The crystal chemistry of the apatites

Cockbain, A. G.

doi:10.1180/minmag.1968.036.281.07

Cited by 26 publications

(21 citation statements)

References 6 publications

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“…Based on the analysis of natural samples, the existence of complete solubility between pyromorphite and mimetite in nature (some of these intermediate, As-rich members even had their own variety name "campylite"; Palache et al 1951) has long been known (e.g., Denen 1959;Wondratschek 1963;Förtsch and Wondratschek 1965;Cockbain 1968). The variety "endlichite" ( = arsenian vanadinite), describes approximately 1:1 solid solutions of vanadate and arsenate end-members (Palache et al 1951).…”

mentioning

confidence: 99%

Major, minor, and trace element composition of pyromorphite-group minerals as recorder of supergene weathering processes from the Schwarzwald mining district, SW Germany

Markl

Marks

Holzäpfel

et al. 2014

American Mineralogist

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More than 150 samples of pyromorphite, mimetite, vanadinite, and minerals of the hedyphane-group (which collectively are summarized here under the term PyGM for pyromorphite-group minerals) from the Schwarzwald mining district, southwest Germany, have been analyzed by electron microprobe and LA-ICP-MS. In this largest study of its kind, the relations of PyGM composition to host rock and fluid compositions and the amount of solid solution between the various end-members were investigated. In addition, we report the colors of the many analyzed mineral compositions. Here is a list of the most important results.• Pyromorphite and mimetite are completely miscible.• At conditions of the oxidation zone in ore deposits, the solvus between pyromorphite and vanadinite appears to asymmetrical with up to about 3 mol% of vanadinite component in pyromorphite and up to about 39 mol% of pyromorphite component in vanadinite in cases where both minerals coexist.• Due to a lack of suitable samples, the solvus between vanadinite and mimetite could not be completely constrained, but we report vanadinite analyses with up to 12 mol% mimetite and 8 mol% pyromorphite component.• There is complete miscibility between pyromorphite and phosphohedyphane and between mimetite and hedyphane.• F-rich varieties appear only to exist in hedyphanes and phosphohedyphanes, while pyromorphites, mimetites, and vanadinites are Cl-or OH-dominated.• We report for the first time analyses suggesting the occurrence of an OH-end-member corresponding to mimetite.• While pyromorphites are preferably green and mimetites yellow, this is not at all a diagnostic feature, as many exceptions exist; major elements are not correlated at all with the color of a specific crystal.• Most PyGM are strongly zoned and display, for example, significant variations in Ca that are likely to be related to variations of the compositions of various fluid pulses from which the crystals formed.• PyGM composition is generally uncorrelated with host rock composition, but PyGM enrich other metals like REE, Cr, Sb, Bi, or U up to a factor of 10 6 ; therefore, they can be regarded as very sensitive recorders of the metal inventory of an oxidation zone and they even record metals only present as traces in the primary ore deposit very reliably.• REE patterns of PyGM show significant variability even at one location; this may suggest that each zone of a PyGM crystal records the REE pattern of a single fluid pulse or it may indicate fractionation of the REE during PyGM growth. In the absence of conclusive data, the former possibility appears the more likely one.• PyGM are extremely efficient filters for heavy metals from supergene solutions in and in the vicinity of ore deposits.

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Major, minor, and trace element composition of pyromorphite-group minerals as recorder of supergene weathering processes from the Schwarzwald mining district, SW Germany

Markl

Marks

Holzäpfel

et al. 2014

American Mineralogist

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“…In the case of HAp, piezoelectricity is due to the polarization of OH - groups confined to the channel formed by the overlapping hexagonal calcium atoms (Ca2). It appears to be the sole property of the inherently disordered, nonstoichiometric P6 3/m HAp and not of its pure, monoclinic, P2 1/b counterpart 61 . The order of magnitude of the piezoelectric response of HAp, with the piezoelectric coefficient, D = 16 pC/N 62 , is lower than that exhibited by lead zirconate titanate (PZT), but higher than that of aluminum nitride and in about the same range as that of polyvinylidene fluoride and zinc oxide 63,64 .…”

Section: Peculiarities Of Hapmentioning

confidence: 93%

The role of hydroxyl channel in defining selected physicochemical peculiarities exhibited by hydroxyapatite

Uskoković

2015

RSC Adv.

122

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Mysteries surrounding the most important mineral for the vertebrate biology, hydroxyapatite, are many. Perhaps the Greek root of its name, απαταo, meaning ‘to deceive’ and given to its mineral form by the early gem collectors who confused it with more precious stones, is still applicable today, though in a different connotation, descriptive of a number of physicochemical peculiarities exhibited by it. Comparable to water as the epitome of peculiarities in the realm of liquids, hydroxyapatite can serve as a paradigm for peculiarities in the world of solids. Ten of the peculiar properties of hydroxyapatite are sketched in this review piece, ranging from (i) the crystal lattice flexibility to (ii) notorious surface layer instability to (iii) finite piezoelectricity, pyroelectricity and conductivity to protons to (iv) accelerated growth and improved osteoconductivity in the electromagnetic fields to (v) high nucleation rate at low supersaturations and low crystal growth rate at high supersaturations to (vi) higher bioactivity and resorbability of biological apatite compared to the synthetic ones, and beyond. An attempt has been made to explain this array of curious characteristics by referring to a particular element of the crystal structure of hydroxyapatite: the hydroxyl ion channel extending in the direction of the c-axis, through a crystallographic column created by the overlapping calcium ion triangles.

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“…Empirically the formula reflects the now wellestablished replacement of P by C in carbonate apatites, whereas F is five-and-a-half times greater than CI. Cockbain (1968) reported that synthetic apatites produced at low temperatures can display non-stoichiometric features as do natural, lowtemperature apatites, e.g. 'francolite'.…”

Section: X-ray and Chemical Datamentioning

confidence: 99%

An apatite high in lead from Wanlockhead, Strathclyde Region, Scotland

Livingstone

1994

Mineral. mag.

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The crystal chemistry of the apatites

Cited by 26 publications

References 6 publications

Major, minor, and trace element composition of pyromorphite-group minerals as recorder of supergene weathering processes from the Schwarzwald mining district, SW Germany

Major, minor, and trace element composition of pyromorphite-group minerals as recorder of supergene weathering processes from the Schwarzwald mining district, SW Germany

The role of hydroxyl channel in defining selected physicochemical peculiarities exhibited by hydroxyapatite

An apatite high in lead from Wanlockhead, Strathclyde Region, Scotland

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