gems, corundum, History.1, Indian gemology, Indian mineralogy, history of gemology, history of mineralogy, Indian lapidary

The Arthashastra by Kautilya (Chanakya) provides detailed regulations concerning the trade in diamonds and other precious stones, including preferred trade routes, tolls, and systems of weights and measures. Land routes are favored over maritime ones for the transport of high-value, low-bulk goods like gems, as they allow for greater state oversight and reduce the risks associated with piracy. Merchants dealing in diamonds were subject to tolls at checkpoints, inspections by the Superintendent of Commerce, and penalties for fraud, evasion, or price manipulation. Diamonds were weighed using a precise metrological system based on the ratti (approximately 0.1215 grams), with larger units such as the masha and tola used for bulk. Pricing and taxation were determined per ratti, and gem quality was assessed based on clarity, shape, and provenance. The state often maintained control or oversight of the gem trade, especially for locally sourced stones, and imposed higher duties on foreign merchants.

gems, jade, nephrite, jadeite, fei cui, Chinese jade carving

Sinkankas: Introduced with a brief history of Chinese jade and the development of carving into the 19th century. Objects include mountains, animals, human figures, vessels, plaques, wands, etc., each depicted and described with dates and dimensions. Handsome catalog of unusual format. Comment by Born, 169.

corundum, Afghanistan.12, Tajikistan.12, spinel, gems, balas ruby, lapis lazuli, Badakhshan

H.A.R. Gibb’s annotated English translation presents Ibn Battuta’s fourteenth-century account of travel through the Islamic world and beyond. Volume 3 follows his journeys through Central Asia, Afghanistan and northern India, including his service at the court of Sultan Muhammad ibn Tughluq in Delhi. Descriptions of towns, religious institutions, commerce and court ceremonial combine personal observations with historical anecdotes and information obtained from others. Of particular gemological interest is the passage on p. 571, where Ibn Battuta describes the ruined city of Balkh and its surviving architectural inscriptions decorated with lapis-blue pigment. He corrects the common attribution of lapis lazuli to Khurasan, explaining that it actually comes from the mountains of Badakhshan. He also connects that region’s name with the gemstone called badakhshi, popularly pronounced balakhshi, providing evidence for the geographical origin of the historical name “balas ruby,” associated with red spinel. Gibb’s accompanying notes locate the lapis lazuli mines in the upper Kokcha valley and compare the passage with Marco Polo’s descriptions of lapis lazuli and balas rubies. The passage documents medieval knowledge of gemstone sources and terminology, without claiming a personal visit to the mines.

corundum, ruby, sapphire, quality.10, gems

The old Palace of the Sultans of the Ottoman Empire stands on a promontory in the city of Istanbul. It is built high above the Bosphorus with a view across to Asia just over one mile away. Istanbul has been on the trade route between East and West throughout the centuries so that some of the choicest silks, jewels, gold, silver and porcelain reached the city. The Palace is really a series of pavilions built by successive Sultans around inner courtyards, cooled by many fountains and surrounded by high walls. Here the Sultans lived in the hey-day of the Ottoman Empire. Originally in the 15th Century, the Treasury was housed in seven towers guarded by 250 Janissaries. The first four towers contained precious jewels, gold coins were consigned to the fifth, whilst the sixth was filled with silver coins. The seventh was reserved for government documents. Sultan Murat III moved the Treasury to seven large rooms in the Palace; and a record taken in the 18th Century showed that it contained 199,371 jewels. Over the years each Sultan added more to the Treasury and when the last Sultan was deposed in 1919, by Kemal Ataturk, the Palace was turned into a museum, so that the treasures have remained intact.

corundum, treatments.6 dyed corundum, gems

gemology, reference, dictionaries, gems, Broken Bangle

The sixth edition of this gemological dictionary, revised and updated by the Gemological Institute of America’s staff, assembles more than 4,000 English and foreign words, technical terms and abbreviations encountered in gemological literature and the gem, jewelry and art trades. Its principal coverage extends to colored gemstones and ornamental, decorative and curio stones, with detailed diamond coverage treated separately. Designed as a compact reference for nonspecialists and beginning students, it also serves jewelers and gemologists who need to resolve unfamiliar terminology or clarify relationships between names. Alphabetical entries combine definitions with information on mineral identity, composition, crystal system, color, optical behavior, hardness, specific gravity and sources. Properties shared by a mineral species are generally placed under the species entry, while varieties receive separate property descriptions when their characteristics are sufficiently distinctive. The vocabulary extends beyond mineral names to organic gem materials, synthetic substances, imitations, treatments, lapidary work, jewelry practices, instruments and testing procedures. Entries explain such subjects as selective absorption, adularescence, durability, crystal forms, gemstone proportions and the operation of gemological equipment. Foreign equivalents, historical names, regional expressions, trademarks and obsolete or misleading commercial designations are included so that readers can interpret terminology encountered outside standardized mineralogical usage. Quotation marks identify names judged incorrect or deceptive, while cross-references connect synonyms and related concepts. This distinction is illustrated by the treatment of “African jade” as a misleading name for green grossular garnet. Pronunciation guides and definitions of abbreviations support accessibility, and unfamiliar technical language used within definitions is itself incorporated into the reference system. The dictionary additionally functions as a professional directory through entries on organizations, laboratories, museums, periodicals and gemological titles. Its presentation brings scientific vocabulary together with the language of commerce and craftsmanship, emphasizing accurate identification and clearer communication. Rather than presenting a continuous instructional narrative, the volume supplies interconnected explanations that allow readers to move from a particular name or problem to the underlying material, property or practice.

gems, topaz, causes of color, spectroscopy

Bank discusses the causes of color in topaz and the changes that may be produced by natural or artificial influences. He examines the behavior of differently colored topaz and considers the effects of irradiation and subsequent heating on color, including the production, alteration, and loss of color centers within the crystal. The paper relates these changes to the structural and chemical characteristics of topaz and discusses their significance for understanding naturally occurring colors as well as artificially induced coloration. The study is of gemological importance in demonstrating that topaz color may be unstable or modified by treatment and that observed color does not necessarily represent the original state of the material.

gems, garnet, pyrope-almandine, rhodolite, Macon County, North Carolina, North America

It is well known that a whole series of garnets exists from pyrope to almandine, due to the isomorphous replacement of Fe for Mg in the basic chemical composition, and for those lying near the middle of the series Anderson has proposed the name “pyrandine”. It is not so well known that a distinct subvariety of the series is recognized which, because of its rose-red to pale violet colour, has been named “rhodolite” (Gr. rhodon, a rose). It is a rare stone and many gemmologists may not have encountered a specimen. According to Phillips, this variety was found, in limited quantity, in Cowee Valley, Macon County, North Carolina. However, a few other sources are known and Sinkankas reports that fine quality material of unprecedented size has recently appeared from Tanzania. Very occasionally, stones having the colour described for rhodolite are encountered, but carrying no qualification other than “garnet”. It seems that there is some reluctance to apply the term “rhodolite” unless it is known that the stone originated from Macon County. If, however, a garnet possesses physical features, in addition to colour, which mark it as a distinctive entity within the pyrope-almandine series, it seems only reasonable that it be granted its status and accorded its value, irrespective of its source. Rhodolite is a subvariety near to pyrope and Webster notes that its composition lies between pyrope and almandine in the ratio of 2:1. The constants for pyrope show a considerable range and the figures given by different authors do not exactly correspond, particularly in the upper limits. This is not surprising, since one is reaching the intermediate (“pyrandine”) type. Phillips states the R.I. range to be from 1.730 to 1.751, but Anderson gives 1.76 as the upper limit and Webster records 1.77. It is perhaps rather curious that the R.I. of rhodolite, which belongs to this series, has only the single figure of 1.76 recorded against it. The same applies to the S.G.; Phillips gives a range of 3.65 to 3.82 for pyrope and other authors quote similarly, yet the single figure of 3.84 is given for rhodolite. Apart from these two constants, the only definite information recorded in standard works is that rhodolite shows the absorption bands characteristic of the almandine spectrum.

corundum, synthetic corundum.7, gems

Webster surveys synthetic crystalline materials developed since 1946 that have entered the gemstone trade or offer potential for ornamental use, bringing together scattered literature and results from his own examinations. Arranged alphabetically by chemical or species name, the review includes synthetic equivalents of natural minerals and manufactured compounds without known natural counterparts. Established pre-war Verneuil corundum and spinel receive only limited attention, while crystal-growth methods are outlined rather than discussed in detail. Identification is approached through physical and optical constants, internal features, absorption spectra, fluorescence and phosphorescence, X-ray transparency, electrical conductivity and, where relevant, magnetism. Particular attention is given to synthetic emeralds from Chatham, Gilson, Zerfass and Linde, together with Lechleitner’s synthetic-emerald-coated beryl and layered constructions. Earlier synthetic emeralds commonly differed from natural stones in refractive indices, birefringence and density and showed characteristic veil-like inclusions and strong luminescence. More recent products increasingly overlap natural emeralds in their measurable properties; the addition of iron can suppress luminescence, making careful examination of inclusions especially important. Flux-grown and hydrothermal rubies likewise present greater identification difficulties than conventional flame-fusion material, with seed remnants, feathers, distinctive inclusion patterns and radiation responses providing possible evidence of synthesis. The diamond section records the progression from commercially useful industrial crystals to General Electric’s May 1970 announcement of gem-quality synthetic diamonds of approximately one carat or more, while noting that production costs still exceeded those of comparable mined stones. Extensive coverage is also given to garnet-structured compounds, particularly yttrium aluminium garnet, and to diamond simulants including strontium titanate, rutile and lithium niobate. Their usefulness and detection are considered in relation to dispersion, birefringence, density, hardness, colour and durability. Other entries discuss coloured synthetic quartz, fluorite, scheelite, periclase, silicon carbide, zincite, zircon and several less familiar or experimental materials. Developments in spinel include red flame-fusion stones, flux-grown crystal groups used uncut in jewellery, sintered material imitating lapis lazuli and material displaying a moonstone effect. Throughout, trace-element additions are shown to influence colour, spectra and luminescence, so that specimens of the same nominal material may behave differently. Photomicrographs, spectral diagrams, a comparative radiograph, tables of constants and a selected bibliography support the descriptions. The compilation distinguishes established commercial products from experimental or merely prospective gemstones and provides a contemporary reference for the increasingly varied identification problems posed by synthetic crystals.

corundum, history.1, India.12, gems, Indian lapidary