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WELO ROUGH FRACTURE FREE 7.70 CTS [VS4240]

4117
12

SKU
Dimensioni (mm)
15.200 x 14.600 x 10.200mm
Peso (cts)
7.700
Tipo
Rough
Colori

WELO OPAL

This is a beautiful natural untreated rough specimen from the welo opal fields in Ethiopia.It has a stunning display of   RED GREEN ORANGE fire.This material is very bright .

The pictures were taken DRY.

Obaque/hydrophane

Weight 7.70 cts app

Size 15.2 x 14.6 x 10.2 mm app

Buy with confidience as we offer a money back guarantee on all our stock provided it is not touched in any way.We recommened viewing under a loop before cutting.

We have cut many stones from this field and some are avaliable as cut stones on this site. VOLCANIC OPALS

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.

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sedaopals
Discover the magic of opals at SedaOpals, where every stone tells a unique story. Paul Sedawie, the heart and soul of SedaOpals, began his journey with a humble piece of boulder rough at 14, sparking a lifelong passion for these mesmerizing gemstones. With over 40 years in the opal industry, Paul’s dedication has taken him from the rugged landscapes of Lightning Ridge to prestigious gem shows around the world. Paul, a former president of the Opal Association and an author of several opal books, shares his vast knowledge and passion with enthusiasts globally. He’s even made the largest donation of opalized fossils and curiosities to the Australian Opal Centre at Lightning Ridge. At SedaOpals, Paul and his sons offer a meticulously curated collection of opals, each handpicked for its exceptional beauty and character. Whether you’re a seasoned collector or new to the world of opals, you’ll find a stunning array of black opals, boulder opals, and crystal opals to explore. Join us in celebrating the timeless beauty and craftsmanship of opals. Welcome to SedaOpals, where every opal is a piece of art.
Mermaid Beach , Australia
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44298 feedback

  • pompey27
    pompey27
    Positivo

    And to this stone is good

  • pompey27
    pompey27
    Positivo

    Very good, good choice, thanks

  • pompey27
    pompey27
    Positivo

    Happy Christmas, good stone thank you!

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Tipo di elenco : Standard
Codice prodotto : 509089
Inizia : 18th December 2024 09:24 pm PST
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