corundum, history.1, gems, Arabic mineralogy, ancient gemology, history of gemology, antique gems, glyptic, early lapidaries

As one progresses in the study of lapidaries, one becomes convinced that they all stem from a common source; but so far, that source has not yet emerged from the obscurity surrounding its origins. In all these treatises, in fact, we find the same legends, the same myths. Whether it concerns lapidaries of precious stones or lapidaries of engraved stones, lapidaries from Antiquity or from the late Middle Ages, whichever manuscript we turn to, whichever author we consult, we always encounter the same fables: they vary only in form, never in substance. To uncover this original source, it would seem at first glance that one need only go back, continually retracing the chain we possess, and that the oldest known lapidary must, in some sense, be the original treatise. That would be a great error. The path is strewn with pitfalls, full of unforeseen twists and turns; just when one believes one firmly holds the guiding thread through this labyrinth, it suddenly breaks, and acquisitions that once seemed definitive abruptly vanish, leaving in their place a new field of exploration where everything must be rediscovered. In this realm of legend, where each century has left something of itself, imagination sometimes takes hold and one believes one can intuit meanings; yet on the contrary, in these scientific and magical treatises, there exists a tradition that has been faithfully transmitted and which one finds absolutely identical at both ends of the historical spectrum. The most precise method, the most scrupulous criticism, are thus essential here: they must accompany every step forward with their checks and allow the inclusion of a document in the general structure of the work only insofar as it appears absolutely indisputable. As of today, one point is absolutely established: it can serve as a reliable foundation. All known lapidaries, whether manuscript or printed, derive from one of the following four origins: 1° Greek: represented by Theophrastus, Dioscorides, the Cyranides, Hermes, Damigeron, the Book of Enoch, the Μετὰ Ζῆλος of Orpheus, the Pseudo-Plutarch, and Psellus. 2° Latin: preserved for us by Pliny, Saint Isidore, and Marbode; this tradition does not appear to have been interrupted in the West. 3° Arabic: the Book of Stones of Aristotle, the Book of Talismans, al-Bīrūnī, Ibn al-Bayṭār, and al-Tīfāshī seem to encapsulate the knowledge of Eastern lapidaries. 4° Hebrew: which certainly shows the greatest affinities with the Arabic lapidaries, but of which we also find absolutely distinctive traces in the Western lapidaries that we possess.

corundum, inclusions.5, gems, spinel, inclusions

Prinz examines microscopic inclusions in sapphire, ruby, and spinel, describing the internal features observed in specimens of these gemstones and illustrating them on an accompanying plate. He discusses the form, distribution, and appearance of the inclusions under magnification and considers their possible nature and origin. The paper is an early application of microscopy to the systematic examination of gemstone inclusions and is particularly significant to gemology because such internal features later became important criteria for identifying gems, determining their natural origin, and distinguishing between closely similar materials.

gems, inclusions, quartz

Sinkankas: In a masterful introduction to the study of inclusions in crystallized minerals, the authors set forth the fundamental principles of paragenesis and the evidence supporting them, considering types of inclusions based on environment and genesis type, such as whether the minerals were grown from solution or in an igneous rock mass. The first part provides 334 examples of inclusions, followed by a table of 107 others, a table of chemical groups into which the minerals containing inclusions fall, and copious notes. In the second part, the authors begin with a brief historical survey of the knowledge of inclusions, mentioning Claudian to show that the ancients were already aware of watery inclusions in rock crystal, and naming mineralogists and collectors thereafter, especially in the latter half of the 18th century, who remarked on or zealously collected inclusions, regardless of cost. Notable authorities such as Pini, Collini, Davila, Rome Delisle, Reuss, Jameson, and others are featured. The text of this part starts with quartz, with no less than 43 examples of inclusions in rock crystal, amethyst, etc., followed by 13 in calcite and numerous others in fluorite, barite, topaz, tourmaline, adularia, beryl, analcime, apophyllite, and more. The second part concludes with a handsome colored plate of inclusions and phantoms in quartz, calcite, and fluorite. The third part begins with a further discussion and a list of periodicals the authors consulted. This is followed by examples of microscopic or “cryptic” inclusions, such as sunstone and bronzite, as well as a brief note on diamond, in which the “ashes of burnt diamonds showed traces of organic structure,” along with several examples of phantom growth and explanations of inclusion growth in minerals like tourmaline, cakite, aragonite, garnet, fluorite, and others. While this is the first systematic monograph to describe and offer paragenetic theories on the growth of inclusions, it does not mention the work of David Brewster of Scotland, who published important discoveries in his Edinburgh Philosophical Journal from 1823 onward, especially recognizing two- and three-phase inclusions in topaz. See also SOCHTING, J.W.E., 1860.

gems, lapidary, gem cutting, France, Jura mountains, diamond cutting, jade, Fischer-Book

Sinkankas: A large, detailed work which embraces not only gemstones but also ornamental and monumental kinds, with much on their extraction, working, and polishing. First volume: gemstones, ornamental stones, with discussion of crystallography, mineral properties, detailed descriptions of hard" and "soft" stones, with diamond receiving most attention; others treated include corundum, chrysoberyl, spine!, topaz, beryl, zircon, garnet, euclase, quartz, the last also given a great deal of space for its treatment of crystalline & cryptocrystalline varieties (p 79-149), and including opal, a large number of trivial jasper varieties, and, briefly, descriptions of figured stones, natural and false, engraved gems, etc. Among "soft" stones are idocrase, peridot, tourmaline, epidote, kyanite, prehnite, feldspars (including jade which Brard believes to be a kind of compact feldspar), hypersthene, lapis lazuli, lepidolite, natrolite, chiastolite, fluorite, calcite, talc and gypsum. This section is quite remarkable for its treatment of so many uncommon or rare gemstones and is one of the earliest treatises to include many of them. In an appendix to the first volume, Brard also treats halite, jet, hard coal, amber, malachite, turquoise, pyrite, hematite, rhodonite and obsidian although there seems to be no explanation why these materials were separately treated. Here also appears a very brief remark on magnetite and "eagle-stone" amulets, followed by a short discus- sion on how to detect differences between real and false gems, among the interesting remarks being Brard's recognition of spherical inclusions as being typical of glasses rather than of real gemstones (p 209). Volume I closes with a good explanation of lapidary techniques and abrasive/polishing agents, and the "agate mills" of ldar-Oberstein, Pl IV. The engraved plates additionally depict crystal forms, a lapidary bench as used in Paris, wire saw, diamond cuts, disk saw, carving tools, a multiple-blade saw, a lapidary in the act of sawing, and a gem-engraver's bench with accessories. In contrast, the second volume is far less interesting to the gemologist inasmuch as it confines itself to monumen- tal/architectural stones, eg, porphyries, variolites, amygdaloids, granites,etc, while others are the numerous varieties of marbles and alabasters, along with explanations of quarrying and process- ing of stones into finished shapes. A scarce and important work giving every evidence of great care in selecting and assembling accurate and useful information, reflecting the state of the stone arts at that time."

gems, corundum, history.1, jade, Fischer, beryl, emerald, opal, turquoise, jasper, malachite, treatments, simulants, lore

The Roman author and historian Gaius Plinius Secundus, a.k.a. Pliny the Elder (23-79 A.D.) compiled the Naturalis Historia (Natural History) from a reported two thousand sources. This thirty-seven volume work, published in 77A.D., embraces the domain of natural history in the broadest sense. It includes astronomy, geography and meteorology. Beyond what is today considered natural history, it also includes fine arts, inventions, and human relations. It stands as the chief source from which future historians have obtained informative descriptions of life in the first century. Much of Pliny’s information on gems was not written from direct observation. His studies were often a retelling from second-hand sources, now lost in antiquity. Many stones are lumped together by color, mining location, or attributes passed on in legends. His recounting of legends and myths, and assumptions drawn from these, are the basis of much of the writing which appeared into the Middle Ages. He became the most often quoted writer on the subject, and his information was relied upon and repeated without question in book after book. In the first thirteen centuries of European history, little scientific in-formation was added to the limited knowledge of gems garnered from Pliny’s accounts. However, many later authors embellished the writings and added their own speculations and unwarranted conclusions. Pliny is credited with his attempts to classify gems according to color and observable external characteristics. This led to the practice of assigning the attributes of one stone to all stones of similar color or appearance. The green stones named smaragdus in Latin are prime examples. Pliny classified most green stones as varieties of emerald. In all, twelve varieties are listed; green sapphire, turquoise, smithsonite, malachite, jasper, and even glass are identifiable by his descriptions. He also is credited with making some astute classifications. It is thought that he was the first to recognize the connection between beryls and emeralds. Some of the stones grouped by Pliny share little in common. It is obvious that some of his “observations” were gathered through other’s eyes. Errors in translation or reliance on oral tradition may have led to the inclusion of misinformation about stones that Pliny was not able to observe in nature. Since the original Latin version, over two hundred and fifty editions of his classic have been published in numerous languages. The first complete edition of Natural History was published in Venice in 1469, and the first critical edition was offered by Hardouin in 1685. The most detailed study of Pliny’s gemstone accounts is a work by S. H. Ball. See also the translations from Eichholz, which many experts consider more authoritative.

gems, corundum, color.4, UV-Vis spectroscopy

A detailed examination of the physical origins and practical measurement of the ultraviolet absorption edge in corundum, with particular attention to its potential application in geographic origin determination. The author explains that the fundamental absorption edge of pure Al₂O₃ arises from electronic transitions across its approximately 9.5 eV band gap, corresponding to about 131 nm, whereas the apparent UV edge measured in natural ruby and sapphire is generally dominated by impurity-related charge-transfer absorptions and light scattering. Particular emphasis is placed on O²⁻–Fe³⁺ charge transfer, with a strong absorption maximum at 259 nm, together with contributions from Ti⁴⁺, Cr³⁺, and V³⁺. Spectra of progressively thinned sapphire samples demonstrate how sample thickness, plotting scales, spectrophotometer dynamic range, and mounting apertures can dramatically alter the apparent position and sharpness of the absorption edge. The author stresses the importance of defining the edge at a specified absorption coefficient, such as 10 cm⁻¹, and discarding measurements exceeding the instrument’s valid dynamic range. Comparisons of UV-edge wavelengths with LA-ICP-MS iron concentrations reveal a partial but complex correlation, complicated by Fe³⁺ absorption bands, titanium-related processes, and scattering from submicroscopic inclusions. A cloudy Vietnamese ruby is examined in detail, with its unusual absorption behavior attributed largely to scattering from probable TiO₂ nanoparticles rather than iron absorption. The author concludes that UV-edge measurements primarily reflect trace-element chemistry and, in some cases, inclusion-related scattering, and that their independent value for geographic origin determination remains unproven. Further research involving larger datasets, controlled spectroscopy, chemical analysis, synthetic reference crystals, and experiments on samples of varying thickness is recommended.

gems, corundum, synthetic corundum.7

Two bluish green faceted samples that resembled Paraíba-type (Cu-bearing) tourmaline (13.94 and 15.95 ct; Figure 36) were recently submitted to the DANAT laboratory for identification. Standard gemmological testing revealed RIs of 1.761–1.770 and a hydrostatic SG of 3.98 for both specimens, which match the values for corundum. The specimens were free of inclusions when viewed with 10×–70× magnification, suggesting a synthetic origin. However, no curved colour banding was observed with diffused lighting while they were immersed in water. As previously documented by Hughes (2019), curved banding in synthetic sapphire and ruby also can be revealed by exposure to short-wave UV radiation. We examined the present samples using a DiamondView, but they did not fluoresce under its ultra-short-wave UV source, nor under long-wave UV radiation. LA-ICP-MS chemical analysis of both samples was performed with an iCAP Q ICP-MS unit coupled with a Q-switched Nd:YAG laser-ablation device operating at a wavelength of 213 nm. The common trace elements in natural corundum—Cr, Ti, V, Fe, Ni and Ga—were all below the detection limits, which proved that the specimens were synthetic. (Detection limits were 1.8 ppmw Cr, 0.44 ppmw Ti, 0.75 ppmw V, 7.9 ppmw Fe, 2.1 ppmw Ni and 1.2 ppmw Ga.) Moreover, the analyses showed an elevated content of Co (51.1–78.1 ppmw).

gems, jade, fei cui, pyroxene jade, 翡翠, 绿辉石, 岩石矿物学, 产地标型, 危地马拉

High-quality green jadeite recently discovered in Guatemala is comparable in quality to the finest green jadeite from Myanmar and has become an increasingly important source of premium jadeite jewelry in the Chinese market. However, its mineralogical characteristics and geographic origin indicators remain poorly understood. This study examines high-quality Guatemalan green jadeite rough and finished jewelry widely available in the Chinese market. Their mineralogical and compositional characteristics were systematically investigated using microscopic observation, Raman spectroscopy, and electron microprobe analysis. The results show that the material, marketed as “Maya Green,” is composed predominantly of omphacite, with minor accessory minerals including phlogopite, phengite, and chlorite. Three generations of omphacite (Omp-I, Omp-II, and Omp-III) were identified, with Omp-III forming the principal constituent of the jadeite. Omp-III is characterized by low Mg (average 7.59%) and Fe (average 1.57%) contents, relatively high Cr (average 0.24%), and a jadeite end-member component of XJd > 0.5 (average 0.53). Previous studies have shown that jadeite from different segments of the Motagua Fault in Guatemala displays distinctive mineral assemblages. In contrast, the high-quality Guatemalan green jadeite examined in this study is mineralogically simple, consisting primarily of nearly pure omphacite but containing two distinctive metallic inclusions, native copper and nickeline. These inclusion characteristics, together with the mineral chemistry and mineral assemblage, differ significantly from those of other high-quality green jadeites and provide important mineralogical criteria for distinguishing premium Guatemalan green jadeite from traditional Myanmar jadeite and similar high-quality jadeites from other localities.

gems, corundum, synthetic corundum.7, quench crackled

One common process used to alter gemstones is the “quench-crackle and dye” treatment, in which a heated stone is quenched in room-temperature water, inducing fractures that allow dye to penetrate the stone and change the appearance of its color. This technique was introduced in the 1990s (S.F. McClure and C.P. Smith, “Gemstone enhancement and detection in the 1990s,” Winter 2000 G&G, pp. 336–359) and is typically applied to quartz, cubic zirconia, glass, and other synthetic gemstones due to their low cost and high availability. The Carlsbad laboratory recently received a 12.65 ct laboratory-grown colorless sapphire that showed signs of treatment (figure 15). At first glance, the overall face-up color of this stone suggested it was a Paraíba tourmaline or a low-quality emerald. With the unaided eye, the color-causing dye-filled fractures were faintly visible. The refractive index, specific gravity, and other basic gemological tests identified the material as sapphire. Along with the lack of natural inclusions, testing with X-ray fluorescence revealed the absence of both gallium and iron, confirming that the stone was laboratory-grown. Visible/near-infrared (Vis-NIR) absorption spectroscopy displayed a broad band around 650 nm that did not match natural color-causing components found in corundum (figure 16). This explains the unnatural color of this sapphire. With a microscope, the fractures within this stone displayed characteristic weblike fractures induced by quenching. Unlike naturally occurring fractures, the fractures produced by this type of treatment have uniform spacing and depth, as shown in figure 17.

gems, spinel, Sri Lanka, cobalt blue spinel, spinel inclusions, spinel chemistry

In November 2024, gem dealer Dudley Blauwet encountered loose crystals and matrix specimens of Co-spinel from a new deposit in Sri Lanka’s Central Province, located between Kandy and Matale. He purchased several dozen pieces from two trusted suppliers, returning in March–April 2025 to acquire more, though production had by then ceased because the site was on private land where mining was no longer permitted. Blauwet noted that in four decades of visiting Sri Lanka he had never before seen Co-spinel matrix specimens from the country; these consisted of aggregates of well-formed crystals lining fractures in weathered host rock. From some of the more transparent fragments, he faceted 22 stones totaling about 7.5 carats.