Gemological Characteristics Research Articles

The Gemological Characteristics of Pipi Pearls Reportedly from Pinctada Maculata

The Gemological Characteristics of Pipi Pearls Reportedly from Pinctada Maculata

Mineral composition and gemological characteristics of the petrified wood of the Ulyanovsk region

For the first time, the mineral composition and gemological characteristics of the petrified wood from the Ulyanovsk region, of jewelry and ornamental quality, have been studied. The petrified wood is associated with the Lower Cretaceous deposits and consists mainly of calcite (up to 73 mass. %); pyrite, apatite, gypsum are present; dolomite, anhydrite, hematite, pyrolusite, organic matter and X-ray amorphous substance have been fixed. According to the technological and decorative characteristics, the petrified wood of the Ulyanovsk region is a quality jewelry and ornamental material of the florogenic group.

Минеральный состав и геммологические характеристики интерьерно-ювелирных аммонитов Ярославской области

Минеральный состав и геммологические характеристики интерьерно-ювелирных аммонитов Ярославской области

Gemological characteristics and the quality of sapphire from Krong H’Nang - Dak Lak

Sapphires in Krong H'Nang area have been found mainly in deluvialor alluvial placers which related to Pliocene-lower Pleistocene basaltoid formations (βN2-Q1). Their main colors are dark green, yellow-green, yellow more rarely dark blue, yellow-blue-green. Sapphires in this area are transparency, translucency and opaqueness, most of them are opaque. The crystals are from 2–7 mm and sometimes their size can be up to 30–4 0mm. Besides the color zoning reduces color quality in dark blue sapphire, there are also many plagioclase or zircon, fingerprint and liquid-filled inclusions which reduce the clarity of the sapphires. Transparent sapphires with green, yellow-green, yellow are evaluated to be good quality and can be used in jewelry. For translucent and opaque sapphires with dark green, dark blue and transparent sapphires with color zoning, they can be used in jewelry but are not estimated well. Therefore, in order to improve the quality of the latter group, suitable methods such as heat treatment, beryllium diffusion and glass filling are needed.

Mineral composition and gemological characteristics of the fossil marine reptiles of the Ulyanovsk region

Fossils of marine reptiles are a new jewelry and ornamental material and collected in the Ulyanovsk region from the Upper Jurassic deposits. They consist of (wt. %): calcite — 52, apatite — 24 and pyrite — 23, and also gypsum presents. The contents of radioactive and carcinogenic elements are close to background. The original bone structure of reptiles is preserved. Apatite replaces the bone tissue of marine reptiles, forming a cellular framework. According to the chemical composition, apatite refers to fluorohydroxyapatite with an increased Sr content. The size of the crystals is finely-dispersed. Calcite and pyrite fill the central parts of the cells. Calcite crystals of isometric and elongated shape, 0,01—0,05 mm in size, form blocks up to 0,3 mm during intergrowth. Calcite fills thin, discontinuous veins along the contour of cells with a width of up to 0,03 mm. In calcite, among the impurity elements, there are (wt. %, on the average): Mg — 0,30, Mn — 0,39 and Fe — 0,96. Pyrite forms a dispersed impregnation in calcite and apatite, content of impurities is, wt. %: Ni — up to 0,96 and Cu — up to 0,24. On technological and decorative characteristics of fossils of sea reptiles of Ulyanovsk region are qualitative jewelry and ornamental materials of biomineral group, allowing to make a wide assortment of jewelry and souvenir products.

Минеральный состав и геммологические характеристики ювелирно-поделочных септарий Республики Адыгея

Минеральный состав и геммологические характеристики ювелирно-поделочных септарий Республики Адыгея

Cultured Pearls from Lake Kasumigaura: Production and Gemological Characteristics

Cultured Pearls from Lake Kasumigaura: Production and Gemological Characteristics

Mineralogical, geochemical, and gemological characteristics of silicic gemstone in Aydıncık (Yozgat-Turkey)

There are chalcedony and amethyst formations in two fields in Aydincik-Yozgat (West of Aydincik District, Keslik area and Southwestern of Haciilyas). The gemstones in this region have been formed within the gaps and cracks of the brecciated rocks of the fault zone in altered andesites. Chalcedony and amethyst are either present in the form of crack fillings from a few millimeters to 10 cm in width, or in the form of generally oval pore fillings reaching a few centimeters to 40 cm in diameter. The chalcedony is composed of 0.1-mm–centimeter-thick bands parallel to each other in varying tones ranging from light blue/white to dark blue to reddish brown, and in some points in the central part of this banded structure are large crystalline quartz and amethysts. Chalcedony occurs as kidney—banded and geodesic forms as cryptocrystalline and macrocrystalline. The altered volcanic rock with brecciated texture, which hosts chalcedony and amethyst occurrences in both regions, is the altered andesite. Petrographic examinations carried out from chalcedony and amethysts indicated that gemstones composed of fine-coarse grained quartz have microcrystalline texture in the rim zones and have macrocrystalline texture toward the core. XRD analysis of chalcedony and amethyst with different colors and crystal grain sizes revealed that gemstones in the region were composed of large and microcrystalline quartz. When amethyst, blue chalcedony, and reddish brown chalcedony were compared to white transparent quartz, there was a significant increase in the amounts of Fe2O3 and Al2O3, and metal elements (Mo, Cu, Pb, Zn, Ni, Co, Mn, Cr) in the case of amethyst and reddish brown chalcedony. The visible reserves of chalcedony and amethysts in the region, their dimensions and varying color range, and large-grained texture and physical properties show that the chalcedonies and amethyst formations can be used as gemstones. Use of these formations as gemstones also makes a significant contribution to the regional economy.

Agates from Sidi Rahal, in the Atlas Mountains of Morocco: Gemological Characteristics and Proposed Origin

Agates from Sidi Rahal, in the Atlas Mountains of Morocco: Gemological Characteristics and Proposed Origin

Gemological Characteristics of Saltwater Cultured Pearls Produced After Xenotransplantation

Gemological Characteristics of Saltwater Cultured Pearls Produced After Xenotransplantation

Study on the Gemological Characteristics of Amber from Myanmar and Chinese Fushun

This paper researches on the gemological characteristics of amber from Myanmar and Chinese Fushun by using of the basic instruments of gemology, SEM and FT-IR. The results show that the refractive index is approximately 1.54 both in Myanmar and Fushun amber, resin glossy as well as conchoidal fracture. While the hardness of Myanmar amber is much higher and it has a dark lyons blue ultraviolet fluorescence; Fushun amber is much more transparent, medium kashima ultraviolet fluorescence and coal coveres on its surface. In addition, the fracture in Myanmar amber is more obvious compared with Fushun amber.The infrared spectrums prove that Myanmar amber has the absorption peak of CO stretching vibration at 1730cm-1, while Fushun amber is at 1700cm; the absorption peak of CH3asymmetric stretching at 2950cm-1of Myanmar amber is also different from Fushun amber which is at 2960cm-1. As a result, this paper provides basic identification between Myanmar amber and Chinese Fushun amber in gemology.

Chrysoprase and Prase Opal from Haneti, Central Tanzania

GEMS & GEMOLOGY WINTER 2009 271 hrysoprase and prase opal are nickel-containing green varieties of chalcedony and nonplay-of-color (common) opal, respectively. Both have been used as gem materials for thousands of years. Chrysoprase was described as being the “most prized” type of chalcedony by Webster (1994, p. 233). Central Tanzania is an important contemporary source of both these gems. The Tanzanian materials were first briefly described by Gubelin (1975, pp. 76–78) and Schmetzer et al. (1976). These reports were followed by a characterization of the green prase opal by Koivula and Fryer (1984), and a more detailed study of the chrysoprase by Kinnunen and Malisa (1990). This article briefly describes the geology, mining, and gemological characteristics of high-quality Tanzanian chrysoprase and prase opal from the Iyobo Mountain mine near Haneti (figure 1). This mine is operated by Dimitri Mantheakis, who hosted two of the authors (JES and BML) there in May 2008. Although both materials have also been found in several other parts of the world (table 1), Tanzania is probably the most important source of chrysoprase after Australia.

Lapis Lazuli from the Coquimbo Region, Chile

GEMS & GEMOLOGY Spring 2000 apis lazuli is a rock composed of lazurite—the source of the blue color—with variable amounts of other minerals depending on its origin and, typically, small particles of pyrite. Prized for its attractive blue color, lapis lazuli was used in jewelry by some of the world’s most ancient civilizations. The stone is mined at relatively few locations, some of which have been worked since the fifth millennium BC (von Rosen, 1990). Considering the extensive history and romance attached to this ornamental gem material, the Chilean deposit is a relative newcomer. The first reference to Chilean lapis lazuli dates back to the 19th century (Field, 1850a and b). Another early mention was made by Ignacio Domeyko (1860), a Polish immigrant and mining engineer who became the first director of the School of Mines at La Serena (about 140 km from the workings). The first detailed geologic studies of the deposit and mine workings were carried out by German geologist J. Bruggen (1921, 1926), who identified the host rock as contact-metamorphosed limestone. Lapis lazuli was officially recognized as the national gemstone of Chile in 1984. The Coquimbo Region is the only known source of lapis lazuli in Chile. Although reference is sometimes made to another Chilean deposit at Vicuna Mackenna Mountain near Antofagasta (Webster, 1994; Sofianides and Harlow, 1990), this material has been identified as dumortierite by Canut de Bon (1991). Once considered a minor or unimportant locality, with the lapis lazuli described as “at best mediocre” (Wyart et al., 1981), the Chilean deposit has produced significant quantities of attractive material in recent years. Today, Chilean lapis lazuli is exported in the rough, or incorporated into jewelry (see, e.g., figure 1), carvings, and decorative building materials by local artisans. This article will review the historical significance of lapis lazuli, and examine the geologic setting and gemological characteristics of material from Chile. LAPIS LAZULI FROM THE COQUIMBO REGION, CHILE

The Gemological Characteristics of Chinese Peridot

Figzzre 1. Two of the rough peridot nodrlles froin Chino that were used in this study. The larger measures 20.6 x 13.7 x 10.1 m m and weighs 23.71 ct. Photo O Tino Hammid. found in San Carlos, Arizona, which also occurs in basalt (Koivula, 1981)) no well-formed single crystals of rough peridot have been found in the Chinese deposits. Gem-quality peridot nodules and fragments 2 cm in diameter and up to 25 ct in weight were examined by the authors (figure 1). Excellent gems (figure 2) can be cut from this rough.