Here are the most dramatic examples of gemstones gaining value with such speed that even Bangkok’s traders are taken by surprise, again and again. Mahenge spinels were a similar rocket drive but with color change garnets it happens every time a new strike is made.
The unique thing about color change garnets is that they come in, seemingly, always new ‘sub-varieties’, new types of color change, from purple to red, pink to green, or pink-orange to blue-green, or yellow-green to brownish green, or... you get the idea.
This broad spectrum of sub-sub-species does not come as a surprise if you recall that almandine and pyrope are just two of six garnet types, each mixing with others in infinitive combinations, almandine with spessartine, andratite joins grossular, hessonite mixes with pyrope etc. and that they all get colored by chemical impurities, chromium, vanadium and the other usual suspects. The result can be almost any imaginable color, and theoretically, color change.
In practice, the classic color change garnets are spessartite-pyropes and move around yellow, orange and green to purple and pink.
But there are also terrific blue to green, and blue-green to red and purple. The latter like alexandrite, only better, the most valuable garnets ever being Bekily garnets from Madagascar, which, now that the mine is empty, sell for several thousand per carat.
These are the cases where everybody in the trade pulled, and still pulls, his or her hair for not having bought more while he could.