Usambara effect Dravite from Nchongo, Umba Valley, Tanzania

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B571 - Usambara effect Dravite $ 3500 SOLD
Nchongo, Umba Valley, Tanzania
miniature - 4.2 x 4 x 2.6 cm


(click on an image to enlarge)

Usambara effect Dravite from Nchongo, Umba Valley, Tanzania [db_pics/pics/b571a.jpg] Usambara effect Dravite from Nchongo, Umba Valley, Tanzania [db_pics/pics/b571b.jpg] Usambara effect Dravite from Nchongo, Umba Valley, Tanzania [db_pics/pics/b571c.jpg]

HUGE single Dravite crystal exhibiting the 'Usambara effect' color change (named after nearby mountains). This is a different type of color change than the Alexandrite effect, where the color changes in different types of lighting. In this case, the Dravite crystal appears green in normal lighting, however when a single light source is transmitted through the crystal, at a certain thickness, a sudden color shift from green to red is observed, while less thick areas remain green. This crystal is so large that the whole thing turns red with transmitted light, though if you hold it under normal lighting it will appear green. This by far the largest I've ever seen, as most are small button shaped crystals of 1-3 cm, and the alrgest I have ever owned was 2.5 x 1.1cm thick. Bottom photo shows the red color when placed over a flashlight.

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