Are there two distinct morphologies in human and bovine bone mineral?

Although the mineral component of bone has long been accepted as an imperfect form of hydroxyapatite, its detailed morphology and spatial arrangement with the collagen fibers has remained the subject of debate. Two conflicting models, which have both received significant support in the literature, visualize the mineral as discrete needle-like crystallites and spheroidal units, respectively. This investigation, using SEM and TEM, suggests that both these forms exist and that past results may have been technique dependent. It is argued that there is a continuous mineral phase consisting of contiguous spheroids which is penetrated by collagen fibers with which small rodlike mineral units are intimately linked.<>