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XRD properties of Phanerozoic conodont apatite material were studied. It was found out that in terms of crystallinity the apatite resembles the enamel tissue of modern vertebrates. In terms of crystal lattice, apatite of conodonts is independent of taxa on the one hand and of chemistry of the surrounding rock type on the other hand

A whole‐pattern fitting of X‐ray diffraction (XRD) patterns, including lattice‐parameter and size–strain analysis, was elaborated and applied to a sample set of extant and fossil vertebrate tooth apatite. Recent and subfossil human tooth enamel and dentine, extant and fossil shark tooth enameloid, sarcopterygian and coelacanth tooth enamels were studied. As comparative materials, a modern coelacanth fish scale and a pharyngeal tooth of bony fish were used. It was found that the enamel apatite of human milk teeth had lattice parameter values a≃ 9.4 Å and c≃ 6.88 Å, which are close to the corresponding values of subfossil human teeth. The apatite of fossilized vertebrate teeth always has a lower a lattice parameter (about 9.37 Å), while the lattice parameter c appears to be more stable, being around 6.88 Å. The strain appears to be correlated with the lattice direction, being around ten times higher in the [hk0] direction. During fossilization, the strain diminished in the [00l] direction, but was random in the perpendicular [hk0] direction. The enamel tissues of vertebrates are built of two discrete crystallite series. About one‐third of the human milk tooth enamel is composed of larger crystallites with dimensions of about 400 × 500 Å, and two‐thirds of smaller crystallites with dimensions of about 50 × 150 Å. The latter range of dimensions is also characteristic for the crystallites forming the mineral part of human dentine and fish scales. Shark tooth enameloid is also built of two distinct series of apatite crystallites of different sizes and shapes. The larger crystallites (amounting to ∼15% of all crystallites) have approximate dimensions of 500 × 1000 Å, while the smaller ones are 400 × 500 Å. Both series are distinguishable in XRD patterns of modern, Jurassic and Devonian shark enamel.

Ferromanganese and phosphatic hardgrounds were recovered during Legs 143 and 144 on the Mid-Pacific Mountains and Marshall Islands guyots within the condensed section between the shallow-water carbonate sequence and the pelagic cap on the guyot summits. Ferromanganese oxyhydroxides and phosphates are coupled because of their formation under the same long-term nondepositional environments. Phosphatization was traced downhole to at least 62 mbsf in Hole 867B (Resolution Guyot) within the Albian shallow-water sequence. Mineralogy and geochemistry indicate a hydrogenetic origin of the ferromanganese oxyhydroxides. Phosphates are formed by metasomatic replacement of pelagic and shallow-water biogenic calcite by carbonate-fluorapatite. Uniform composition and lattice structure of the apatite are evidence of equilibrium with normal seawater. Phosphorus for the hardground formation can be supplied from the deep-water reservoir or from the intermediate oxygen-minimum zone. An alternative endo-upwelling model is also discussed.