corundum, Sri Lanka.12, treatments.6, gems

corundum, sapphire, Sri Lanka.12, treatments.6, gems

corundum, India.12, Kashmir, gems

gems, lapis lazuli, Afghanistan, history of gemology, gem trade, Central Asia

The entry surveys lapis lazuli in the ancient Near East, beginning with the Sumerian ZA.GÌN and Akkadian uqnû, and considers its identification, terminology, sources, trade, archaeological occurrence, and uses. Lapis lazuli was an imported and highly valued material in Mesopotamia, occurring from very early periods and employed for beads, seals, inlays, amulets, vessels, and other prestigious objects; it also acquired important religious, magical, and literary associations. The discussion considers the problem of determining the geographical sources of ancient Near Eastern lapis lazuli, with Badakhshan in Afghanistan regarded as the principal probable source, and places the stone within the extensive long-distance exchange networks connecting Mesopotamia with Iran and regions farther east.

scapolite, Tanzania, gems

Gübelin and Graziani investigate gem-quality scapolites from central Tanzania, examining their gemological, optical, and mineralogical properties and the variations among specimens. The study is particularly concerned with characterizing the Tanzanian material and relating its properties to scapolite composition; it subsequently appeared in an expanded English version as “Observations on some scapolites of central Tanzania,” Journal of Gemmology, Vol. 17, No. 6 (1981), pp. 395–405, with further investigations published in 1983.

gems, jade, nephrite, Taiwan, amphibole jade, jade cat’s eye, tremolite cat’s eye

Mineralogy of semi-precious gems, such as nephrite, tremolite cat's-eye, blue chalcedony and veined stones, from Taiwan are reviewed, supplemented with some data (Fig.1). Nephrite and cat's-eye tremolite occur at the contacts of graphite-sericite schist and serpentinite sills in association with asbestus, talc and diopside-dominant skarn near Hualien (Fig.2). Cat's-eye tremolite was formed evidently later than nephrite. Nephrite jade is spinach-green to yellowish green in color; translucent to opaque. H. : 6.5; G. : 3.007-3.014. It is composed of sub-parallel tufts of fibrous tremolite in interfelted base with nephritic texture, accompanied by minor chromite, magnetite, picotite, garnet and chlorite which give rise to black spots or streaks (Fig.3). α : 1.609-1.612, β : 1.620-1.621, γ : 1.631-1.633; γ-α : 0.021-0.022. Noteworthy is that the Taiwan jade is similar in mineralogy to the New Zealand jade. Tremolite cat's-eye varies in color, from greenish yellow to black; translucent to opaque. H : 6-7, G. : 3.000-3.045. It consists solely of fine, Ionger sub-parallel fibers of tremolite without nephritic texture. α : 1.612-1.613. β : 1.620-1.626, γ : 1.637=1.639; γ-α : 0.024-0.027. Both nephrite and cat's-eye are similar in X-ray data to tremolite from St. Gotthard, Switzerland (Table 1). Chemical analyses also revealed that no marked differences in cornposition exislt between nephrite jade and cat's-eye and between cat's-eyes of various colors, all showing about 10 % of the ferro-actinolite molecule (Tables 2 & 3). Minor uvarovite with 10% Cr_2O_3 and vesuvianite were first found in Taiwan (Tables 5 & 6). Blue chalcedony occurs as irregular small veins in andesitic agglomerate north of Taitung. It is deep sky-blue to greenish blue in color; opaque to translucent. H. : 7; G. : 2.581; n : 1.539. Traversed by veinlets of chalcedony-quartz and quartz-pyrite, it consists mainly of radial-fibrous aggregates of chalcedony, with minor chlorite, opal and iron hydroxides (Fig. 5). Veined stones are produced on the Penghu Islands as globular concentric aggregates chiefly of calcite, aragonite and siderite in the amygdaloidal cavities of olivine-augite basalt (Figs.5 & 6). H : 3-4; G. : 2.83-3.30. Some gemological features of these gem materials are also given (Fig.4).

synthetic corundum.7, flux, inclusions.5, gems

corundum, color.4, treatments.6, gems

jade, jadeite, fei cui, Burma, maw-sit-sit, gems, Broken Bangle

corundum, Australia.12, gems