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12.81 CTS ALEXANDRITE - SPECIMEN FROM TANZANIA [S-SAFE255]

4474
12

Artikelnummer
Abmessungen (mm)
12.000 x 10.000 x 4.000mm
Gewicht (cts)
12.810
Typ
Specimen
Farben

ALEXANDRITE SPECIMEN

 

This is a natural untreated Alexandrite specimen  from Tanzania which i bought from the miner on my last trip there. They are not suitable for faceting but can be cabbed or kept as a specimen.

 

The most sensational feature about this stone, however, is its surprising ability to change its colour. Green or bluish-green in daylight, alexandrite turns a soft shade of red, purplish-red or raspberry red in incandescent light. This unique optical characteristic makes it one of the most valuable gemstones of all, especially in fine qualities.

 

Alexandrite is very scarce: this is due to its chemical composition. It is basically a chrysoberyl, a mineral consisting of colourless or yellow transparent chrysoberyl, chrysoberyl cat’s eye and colour-changing alexandrite (also in cat’s eye varieties). It differs from other chrysoberyls in that it not only contains iron and titanium, but also chromium as a major impurity. And it is this very element which accounts for the spectacular colour change. Rarely, vanadium may also play a part. According to CIBJO nomenclature, only chrysoberyls displaying a distinct change of colour may be termed alexandrite.

 

Like many other gemstones, alexandrite emerged millions of years ago in a metamorphic environment. But unlike many others, its formation required specific geological conditions. The chemical elements beryllium (a major constituent in chrysoberyl) and chromium (the colouring agent in alexandrite) have contrasting chemical characteristics and do not as a rule occur together, usually being found in contrasting rock types. Not only has Nature brought these contrasting rock types into contact with each other, but a lack of the chemical element silica (the second most common element in the Earth’s crust) is also required to prevent the growth of emerald. This geological scenario has occurred only rarely in the Earth’s history and, as a result, alexandrite crystals are very scarce indeed.

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sedagems
Hi Welcome to the Sedagems store, Run by Paul Sedawie and specializing in Australian sapphires and gems stones he has collected on his many buying trips world wide. All stock has a money back guarantee as your continued business is our business.
Mermaid Waters , Australia
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19061 Feedback

  • rustynut
    rustynut
    Positiv

    Good stone great service

  • martin11
    martin11
    Positiv

    Great thank very much, lovely pearls.

  • philsgems
    philsgems
    Positiv

    Nice piece of rough. thankyou

  • philsgems
    philsgems
    Positiv

    Nice stone. Thankyou

  • philsgems
    philsgems
    Positiv

    Have received the rough. Nice colour. Thankyou

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Gutscheincode SEDADEALS
Gültig bis
2nd Jan 2025

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Versand:
$16.00 21 über Registered Shipping
Schiffe von:
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Auflistungstyp : Standard
Produkt ID : 862250
Beginnt : 19th December 2024 06:06 pm PST
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