How are bones formed? There are prevailing theories regarding bone formation. For almost 25 years researchers have debated whether or not bone formation occurs from an amorphous precursor phase.
Recently Olszta et al., 2007, wrote a review. In the review, they cover how organics (a collagen matrix) direct the growth of bone where non-collageous proteins (NCPs) are thought to play a role. The mineral phase (bone) is a nanostructured architecture consisting of uniaxially oriented nanocrystals of hydroxyapatite emedded within and roughly aligned parallel to the long collagen axes. Secondry (osteonal) bone, is laminated organic-inorganic composite composed of collagen, hydroxyapatite, and water.
Indeed, within the human body, organic matrices are used as mechanisms for direct crystallization of bones (primarily apatite; (Olszta et al., 2007)). This work is interesting to me today because it relates to work I've done looking at organic matrices produced by microorganisms. The organic matrices direct the growth of elemental sulfur.