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At its breathtaking best, tanzanite is the spitting image of Kashmir sapphire, exhibiting the rich, royal velvety blue those gems are prized for. At a fraction of the price.

Only the merest hint of violet tips off experts that the stone is something else.

That something else is blue zoisite, rechristened tanzanite by Tiffany’s in 1969 to honor its one source, Tanzania.

But the fact that some tanzanites resemble fine sapphire doesn’t explain the demand for all shades of this gem. Statring out as an exotic gem coveted by collectors, tanzanites increased availability in the last decade has transformed it into a jewelry store staple.

Obviously, price has a lot to do with its success. Tanzanite generally commands hundreds, not thousands, per carat.

No substitute

As jewelry designers learned to love tanzanite, this gem has begun to be appreciated for itself rather than as a sapphire substitute. This isn’t to say that the old connoisseur color ideal for this gem, a Kashmir blue, has been abandoned. But now there is greater admiration for tanzanites that don’t mimic sapphire as well. As one importer puts it, “There is a need for a violet-blue gem in between sapphire and amethyst that tanzanite fills.” This means that violetish or periwinkle blue tanzanites now receive almost as much praise as pure blue ones.

It is also a matter of economics as well as aesthetics.

Strong violetish blue tanzanites will always dominate market supply, but it’s not entirely nature’s fault. The truth is that there could be more true-blue tanzanites: often it is a matter of which direction the rough is oriented for cutting.

Tanzanite is a trichroic stone. That means it has different colors when viewed from different directions because axes of the gem crystal handle light differently. In tanzanite, one axis is blue, another violet, and the third reddish brown or bronze. When buying tanzanite rough, cutters look for strong trichroism as well as intense colors to indicate desirable material.

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