page_title: Hydroxyapatite
hierarchical_section_title: Hydroxyapatite
caption_attribution_description: Українська: Поверхня гідроксиапатиту кальцію, отримана на сканувальному зондовому мікроскопіEnglish: Calcium hydroxylapatite surface taken from scanning probe microscope. There are nanoclasters of Ca-HAp with characteristic size around 30 nm
context_page_description: Hydroxyapatite, also called hydroxylapatite, is a naturally occurring mineral form of calcium apatite with the formula Ca₅(PO₄)₃, but it is usually written Ca₁₀(PO₄)₆(OH)₂ to denote that the crystal unit cell comprises two entities. Hydroxyapatite is the hydroxyl endmember of the complex apatite group. The OH⁻ ion can be replaced by fluoride, chloride or carbonate, producing fluorapatite or chlorapatite. It crystallizes in the hexagonal crystal system. Pure hydroxyapatite powder is white. Naturally occurring apatites can, however, also have brown, yellow, or green colorations, comparable to the discolorations of dental fluorosis.
  Up to 50% by volume and 70% by weight of human bone is a modified form of hydroxyapatite, known as bone mineral. Carbonated calcium-deficient hydroxyapatite is the main mineral of which dental enamel and dentin are composed. Hydroxyapatite crystals are also found in the small calcifications, within the pineal gland and other structures, known as corpora arenacea or 'brain sand'.
context_section_description: Hydroxyapatite, also called hydroxylapatite (HA), is a naturally occurring mineral form of calcium apatite with the formula Ca₅(PO₄)₃(OH), but it is usually written Ca₁₀(PO₄)₆(OH)₂ to denote that the crystal unit cell comprises two entities.  Hydroxyapatite is the hydroxyl endmember of the complex apatite group. The OH⁻ ion can be replaced by fluoride, chloride or carbonate, producing fluorapatite or chlorapatite. It crystallizes in the hexagonal crystal system. Pure hydroxyapatite powder is white. Naturally occurring apatites can, however, also have brown, yellow, or green colorations, comparable to the discolorations of dental fluorosis.
  Up to 50% by volume and 70% by weight of human bone is a modified form of hydroxyapatite, known as bone mineral. Carbonated calcium-deficient hydroxyapatite is the main mineral of which dental enamel and dentin are composed.  Hydroxyapatite crystals are also found in the small calcifications, within the pineal gland and other structures, known as corpora arenacea or 'brain sand'.
caption: Nanoscale coating of Ca-HAp, image taken with scanning probe microscope
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