Some tourmaline localities are nice to have. Pederneira is one you save up for, and this little piece shows why pretty well.
It's a small cabinet specimen, 7 x 6 x 6 cm, from the Pederneira mine near São José da Safira in Minas Gerais. A fan of raspberry red elbaite prisms comes up off a bright white feldspar base, with purplish lepidolite mica packed in around the bottom of the crystals. Nearly every crystal ends in a dark green, almost black cap. That's the color change I care about here. Pink body, then a hard switch to green right at the top.
Tourmaline keeps a running record of the fluid it grew from. For most of this growth the pocket fluid apparently gave the crystals the manganese heavy, low iron recipe that makes pink elbaite. Then near the end something changed, and the easy explanation is iron getting back into the system. That flips the color to green, and it's why those caps look like somebody dipped each crystal in ink. Every crystal on the piece stops at about the same point, which is a decent clue they were all sitting in the same pocket when the chemistry shifted.
The prism faces have the long lengthwise striations tourmaline is known for, and in the photo you can see light running up the grooves. The pink sections are gemmy enough that you get depth instead of a flat opaque red. Pederneira luster is glassy and wet looking, and that's a big part of why people get a little reverent about the name.
From what I've read, the mine got noticed after a small pocket at the end of 1999, later called Keké's Pocket, and it went on to be one of the few operations anywhere run mainly for collector specimens rather than gem rough or ore. You can tell from what reaches the market. Crystals still sitting on matrix like this are the goal, not a lucky accident. I've also always liked that the town's name, Safira, supposedly comes from blue tourmaline being mistaken for sapphire long ago. So the whole district started with a case of mistaken identity.
I've never been down in a Safira pegmatite, and honestly the Pederneira mining write ups are about as close as I'm going to get. I still think about pockets like this more than any other geological setting. A cavity in a lithium rich pegmatite, sealed up and crystallizing slowly while the chemistry wanders around, and nobody knows what's in there until a miner breaks through. If one like that turns up, don't expect to pay for it with pocket change.
What gets me most is how clean that pink to green boundary is. Lots of bicolor tourmaline fades gradually. This looks more like somebody flipped a switch.
What's your favorite Brazilian tourmaline, or the one that got away? I'm especially curious whether anyone out there is loyal to Cruzeiro or Jonas over Pederneira.
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