MSH is the type locality for petersenite-(Ce). Petersenite-(Ce) is also known from the Kola peninsula, but the best specimens are from MSH.

It is a rare mineral here, and certainly world-wide.  Most crystals are in the 1-3 mm range, but larger ones do exist and pseudomorphs of synchysite-(Ce) after petersenite-(Ce) as large as 10 cm or more were fairly abundant in parts of the Poudrette pegmatite. Fairly large pseudomorphs of ancylite-(Ce) (and other minerals) after petersenite-(Ce) also exist. Unaltered crystals of petersenite-(Ce) are relatively uncommon, and the terminations are often lacking.

This specimen features several unaltered crystals, up to 3.3 mm, with excellent, relatively complex terminations. There is also a partial, much larger (7.3 mm) crystal, possibly terminated at one end. The crystals are flesh-pink (under tungsten lighting), but are coated with the bronzy/brown “cavity scum” that is nearly ubiquitous at MSH.

Not all of the crystals are terminated, but at least some of the breaks are encrusted by cavity scum or other minerals, indicating that the predate mining and collecting activities. In addition, petersenite-(Ce) often has pinacoidal terminations, and it is sometimes difficult to distinguish such terminations from natural breaks.

The first pair of photos shows the largest crystal (ca 7.3 mm) on the specimen. It is only partly coated, and the gemmy, flesh-pink, color is clearly discernible. One end of the crystal is broken. (The break is just out of sight in the photos because I only have fixed magnifications on my scope and was not able to quite squeeze the entire crystal into the frame.) The other end looks even, but it is encrysted by another mineral, so it is hard to tell if this is a pre-mining break or just multiple pinacoidal terminations.

The next pair of photos (FOV 6.8 x 4.4 mm) shows all of the clearly terminated crystals on the specimen. Note especially the sharp and complex termination on the crystal at far left. The longest crystal hers is about 3.3 mm.

Single item shipping weight 2.9 oz (82 g). For non-USA destinations, up to a total weight < 8 oz (225 g), this can be combined with other items for the same postage. Within the USA, each additional ounce costs about $0.20 For a total weight of 13 oz or more, I will use “own box” Priority Mail ($9.25), which good is up to 16 oz.