This is a small but good example of petersenite-(Ce) being replaced by synchysite-(Ce). In the first photo the petersenite prisms are up to about 5.8 mm long. There are other crystals, up to about 9 mm long, on the specimen.

Another interesting feature of this specimen is gaidonnayite in the form of small, blocky, chalky or porcelain like white crystals (second photo – FOV 2.3 mm). They don’t look like any other gaidonnayite crystals that I have ever seen. EDS (see third “photo”) suggested gaidonayite/hilairite (same chemistry) or – more interestingly – georgechaoite. However pXRD was very consistent with gaidonnayite. (I was unable to get anyone interested in doing microprobe – maybe you will have better luck. Georgechaoite would be new for MSH.) The red arrow point to the crystals in the second photo.

Such synchysite replacements are very characteristic of the Poudrette pegmatite. In this case, some of the petersenite prisms are only partly replaced. Note: In the photo, this sample may look similar to calcioburbankite on petersenite from the same pegmatite. But the synchysite replacemens have a very distinctive “swirly” texture, clearly visible under a scope, if not so well in the photo.

Weight 0.2 oz. Single item shipping weight 3.2 oz (including TN case). Up to 4 oz, this might be combined with one or two other small items for the same postage. Not suitable for a padded envelope.