject Matter and Development, by Herbert J. Spinden (1913); and The Inscriptions of Peten, by Sylvanus G. Morley (1937–38). The first established, with notable success, a series of stylistic changes in sculpture at a number of the larger Maya sites; the second provided epigraphic decipherments which permitted the dating of many more monuments in the Peten than was formerly possible. With this much more substantial body of dated material than was available at the time of Spinden’s study, we are now able to confirm many of his findings and to elaborate the basis of stylistic appraisal, extending it to all Classic Maya sites. It is because so much reliance has been placed on Morley’s epigraphic work that disagreements between his stylistic appraisals and mine have been stressed in this book. This, however, should not be construed as a derogation of his conclusions, which rest primarily on epigraphic sources. Our differences serve only to indicate the need to establish definite and significant style characteristics on which future discussion can be based. This is the principal aim of this study; it would have been futile to pursue it without the collection of epigraphic data and interpretation which Morley’s work makes available.

synthetic spinel, Verneuil, gems

corundum, synthetic corundum.7, Verneuil, Linde, gems

synthetic corundum.7, ruby, Verneuil, gems

corundum, ruby, sapphire, inclusions.5, Kashmir.11, India.12, gems

Gübelin reviews the diagnostic value of gemstone inclusions and their significance for understanding mineral formation. Improved dark-field binocular microscopy permits examination of inclusions throughout a faceted stone, revealing characteristic differences in their composition, form, orientation, and distribution. Inclusions are classified both by their timing relative to host-crystal growth and as solid, liquid, or gaseous components. Examples from diamond, corundum, beryl, garnet, tourmaline, spinel, moonstone, and fluorite illustrate their use in gemstone identification and, in some cases, determining geographical origin. Particular attention is given to locality-specific inclusion assemblages in rubies and sapphires, three-phase inclusions in emeralds, and characteristic mineral inclusions in garnets. The paper emphasizes that diagnostic value frequently resides in the overall inclusion pattern and its relationship to crystal structure, rather than in an isolated inclusion. Five plates illustrate representative features. Gübelin advocates closer collaboration between gemmology and mineralogy to advance both practical identification and interpretation of crystal growth.