corundum, ruby, sapphire, Kenya.12, Tanzania.12, East Africa, geology.11, gems

An illustrated survey of East African gemstones, emphasizing the deposits of Kenya and Tanzania and combining regional geology with accounts of discovery, exploration, mining, and gemological properties. Following an introduction to the geological setting, Keller discusses diamonds, ruby and sapphire, emerald and alexandrite, tanzanite, garnets, tourmaline, and green opal, with a concluding chapter on less prominent gem materials. Individual accounts place the deposits within their geological environments while recording their development and the people involved. Particular subjects include tanzanite from Merelani and prase opal from Haneti Hill, Tanzania. Photographs of rough and cut stones, inclusions, mining operations, and historical scenes complement locality maps, including some previously unpublished examples. Contributors include E.J. Gübelin, Harold and Erica Van Pelt, and J.I. Koivula. Appendices list 177 noteworthy gem localities with geographical coordinates and document East African gemstones in the collections of the Los Angeles County Natural History Museum and the Smithsonian Institution. References accompanying each chapter provide access to the region’s geological and gemological literature. The volume offers a substantial record of East African gem deposits and industry as understood at the beginning of the 1990s.

gems, inclusions, beryl, emerald, Austria, Russia

The third installment of Schwarz’s comparative study of the chemical properties of emeralds from different deposits, here treating Habachtal, Austria, and the Ural Mountains of the USSR. After reviewing the regional geology, occurrence and genesis of emerald at the two localities, Schwarz presents chemical data and compares the ranges and average concentrations of the principal minor and trace constituents. Particular attention is given to variations in chromium, iron, magnesium and sodium, demonstrating compositional differences both within and between the two deposits. The study evaluates chemical composition as an aid to characterizing emerald populations and determining geographic origin, while placing the analytical results within their geological and genetic settings.

corundum, synthetic corundum.7, gems, general gemology, beryl, emerald, garnet, topaz, tourmaline, chrysoberyl, alexandrite, diamond, gem testing

gems, gem localities, beryl, emerald, aquamarine, morganite, chrysoberyl, alexandrite, corundum, ruby, sapphire, diamond, garnet, opal, quartz, spinel, spodumene, tourmaline, paraiba, zoisite

The 1980s witnessed significant developments in the discovery of new sources for diamonds and colored gemstones, alongside increased production at many established mining sites. This article highlights important new finds and major gem-producing localities from the decade, offering brief descriptions of each and assessing their impact on the jewelry industry. Additionally, it includes an index of key recent publications related to these gemstone occurrences.

corundum, Tajikistan.12, Afghanistan.12, Tanzania.12, Malawi.12, geology.11, gems

gems, beryl, emerald, Egypt, inclusions

The aim of latest expedition to Djebel Sikeit and Djebel Zabarah by the brothers Angelo and Alfredo Castiglioni was the re-discovery of the Pharaoh's emerald mines. The Castiglioni expedition was successful in the re-discovery of these forgotten ancient mines and has collected samples and documents on these famous deposits of precious stones, providing emer- ald specimens of great interest to gemmologists and archaeologists, as will be revealed in this paper.

gems, inclusions, beryl, emerald, Brazil, Santa Terezinha de Goiás

Describes the emerald deposits of Santa Terezinha de Goiás, Brazil, presenting evidence for their stratiform occurrence and documenting the stones’ gemological properties, chemistry and inclusions. Refractive indices reach 1.593–1.602, with birefringence of 0.008–0.010, reported as the highest values then observed in emerald. Chromium and iron show the highest mean concentrations among Brazilian emeralds. Fluid inclusions are generally very small. Mineral inclusions include spinel, carbonates, mica, talc, amphibole and pyrite, with rutile, hematite, chalcopyrite, pentlandite and ilmenite also recorded.

corundum, synthetic corundum.7, gems

Discusses seven misconceptions about flux-grown synthetic rubies from the perspective of a partner in the J.O. Crystal Company, producer of Ramaura ruby. The author first rejects the assumption that laboratory growth permits unlimited control over crystal size, clarity, variety and cost, stressing that synthesis remains constrained by physical laws and practical growth conditions. Inclusions are not deliberately inserted to imitate natural ruby: trapped flux, internal fractures, fingerprints and feathers arise during growth, and the producer seeks to minimise them because cleaner material commands higher prices. The article distinguishes the implications of the terms laboratory-grown, flux-grown, created and cultured, explaining the company’s preference for “cultured” as a description of crystals grown from a nutrient solution with human involvement. It contrasts flux growth with inexpensive, high-volume flame-fusion production and argues that the two products differ substantially in appearance and manufacturing cost. Carter attributes Ramaura ruby’s natural-looking appearance to slow precipitation from a supersaturated solution, spontaneous nucleation without a seed, and a relatively regular crystal lattice with few dislocations. Addressing fears that synthetic stones will overwhelm the market, she states that annual flux-grown ruby and emerald production amounts to no more than approximately 1% of the number of newly mined and faceted natural counterparts, and that difficult, costly production prevents supply from meeting demand. Particular attention is given to the identification dopant intentionally incorporated into every marketed Ramaura ruby. According to the author, this shifts long-wave ultraviolet fluorescence towards yellow-orange relative to natural ruby; its effect varies with the dopant concentration prevailing when individual crystals form. Examination should therefore take place in a darkened room, using a long-wave ultraviolet lamp and direct comparison with a natural ruby. The company describes doping as a voluntary measure intended to preserve reliable distinction from natural material. Finally, the article explains why synthetic origin does not imply negligible value: high-purity platinum crucibles, months of furnace operation, substantial electricity consumption and low cutting yields all contribute to cost. Reported prices range from US$50–350 per carat according to size and grade, or approximately 5–10% of the price of comparable natural ruby. Company and partner biographies provide context for these explanations and the commercial position from which they are presented.

gems, beryl, emerald, Brazil, Santa Terezinha

Emeralds from Santa Terezinha de Goiás, a major global producer, contain a diverse range of primary inclusions identified through X-ray diffraction, energy dispersive analysis, and electron microprobe techniques. These inclusions include chromite, dolomite, magnesite, talc, phlogopite, pyrite, quartz, beryl, barite, patronite, ferropargasite, anthophyllite-cummingtonite, epidote, melanterite, and dumortierite, which reflect the metamorphic nature of the host rocks. Chromite, the most characteristic inclusion, appears as isolated or clustered idiomorphic crystals that exhibit a distinctive red-brown hue under magnification. Carbonates like dolomite and magnesite occur as rhombohedral crystals, while talc is present as dispersed flakes. Other notable inclusions include yellow cubic pyrite, phlogopite (less common than in emeralds from Itabira and Socotó), idiomorphic beryl, and quartz filling fractures. Barite and patronite are rare, while epidote, cummingtonite-anthophyllite, dumortierite, and melanterite were detected only in mixtures via X-ray methods. Fluid inclusions, visible only at high magnifications, contain gas, liquid, and solid phases. The observed inclusions align with the paragenesis of the metamorphic country rocks, and chemical analysis indicates significant variations in the crystallization conditions of these emeralds.

corundum, Australia.12, gems

H. Bracewell presents an informal account of gemstone collecting during a journey with her husband through New South Wales and Queensland, drawing attention to both established gemfields and isolated, less familiar localities. The account responds to the fragmented information available on Australian gem occurrences and the difficulty visitors may encounter in obtaining collecting advice. Beginning at Torrington, the author describes topaz associated with historic tin workings, including extensive deposits of massive topaz known as silexite, and notes that old mine dumps yield gem beryl, smoky quartz and fluorite, together with wolframite and bismuth specimens. Nearby Emmaville is identified as the site of Australia’s first commercial emerald mine; its history includes the recognition of emerald in an abandoned cassiterite working in 1890, production exceeding 25,000 carats in 1891, and subsequent intermittent activity. In Queensland, commercial chrysoprase workings at Marlborough expose narrow veins of bright apple-green material associated with common opal. At Mount Surprise, hydraulic removal of overburden reveals cavities among granite boulders from which aquamarine is recovered manually; these cavities also contain feldspar and smoky quartz, some of exceptional gem quality. The author additionally records topaz-bearing pegmatites in the district and illustrates both crystals and faceted stones. Mount Hay offers thundereggs and attractive spherulitic rhyolite for lapidary use, while a locality north of Muttaburra provides abundant rounded quartz, agate and petrified wood weathered from a nearby hill. At Chudleigh Park station, gem peridot is obtained by sieving soil beneath weathered basalt; iron coatings must be removed by chipping or tumbling before quality can be assessed. Sapphire, zircon and moonstone accompany the peridot. Agate Creek is described as a prominent collecting locality for multicoloured agate and thundereggs containing coloured chert. The Cloncurry district yields cabochon-quality chrysocolla and specimens of azurite and malachite, while Kuridala supplies gem amethyst and well-formed doubly terminated crystals. Additional occurrences west of Cloncurry include calcite, chalcopyrite, rutile, staurolite and gem quartz. Fourteen colour illustrations document representative materials, deposits and collecting results, supporting an account intended as the opening instalment of a broader record of the couple’s Australian travels.