The original idea that framboids were generally spherical was due to the limitations of the contemporary optical microscopic methods. Later scanning microscopic investigations showed that many framboids were at least partly faceted and some display polygonal icosahedral forms. This is significant since the assumption of framboid sphericity informed earlier explanations of how they could form. It cannot be assumed, for example, that framboids necessarily require a precursor template, such as a spherical space or spherical organic globule, to develop. There is a continuum in original framboid shapes between ellipsoid, oblate spheroids, prolate spheroids, and spheroids. Irregularly curved shapes are common, especially in clusters of framboids, and result from deformation under the influence of gravity, analogous to soft sediment deformation. Framboidal icosahedra have varying triangular faces and are similar to the pseudo-icosahedral habit of pyrite macrocrystals. Framboids with mixtures of curved and faceted faces are common and these may result in part by local organized internal microcrystal domains. Various framboid clusters have been described as polyframboids, but the term is strictly reserved to spherical clusters of framboids. The constituent framboids may number 100–200 in these polyframboids, and they commonly show evidence of soft-sediment deformation.
Langerhans Cell Histiocytosis of the Right Scapula
