corundum, history.1, chemistry.2, properties.3, gems

An early crystallographic study by Jacques-Louis, Comte de Bournon, devoted to corundum specimens from the East Indies and China. Bournon describes the principal crystal forms and their modifications, using geometrical relationships to characterize the mineral more precisely. The paper was closely associated with contemporary work by Charles Francis Greville on corundum and helped establish crystallography as an important means of distinguishing corundum from other hard stones then confused with it. Of particular gemological significance, the study contributed to the scientific recognition of corundum as the mineral species that includes ruby and sapphire.

gems, topaz

Early analysis of topaz. The analysis of this stone has already been carried out by Torbern Olof Bergman; but the results which he obtained being very different from mine, either as regards the number of the elements which constitute it, or their respective proportions, I believed it my duty to make my analysis public. The reason for this difference doubtless arises from the difference in the methods employed. The art of lithogeognosy has become so perfected during the past few years that there is reason to think that most of the analyses of sparkling stones formerly made do not provide a complete knowledge of their principles, and above all of the exact relation of these latter: we already have striking proofs of this for several stones examined by Bergmann, and among others for the oriental sapphire and the hyacinth, in which he found silica, alumina, lime, and iron, whereas Martin Heinrich Klaproth, who repeated this work, found only alumina in the first, and in the second a new earth united with a small quantity of silica.

gems, corundum, history.1, spinel, beryl, emerald

Vauquelin reports chemical analyses of spinel ruby and emerald from Peru. His investigation of spinel distinguishes its composition from that of true ruby, while the emerald analysis is historically important for the identification of a previously unknown constituent, later named beryllium (beryllia as the oxide). The paper represents an important early application of quantitative chemical analysis to gemstones and contributed to the mineralogical distinction of visually similar gem materials.

gems, Ceylon, Sri Lanka, colored gemstones, travel

Volume 4 contains a substantial firsthand account of the minerals and precious stones of Ceylon, which Thunberg collected both rough and polished. He notes that transparent stones sufficiently hard to take a polish were locally classed as precious stones, and records their Dutch, Malabar and Cingalese names. His list includes ruby, amethyst, garnet, hyacinth, red, blue, green, yellow and white tourmaline, blue and green sapphire, topaz, cinnamon-stone, rock crystal, water-sapphire, smoky crystals, black tourmaline and cat’s-eye. He gives detailed observations on their colors, transparency, crystal forms, water-worn appearance, relative abundance, value and lapidary uses. Rubies are described as generally small, with value increasing with depth of red color, size, transparency and freedom from flaws. Particularly noteworthy are his descriptions of cinnamon-stone as a flame-colored or yellowish-brown garnet and of the various materials then sold under the name “tourmaline” or “Maturese diamond.” He also describes heat treatment of the so-called white tourmaline: milky stones were calcined, enclosed in fine lime and burned with rice chaff to improve their transparency. Gem cutting and polishing were largely carried out by poorer Moors on lead plates, and Thunberg purchased suites of both rough and polished specimens for his collections.

gems, corundum, history.1, chemistry.2, mineralogy, crystallography

A concise practical introduction to crystallography based on the system of Jean-Baptiste Louis de Romé de l’Isle. Published in Paris in 1792, the work abridges Romé de l’Isle’s much larger Cristallographie (1783) and presents a simplified method for recognising and distinguishing the crystal forms of minerals in a collection. It was intended for use with a collection of polyhedral models, which served as three-dimensional representations of the forms described in the text. The manual was designed particularly for mineral collectors, providing an accessible means of identifying and arranging specimens according to their crystallisation. It thus served both as an elementary guide to Romé de l’Isle’s crystallographic system and as an explanation of the accompanying crystal models.

gems, corundum, chemistry.2, ruby, spinel

Since precious stones have, from time immemorial and among all nations, attracted universal admiration through the charm of their beauty, and have attained the rank of the most costly treasures and objects of splendour, it was inevitable that their outward properties—so remarkably distinguished by clarity, lustre, hardness, and rich colours—should become the subject of special study both for science and for connoisseurship. Knowledge of their chemical constituents, however, remained obscure for much longer, since their analysis was in fact one of the most difficult and uncertain tasks in analytical chemistry, until Marggraf, the father of more rigorous analytical chemistry, opened the way; after him Bergmann, Scheele, and other celebrated men attempted to pursue it further. On the occasion of his analysis of topaz, he found that precious stones were not, as had previously been believed, simple natural products consisting solely of the most homogeneous and pure siliceous or quartz substance, but that their composition was more complex, and particularly that pure alumina constituted a considerable proportion of them. Bergmann confirmed this finding in his treatise on the earth of precious stones, published in 1777,* in which he gave an account particularly of the constituents found in ruby, sapphire, topaz, hyacinth, and emerald. Soon afterwards another celebrated chemist, Director Achard, published a treatise on the same subject,** whose account of the constituents of precious stones agreed entirely with Bergmann’s, differing only slightly in their proportions.

corundum, history.1, gems, Arabic mineralogy, jade, Fischer, early lapidaries

A Latin scholarly edition presenting a description of, and selected extracts from, the Arabic gemstone treatise of Aḥmad al-Tīfāshī (Teifaschi), the thirteenth-century author of one of the most important medieval works on precious stones. The volume introduces al-Tīfāshī’s text to European readers and reproduces passages dealing with individual gems and precious materials, their names, properties, sources, qualities and uses. It is of particular importance to the history of gemology as an early printed European engagement with the Arabic lapidary tradition and as a conduit through which medieval Islamic knowledge of gemstones entered eighteenth-century Orientalist scholarship.

gems, jade, Fischer-Book

Jonathan Hill: First edition of this introduction to precious stones written for collectors and jewelers; according to the author this is the first complete treatise on precious stones. Dutens describes the chief varieties including diamonds, rubies, sapphires, emeralds, etc. He has also provided an interesting table at the end of current prices of diamonds of increasing carats. In the Preface, Dutens reviews the writings on precious stones of earlier authors including Pliny, Theophrastus, Boyle, and Romé de l’Isle. This work is a notable work in typography as well: it is the first book printed by François Ambroise Didot, l’aîné (1730-1804), who promoted technical innovation in printing and papermaking and introduced the new form of typographical measurement, the “point Didot.” We quote from the 1783 catalogue of Mérard de Saint-Just: “Ce petit Traité est le premier Ouvrage sorti des presses de M. Didot l'aîné, où l’on ait aperçu cette supériorité de talents qui l’a mis tout de suite au-dessus de tous ses confrères de France, d’Italie, d’Allemagne et de Hollande, et qui l’associe dès lors à la gloire de Baskerville, et surtout à celle d’Ibarra.”–from André Jammes’ wonderful Les Didots catalogue, no. 73. Dutens (1730-1812), diplomat and man of letters, edited the works of Leibniz (1768), was a fellow of the Royal Society, and was historiographer to the King of England. Sinkankas: In his preface, Dutens discusses the merits of previous works on gemstones and explains why he decided to write this one. A connoisseur of arts and of gems, he traveled widely throughout Europe and spent much time visiting collections and discussing their contents with their owners. One would therefore expect that the book was based on his experiences, but it seems that it is no more than a reworking of information available in earlier books treating gemstones, as remarked by King above, who believes Dutens derived most of his information from De Boodt and De Laet. In the first part, Dutens explains his system of classification whereby the finest and most durable of gemstones are dubbed “oriental,” while those of lesser quality and hardness receive the title of “occidental,” thus perpetuating in a highly popular and widely distributed work these unfortunate and misleading terms that persisted in use well into the last century. Some generalities on gemstones also appear here, such as curious lore, origin of gemstones, and other topics, followed by separate chapters on the major gemstones beginning with diamond. The latter chapter records recent experiments in France and elsewhere on the combustibility of diamond, one such experiment he personally observed. The second part describes lesser gemstones, mainly massive types used mostly in cabochons or in the manufacture of small to large ornamental articles or decorations. Despite King’s criticisms, Dutens’ work did provide useful, accurate information and received acclaim and wide distribution.

corundum, Thailand.12, gems

A historical and natural account of the Kingdom of Siam by François-Henri Turpin, compiled from earlier European sources rather than from personal travel in the country. The work describes Siam’s geography, government, religion, customs, commerce and natural products, drawing particularly upon seventeenth-century French accounts produced during the reign of Louis XIV and King Narai. Of interest to gemological research are its notices of the mineral and commercial resources of Siam, including precious materials and luxury goods traded in the kingdom. The book provides a useful eighteenth-century synthesis of European knowledge of Siam, although its statements should be treated as derivative rather than eyewitness observations.

gems, mineralogy, Naldi

A systematic survey of the mineral kingdom intended to arrange minerals in what Bomare regarded as the most natural order and to describe their physical properties and practical uses. The work treats earths, salts, stones, ores, metals, waters, and related mineral substances, with attention to color, transparency, hardness, fracture, crystallization, fusibility, occurrence, and uses. Gemologically important material is included under precious and ornamental stones, including quartz, crystal, chalcedony, jasper, ruby and other “Oriental” stones, together with discussion of crystal form and mineral nomenclature. The two volumes are supplemented by an alphabetical subject index, a nomenclatural dictionary, and folding synoptic tables intended to clarify the proposed classification. It is representative of mid-eighteenth-century mineralogy at the transition from descriptive natural history toward more systematic chemical and crystallographic classification.