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Tanzanite, near Arusha, Tanzania; 2" tall

This crystal is from the Merelani III Mine. It is of unextraordinary size. What sets this crystal apart is that it is on a graphite matrix.  This crystal is also not heat treated.  Tanzanite is one of the most popular gemmological materials despite only being discovered in 1967.  Heat treated tanzanite rough is much deeper blue and more desirable when faceted into jewels.  This tanzanite crystal is only small by modern standards but is on a matrix of graphite partly encrusted by crystallized diopside, pyrite and a white crystalline mineral which is probably calcite.  If this crystal had been heat treated, it is extremely unlikely that it would still be attached to matrix.  Very few matrix tanzanite specimens are mined from the Merelani III Mine near the town of Arusha, Tanzania.  In the context of a working gem mine, it is common for any type of gem crystal to become detached from a matrix.  Since graphite is so soft, tanzanite crystals probably become detached from their matrix more easily that tourmaline, aquamarine or topaz crystals that are normally found in hard rock pegmatite deposits.

 

Jeff Scovil Photo


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