{
  "spore": "profile",
  "id": "calcium",
  "spore_version": "0.2",
  "family": "alkali-and-alkaline-earth-metals",
  "name": "Calcium",
  "abbreviation": "Ca",
  "role": "deoxidiser, vacuum getter and research battery anode",
  "category": "metals",
  "type": "magnesium",
  "summary": "Calcium is a silvery alkaline-earth metal, the fifth most abundant element in the Earth's crust, and it is never found as the free metal in nature. Its main industrial use is as a deoxidiser and desulphuriser in steelmaking, and it has been used as a getter for residual gases in vacuum tubes. It reacts with water to release flammable hydrogen, burns in air once ignited, and melts at 842 degC. Calcium metal is studied as an anode for rechargeable calcium batteries because its volumetric capacity is high, but only a handful of electrolytes have been shown to plate and strip it reversibly.\n",
  "best_for": "Deoxidising steel and as a reactive getter for residual gases; research anodes for calcium batteries, where its theoretical volumetric capacity is 2073 mAh/cm3",
  "weakest_at": "Any contact with water or moist air, which releases flammable hydrogen (H261), and self-ignition at about 730 to 750 degC in air",
  "identity": {
    "formula": "Ca",
    "cas": "7440-70-2",
    "designations": [],
    "source": "chemos-sds",
    "where": "Section 1.1 Product identifier (CAS number 7440-70-2, substance Calcium)"
  },
  "tags": {
    "environments": [],
    "stresses": [
      "extreme-heat"
    ],
    "applications": [
      "batteries",
      "structures",
      "electronics-and-chips"
    ]
  },
  "properties": [
    {
      "benchmark": "density",
      "value": 1550,
      "bound": "exact",
      "unit": "kg/m3",
      "scope": "material",
      "conditions": {
        "basis": "density of solid as printed by the source",
        "temperature": "not stated by the source"
      },
      "method": "Value printed in a database element page (WebElements)",
      "status": "ground",
      "source": "webelements-physics",
      "where": "Physical properties, Density properties: Density of solid",
      "source_detail": {
        "title": "WebElements: Calcium, physical properties",
        "id": "WebElements, Mark Winter, University of Sheffield",
        "url": "https://www.webelements.com/calcium/physics.html",
        "year": 2026,
        "kind": "database",
        "license": "WebElements copyright (cited, not reproduced)"
      }
    },
    {
      "benchmark": "density",
      "value": 1.54,
      "bound": "exact",
      "unit": "g/cm3",
      "scope": "material",
      "conditions": {
        "temperature": "20 degC"
      },
      "method": "Value printed in a supplier safety data sheet under REACH",
      "status": "ground",
      "source": "chemos-sds",
      "where": "Section 9, Density and/or relative density",
      "source_detail": {
        "title": "Safety Data Sheet: Calcium (Chemos GmbH and Co. KG, REACH format)",
        "id": "CAS 7440-70-2; article A0010604; version GHS 1.0",
        "url": "https://www.chemos.de/import/data/msds/GB_en/7440-70-2-A0010604-GB-en.pdf",
        "year": 2021,
        "kind": "datasheet",
        "license": "supplier document, linked not reproduced"
      }
    },
    {
      "benchmark": "density",
      "label": "Density used for calcium metal in an electrode model",
      "value": 1.57,
      "bound": "exact",
      "unit": "g/cm3",
      "scope": "material",
      "conditions": {
        "basis": "density the review uses for calcium metal in its electrode model, not a measured value",
        "temperature": "not stated by the source"
      },
      "method": "Table value in an open-access review of multivalent batteries",
      "status": "ground",
      "source": "frontiers-ca-2019",
      "where": "Table 1, row Calcium metal (conf. 1), density column",
      "source_detail": {
        "title": "Multivalent Batteries: Prospects for High Energy Density, Ca Batteries (Frontiers in Chemistry)",
        "id": "doi:10.3389/fchem.2019.00079",
        "url": "https://doi.org/10.3389/fchem.2019.00079",
        "year": 2019,
        "kind": "paper",
        "license": "CC BY 4.0"
      }
    },
    {
      "benchmark": "melting_point",
      "value": 842,
      "bound": "exact",
      "unit": "degC",
      "scope": "material",
      "conditions": {
        "basis": "melting point as printed (the page also gives 1115 K)"
      },
      "method": "Value printed in a database element page (WebElements) and in a supplier safety data sheet",
      "status": "ground",
      "source": "webelements-thermo",
      "where": "Thermochemistry: Melting point, 1115 [842 degC (1548 degF)] K",
      "source_detail": {
        "title": "WebElements: Calcium, thermochemistry",
        "id": "WebElements, Mark Winter, University of Sheffield",
        "url": "https://www.webelements.com/calcium/thermochemistry.html",
        "year": 2026,
        "kind": "database",
        "license": "WebElements copyright (cited, not reproduced)"
      }
    },
    {
      "benchmark": "boiling_point",
      "value": 1484,
      "bound": "exact",
      "unit": "degC",
      "scope": "material",
      "conditions": {
        "pressure": "1 atm"
      },
      "method": "Value printed in a database element page (WebElements) and in a supplier safety data sheet",
      "status": "ground",
      "source": "webelements-thermo",
      "where": "Thermochemistry: Boiling point, 1757 [1484 degC (2703 degF)] K",
      "source_detail": {
        "title": "WebElements: Calcium, thermochemistry",
        "id": "WebElements, Mark Winter, University of Sheffield",
        "url": "https://www.webelements.com/calcium/thermochemistry.html",
        "year": 2026,
        "kind": "database",
        "license": "WebElements copyright (cited, not reproduced)"
      }
    },
    {
      "benchmark": "enthalpy_of_fusion",
      "value": 8.54,
      "bound": "exact",
      "unit": "kJ/mol",
      "scope": "material",
      "conditions": {
        "temperature": "at the melting point"
      },
      "method": "Value printed in a database element page (WebElements)",
      "status": "ground",
      "source": "webelements-thermo",
      "where": "Thermochemistry: Enthalpy of fusion",
      "source_detail": {
        "title": "WebElements: Calcium, thermochemistry",
        "id": "WebElements, Mark Winter, University of Sheffield",
        "url": "https://www.webelements.com/calcium/thermochemistry.html",
        "year": 2026,
        "kind": "database",
        "license": "WebElements copyright (cited, not reproduced)"
      }
    },
    {
      "benchmark": "elastic_modulus",
      "label": "Young's modulus",
      "value": 20,
      "bound": "exact",
      "unit": "GPa",
      "scope": "material",
      "conditions": {
        "basis": "polycrystalline metal as printed; temperature not stated"
      },
      "method": "Value printed in a database element page (WebElements)",
      "status": "ground",
      "source": "webelements-physics",
      "where": "Physical properties, Elastic properties: Young's modulus",
      "source_detail": {
        "title": "WebElements: Calcium, physical properties",
        "id": "WebElements, Mark Winter, University of Sheffield",
        "url": "https://www.webelements.com/calcium/physics.html",
        "year": 2026,
        "kind": "database",
        "license": "WebElements copyright (cited, not reproduced)"
      }
    },
    {
      "benchmark": "bulk_modulus",
      "value": 17,
      "bound": "exact",
      "unit": "GPa",
      "scope": "material",
      "conditions": {
        "basis": "as printed; temperature not stated"
      },
      "method": "Value printed in a database element page (WebElements)",
      "status": "ground",
      "source": "webelements-physics",
      "where": "Physical properties, Elastic properties: Bulk modulus",
      "source_detail": {
        "title": "WebElements: Calcium, physical properties",
        "id": "WebElements, Mark Winter, University of Sheffield",
        "url": "https://www.webelements.com/calcium/physics.html",
        "year": 2026,
        "kind": "database",
        "license": "WebElements copyright (cited, not reproduced)"
      }
    },
    {
      "benchmark": "poissons_ratio",
      "value": 0.31,
      "bound": "exact",
      "unit": "-",
      "scope": "material",
      "conditions": {
        "basis": "as printed (no units)"
      },
      "method": "Value printed in a database element page (WebElements)",
      "status": "ground",
      "source": "webelements-physics",
      "where": "Physical properties, Elastic properties: Poisson's ratio",
      "source_detail": {
        "title": "WebElements: Calcium, physical properties",
        "id": "WebElements, Mark Winter, University of Sheffield",
        "url": "https://www.webelements.com/calcium/physics.html",
        "year": 2026,
        "kind": "database",
        "license": "WebElements copyright (cited, not reproduced)"
      }
    },
    {
      "benchmark": "electrical_resistivity",
      "value": 3.4,
      "bound": "exact",
      "unit": "microohm cm",
      "scope": "material",
      "conditions": {
        "unit_in_source": "3.4 x 10^-8 ohm m, printed as 3.4 x 10-8 ohm m with the alternative unit mohm cm",
        "temperature": "not stated by the source"
      },
      "method": "Converted by Space Mushroom from ohm m to microohm cm (1 ohm m is 100 million microohm cm); the source prints the value in ohm m",
      "status": "ground",
      "source": "webelements-physics",
      "where": "Electrical properties: Electrical resistivity",
      "source_detail": {
        "title": "WebElements: Calcium, physical properties",
        "id": "WebElements, Mark Winter, University of Sheffield",
        "url": "https://www.webelements.com/calcium/physics.html",
        "year": 2026,
        "kind": "database",
        "license": "WebElements copyright (cited, not reproduced)"
      }
    },
    {
      "benchmark": "thermal_conductivity",
      "value": 200,
      "bound": "exact",
      "unit": "W/(m K)",
      "scope": "material",
      "conditions": {
        "basis": "as printed; temperature not stated"
      },
      "method": "Value printed in a database element page (WebElements)",
      "status": "ground",
      "source": "webelements-physics",
      "where": "Heat and conduction: Thermal conductivity",
      "source_detail": {
        "title": "WebElements: Calcium, physical properties",
        "id": "WebElements, Mark Winter, University of Sheffield",
        "url": "https://www.webelements.com/calcium/physics.html",
        "year": 2026,
        "kind": "database",
        "license": "WebElements copyright (cited, not reproduced)"
      }
    },
    {
      "benchmark": "cte",
      "value": 22.3,
      "bound": "exact",
      "unit": "10^-6/K",
      "scope": "material",
      "conditions": {
        "basis": "linear coefficient as printed (22.3 x 10-6 per K); temperature not stated"
      },
      "method": "Value printed in a database element page (WebElements)",
      "status": "ground",
      "source": "webelements-physics",
      "where": "Heat and conduction: Coefficient of linear thermal expansion",
      "source_detail": {
        "title": "WebElements: Calcium, physical properties",
        "id": "WebElements, Mark Winter, University of Sheffield",
        "url": "https://www.webelements.com/calcium/physics.html",
        "year": 2026,
        "kind": "database",
        "license": "WebElements copyright (cited, not reproduced)"
      }
    },
    {
      "benchmark": "theoretical_capacity",
      "value": 1338,
      "bound": "exact",
      "unit": "mAh/g",
      "scope": "material",
      "conditions": {
        "reaction": "Ca to Ca2+, two electrons per calcium atom",
        "electrode": "calcium metal anode (conf. 1 and conf. 2 in the source both list 1338)"
      },
      "method": "Value stated in an open-access review of multivalent batteries; no working is shown",
      "status": "calculated",
      "source": "frontiers-ca-2019",
      "where": "Table 1, row Calcium metal (conf. 1), capacity column",
      "source_detail": {
        "title": "Multivalent Batteries: Prospects for High Energy Density, Ca Batteries (Frontiers in Chemistry)",
        "id": "doi:10.3389/fchem.2019.00079",
        "url": "https://doi.org/10.3389/fchem.2019.00079",
        "year": 2019,
        "kind": "paper",
        "license": "CC BY 4.0"
      }
    },
    {
      "benchmark": "volumetric_capacity",
      "label": "Theoretical volumetric capacity",
      "value": 2073,
      "bound": "exact",
      "unit": "mAh/cm3",
      "scope": "material",
      "conditions": {
        "electrode": "calcium metal anode",
        "comparison": "graphite 850 mAh/cm3 and lithium metal 2062 mAh/cm3 as quoted in the same abstract"
      },
      "method": "Value stated in a doctoral thesis abstract; no working is shown",
      "status": "calculated",
      "source": "mit-calcium-thesis",
      "where": "Abstract, sentence beginning 'Ca metal also offers attractive electrochemical metrics'",
      "source_detail": {
        "title": "Calcium metal battery thesis, abstract (MIT DSpace record 1721.1/159078)",
        "id": "MIT DSpace handle 1721.1/159078",
        "url": "https://dspace.mit.edu/handle/1721.1/159078",
        "kind": "paper",
        "license": "MIT DSpace abstract, cited"
      }
    },
    {
      "benchmark": "auto_ignition_temperature",
      "label": "Relative self-ignition temperature of solid calcium",
      "value": 730,
      "value_high": 750,
      "bound": "range",
      "unit": "degC",
      "scope": "material",
      "conditions": {
        "basis": "relative self-ignition temperature for solids (ECHA), printed as more than 730 and less than 750 degC"
      },
      "method": "Value printed in a supplier safety data sheet",
      "status": "ground",
      "source": "chemos-sds",
      "where": "Section 9, Auto-ignition temperature",
      "source_detail": {
        "title": "Safety Data Sheet: Calcium (Chemos GmbH and Co. KG, REACH format)",
        "id": "CAS 7440-70-2; article A0010604; version GHS 1.0",
        "url": "https://www.chemos.de/import/data/msds/GB_en/7440-70-2-A0010604-GB-en.pdf",
        "year": 2021,
        "kind": "datasheet",
        "license": "supplier document, linked not reproduced"
      }
    }
  ],
  "corrosion": [
    {
      "environment": "Liquid water",
      "headline": "Calcium reacts with water to form calcium hydroxide and hydrogen. The supplier safety data sheet calls the reaction violent.",
      "effect": "The metal sinks in water and after about an hour hydrogen bubbles stick to its surface (WebElements, which calls the reaction slow). The Chemos safety data sheet classifies calcium as water-reactive, category 2, with H261 (in contact with water releases flammable gases) and EUH014 (reacts violently with water).",
      "rating": "severe",
      "conditions": {
        "form": "calcium metal in water, form not stated by the source",
        "note": "the two sources disagree on speed: slow in WebElements, violent in the safety data sheet"
      },
      "source": "chemos-sds",
      "where": "Section 2.1 (Water-react 2), Section 2.2 (H261, EUH014), Section 5.2"
    },
    {
      "environment": "Room air at room temperature",
      "headline": "A thin oxide layer protects calcium in air, though less well than the layer on magnesium.",
      "effect": "The surface of calcium metal is covered with a thin oxide layer that protects it from air, but less well than the layer on magnesium. Once ignited it burns to calcium oxide and calcium nitride. No corrosion rate is given in the source.",
      "rating": "moderate",
      "conditions": {
        "atmosphere": "air at room temperature",
        "rate": "not measured in the source"
      },
      "source": "webelements-chem",
      "where": "Element reactions: Reaction of calcium with air"
    },
    {
      "environment": "Air or oxygen when heated",
      "headline": "Calcium self-ignites at about 730 to 750 degC in air.",
      "effect": "The supplier safety data sheet gives a relative self-ignition temperature for solid calcium of more than 730 and less than 750 degC (ECHA). Burning calcium forms calcium oxide and calcium nitride (WebElements).",
      "rating": "severe",
      "conditions": {
        "state": "solid",
        "basis": "relative self-ignition temperature, not a single ignition point"
      },
      "source": "chemos-sds",
      "where": "Section 9, Auto-ignition temperature"
    },
    {
      "environment": "Halogen gases (fluorine, chlorine, bromine, iodine)",
      "headline": "Calcium burns in fluorine and chlorine and reacts with bromine and iodine when heated.",
      "effect": "Calcium is very reactive towards the halogens and forms calcium fluoride, chloride, bromide and iodide. The reactions with bromine and iodine need heat to start.",
      "rating": "severe",
      "conditions": {
        "state": "gas phase, temperature not stated by the source"
      },
      "source": "webelements-chem",
      "where": "Element reactions: Reaction of calcium with the halogens"
    },
    {
      "environment": "Dilute or concentrated hydrochloric acid",
      "headline": "Calcium dissolves readily in hydrochloric acid and releases hydrogen.",
      "effect": "Calcium metal dissolves readily in dilute or concentrated hydrochloric acid, forming calcium ions in solution and hydrogen gas (Ca + 2HCl gives Ca2+ + 2Cl- + H2).",
      "rating": "severe",
      "conditions": {
        "acid": "hydrochloric acid, dilute or concentrated"
      },
      "source": "webelements-chem",
      "where": "Element reactions: Reaction of calcium with acids"
    },
    {
      "environment": "Electrolyte in a calcium battery cell (research)",
      "headline": "In battery electrolytes a passivating interphase forms on calcium and blocks calcium-ion transport.",
      "effect": "The thesis names two key problems for calcium metal anodes: a passivating solid electrolyte interphase between calcium and the electrolyte, which inhibits Ca2+ transport to the anode, and strong Ca2+-anion interactions that suppress ionic conductivity. Only a handful of reversible electrolytes have been reported since the first plating and stripping demonstration in 2015.",
      "rating": "moderate",
      "conditions": {
        "setting": "laboratory calcium-metal cells; electrolyte types not listed in the abstract"
      },
      "source": "mit-calcium-thesis",
      "where": "Abstract"
    }
  ],
  "risks": {
    "hazards": [
      {
        "text": "Classified under CLP as water-reactive, category 2 (H261: in contact with water releases flammable gases). The signal word is Danger and the pictogram is GHS02 (flame).",
        "ghs": [
          "H261"
        ],
        "source": "chemos-sds",
        "where": "Section 2.1 (Classification), Section 2.2 (Label elements)"
      },
      {
        "text": "Supplemental hazard EUH014: reacts violently with water.",
        "ghs": [
          "EUH014"
        ],
        "source": "chemos-sds",
        "where": "Section 2.2, Supplemental hazard information"
      },
      {
        "text": "OSHA HCS classification of the granular lab-grade metal: water-reactive, category 2, with the hazard statement that in contact with water it releases flammable gases.",
        "ghs": [],
        "source": "laballey-sds",
        "where": "Section 2.1 (Classification) and Section 2.2 (Label elements)"
      }
    ],
    "failure_risks": [
      {
        "mode": "Hydrogen release on contact with water",
        "trigger": "Water, moisture or a wet surface contacts the metal",
        "consequence": "Flammable hydrogen is released and may ignite spontaneously, according to the safety data sheet. Storage at higher temperature speeds the release.",
        "severity": "high",
        "source": "chemos-sds",
        "where": "Section 2.1, Section 5.2"
      },
      {
        "mode": "Self-ignition when heated in air",
        "trigger": "Heating solid calcium in air to its self-ignition range",
        "consequence": "Calcium self-ignites at about 730 to 750 degC and burns to calcium oxide and calcium nitride (ECHA value in the safety data sheet; WebElements for the products).",
        "severity": "high",
        "source": "chemos-sds",
        "where": "Section 9, Auto-ignition temperature; WebElements Element reactions: Reaction of calcium with air"
      },
      {
        "mode": "Passivating interphase in calcium battery cells (research)",
        "trigger": "Calcium metal in contact with the electrolyte during plating and stripping",
        "consequence": "A passivating interphase and poor ionic conductivity stop reversible plating and stripping, so the anode cannot be recharged reliably.",
        "severity": "moderate",
        "source": "mit-calcium-thesis",
        "where": "Abstract"
      }
    ],
    "side_effects": [
      {
        "text": "Product may release hydrogen gas, and storage at increased temperature accelerates this.",
        "affects": "Sealed containers and storage areas",
        "source": "chemos-sds",
        "where": "Section 5.2 Special hazards"
      },
      {
        "text": "Burning calcium gives calcium oxide and calcium nitride, and reaction with water gives calcium hydroxide.",
        "affects": "Nearby surfaces and equipment",
        "source": "webelements-chem",
        "where": "Element reactions: reaction with air and with water"
      }
    ],
    "handling": [
      {
        "text": "Keep in an inert gas, protect from moisture and do not allow contact with water (P231+P232, P223).",
        "source": "chemos-sds",
        "where": "Section 7 (precautionary statements P223, P231+P232)"
      },
      {
        "text": "Store in a dry place in a closed container (P402+P404).",
        "source": "chemos-sds",
        "where": "Section 2.2 precautionary statements"
      },
      {
        "text": "Fire extinguishing media differ between the two safety data sheets. Chemos lists foam, dry powder and dry sand and names a water jet as unsuitable. Laboratory-grade granules from Lab Alley list extinguisher powder or CO2 and warn against a direct water stream.",
        "source": "laballey-sds",
        "where": "Section 5.1 Extinguishing media"
      },
      {
        "text": "Skin contact: brush off loose particles and immerse the skin in cool water (P302+P335+P334).",
        "source": "chemos-sds",
        "where": "Section 2.2 precautionary statements"
      }
    ],
    "mitigations": [
      {
        "text": "Handle and store under inert gas, and keep the metal dry, so that it does not react with air or moisture.",
        "source": "chemos-sds",
        "where": "Section 7 (P231+P232)"
      }
    ]
  },
  "uses": [
    {
      "application": "batteries",
      "device": "Rechargeable calcium-metal battery (research stage)",
      "example": "Calcium metal has a theoretical volumetric capacity of 2073 mAh/cm3, against 850 mAh/cm3 for graphite and 2062 mAh/cm3 for lithium metal, and the thesis says it is the basis of calcium battery research. Only a handful of reversible electrolytes have been reported since 2015.",
      "source": "mit-calcium-thesis",
      "where": "Abstract"
    },
    {
      "application": "electronics-and-chips",
      "device": "Vacuum tubes (calcium as a getter)",
      "example": "Calcium is used as a getter for residual gases in vacuum tubes, and WebElements lists it among the uses of the metal.",
      "source": "webelements-uses",
      "where": "Uses list, item on getter for residual gases in vacuum tubes"
    },
    {
      "application": "structures",
      "device": "Steel and alloys (deoxidiser and desulphuriser)",
      "example": "Calcium is used as a deoxidiser, desulphuriser or decarbonizer for various alloys, according to WebElements. The metal is not a common alloying element in steel because its solubility is low.",
      "source": "webelements-uses",
      "where": "Uses list, item on deoxidiser, desulphurizer or decarbonizer"
    }
  ],
  "supply": [
    {
      "subject": "Calcium (producer shares are for lime, not calcium metal, because USGS reports no calcium metal production)",
      "abundance": "41,500 ppm in the Earth's crust (thesis abstract). WebElements: fifth in abundance in the crust, forming more than 3 per cent, and found in limestone, gypsum and fluorite but never as the free metal. Crustal rocks row: 50000000 ppb by weight.",
      "producers": [
        {
          "country": "China",
          "share_percent": 73.8,
          "year": 2025
        },
        {
          "country": "India",
          "share_percent": 4,
          "year": 2025
        },
        {
          "country": "United States",
          "share_percent": 3.6,
          "year": 2025
        },
        {
          "country": "Russia",
          "share_percent": 2.9,
          "year": 2025
        }
      ],
      "critical_lists": [
        {
          "list": "USGS Final 2025 List of Critical Minerals (Table 6)",
          "listed": false
        },
        {
          "list": "EU critical raw materials list (RMIS, 34 materials)",
          "listed": false
        }
      ],
      "recycling": "No recycling figure for calcium metal was found in the sources read.",
      "substitutes": [],
      "source": "usgs-mcs-2026",
      "where": "Lime chapter, World Lime Production and Reserves table (2025e; shares calculated by Space Mushroom against the 420,000 thousand t world total); Table 6 of the USGS summaries for the US list; EU RMIS page for the EU list; WebElements Geology page for abundance."
    }
  ],
  "media": [],
  "documents": [
    {
      "title": "Safety data sheet: Calcium (Chemos GmbH, CAS 7440-70-2, version GHS 1.0, compiled 2021-04-08)",
      "type": "sds",
      "url": "https://www.chemos.de/import/data/msds/GB_en/7440-70-2-A0010604-GB-en.pdf",
      "year": 2021
    },
    {
      "title": "Safety data sheet: Calcium metal, granular lab grade (Lab Alley, revision 2 dated 2025-07-03)",
      "type": "sds",
      "url": "https://media.laballey.com/docbuilder/calcium-metal-granular-lab-grade-safety-data-sheet-6866d1beb0d43.pdf",
      "year": 2025
    },
    {
      "title": "Calcium (WebElements periodic table, physical, thermochemistry, chemistry, geology and uses pages)",
      "type": "database",
      "url": "https://www.webelements.com/calcium/",
      "year": 2026
    },
    {
      "title": "Multivalent Batteries: Prospects for High Energy Density, Ca Batteries (Frontiers in Chemistry, open access)",
      "type": "paper",
      "url": "https://doi.org/10.3389/fchem.2019.00079",
      "year": 2019
    },
    {
      "title": "Mineral Commodity Summaries 2026 (lime chapter and Table 6, Final 2025 Critical Minerals List)",
      "type": "report",
      "url": "https://pubs.usgs.gov/periodicals/mcs2026/mcs2026.pdf",
      "year": 2026
    }
  ],
  "gaps": [
    "Calcium metal production by country is not reported separately; the supply shares are for lime (quicklime and hydrated lime), which is a calcium compound, not the metal.",
    "No recycling figure and no substitute list for calcium metal were found in the sources read.",
    "The standard potential of the Ca2+/Ca couple (-2.868 V vs SHE) is printed on a LibreTexts table with a Unicode minus sign, so it was not entered; it can be added once a source prints an ASCII minus sign.",
    "Auto-ignition is entered as a range under the non-canonical name auto_ignition_temperature; it is not in the canonical property list.",
    "No vacuum, outgassing, radiation, cold or thermal-vacuum data for calcium were found. The getter use has no numbers in the sources read.",
    "The two safety data sheets disagree on suitable fire extinguishing media (foam and dry sand in one, powder and CO2 in the other). Both are recorded; check the sheet for the product you hold.",
    "WebElements describes the reaction with water as slow, while the Chemos safety data sheet classifies it as violent (EUH014). Both are recorded in the corrosion section.",
    "Specific heat capacity and Brinell hardness (167 MN m-2, WebElements) are printed in the physical properties page but were not entered because no canonical name fitted the unit as printed.",
    "Gravimetric and volumetric capacities come from a 2019 review and a thesis abstract, and no measured capacity of calcium metal in a cell was read."
  ],
  "story": {
    "why": "Calcium is the fifth most abundant element in the Earth's crust but is never found as the free metal. As a metal it is a strong reducing agent. Industry uses it to remove oxygen and sulphur from steel, and it has been used as a getter for residual gases in vacuum tubes. It is studied as a battery anode because its volumetric capacity is high. Its reactivity with water and air is the main problem for handling and for any cell that uses it.",
    "uses": [
      {
        "where": "Steelmaking",
        "line": "WebElements lists calcium as a deoxidiser, desulphuriser and decarbonizer for various alloys, and as a reducing agent for preparing other metals such as thorium, uranium and zirconium."
      },
      {
        "where": "Vacuum tubes",
        "line": "Calcium is used as a getter for residual gases in vacuum tubes, according to WebElements. The sources read give no pumping numbers."
      },
      {
        "where": "Rechargeable batteries, still under research",
        "line": "A thesis abstract gives calcium metal a theoretical volumetric capacity of 2073 mAh/cm3, against 850 for graphite. It also says only a handful of reversible electrolytes have been reported since 2015, so calcium metal anodes are not yet in use."
      }
    ],
    "can_do": [
      {
        "label": "Capacity",
        "line": "A 2019 review gives 1338 mAh/g for calcium metal as an anode, with each calcium atom giving two electrons. Its volumetric capacity is 2073 mAh/cm3 in the thesis abstract.",
        "scope": "material",
        "value": "1338 mAh/g"
      },
      {
        "label": "Melting",
        "line": "Calcium melts at 842 degC and boils at 1484 degC. Its heat of fusion is 8.54 kJ/mol.",
        "scope": "material",
        "value": "842 degC"
      },
      {
        "label": "Stiffness",
        "line": "Young's modulus is 20 GPa, bulk modulus 17 GPa and Poisson's ratio 0.31, as printed by WebElements.",
        "scope": "material",
        "value": "20 GPa"
      },
      {
        "label": "Heat and electricity",
        "line": "Thermal conductivity is 200 W/(m K), and electrical resistivity is 3.4 microohm cm at a temperature the source does not state.",
        "scope": "material",
        "value": "200 W/(m K)"
      }
    ],
    "compare": "Calcium sits directly below magnesium in the periodic table, the closest metal type in this collection. WebElements describes calcium as more reactive with air and water than magnesium, which is virtually unreactive with cold water. For a battery anode, the thesis abstract gives calcium metal 2073 mAh/cm3 by volume, against 850 mAh/cm3 for graphite.",
    "compare_rows": [
      {
        "label": "Density",
        "benchmark": "density",
        "scope": "material"
      },
      {
        "label": "Melting point",
        "benchmark": "melting_point",
        "scope": "material"
      },
      {
        "label": "Theoretical capacity as an anode",
        "benchmark": "theoretical_capacity",
        "scope": "material"
      }
    ],
    "handling": [
      "Store in an inert gas in a dry, closed container, away from water.",
      "Protect from moisture; contact with water releases flammable hydrogen.",
      "Choose the extinguisher from the product's own safety data sheet. Do not use a water jet."
    ],
    "good_for": [
      "Deoxidising steel, where it removes oxygen and sulphur.",
      "Research anodes for calcium batteries, where its volumetric capacity is high."
    ],
    "watch_out": [
      "Water and moist air. Calcium releases hydrogen on contact with water, and its surface reacts with air.",
      "Heat. Solid calcium self-ignites at about 730 to 750 degC in air.",
      "Rechargeable cells. Electrolytes that plate and strip calcium reversibly are few, and a passivating layer forms on the metal."
    ],
    "verdict": "Calcium is a useful reactive metal for steel and getters, and a promising but unproven anode for rechargeable batteries. Handling needs inert, dry conditions.",
    "recipe": {
      "line": "Calcium metal is the pure element, Ca, with one atom per formula unit. It is not an alloy in this profile.",
      "parts": [
        {
          "name": "Calcium",
          "symbol": "Ca",
          "role": "The only element in the metal. The NIST standard atomic weight is 40.078, as printed.",
          "atoms": 1,
          "atomic_weight": 40.078
        }
      ]
    },
    "risk_groups": [
      {
        "title": "For people",
        "lead": "Calcium metal is classified under CLP as water-reactive, category 2. It releases flammable hydrogen on contact with water and self-ignites at about 730 to 750 degC in air.",
        "points": [
          {
            "label": "Classification",
            "line": "The Chemos safety data sheet uses the signal word Danger and the GHS02 flame pictogram, with H261 (in contact with water releases flammable gases) and EUH014 (reacts violently with water)."
          },
          {
            "label": "Fire",
            "line": "Fire extinguishing advice differs between the two safety data sheets, so use the sheet for the product you hold. Avoid water jets; one sheet names sand, dry powder and foam, the other powder and CO2."
          },
          {
            "label": "Skin",
            "line": "Brush off loose particles and immerse the skin in cool water, following the precautionary statement P302+P335+P334."
          }
        ],
        "level": 4,
        "verdict": "Water-reactive and flammable on contact with water"
      },
      {
        "title": "If the metal meets water or heat",
        "lead": "These are hazard properties from the safety data sheets and reference pages, not field incidents.",
        "points": [
          {
            "label": "Water",
            "line": "Water releases flammable hydrogen, which may ignite. Storage at higher temperature speeds the release."
          },
          {
            "label": "Heat in air",
            "line": "Solid calcium self-ignites at about 730 to 750 degC and burns to calcium oxide and calcium nitride."
          },
          {
            "label": "Halogens and acids",
            "line": "Calcium burns in fluorine and chlorine, reacts with bromine and iodine when heated, and dissolves readily in hydrochloric acid with release of hydrogen."
          }
        ]
      },
      {
        "title": "Handling and storage",
        "points": [
          {
            "label": "Storage",
            "line": "Store in an inert gas, in a dry place, in a closed container, and keep away from water (P223, P231+P232, P402+P404)."
          }
        ]
      }
    ]
  },
  "updated": "2026-10-26",
  "review": {
    "status": "draft",
    "method": "assistant",
    "checked_values": 15,
    "unreachable": 0,
    "caveats": 3,
    "note": "Written by an AI assistant on 2026-10-26 from pages read in this run; values to be checked with verify-values."
  },
  "sources": {
    "webelements-physics": {
      "title": "WebElements: Calcium, physical properties",
      "id": "WebElements, Mark Winter, University of Sheffield",
      "url": "https://www.webelements.com/calcium/physics.html",
      "year": 2026,
      "kind": "database",
      "license": "WebElements copyright (cited, not reproduced)"
    },
    "webelements-thermo": {
      "title": "WebElements: Calcium, thermochemistry",
      "id": "WebElements, Mark Winter, University of Sheffield",
      "url": "https://www.webelements.com/calcium/thermochemistry.html",
      "year": 2026,
      "kind": "database",
      "license": "WebElements copyright (cited, not reproduced)"
    },
    "webelements-chem": {
      "title": "WebElements: Calcium, element reactions",
      "id": "WebElements, Mark Winter, University of Sheffield",
      "url": "https://www.webelements.com/calcium/chemistry.html",
      "year": 2026,
      "kind": "database",
      "license": "WebElements copyright (cited, not reproduced)"
    },
    "webelements-uses": {
      "title": "WebElements: Calcium, uses",
      "id": "WebElements, Mark Winter, University of Sheffield",
      "url": "https://www.webelements.com/calcium/uses.html",
      "year": 2026,
      "kind": "database",
      "license": "WebElements copyright (cited, not reproduced)"
    },
    "webelements-geo": {
      "title": "WebElements: Calcium, geology",
      "id": "WebElements, Mark Winter, University of Sheffield",
      "url": "https://www.webelements.com/calcium/geology.html",
      "year": 2026,
      "kind": "database",
      "license": "WebElements copyright (cited, not reproduced)"
    },
    "nist-atomic-weights": {
      "title": "NIST Atomic Weights and Isotopic Compositions, element Ca",
      "id": "NIST, standard atomic weight of calcium",
      "url": "https://physics.nist.gov/cgi-bin/Compositions/stand_alone.pl?ele=Ca&all=all",
      "year": 2026,
      "kind": "database",
      "license": "public domain (US government work)"
    },
    "chemos-sds": {
      "title": "Safety Data Sheet: Calcium (Chemos GmbH and Co. KG, REACH format)",
      "id": "CAS 7440-70-2; article A0010604; version GHS 1.0",
      "url": "https://www.chemos.de/import/data/msds/GB_en/7440-70-2-A0010604-GB-en.pdf",
      "year": 2021,
      "kind": "datasheet",
      "license": "supplier document, linked not reproduced"
    },
    "laballey-sds": {
      "title": "Safety Data Sheet: Calcium Metal Granular Lab Grade (Lab Alley)",
      "id": "Revision 2, 2025-07-03",
      "url": "https://media.laballey.com/docbuilder/calcium-metal-granular-lab-grade-safety-data-sheet-6866d1beb0d43.pdf",
      "year": 2025,
      "kind": "datasheet",
      "license": "supplier document, linked not reproduced"
    },
    "mit-calcium-thesis": {
      "title": "Calcium metal battery thesis, abstract (MIT DSpace record 1721.1/159078)",
      "id": "MIT DSpace handle 1721.1/159078",
      "url": "https://dspace.mit.edu/handle/1721.1/159078",
      "kind": "paper",
      "license": "MIT DSpace abstract, cited"
    },
    "frontiers-ca-2019": {
      "title": "Multivalent Batteries: Prospects for High Energy Density, Ca Batteries (Frontiers in Chemistry)",
      "id": "doi:10.3389/fchem.2019.00079",
      "url": "https://doi.org/10.3389/fchem.2019.00079",
      "year": 2019,
      "kind": "paper",
      "license": "CC BY 4.0"
    },
    "usgs-mcs-2026": {
      "title": "Mineral Commodity Summaries 2026 (USGS), lime chapter and Table 6 Final 2025 Critical Minerals List",
      "id": "USGS MCS 2026, February 2026",
      "url": "https://pubs.usgs.gov/periodicals/mcs2026/mcs2026.pdf",
      "year": 2026,
      "kind": "report",
      "license": "public domain (USGS)"
    },
    "rmis-eu-crm": {
      "title": "EU Raw Materials Information System: critical raw materials",
      "id": "Regulation (EU) 2024/1252 list of critical raw materials",
      "url": "https://rmis.jrc.ec.europa.eu/eu-critical-raw-materials",
      "year": 2026,
      "kind": "web",
      "license": "European Commission web page"
    }
  },
  "license": "CC-BY-4.0",
  "url": "https://spacemushroom.com/profiles/calcium/"
}