Description
This Tanzanian Colour Change Garnet dispays a very rare Usambara effect inconjunction with its colour change.
It also boasts an impressive three colour display packaged into this one gemstone!
When viewed outside or daylight equivalent white light this gemstones displays a olive browny green colour with flashes of red around the outer facet edges which is known as the very rare “Usambara effect”.
When it is exposed to warm incandescent light it displays a very rich red colour and will then change again to a dark purple colour under fluorescent light.
So all up there are three distinct colours this gemstone will display under different lighting conditions, with the added benefit of also displaying the very rare Usambara effect, making this a very collectable gemstone indeed!
The Usambara effect can bee seen in daylight or when using a daylight equivalent light source by noting the brownish-green colour in the main part of the gemstone below and around the table, which then displays reddish facet reflections around the girdle edges of the gemstone which is ocurring because of the increased or “doubled” path lengths of light produced by internal reflections within the gemstone creating the “Usambara Effect”.
Also note the lack of reddish facet reflections on the pavilion side of the gemstone when the same colour change Garnet is rotated around under a daylight equivalent light source, creating the “appearance” of Pleochroism in this singly refractive Garnet.
So while the Usambara effect is not something typically seen in colour change gemstones, they are sought after curiosities of nature and highly appreciated by gem collectors, connoisseurs and gemologists alike.
This gemstone has been faceted very well, weighs in at 1.12cts and has a small crystal inclusion at the back of the gemstone.
This stone is untreated and completely natural, it has a clarity rating of VS – Very slightly included.
Videos of this gemstone stone displaying its impressive colour changes can be seen by clicking the video buttons below:
