|Dimensions (mm)||5 x 2.5 x 4mm|
|Weight (carats)||25.42 carats|
|Ring Size||6 US|
STYLISH TANZANITE OPAL RING
This is a stylish stunning dress ring with Tanzanites enhanced with Ethiopian opals.The opals have a beautiful pastel colour which sparkle when moved-the photo dosent do justice to the opals.
The workmanship and quality is excellent.
Size of opal 4 mm app
Size of tanzanites 5 X 2.5
Total weigh cts 25.42 app
Ring size[USA] :6
Note This ring was not made by our factory so we dont have the accurate weights of the opals and Tanzanites. i bought them as i thought the quality was excellent.
Tanzanite is an extraordinary gemstone. It occurs in only one place worldwide -Tanzair africa. Its blue, surrounded by a fine hint of purple, is a wonderful colour. Thanks to its unusual aura and the help of the New York jeweller’s Tiffany, it has rapidly become one of the most coveted gemstones in the world.
Tanzanite is a blue variety of the gemstone zoisite. It consists of calcium aluminium silicate and is not particularly hard, having a value of 6.5 to 7 on the Mohs scale. For that reason, it should always be worn carefully and never placed in an ultrasonic bath for cleaning or brought into contact with acids.
The deep blue of the tanzanite is fantastic, and runs from ultramarine blue to light violet-blue. The most coveted colour is a blue surrounded by a delicate hint of purple, which has a particularly wonderful effect in sizes of over 10 carats. The well developed polychromaticity of the tanzanite is typical: depending on the angle from which you look at it, the stone may appear blue, purple or brownish-yellow. Having said that, most raw crystals are somewhat spoiled by a brownish-yellow component, though it can be made to disappear by the cutter if he heats the stone carefully in an oven to approximately 500°. During the procedure he must pay careful attention to the moment at which the colour turns to blue. This burning is a method of treatment which is regarded as customary in the trade, but the raw stones must be as free of inclusions as possible, since otherwise fissures may occur. In fact working with tanzanite can sometimes give even the most experienced cutter a bit of a headache, the cleavage of this gemstone being very pronounced in one direction. This exclusive gemstone is cut in every imaginable shape from the classical round shape to a number of imaginative designer cuts.
This is what the GIA has to say about this type of opal
New Play-of-Color Opal from Welo, Ethiopia
A new source of high-quality play-of-color opal was discovered in early 2008 in Welo Province, Ethiopia, about 500 km north of Addis Ababa. This deposit is geographically distinct from the Mezezo deposit in Shewa Province, which was discovered in the early 1990s (see, e.g., Spring 1994 Gem News, pp. 52–53).
These contributors examined a parcel of about five rough and 30 cut Welo opals. The cabochons showed good play-of-color ; the vast majority were white and transparent, but some had a bodycolor varying from light yellow to dark “chocolate” brown. Compared to Mezezo opals (e.g., J.-P. Gauthier et al., “L’opale d’Ethiopie: Gemmologie ordinaire et caractéristiques exceptionnelles,” Revue de Gemmologie a.f.g., No. 149, 2004, pp. 15–23), those from the new deposit generally appear much whiter. We noted all spectral colors in the play-of-color in our samples. Most of the cabochons were similar in appearance to opals from Australia or Brazil. However, many samples displayed a columnar structure of play-of-color opal within common opal (figure 2), as first described in material from Mezezo (again, see Gauthier et al., 2004). This feature is only very rarely observed in opals from sources outside Ethiopia.
The hydrostatic SG of the opals ranged from 1.80 to 2.10. This broad range is in part due to the high porosity of some samples, as revealed by a significant weight increase after immersion in water (up to 8%). Fluorescence varied from inert to moderate yellowish white to both long- and short-wave ultraviolet (UV) radiation. Samples that were inert displayed an unexpected greenish phosphorescence of moderate intensity. No luminescence was observed in the opals with a yellow-to-brown bodycolor, even the light ones; these darker bodycolors are probably due to the presence of iron, which quenches luminescence. The yellow-to-green luminescence is likely due to the presence of uranium (E. Gaillou et al., “The geochemistry of gem opals as evidence of their origin,” Ore Geology Reviews, Vol. 34, 2008, pp. 113–126). Fourier-transform Raman spectra were obtained for several samples using a Bruker RFS 100 spectrometer. All spectra were consistent with opal-CT, with Raman bands at about 1070, 780, 670, and 345 cm-1, and water-related bands at about 3200 and 2950 cm-1.
Welo opal is found in volcanic rock, possibly a rhyolite. The rough samples we examined consisted of opal (either common or play-of-color) cementing fragments of the host rock. By contrast, opal from Mezezo fills cavities in rhyolite, forming nodules. Despite these differences, the fact that columnar structures are seen in opals from both deposits (but very rarely from elsewhere) seems to indicate similarities in the conditions of their formation.
The Opal Sheriff program allows our members to request an audit on any auction, which is completed by an independent Gemologist who assesses the accuracy of the item description and pictures.
|Starts||16th Aug 2012 7:45pm PDT|
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