feldspar, inclusions, gems

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

corundum, treatments.6, inclusions.5, gems

corundum, inclusions.5, gems

gems, fluorite, inclusions in fluorite, fluid inclusions

Several fluorite ± barite mineralizations, mainly controlled by post-Pliocene disjunctive faults, occur in silicified and altered Mesozoic limestones in the area of Termini Imerese (NW Sicily). In this study, we examined fluid inclusions in fluorite from the localities of Rocca Grande and Poggio Balate. Fluorite from both localities contains abundant two-phase liquid-rich aqueous inclusions. Less common types are: (a) monophase (liquid or gas); (b) two-phase, mostly gas-rich, hydrocarbon inclusions; (c) three-phase (liquid + gas + an accidentally trapped solid); and (d) three-phase (gas + two liquids: an aqueous brine and a hydrocarbonic fluid). In many inclusions, the presence of gas under pressure (most probably methane) is revealed by crushing tests. Homogenization temperatures (Th) of aqueous inclusions spread over a large range (60° to over 300 °C), being on average higher at Rocca Grande (∼200 °C) than at Poggio Balate (∼150 °C). Pressure corrections to Th are presumably minimal. However, several factors concur in suggesting that most Th’s are probably too high with respect to true trapping temperatures. Tentatively, the lowest Th-values (∼100 °C at Poggio Balate, and ∼150 °C at Rocca Grande) may be taken as indicative of trapping conditions. Temperatures of final melting of ice are, with few exceptions, higher than −3 °C. The geological setting and previous geochemical studies suggest that the fluorite-forming fluids were essentially heated meteoric waters. This is in agreement with the low salinities of most inclusions. On the other hand, reconnaissance δD determinations on bulk sample inclusions (‰ vs. SMOW) may reflect minor contributions of seawater to the hydrothermal fluids. The presence of abundant oil and methane is ascribed to interaction with organic matter-rich beds occurring in the local stratigraphic sequence.

fluorite, inclusions, gems

corundum, inclusions.5, Thailand.12, gems

corundum, treatments.6, gems

A beautiful orangy yellow oval mixed-cut stone weighing 7.60 ct (figure9)was submitted to the Santa Monica laboratory for identification. The refractive index, birefringence, and optic figure proved that the stone is sapphire. Microscopic examina-tion revealed natural inclusions as well as the strain discs, very fine dot-like silk," and round cotton-like inclusions that are indicative of heat treatment. Exposure to short-waveultravio-let radiation revealed three zones of chalky blue fluorescence close to the girdle, another sign of heat treat-ment. When the stone was immersed in methylene iodide, some interest-ing structural characteristics be-came visible. In addition to the straight angular yellow color zoning alternating with near-colorless areas, which is characteristic of natural origin, three straight blue zones close to the girdle (coinciding with the areas of chalky blue fluores cence] were seen. Figure 10 showo these blue areas, which could be the result of the heat treatment."

gems, synthetic diamond

Gem-quality synthetic diamond crystals weighing up to 11 carats have been grown experimentally in limited quantities at the De Beers Diamond Research Laboratory since the 1970s, though they are not commercially available. Examination of 14 synthetic diamonds in shades of brownish yellow, yellow, and greenish yellow reveals distinctive gemological features, including uneven color distribution, geometric graining patterns, metallic inclusions, and, in most cases, fluorescence under short-wave but not long-wave ultraviolet radiation.

corundum, sapphire, inclusions.5, treatments.6, Montana.12, USA.12, gems