Usambara Effect Color Change Tourmaline

Color change Dravite crystals from the Umba Valley of Tanzania.  The crystals appear green, but in transmitted light, exhibit a sharp color change to red when the crystal reaches a certain thickness. In the photos where the crystals are backlit, you can see this effect - in the thicker zones the color changes to red, and along the thinner edges, the color remains green. This color change (which is different from the "alexandrite effect", which is color change dependant on type of light) has been called "Usambara effect", after the nearby mountains where they are found.  The vast majority of this material is only suitable for gemstones and good crystals are rare.  Follow this link for more information on these fascinating Tourmalines: http://www.nordskip.com/usambara.html


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AF454 - Dravite $ 240 SOLD
Nchongo, Umba Valley, Tanzania
thumbnail - 1.3 x 1.3 x 1.1 cm


Dravite from Nchongo, Umba Valley, Tanzania [db_pics/pics/af454a.jpg] Dravite from Nchongo, Umba Valley, Tanzania [db_pics/pics/af454b.jpg]

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. Well terminated, complete crystal.


AF455 - Dravite $ 280 SOLD
Nchongo, Umba Valley, Tanzania
thumbnail - 1.5 x 1.1 x 0.8 cm


Dravite from Nchongo, Umba Valley, Tanzania [db_pics/pics/af455a.jpg] Dravite from Nchongo, Umba Valley, Tanzania [db_pics/pics/af455b.jpg] Dravite from Nchongo, Umba Valley, Tanzania [db_pics/pics/af455c.jpg]

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.


AF456 - Dravite $ 250 SOLD
Nchongo, Umba Valley, Tanzania
thumbnail - 1.5 x 1.4 x 0.8 cm


Dravite from Nchongo, Umba Valley, Tanzania [db_pics/pics/af456a.jpg] Dravite from Nchongo, Umba Valley, Tanzania [db_pics/pics/af456b.jpg] Dravite from Nchongo, Umba Valley, Tanzania [db_pics/pics/af456c.jpg]

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.


AF457 - Dravite $ 400 SOLD
Nchongo, Umba Valley, Tanzania
thumbnail - 2.5 x 2.2 x 1.1 cm


Dravite from Nchongo, Umba Valley, Tanzania [db_pics/pics/af457a.jpg] Dravite from Nchongo, Umba Valley, Tanzania [db_pics/pics/af457b.jpg] Dravite from Nchongo, Umba Valley, Tanzania [db_pics/pics/af457c.jpg]

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.


AF458 - Dravite $ 400 SOLD
Nchongo, Umba Valley, Tanzania
thumbnail - 2 x 2 x 1.1 cm


Dravite from Nchongo, Umba Valley, Tanzania [db_pics/pics/af458a.jpg] Dravite from Nchongo, Umba Valley, Tanzania [db_pics/pics/af458b.jpg] Dravite from Nchongo, Umba Valley, Tanzania [db_pics/pics/af458c.jpg]

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.


AF459 - Dravite $ 280 SOLD
Nchongo, Umba Valley, Tanzania
thumbnail - 1.7 x 1.5 x 1.1 cm


Dravite from Nchongo, Umba Valley, Tanzania [db_pics/pics/af459a.jpg] Dravite from Nchongo, Umba Valley, Tanzania [db_pics/pics/af459b.jpg]

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.


AF460 - Dravite $ 240 SOLD
Nchongo, Umba Valley, Tanzania
thumbnail - 2.1 x 1.3 x 0.8 cm


Dravite from Nchongo, Umba Valley, Tanzania [db_pics/pics/af460a.jpg] Dravite from Nchongo, Umba Valley, Tanzania [db_pics/pics/af460b.jpg] Dravite from Nchongo, Umba Valley, Tanzania [db_pics/pics/af460c.jpg]

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.


AF461 - Dravite $ 400 SOLD
Nchongo, Umba Valley, Tanzania
thumbnail - 2.3 x 2.0 x 1.1 cm


Dravite from Nchongo, Umba Valley, Tanzania [db_pics/pics/af461a.jpg] Dravite from Nchongo, Umba Valley, Tanzania [db_pics/pics/af461b.jpg]

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.


AF462 - Dravite $ 240 SOLD
Nchongo, Umba Valley, Tanzania
thumbnail - 1.0 x 1.0 x 0.9 cm


Dravite from Nchongo, Umba Valley, Tanzania [db_pics/pics/af462a.jpg] Dravite from Nchongo, Umba Valley, Tanzania [db_pics/pics/af462b.jpg]

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. Double terminated crystal.


AF463 - Dravite $ 300 SOLD
Nchongo, Umba Valley, Tanzania
thumbnail - 1.8 x 1.6 x 0.7 cm


Dravite from Nchongo, Umba Valley, Tanzania [db_pics/pics/af463a.jpg] Dravite from Nchongo, Umba Valley, Tanzania [db_pics/pics/af463b.jpg] Dravite from Nchongo, Umba Valley, Tanzania [db_pics/pics/af463c.jpg]

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.


AF464 - Dravite $ 260 SOLD
Nchongo, Umba Valley, Tanzania
thumbnail - 1.6 x 1.5 x 1.0 cm


Dravite from Nchongo, Umba Valley, Tanzania [db_pics/pics/af464a.jpg] Dravite from Nchongo, Umba Valley, Tanzania [db_pics/pics/af464b.jpg]

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.


AF465 - Dravite $ 260 SOLD
Nchongo, Umba Valley, Tanzania
thumbnail - 1.6 x 1.5 x 0.9 cm


Dravite from Nchongo, Umba Valley, Tanzania [db_pics/pics/af465a.jpg] Dravite from Nchongo, Umba Valley, Tanzania [db_pics/pics/af465b.jpg]

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.


AF466 - Dravite $ 260 SOLD
Nchongo, Umba Valley, Tanzania
thumbnail - 1.3 x 1.2 x 1.0 cm


Dravite from Nchongo, Umba Valley, Tanzania [db_pics/pics/af466a.jpg] Dravite from Nchongo, Umba Valley, Tanzania [db_pics/pics/af466b.jpg] Dravite from Nchongo, Umba Valley, Tanzania [db_pics/pics/af466c.jpg]

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. Double terminated crystal.


AF467 - Dravite $ 250 SOLD
Nchongo, Umba Valley, Tanzania
thumbnail - 1.0 x 1.0 x 1.0 cm


Dravite from Nchongo, Umba Valley, Tanzania [db_pics/pics/af467a.jpg] Dravite from Nchongo, Umba Valley, Tanzania [db_pics/pics/af467b.jpg] Dravite from Nchongo, Umba Valley, Tanzania [db_pics/pics/af467c.jpg] Dravite from Nchongo, Umba Valley, Tanzania [db_pics/pics/af467d.jpg]

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. Well terminated, complete crystal.



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