珠寶鑒賞english-資料下載頁(yè)
2025-02-13 03:52本頁(yè)面
【正文】 how evidence of heat treatment. ? Beginning middecade, demand and scarcity significantly drove up prices for colorless or white sapphire. As a result, dealers in Sri Lanka reported that lightly colored sapphires had been heated to render them colorless (Robertson, 2023). Ironically, the scarcity of natural white sapphire was caused in part by the large quantities that were being used for Ti blue diffusion and, to a lesser extent, Cr red diffusion. ? Since the two previous GG retrospective articles on treatments (Kammerling et al.， 1990a。 McClure and Smith, 2023), heattreatment technology— in the form of electric furnaces with precise temperature and atmospheric controls—has bee more sophisticated and accessible. During the 1980s and 1990s, nearly all mercial corundum heat treatment was being conducted in Thailand. ? While Thailand remains important, Sri Lanka is now a major force, and smaller yet very effective corundumheating capabilities exist in other producing regions such as Africa, Myanmar, China, and the . (Montana). Nevertheless, some pink sapphires and rubies continue to be heated using simple blowpipe methods at mine sites and trading centers in Vietnam, Sri Lanka, and elsewhere (R. Hughes, pers. m., 2023). ? Heat treatment, particularly at high temperatures, can dramatically alter the internal characteristics and properties of sapphires and rubies. During the past decade, a number of articles addressed heattreatment techniques and their effects on gem corundum from localities such as Madagascar (Wang et al., 2023a), Montana (Schmetzer and Schwarz, 2023。 Kane, 2023), Australia (Maxwell, 2023), Vietnam (Winotai et al. 2023), Myanmar (Kyi et al., 1999), and Malawi (Rankin, 2023。 Rankin and Edwards, 2023). ? Schmetzer and Schwarz (2023) discussed the identification of natural, heated, and Bediffused yellow to reddish orange sapphires from Sri Lanka, Montana, Madagascar, and Tanzania. David and Fritsch (2023) contributed a valuable study on the use of infrared spectra to distinguish heated rubies and sapphires from 20 different geographic origins. ? Proof that a ruby or sapphire has been heat treated is sometimes readily apparent, but in many cases it requires considerable knowledge and observational skills. The criteria for identifying heat treatment in rubies and sapphires using a microscope were set forth during the 1980s and 90s (for a summary, see Kammerling et al., 1990a). ? Most still apply. They include stress fractures surrounding melted or heataltered inclusions。 spotty coloration in blue stones, best seen with diffused illumination。 colored halos surrounding altered solid mineral inclusions。 stubby, partially absorbed (dotlike) silk。 and pockmarked, resorbed facets. ? Relatively lowtemperature heating (1200176。 C), particularly of purplish pink sapphires (and some purplish red rubies) to remove the blue color ponent, is still very difficult to detect with standard microscopic testing. The lower the temperature used, the more difficult the detection will be (Krzemnicki, 2023). ? Equally important is being able to prove that a ruby or sapphire has not been heat treated. The decade yielded rich contributions in this area。 see Shor and Weldon (2023) and Shigley et al. (2023) for important literature references. Smith et al. (2023d) and Smith (2023) provided useful charts for identifying the natural or treated state in rubies and sapphires from around the world. 謝謝觀看 /歡迎下載 BY FAITH I MEAN A VISION OF GOOD ONE CHERISHES AND THE ENTHUSIASM THAT PUSHES ONE TO SEEK ITS FULFILLMENT REGARDLESS OF OBSTACLES. BY FAITH I BY FAITH
教學(xué)課件相關(guān)推薦
鄂ICP備17016276號(hào)-1