rare earth element
Enable an agent to recognise a rare-earth element, assess the identity and condition of material representing it, and determine which handling, comparison or use decisions its evidence supports.
Research draft, second pass
A second pass drafted this model: the structure a model of this thing needs, and what is known about it in the world. The line under this one says how the second half was obtained - researched against sources, or recalled without web access, in which case nothing here was read anywhere and every claim is a lead to verify. Unreviewed either way.
recalled by Codex without web access - no source was read
Researched by: Codex
Purpose and description
Enable an agent to recognise a rare-earth element, assess the identity and condition of material representing it, and determine which handling, comparison or use decisions its evidence supports.
A rare earth element is any of the 15 lanthanides, from lanthanum to lutetium, or scandium or yttrium, grouped because of similarities in their chemistry, especially their commonly trivalent states.
It can be Resolve a rare-earth label to an individual element and identify unresolved mixture or chemical-form ambiguity.; Compare assays after aligning included elements, purity denominators and element-versus-oxide reporting bases.; Assess whether separation and impurity evidence support a claimed element grade.; Identify missing measurements needed to qualify a material for a specified magnetic, optical, catalytic or alloying role.; Determine whether documented material condition and applicable handling evidence support a proposed operation.; Link the element to its host compound, product or recovery stream without duplicating those neighbouring models..
Distinguishing features
Check the element name, symbol and atomic number against the declared rare-earth membership convention; the word 'rare' alone does not establish membership.
Distinguish rare-earth family membership from lanthanide membership, since the adopted family convention also includes scandium and yttrium.
Require an individual element identity before treating a record as a single element; a mixed rare-earth concentrate or aggregate assay does not supply one.
Determine whether the identified element is present as elemental metal, an ion in a compound or a constituent of a mixture; an element-content measurement does not establish metallic form.
Keep family identity separate from abundance, critical-material designation and commercial grade, each of which requires its own evidence.
Scope
+ Rare-earth family membership, individual element identity and explicitly attributed subgroup conventions.
+ The distinction between elemental material and an element present in a compound, alloy or mixture.
+ Element-specific purity, impurity profile, isotope composition and assay basis.
+ Physical state and measured properties under stated conditions.
+ Evidence needed to qualify material for handling, transformation and an intended function.
- Complete models of rare-earth-bearing minerals, ores and geological deposits.
- Independent chemical identities and full specifications of rare-earth oxides, salts and complexes.
- Complete formulations and performance models of magnets, phosphors, catalysts and alloys containing rare earths.
- Mining, beneficiation, separation and refining process design.
- Commodity markets, supplier organisations and jurisdiction-wide regulatory systems.
Characteristics
- Element identity
- Verified element name, symbol and atomic number Anchors measurements and identifiers to a specific family member.
- Membership and subgroup convention
- Named membership authority; light, heavy, other or unassigned under a cited convention Makes differences between scientific and commercial groupings explicit.
- Chemical form and host
- Elemental substance, compound, alloy, mineral or mixture record; oxidation state where established Prevents properties of a host material from being attributed to the element itself.
- Element content and purity basis
- Mass fraction or mass %, with denominator, dry or wet basis, method and uncertainty Distinguishes whole-sample purity from purity relative only to measured rare-earth constituents.
- Rare-earth reporting basis
- Element mass, specified oxide equivalent or declared total rare-earth measure with included elements Supports valid comparison of differently reported assays.
- Impurity profile
- mg/kg or mass % for named other rare earths and non-rare-earth contaminants; detection limits Exposes contaminants hidden by a single headline purity value.
- Isotopic and radiological profile
- Isotope fractions; Bq/g where relevant; radionuclide identity, method and reference date Separates isotope-specific properties from contamination associated with material provenance.
- Material condition
- Phase, morphology, particle-size distribution, surface condition and storage atmosphere at stated temperature and pressure Connects a material assessment to its actual condition.
- Physical property evidence
- Density in kg/m³; melting and boiling temperatures in K; applicable magnetic, optical or electrical quantities with units and conditions Prevents a family-wide constant from replacing element- and form-specific measurements.
- Regulatory and hazard identity
- Verified applicable CAS, EC and PubChem records; dated classification and exposure-limit sources for the specified substance and form Connects proposed actions to the correct substance record instead of the broad family label.
Where this came from
wikidata · CC0 1.0
Drafted structure
Bundle to layer to finding to question, as the second pass will find it: 6 bundles · 11 layers · 19 findings · 29 questions.
Element identity and family boundaries Resolve what the rare-earth designation identifies and which convention supports it.
A family name cannot substitute for an individual chemical identity or an explicitly defined grouping.
Family membership
Establish membership and any subgroup assignment.
Declared membership convention
Record the authority defining the family and any light or heavy subgroup labels.
- Which element name, symbol and atomic number does this record identify? definition
- Which cited convention includes this element and assigns any light or heavy subgroup? provenance
Element versus containing material
Separate elemental identity from the substance or material in which it occurs.
Chemical identity boundary
Connect the element to the actual material identity without treating a compound or mixture as a single elemental substance.
- Does the label denote elemental metal, a compound, an alloy or a mixture containing this element? boundary
- Which verified identifiers describe that specific substance, and which neighbouring record owns its full specification? provenance
Assay, purity and separation Determine what an analytical result establishes about element content and separation from other constituents.
Rare-earth content, relative rare-earth purity and whole-material purity answer different qualification questions.
Assay denominators
Make element and oxide reporting bases explicit.
Comparable content values
Require declared denominators and conversion assumptions before comparing assays.
- Is content reported as element mass, a specified oxide equivalent or a total rare-earth measure, and which constituents are included? measurement
- Does the purity percentage refer to the whole sample or only its rare-earth fraction, and is the sample basis dry or wet? measurement
Separation quality
Assess residual rare-earth constituents and other contaminants.
Supported grade claim
Tie a claimed isolated-element grade to a representative sample and an adequate impurity assay.
- Which other rare-earth elements and non-rare-earth impurities were quantified, with what detection limits and uncertainty? measurement
- Which batch, sampling procedure and analytical report support the claimed separation quality? provenance
Chemical state and property evidence Connect observed behaviour to the element's chemical form and material condition.
An element's measured behaviour must not be transferred automatically between metal, compound and host material.
Form and condition
Identify the specimen state relevant to interpretation and use.
Established material state
Record chemical form, oxidation state where meaningful, and evidence of surface or bulk change.
- What evidence establishes elemental versus compound form and any relevant oxidation state? measurement
- What phase, particle size, surface condition, atmosphere, temperature and pressure describe the assessed specimen? measurement
Conditional properties
Qualify physical constants and functional measurements by their actual test conditions.
Attributable property values
Distinguish measurements of the element from measurements of a compound or engineered host.
- Which density and phase-transition values are established for this element, purity and pressure, with units and uncertainty? measurement
- Do cited magnetic, optical or electrical measurements describe this elemental specimen or a containing material? boundary
Form-specific handling and controls Establish the evidence needed to assess operations on the actual rare-earth material.
A family label alone cannot establish chemical, particulate or radiological handling requirements.
Hazard attribution
Separate hazards of the substance and physical form from those of associated contaminants.
Material-specific hazard evidence
Require hazard evidence that matches the assessed substance, morphology and composition.
- Which documented hazards apply to this metal, powder or containing substance at its actual particle size and condition? provenance
- Where radiological assessment is relevant, which measured radionuclides belong to the element and which are contaminants? measurement
Operation qualification
Connect proposed handling to applicable and current evidence.
Supported handling decision
Evaluate a specific operation using the correct material identity, conditions and jurisdiction.
- Which current classification, exposure limits and substance identifiers apply in the relevant jurisdiction? provenance
- What documented conditions support the proposed storage, transfer, heating or machining operation, and what evidence is missing? action
Functional qualification and material lineage Connect an identified rare-earth material to an intended role and a traceable source or recovery stream.
Family membership does not establish interchangeability, application suitability or equivalence between supplied lots.
Role-specific qualification
Define the requirements contributed by the rare-earth constituent.
Element contribution to use
Assess the required element, form and grade while leaving finished-product performance to its own model.
- Which element-specific function, chemical form and impurity limits does the intended application require? definition
- What qualification evidence is required before accepting a different rare-earth element, grade or source for this role? action
Source and recovery links
Preserve material lineage across primary and recovered sources.
Traceable element-bearing stream
Link the assessed lot to its source and transformations without modelling the entire production process.
- Which source, separation or recovery records connect this lot to its reported composition and grade? provenance
- Which host-material and process records must be consulted to judge recovery or reuse of this element from the identified stream? action
Evidence and external alignment What the world already says about this thing, gathered so the model can be checked against it.
A model that cannot be lined up against existing standards, identifiers and practice cannot be adopted by anyone who already uses them.
Reported evidence
Findings from the breadth pass, kept separate from the structural claims.
Check these first
Recalled without web access and unsourced; every item is a lead to verify.
- Light and heavy rare earth subgroup boundaries vary; treatment of yttrium and scandium should be stated explicitly.
- Melting points, boiling points, purity specifications and hazard classifications must be assigned to individual substances rather than to the group.
- This is recalled knowledge, not source-verified research; 'rare earth' does not imply that every member is scarce in Earth's crust.
- Which of these check these first hold for the sense of rare earth element this model covers, and on what evidence? provenance
Kinds and varieties
Recalled without web access and unsourced; every item is a lead to verify.
- Light rare earth elements
- Heavy rare earth elements
- Which of these kinds and varieties hold for the sense of rare earth element this model covers, and on what evidence? provenance
Identifiers and schemes
Recalled without web access and unsourced; every item is a lead to verify.
- IUPAC element names and symbols - Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu - These identify the 17 constituent elements; the group is not a single substance.
- Atomic number - 21, 39, 57-71 - Identifies scandium, yttrium and the lanthanides, respectively.
- CAS Registry Number - Individual substances have separate registry numbers. - An element, its oxide and its salts require distinct substance identities; no single number represents the whole group.
- Which of these identifiers and schemes hold for the sense of rare earth element this model covers, and on what evidence? provenance
Standards and regulation
Recalled without web access and unsourced; every item is a lead to verify.
- United Nations Globally Harmonized System of Classification and Labelling of Chemicals (GHS): classification depends on the specific substance and form.
- European Union REACH Regulation: registration and other obligations depend on substance identity and applicable conditions.
- Which of these standards and regulation hold for the sense of rare earth element this model covers, and on what evidence? provenance
Real-world use
Recalled without web access and unsourced; every item is a lead to verify.
- Neodymium and praseodymium in permanent magnets, with dysprosium or terbium used in some magnet compositions.
- Cerium oxide in glass polishing.
- Lanthanum-containing materials in petroleum-refining catalysts.
- Europium and terbium compounds in phosphors.
- Rare-earth-containing alloys in nickel-metal hydride battery electrodes.
- Which of these real-world use hold for the sense of rare earth element this model covers, and on what evidence? provenance
Typical measurements
Recalled without web access and unsourced; every item is a lead to verify.
- Total rare earth oxide content - Material-dependent; no group-wide typical range. - mass % -
- Which of these typical measurements hold for the sense of rare earth element this model covers, and on what evidence? provenance
Failure modes and hazards
Recalled without web access and unsourced; every item is a lead to verify.
- Finely divided forms of some rare earth metals can ignite; fire behaviour depends on the element and particle size.
- Dust inhalation and chemical toxicity require assessment of the specific metal, compound and physical form.
- Some rare earth ores contain thorium or uranium, creating radiological hazards during processing and waste management.
- Similar chemistry makes separation difficult, so residual neighbouring elements can compromise product purity.
- Promethium has no stable isotopes and requires radiological controls.
- Which of these failure modes and hazards hold for the sense of rare earth element this model covers, and on what evidence? provenance
Regional variation
Recalled without web access and unsourced; every item is a lead to verify.
- Hazard labelling, workplace exposure requirements and waste controls depend on jurisdiction and the particular substance.
- Commercial reporting may express quantities as contained elements or oxide equivalents, requiring conversion before comparison.
- Which of these regional variation hold for the sense of rare earth element this model covers, and on what evidence? provenance
Neighbouring kinds and how to tell them apart
Recalled without web access and unsourced; every item is a lead to verify.
- lanthanide - The lanthanides are elements 57-71; the rare earth group additionally includes scandium and yttrium.
- rare earth oxide - An oxide is a compound of a rare earth element with oxygen, rather than the element itself.
- rare earth mineral - A mineral is a naturally occurring crystalline substance that may contain rare earth elements alongside other constituents.
- rare metal - Rare metal is a broader, context-dependent economic or technical category rather than the defined rare earth element group.
- Which of these neighbouring kinds and how to tell them apart hold for the sense of rare earth element this model covers, and on what evidence? provenance
What the second pass must settle
- Does an existing Vercy world model already own this family concept, requiring this registry entry to link to it?
- Which authority should govern family membership and light versus heavy subgroup labels when sources use different conventions?
- Which authoritative element-specific identity and property references will populate the model, including isotope-dependent cases?
- Which assay conventions and application specifications are needed to interpret commercial purity labels and oxide-equivalent reporting consistently?
- Which material forms, operations and jurisdictions should receive researched hazard and regulatory coverage first?