{ "spore": "profile", "id": "hydroxyapatite", "spore_version": "0.2", "family": "calcium-phosphate", "name": "Hydroxyapatite (bone mineral bioceramic)", "abbreviation": "HA", "role": "bioceramic (bone-mineral analogue)", "category": "living", "type": "bio-grown-building-materials", "summary": "Hydroxyapatite (HA, Ca10(PO4)6(OH)2) is the calcium phosphate mineral of bone. The NIST reference powder SRM 2910 has a Ca/P molar ratio of 1.664 ± 0.005 and a hexagonal unit cell with a = 0.94238 ± 0.00009 nm and c = 0.68854 ± 0.00006 nm (Markovic et al., 2004). Measured specific gravity is 3.14 to 3.21 and Mohs hardness is 5 (Wikipedia infobox). No strength or stiffness value for dense sintered HA is recorded in this profile.\n", "best_for": "Calcium phosphate work where composition and crystal structure must be documented (NIST reference powder SRM 2910)", "weakest_at": "Mechanical strength and stiffness: no modulus, hardness or strength value for dense sintered HA is recorded in this profile", "identity": { "formula": "Ca10(PO4)6(OH)2 (two formula units per unit cell, as written on the Wikipedia page)", "cas": "1306-06-5", "crystal_system": "hexagonal", "space_group": "P63/m", "designations": [], "source": "wiki-ha", "where": "Infobox (Identification): crystal system hexagonal, space group P63/m, Z = 2; formula in the Lead section. CAS number from PubChem CID 14781 (source pubchem-ha)." }, "tags": { "environments": [], "stresses": [], "applications": [ "structures" ] }, "properties": [ { "benchmark": "ca_p_molar_ratio", "label": "Calcium-to-phosphorus molar ratio, SRM 2910 powder", "value": 1.664, "bound": "exact", "unit": "-", "scope": "material", "conditions": { "material": "HA reference powder SRM 2910, precipitated", "basis": "mean Ca and total P contents", "uncertainty": "± 0.005 as printed" }, "method": "Calculated by the authors from mean Ca and total P contents (Section 3.1.3). The independent thermal-product check gave 1.6649 ± 0.0005 (not recorded here).", "status": "ground", "source": "markovic2004", "where": "Section 3.1.3", "source_detail": { "title": "Preparation and Comprehensive Characterization of a Calcium Hydroxyapatite Reference Material", "id": "doi:10.6028/jres.109.042 (J. Res. NIST 109, 553-568; PMC4856200)", "url": "https://pmc.ncbi.nlm.nih.gov/articles/PMC4856200/", "year": 2004, "kind": "paper", "license": "not read in this run" } }, { "benchmark": "lattice_parameter_a", "label": "Unit-cell parameter a, SRM 2910 powder", "value": 0.94238, "bound": "exact", "unit": "nm", "scope": "material", "conditions": { "material": "HA-SRM powder", "method_as_printed": "Standard", "uncertainty": "± 0.00009, expanded U as printed" }, "method": "Unit-cell parameter from the authors' own analysis, row HA-SRM Standard in Table 6. Other rows of the same table give Rietveld values from other work.", "status": "ground", "source": "markovic2004", "where": "Table 6, row HA-SRM (Standard)", "source_detail": { "title": "Preparation and Comprehensive Characterization of a Calcium Hydroxyapatite Reference Material", "id": "doi:10.6028/jres.109.042 (J. Res. NIST 109, 553-568; PMC4856200)", "url": "https://pmc.ncbi.nlm.nih.gov/articles/PMC4856200/", "year": 2004, "kind": "paper", "license": "not read in this run" } }, { "benchmark": "lattice_parameter_c", "label": "Unit-cell parameter c, SRM 2910 powder", "value": 0.68854, "bound": "exact", "unit": "nm", "scope": "material", "conditions": { "material": "HA-SRM powder", "method_as_printed": "Standard", "uncertainty": "± 0.00006, expanded U as printed" }, "method": "Unit-cell parameter from the authors' own analysis, row HA-SRM Standard in Table 6.", "status": "ground", "source": "markovic2004", "where": "Table 6, row HA-SRM (Standard)", "source_detail": { "title": "Preparation and Comprehensive Characterization of a Calcium Hydroxyapatite Reference Material", "id": "doi:10.6028/jres.109.042 (J. Res. NIST 109, 553-568; PMC4856200)", "url": "https://pmc.ncbi.nlm.nih.gov/articles/PMC4856200/", "year": 2004, "kind": "paper", "license": "not read in this run" } }, { "benchmark": "bet_surface_area", "label": "BET specific surface area, precipitated SRM 2910 powder", "value": 18.3, "bound": "exact", "unit": "m2/g", "scope": "material", "conditions": { "material": "precipitated HA-SRM powder", "adsorbate": "N2", "uncertainty": "± 0.3 m2/g as printed", "samples": "mean of 12 samples; individual samples 17.7 to 19.1 m2/g" }, "method": "BET nitrogen adsorption, mean of 12 samples as printed in Section 3.2", "status": "ground", "source": "markovic2004", "where": "Section 3.2", "source_detail": { "title": "Preparation and Comprehensive Characterization of a Calcium Hydroxyapatite Reference Material", "id": "doi:10.6028/jres.109.042 (J. Res. NIST 109, 553-568; PMC4856200)", "url": "https://pmc.ncbi.nlm.nih.gov/articles/PMC4856200/", "year": 2004, "kind": "paper", "license": "not read in this run" } }, { "benchmark": "solubility_product", "label": "Solubility product of HA (Ksp)", "value": 2.03e-59, "bound": "exact", "unit": "-", "scope": "material", "conditions": { "temperature": "37.0 ± 0.1 °C", "equilibration": "60 days in phosphoric acid", "uncertainty": "± 0.71e-59, expanded uncertainty with U = 2uc as printed" }, "method": "Saturated-solution measurement. The paper also gives pKsp 58.69 ± 0.15. No unit is printed for Ksp, so the unit is entered as -.", "status": "ground", "source": "markovic2004", "where": "Section 3.9", "source_detail": { "title": "Preparation and Comprehensive Characterization of a Calcium Hydroxyapatite Reference Material", "id": "doi:10.6028/jres.109.042 (J. Res. NIST 109, 553-568; PMC4856200)", "url": "https://pmc.ncbi.nlm.nih.gov/articles/PMC4856200/", "year": 2004, "kind": "paper", "license": "not read in this run" } }, { "benchmark": "thermal_mass_loss", "label": "Total mass loss on heating, SRM 2910 powder", "value": 1.7, "bound": "exact", "unit": "%", "scope": "material", "conditions": { "atmosphere": "nitrogen (N2)", "temperature_range": "30 to 900 °C", "heating_rate": "10 °C/min", "uncertainty": "± 0.05 % as printed" }, "method": "Thermogravimetry. The paper reports no decomposition temperature for hydroxyapatite itself.", "status": "ground", "source": "markovic2004", "where": "Sections 2.3.3 and 3.1.5 (thermogravimetry)", "source_detail": { "title": "Preparation and Comprehensive Characterization of a Calcium Hydroxyapatite Reference Material", "id": "doi:10.6028/jres.109.042 (J. Res. NIST 109, 553-568; PMC4856200)", "url": "https://pmc.ncbi.nlm.nih.gov/articles/PMC4856200/", "year": 2004, "kind": "paper", "license": "not read in this run" } }, { "benchmark": "mass_fraction_calcium", "label": "Calcium (Ca2+) mass fraction, SRM 2910 unit cell", "value": 39.15, "bound": "exact", "unit": "%", "scope": "material", "conditions": { "material": "HA-SRM, mass fraction per unit cell", "uncertainty": "± 0.10 %" }, "method": "Chemical composition table (Table 1, Ca2+ row, n = 20 as printed)", "status": "ground", "source": "markovic2004", "where": "Table 1, Ca2+ row", "source_detail": { "title": "Preparation and Comprehensive Characterization of a Calcium Hydroxyapatite Reference Material", "id": "doi:10.6028/jres.109.042 (J. Res. NIST 109, 553-568; PMC4856200)", "url": "https://pmc.ncbi.nlm.nih.gov/articles/PMC4856200/", "year": 2004, "kind": "paper", "license": "not read in this run" } }, { "benchmark": "mass_fraction_phosphate", "label": "Phosphate (PO4 3-) mass fraction, SRM 2910 unit cell", "value": 55.16, "bound": "exact", "unit": "%", "scope": "material", "conditions": { "material": "HA-SRM, mass fraction per unit cell", "uncertainty": "± 0.15 %" }, "method": "Chemical composition table (Table 1, PO4 3- row, n = 20 as printed)", "status": "ground", "source": "markovic2004", "where": "Table 1, PO4 3- row", "source_detail": { "title": "Preparation and Comprehensive Characterization of a Calcium Hydroxyapatite Reference Material", "id": "doi:10.6028/jres.109.042 (J. Res. NIST 109, 553-568; PMC4856200)", "url": "https://pmc.ncbi.nlm.nih.gov/articles/PMC4856200/", "year": 2004, "kind": "paper", "license": "not read in this run" } }, { "benchmark": "mass_fraction_water", "label": "Water (H2O) mass fraction, SRM 2910 unit cell", "value": 1.59, "bound": "exact", "unit": "%", "scope": "material", "conditions": { "material": "HA-SRM, mass fraction per unit cell", "uncertainty": "± 0.05 %" }, "method": "Chemical composition table (Table 1, H2O row, n = 5 as printed)", "status": "ground", "source": "markovic2004", "where": "Table 1, H2O row", "source_detail": { "title": "Preparation and Comprehensive Characterization of a Calcium Hydroxyapatite Reference Material", "id": "doi:10.6028/jres.109.042 (J. Res. NIST 109, 553-568; PMC4856200)", "url": "https://pmc.ncbi.nlm.nih.gov/articles/PMC4856200/", "year": 2004, "kind": "paper", "license": "not read in this run" } }, { "benchmark": "particle_height", "label": "Crystal height, SRM 2910 powder", "value": 0.1, "value_high": 0.3, "bound": "range", "unit": "μm", "scope": "material", "conditions": { "form": "cylindrical crystals of precipitated HA-SRM powder", "method_as_printed": "TEM and SEM" }, "method": "Range printed with the approximate sign in Section 3.2", "status": "ground", "source": "markovic2004", "where": "Section 3.2", "source_detail": { "title": "Preparation and Comprehensive Characterization of a Calcium Hydroxyapatite Reference Material", "id": "doi:10.6028/jres.109.042 (J. Res. NIST 109, 553-568; PMC4856200)", "url": "https://pmc.ncbi.nlm.nih.gov/articles/PMC4856200/", "year": 2004, "kind": "paper", "license": "not read in this run" } }, { "benchmark": "particle_diameter", "label": "Crystal diameter, SRM 2910 powder", "value": 0.05, "value_high": 0.15, "bound": "range", "unit": "μm", "scope": "material", "conditions": { "form": "cylindrical crystals of precipitated HA-SRM powder", "method_as_printed": "TEM and SEM" }, "method": "Range printed with the approximate sign in Section 3.2", "status": "ground", "source": "markovic2004", "where": "Section 3.2", "source_detail": { "title": "Preparation and Comprehensive Characterization of a Calcium Hydroxyapatite Reference Material", "id": "doi:10.6028/jres.109.042 (J. Res. NIST 109, 553-568; PMC4856200)", "url": "https://pmc.ncbi.nlm.nih.gov/articles/PMC4856200/", "year": 2004, "kind": "paper", "license": "not read in this run" } }, { "benchmark": "specific_gravity", "label": "Specific gravity, measured", "value": 3.14, "value_high": 3.21, "bound": "range", "unit": "-", "scope": "material", "conditions": { "basis": "measured value as printed in the infobox; form and test not stated" }, "method": "Infobox value printed as 3.14–3.21 (measured). The page prints no unit; specific gravity is dimensionless.", "status": "ground", "source": "wiki-ha", "where": "Infobox (Identification), Specific gravity row", "source_detail": { "title": "Hydroxyapatite (Wikipedia article)", "id": "en.wikipedia.org, read 2026-11-01", "url": "https://en.wikipedia.org/wiki/Hydroxyapatite", "year": 2026, "kind": "web", "license": "CC BY-SA 4.0 (Wikipedia text)" } }, { "benchmark": "specific_gravity", "label": "Specific gravity, calculated", "value": 3.16, "bound": "exact", "unit": "-", "scope": "material", "conditions": { "basis": "calculated value as printed in the infobox" }, "method": "Infobox value marked as calculated by the source", "status": "calculated", "source": "wiki-ha", "where": "Infobox (Identification), Specific gravity row", "source_detail": { "title": "Hydroxyapatite (Wikipedia article)", "id": "en.wikipedia.org, read 2026-11-01", "url": "https://en.wikipedia.org/wiki/Hydroxyapatite", "year": 2026, "kind": "web", "license": "CC BY-SA 4.0 (Wikipedia text)" } }, { "benchmark": "mohs_hardness", "label": "Mohs scale hardness", "value": 5, "bound": "exact", "unit": "-", "scope": "material", "conditions": { "basis": "mineral hardness as printed in the infobox; no test method stated" }, "method": "Infobox value, Mohs scale hardness row", "status": "ground", "source": "wiki-ha", "where": "Infobox (Identification), Mohs scale hardness row", "source_detail": { "title": "Hydroxyapatite (Wikipedia article)", "id": "en.wikipedia.org, read 2026-11-01", "url": "https://en.wikipedia.org/wiki/Hydroxyapatite", "year": 2026, "kind": "web", "license": "CC BY-SA 4.0 (Wikipedia text)" } }, { "benchmark": "refractive_index", "label": "Refractive index, nω", "value": 1.651, "bound": "exact", "unit": "-", "scope": "material", "conditions": { "basis": "optical value printed for the mineral; wavelength not stated on the page" }, "method": "Infobox value, refractive index row", "status": "ground", "source": "wiki-ha", "where": "Infobox (Identification), Refractive index row", "source_detail": { "title": "Hydroxyapatite (Wikipedia article)", "id": "en.wikipedia.org, read 2026-11-01", "url": "https://en.wikipedia.org/wiki/Hydroxyapatite", "year": 2026, "kind": "web", "license": "CC BY-SA 4.0 (Wikipedia text)" } }, { "benchmark": "refractive_index", "label": "Refractive index, nε", "value": 1.644, "bound": "exact", "unit": "-", "scope": "material", "conditions": { "basis": "optical value printed for the mineral; wavelength not stated on the page" }, "method": "Infobox value, refractive index row", "status": "ground", "source": "wiki-ha", "where": "Infobox (Identification), Refractive index row", "source_detail": { "title": "Hydroxyapatite (Wikipedia article)", "id": "en.wikipedia.org, read 2026-11-01", "url": "https://en.wikipedia.org/wiki/Hydroxyapatite", "year": 2026, "kind": "web", "license": "CC BY-SA 4.0 (Wikipedia text)" } }, { "benchmark": "birefringence", "label": "Birefringence (δ)", "value": 0.007, "bound": "exact", "unit": "-", "scope": "material", "conditions": { "basis": "optical value printed for the mineral; wavelength not stated on the page" }, "method": "Infobox value, birefringence row", "status": "ground", "source": "wiki-ha", "where": "Infobox (Identification), Birefringence row", "source_detail": { "title": "Hydroxyapatite (Wikipedia article)", "id": "en.wikipedia.org, read 2026-11-01", "url": "https://en.wikipedia.org/wiki/Hydroxyapatite", "year": 2026, "kind": "web", "license": "CC BY-SA 4.0 (Wikipedia text)" } }, { "benchmark": "molar_mass", "label": "Formula mass", "value": 502.31, "bound": "exact", "unit": "g/mol", "scope": "material", "conditions": { "formula": "Ca5(PO4)3OH, as written in the infobox" }, "method": "Infobox value, formula mass row. The infobox formula is the one-half form of the Ca10(PO4)6(OH)2 formula used in the lead.", "status": "ground", "source": "wiki-ha", "where": "Infobox (General), Formula mass row", "source_detail": { "title": "Hydroxyapatite (Wikipedia article)", "id": "en.wikipedia.org, read 2026-11-01", "url": "https://en.wikipedia.org/wiki/Hydroxyapatite", "year": 2026, "kind": "web", "license": "CC BY-SA 4.0 (Wikipedia text)" } }, { "benchmark": "hap_mass_fraction_bone", "label": "Hydroxyapatite share of bone, by mass", "value": 65, "value_high": 70, "bound": "range", "unit": "%", "scope": "material", "conditions": { "basis": "bone, by mass, as printed" }, "method": "Biological content sentence in the lead section, printed as 'Bone is 65 to 70% HA by mass'", "status": "ground", "source": "wiki-ha", "where": "Lead section, biological content", "source_detail": { "title": "Hydroxyapatite (Wikipedia article)", "id": "en.wikipedia.org, read 2026-11-01", "url": "https://en.wikipedia.org/wiki/Hydroxyapatite", "year": 2026, "kind": "web", "license": "CC BY-SA 4.0 (Wikipedia text)" } }, { "benchmark": "hap_mass_fraction_enamel_dentin", "label": "Hydroxyapatite share of dentin and enamel, by mass", "value": 70, "value_high": 80, "bound": "range", "unit": "%", "scope": "material", "conditions": { "basis": "dentin and enamel, by mass, as printed" }, "method": "Biological content sentence in the lead section, printed as 'dentin and enamel are 70 to 80% HA by mass'", "status": "ground", "source": "wiki-ha", "where": "Lead section, biological content", "source_detail": { "title": "Hydroxyapatite (Wikipedia article)", "id": "en.wikipedia.org, read 2026-11-01", "url": "https://en.wikipedia.org/wiki/Hydroxyapatite", "year": 2026, "kind": "web", "license": "CC BY-SA 4.0 (Wikipedia text)" } } ], "corrosion": [ { "environment": "Heating in nitrogen from 30 to 900 °C at 10 °C/min (thermogravimetry)", "headline": "The NIST reference powder lost 1.70 % of its mass on heating to 900 °C.", "effect": "Total mass loss of 1.70 ± 0.05 % over 30 to 900 °C in nitrogen. The paper reports no decomposition temperature for hydroxyapatite itself. Table 1 separately gives a water mass fraction of 1.59 ± 0.05 %.", "rating": "low", "conditions": { "atmosphere": "N2", "heating_rate": "10 °C/min", "temperature_range": "30 to 900 °C" }, "source": "markovic2004", "where": "Sections 2.3.3 and 3.1.5; Table 1 (H2O row)" }, { "environment": "Saturated solutions at 37.0 °C, equilibrated for 60 days in phosphoric acid", "headline": "The solubility product of HA at 37.0 °C is (2.03 ± 0.71) × 10^-59, expanded uncertainty with U = 2uc.", "effect": "The paper reports the solubility product only. A very small solubility product indicates low solubility of the solid under these conditions. The paper gives no rating, and no corrosion or dissolution test on coatings or bodies was found.", "rating": "low", "conditions": { "temperature": "37.0 ± 0.1 °C", "equilibration": "60 days", "medium": "phosphoric acid" }, "source": "markovic2004", "where": "Section 3.9" } ], "risks": { "hazards": [ { "text": "PubChem's aggregated GHS record for hydroxylapatite reads 'Not Classified'. It says 'Reported as not meeting GHS hazard criteria by 362 of 370 companies'. Its ECHA notifications summary says 'There are 3 notifications provided by 8 of 370 reports by companies with hazard statement code(s).' The hazard statement codes are not printed on the page read.", "ghs": [], "source": "pubchem-ha", "where": "Safety and Hazards, 12.1.1 GHS Classification and 12.1.2 Hazard Classes (CID 14781, ECHA C&L summary)" }, { "text": "PubChem's hazards summary, credited to Haz-Map and MSDSonline, reads 'May cause irritation'. This sits alongside the 'Not Classified' GHS record. No supplier safety data sheet was read to settle the difference, so check the supplier's SDS for the grade in use.", "ghs": [], "source": "pubchem-ha", "where": "Safety and Hazards, 12.1.3 Hazards Summary (CID 14781)" } ], "failure_risks": [ { "mode": "Mass loss on heating", "trigger": "Heating the HA reference powder from 30 to 900 °C in nitrogen at 10 °C/min", "consequence": "Total mass loss of 1.70 ± 0.05 % over that range (thermogravimetry)", "severity": "low", "source": "markovic2004", "where": "Sections 2.3.3 and 3.1.5" } ], "side_effects": [], "handling": [], "mitigations": [] }, "uses": [ { "application": "structures", "device": "Bone-graft substitute, and coating for orthopaedic and dental implants", "example": "Wikipedia says calcium phosphate ceramics are the preferred bone substitute material in orthopaedic and maxillofacial applications. It also says an HA/polymer composite (HAPEX) is marketed as a plasma-sprayed coating for orthopaedic and dental implants.", "source": "wiki-bioceramic", "where": "Section 2.1 and Section 8 (commercial usage)" }, { "application": "structures", "device": "Dermal filler (calcium hydroxyapatite microspheres, Radiesse)", "example": "Wikipedia describes microspheres of 20–45 μm diameter that clear in about 12 to 30 months after injection. The product was FDA approved in 2006.", "source": "wiki-ha", "where": "Dermal filler (Radiesse) paragraph in the Uses section" } ], "supply": [ { "subject": "Phosphorus (phosphate rock, the source of the phosphate group)", "producers": [ { "country": "China", "share_percent": 44, "year": 2025 }, { "country": "Morocco", "share_percent": 14.4, "year": 2025 }, { "country": "United States", "share_percent": 8, "year": 2025 }, { "country": "Russia", "share_percent": 5.6, "year": 2025 } ], "critical_lists": [ { "list": "USGS 2025 List of Critical Minerals (phosphate rock added in the final 2025 list)", "listed": true } ], "recycling": "The USGS phosphate rock chapter gives recycling as None.", "substitutes": [ "USGS: there are no substitutes for phosphorus in agriculture. The chapter does not discuss ceramic or biomedical uses." ], "source": "usgs-mcs2026-phosphate", "where": "World Mine Production table, 2025 (world total 250,000 thousand t; shares calculated by Space Mushroom from the thousand-tonne figures, not printed by USGS); Recycling; Substitutes; introductory text on the final 2025 critical list" } ], "media": [], "documents": [ { "title": "Preparation and Comprehensive Characterization of a Calcium Hydroxyapatite Reference Material (J. Res. NIST 109, 553-568)", "type": "paper", "url": "https://pmc.ncbi.nlm.nih.gov/articles/PMC4856200/", "year": 2004 }, { "title": "Mineral Commodity Summaries 2026, Phosphate Rock", "type": "report", "url": "https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-phosphate.pdf", "year": 2026 }, { "title": "Hydroxylapatite, PubChem compound record CID 14781", "type": "database", "url": "https://pubchem.ncbi.nlm.nih.gov/compound/14781", "year": 2026 }, { "title": "Resistive coupled microwave sintering - A promising technique to fabricate bioceramics with improved properties", "type": "paper", "url": "https://pubmed.ncbi.nlm.nih.gov/36201940/", "year": 2022 }, { "title": "Young's Modulus and Vickers Hardness of the Hydroxyapatite Bioceramics with a Small Amount of the Multi-Walled Carbon Nanotubes", "type": "paper", "url": "https://pmc.ncbi.nlm.nih.gov/articles/PMC9369948/", "year": 2022 } ], "gaps": [ "No space, vacuum, radiation, thermal-cycling or flight data for HA was found in the sources read. The space use list is empty.", "Elastic modulus, Vickers hardness, and compressive or flexural strength for dense sintered HA are not recorded in this profile. A 2022 microwave-sintering study (source swapna2022) and a 2022 Materials study (source mat2022) report such values for their own sintered HA, but both describe processes that are not the reference powder's, so neither value is recorded here. The Wikipedia Bioceramic table lists Young's modulus of 73-117 GPa for 'Bioactive HAP' with no form or test stated, so it is not used.", "Density: only specific gravity was read (3.14 to 3.21 measured). The Wikipedia Bioceramic table gives density 3.1 g/cm3 with no form or test, so it is not used.", "Melting or decomposition temperature of HA was not found. The melting point in the Wikipedia calcium phosphate infobox belongs to tricalcium phosphate and is not used.", "Solubility in water or body fluid at pH 7.4 was not found. Only the solubility product is recorded.", "UNS, EN or AISI designations were not read and are not recorded. The CAS number is recorded from PubChem CID 14781.", "No supplier safety data sheet was retrieved in this run. The Tosoh, Parchem and Sigma-Aldrich SDS pages tried here did not return a readable HA safety data sheet. The hazards entries come from PubChem's aggregated GHS and hazards-summary data, so the handling and mitigations lists are empty and the side_effects list is empty.", "Atomic weights were not read in this run, so the recipe parts give atom counts only.", "Calcium supply and abundance were not read (no USGS calcium data). Only phosphate rock supply is recorded.", "EU critical raw materials status for phosphate rock was not checked in this run.", "Ageing in humidity or UV, and thermal expansion of HA, were not found.", "The Ca/P independent check (1.6649 ± 0.0005) and the stoichiometric Ca/P value stated in the NIST paper are not recorded as properties.", "The PMC article page (PMC4856200) returned a browser check during this run. The values were read from the Europe PMC full-text copy of the same article, so the source URL may not verify automatically.", "The NIST SRM 2910 certificate PDF did not download in this run (the server returned an HTML page), so no certified values beyond Table 1 and Table 6 of the paper are used.", "The application list has no medical or dental category. Both medical uses are filed under 'structures' as the nearest option. No space application was found.", "The brief proposes a new 'Bioceramics' type. This file uses the existing bio-grown-building-materials type, and taxonomy was not changed.", "No image (media) was read or licensed in this run." ], "story": { "why": "Hydroxyapatite (HA, Ca10(PO4)6(OH)2) is the calcium phosphate mineral of bone. Wikipedia gives bone as 65 to 70 % HA by mass and dentin and enamel as 70 to 80 % HA by mass. NIST characterised a calcium hydroxyapatite reference powder, SRM 2910, and reports its composition, unit cell, surface area and thermal behaviour (Markovic et al., 2004). NIST now orders its Standard Reference Materials through its shop at shop.nist.gov.", "uses": [ { "where": "Bone substitutes and implant coatings", "line": "Wikipedia says calcium phosphate ceramics are the preferred bone substitute material in orthopaedic and maxillofacial applications. It also says an HA/polymer composite (HAPEX) is marketed as a plasma-sprayed coating for orthopaedic and dental implants." }, { "where": "Dermal filler", "line": "Wikipedia describes a calcium hydroxyapatite dermal filler (Radiesse) with microspheres of 20 to 45 μm diameter. The microspheres clear in about 12 to 30 months, and the product was FDA approved in 2006." } ], "can_do": [ { "label": "Calcium-to-phosphorus ratio", "line": "The NIST reference powder has a Ca/P molar ratio of 1.664 ± 0.005, close to the ratio the formula Ca10(PO4)6(OH)2 requires.", "benchmark": "ca_p_molar_ratio", "scope": "material", "value": "1.664 ± 0.005" }, { "label": "Crystal lattice", "line": "The reference powder is hexagonal, with a = 0.94238 ± 0.00009 nm and c = 0.68854 ± 0.00006 nm (Table 6, Standard row).", "benchmark": "lattice_parameter_a", "scope": "material", "value": "a = 0.94238 nm, c = 0.68854 nm" }, { "label": "Surface area", "line": "The BET surface area of the precipitated reference powder is 18.3 ± 0.3 m2/g, from the mean of 12 samples. Individual samples ranged from 17.7 to 19.1 m2/g.", "benchmark": "bet_surface_area", "scope": "material", "value": "18.3 m2/g" }, { "label": "Solubility", "line": "At 37.0 °C the solubility product of HA is (2.03 ± 0.71) × 10^-59, an expanded uncertainty. Dissolution rates in body fluid were not found.", "benchmark": "solubility_product", "scope": "material", "value": "(2.03 ± 0.71) × 10^-59" }, { "label": "Heating", "line": "Heated from 30 to 900 °C in nitrogen, the powder lost 1.70 ± 0.05 % of its mass. The paper gives no decomposition temperature for HA itself.", "benchmark": "thermal_mass_loss", "scope": "material", "value": "1.70 %" }, { "label": "Specific gravity", "line": "Measured specific gravity is 3.14 to 3.21, and the calculated value is 3.16 (Wikipedia infobox). Specific gravity is the ratio of density to the density of water, so it has no unit.", "benchmark": "specific_gravity", "scope": "material", "value": "3.14 to 3.21" }, { "label": "Hardness", "line": "Mohs hardness is 5 (Wikipedia infobox). No Vickers hardness, elastic modulus or strength value for dense HA is recorded in this profile.", "benchmark": "mohs_hardness", "scope": "material", "value": "5" } ], "compare": "Hydroxyapatite is the calcium phosphate that bone and enamel are built from. In the sources read, its reference powder sits very close to the stoichiometric Ca/P ratio, which is why the composition is well defined. The sources read give no like-for-like mechanical comparison with other bioceramics, so this profile makes no ranking on strength or stiffness.", "compare_rows": [ { "label": "Ca/P molar ratio", "benchmark": "ca_p_molar_ratio", "scope": "material" }, { "label": "Surface area (BET)", "benchmark": "bet_surface_area", "scope": "material" }, { "label": "Mohs hardness", "benchmark": "mohs_hardness", "scope": "material" } ], "handling": [ "No supplier safety data sheet or handling instruction for HA powder was read in this run.", "Check the supplier's data sheet for dust and storage advice before use." ], "good_for": [ "Calcium phosphate composition work: the NIST reference powder has a Ca/P ratio of 1.664 ± 0.005 and documented unit-cell parameters.", "Bone-substitute and implant-coating context: Wikipedia describes calcium phosphate ceramics as the preferred bone substitute in orthopaedic and maxillofacial applications." ], "watch_out": [ "No modulus, hardness or strength value for dense sintered HA is recorded in this profile.", "The surface area and crystal size given here describe the precipitated reference powder, not a sintered body.", "The Wikipedia calcium phosphate infobox values belong to tricalcium phosphate, a different compound, and are not used here." ], "verdict": "Hydroxyapatite has documented composition, unit-cell and surface-area data from NIST. Its mechanical data are missing from this record, so no structural ranking is made.", "recipe": { "line": "Hydroxyapatite is a calcium phosphate with the formula Ca10(PO4)6(OH)2. Each formula unit joins ten calcium ions, six phosphate groups (PO4) and two hydroxide groups (OH). The synthesis equation printed on Wikipedia is 10 Ca(OH)2 + 6 H3PO4 → Ca10(PO4)6(OH)2 + 18 H2O.", "parts": [ { "name": "Calcium", "symbol": "Ca", "role": "The ion that sets the Ca/P ratio. The reference powder has 39.15 % calcium by mass (Table 1)." }, { "name": "Phosphorus", "symbol": "P", "role": "Sits at the centre of each phosphate group. Phosphate makes up 55.16 % of the reference powder by mass (Table 1)." }, { "name": "Oxygen", "symbol": "O", "role": "Oxygen atoms of the phosphate and hydroxide groups. Atomic weight not read in this run." }, { "name": "Hydrogen", "symbol": "H", "role": "Hydrogen of the hydroxide groups. Water is 1.59 % of the reference powder by mass (Table 1)." } ] }, "risk_groups": [ { "title": "For people", "lead": "PubChem's aggregated GHS record lists hydroxyapatite as Not Classified, and its hazards summary reads May cause irritation. No supplier safety data sheet was read in this run.", "points": [ { "label": "Dust", "line": "Dust exposure was not assessed in the sources read. Check the supplier's safety data sheet before handling the powder." } ], "level": 0, "verdict": "Not GHS-classified in PubChem; irritation noted" }, { "title": "If the material is heated", "lead": "The heating data here are thermogravimetry results on a reference powder, not incident reports.", "points": [ { "label": "Mass loss", "line": "On heating from 30 to 900 °C in nitrogen at 10 °C/min, the NIST reference powder lost 1.70 ± 0.05 % of its mass." } ] }, { "title": "Handling and storage", "points": [ { "label": "Source gap", "line": "The sources read here give no storage or handling instructions for HA powder." } ] } ] }, "updated": "2026-11-01", "review": { "status": "draft", "method": "assistant", "checked_values": 20, "unreachable": 2, "caveats": 3, "note": "Read by an AI assistant on 2026-11-01. Values taken from NIST paper Tables 1 and 6 and Sections 3.1.3, 3.2, 3.9 and 2.3.3 (via the Europe PMC full-text copy) and from the Wikipedia infobox for HA. PMC and PubChem pages returned browser checks; the SRM certificate PDF did not download. Hazard data come from PubChem's GHS record. Modulus data are not recorded in this profile." }, "sources": { "markovic2004": { "title": "Preparation and Comprehensive Characterization of a Calcium Hydroxyapatite Reference Material", "id": "doi:10.6028/jres.109.042 (J. Res. NIST 109, 553-568; PMC4856200)", "url": "https://pmc.ncbi.nlm.nih.gov/articles/PMC4856200/", "year": 2004, "kind": "paper", "license": "not read in this run" }, "wiki-ha": { "title": "Hydroxyapatite (Wikipedia article)", "id": "en.wikipedia.org, read 2026-11-01", "url": "https://en.wikipedia.org/wiki/Hydroxyapatite", "year": 2026, "kind": "web", "license": "CC BY-SA 4.0 (Wikipedia text)" }, "wiki-bioceramic": { "title": "Bioceramic (Wikipedia article)", "id": "en.wikipedia.org, read 2026-11-01", "url": "https://en.wikipedia.org/wiki/Bioceramic", "year": 2026, "kind": "web", "license": "CC BY-SA 4.0 (Wikipedia text)" }, "usgs-mcs2026-phosphate": { "title": "Mineral Commodity Summaries 2026, Phosphate Rock", "id": "USGS MCS 2026, February 2026", "url": "https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-phosphate.pdf", "year": 2026, "kind": "report", "license": "public domain (USGS)" }, "nist-srm-shop": { "title": "NIST SRM Online Request System redirect page (SRM ordering moved to the NIST shop)", "id": "shop.nist.gov, page pageKey=SRMORS, read 2026-11-01", "url": "https://shop.nist.gov/ccrz__CCPage?pageKey=SRMORS", "year": 2026, "kind": "web", "license": "not read in this run" }, "pubchem-ha": { "title": "Hydroxylapatite (Ca5(OH)(PO4)3), PubChem compound record CID 14781", "id": "PubChem CID 14781, CAS 1306-06-5, read 2026-11-01", "url": "https://pubchem.ncbi.nlm.nih.gov/compound/14781", "year": 2026, "kind": "database", "license": "PubChem public record; ECHA data as cited by PubChem under the ECHA legal notice" }, "swapna2022": { "title": "Resistive coupled microwave sintering - A promising technique to fabricate bioceramics with improved properties", "id": "doi:10.1016/j.jmbbm.2022.105488 (J Mech Behav Biomed Mater, 2022; PubMed 36201940)", "url": "https://pubmed.ncbi.nlm.nih.gov/36201940/", "year": 2022, "kind": "paper", "license": "not read in this run" }, "mat2022": { "title": "Young's Modulus and Vickers Hardness of the Hydroxyapatite Bioceramics with a Small Amount of the Multi-Walled Carbon Nanotubes", "id": "doi:10.3390/ma15155304 (Materials, 2022; PMC9369948)", "url": "https://pmc.ncbi.nlm.nih.gov/articles/PMC9369948/", "year": 2022, "kind": "paper", "license": "not read in this run" } }, "license": "CC-BY-4.0", "url": "https://spacemushroom.com/profiles/hydroxyapatite/" }