I have labeled this as a pseudomorph after petersenite-(Ce), but the only thing that is certain is that it is “interesting”. The shape suggests petersenite-(Ce), and the surface texture suggests that the crystal was first replaced by synchysite-(Ce). But unless one is willing to poke a hole in the “crystal”, and unless there is relict material in the interior – something that is not very likely – there is no way to be sure. Remondite-(Ce) and calcioburbankite are other possibilities – among others.

The specimen is from the Poudretee pegmatite - famous for many rare minerals. And infamous for many maddening pseudomorphs.

Whatver the pseudomorph is, the part visible in the first photo is about 6.6 mm and the total length is about twice that.

But there is no doubt that the tiny, water clear crystal on the termination is a perfect analcime trisoctahedron. And there is quite a bit of gobbinsite on the specimen (second photo). Unfortunately the crystals are so small that the typical “chevron” twins are not readily apparent.

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