This is perhaps the rarest crystallization habit from Mexico for ludlamite, which already is famous for Mexico but this style was unique to one pocket (see Megaw's article in Mineralogical Record). Without knowing about this one small pocket from reading old articles in the MR, one would convincingly believe and give the location as the Idaho locality for vivianite and ludlamite. Also, these are more lustrous than the USA specimens were, and more translucent. As you see in the photo, the stepped growth seems to be rising along a central plane, almost as if it were a faden growth line (more commonly seen in quartz and apatite!). These are so rare in this crystal habit, I have never had one for sale and do not expect to again. It is a significant Mexican thumbnail specimen of large thumbnail size and dramatic impact. From the award-winning thumbnail collection of Sharon and William Panczner, author of the book Minerals Of Mexico, and last seen and exhibited in the 1960s.