corundum
Enable an agent to identify corundum, assess its composition and condition, and determine whether a specimen or material lot is suitable for a proposed use or treatment.
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 identify corundum, assess its composition and condition, and determine whether a specimen or material lot is suitable for a proposed use or treatment.
Corundum is the crystalline mineral form of aluminium oxide (Al₂O₃) with the alpha-alumina structure, belonging to the trigonal crystal system and including the gem varieties ruby and sapphire.
It can be Select suitable phase, chemical and optical tests to resolve a corundum identification.; Compare a specimen or lot with explicit gem, abrasive, optical or ceramic material requirements.; Assess natural-origin and treatment claims against laboratory evidence and retain unresolved status.; Evaluate proposed cutting, grinding, polishing, cleaning or heating against material condition and treatment history.; Separate corundum properties from those of inclusions, coatings, fillers and surrounding material.; Request missing analytical or handling evidence before accepting a material for a specified use..
Distinguishing features
Require composition consistent with Al2O3 together with a matching corundum diffraction or spectroscopic signature; chemistry alone does not establish the crystalline phase. Reference: [Handbook of Mineralogy](https://www.handbookofmineralogy.org/pdfs/corundum.pdf).
Use hardness near Mohs 9 and density near 4 g/cm³ as supporting checks, with test limitations recorded; neither measurement establishes identity alone. Reference: [Handbook of Mineralogy](https://www.handbookofmineralogy.org/pdfs/corundum.pdf).
For suitable transparent crystals, compare measured refractive indices and optical behaviour with corundum references to test visually similar gemstone candidates. Reference: [Handbook of Mineralogy](https://www.handbookofmineralogy.org/pdfs/corundum.pdf).
Treat ruby and sapphire as varieties of corundum rather than separate mineral species; record the naming convention for borderline colours. Reference: [GIA sapphire overview](https://www.gia.edu/sapphire?lang=en).
Distinguish synthetic corundum from simulants: synthetic material shares the natural counterpart's principal material properties, so origin requires additional evidence. Reference: [GIA synthetic gem materials](https://www.gia.edu/gem-synthetic).
Scope
+ Corundum phase identification and distinction from other forms of alumina
+ Composition, purity, trace elements, inclusions and associated phases
+ Natural or synthetic origin, variety assignment and treatment evidence
+ Crystal, grain and aggregate condition and measured material properties
+ Grade suitability, handling constraints and applicable substance identifiers
- Other alumina phases and aluminium compounds as independent substances
- Corundum-bearing rocks, deposits and mining operations as whole systems
- Jewellery, abrasive tools, optical components and ceramic products as finished objects
- Crystal-growth, refining, cutting and heat-treatment processes as operational models
- Gemstone pricing, ownership and commercial transactions
Characteristics
- Phase identity and phase fraction
- Identified phases; corundum mass fraction in wt%; method and uncertainty Distinguishes corundum from other alumina phases and prevents treating a mixture as pure material.
- Chemical purity and trace-element profile
- Al2O3 wt%; trace elements in mg/kg or atomic ppm with basis and detection limits Supports grade selection and investigation of colour, contamination and deliberate doping.
- Material form and microstructure
- Single crystal, polycrystalline aggregate, grain or powder; grain size in µm; porosity in vol% Determines which measurements and application criteria are meaningful.
- Origin assessment
- Natural, synthetic, mixed-origin assembly or undetermined; evidence and confidence Separates mineral identity from formation history and identifies unresolved origin claims.
- Colour and variety
- Observed colour under specified illumination; ruby, sapphire, unassigned or not applicable Makes variety labels traceable without equating colour with origin or purity.
- Optical response
- Refractive indices, birefringence, transmission %, absorption spectrum and fluorescence conditions Supports identification and optical suitability when specimen form permits measurement.
- Mechanical response
- Mohs hardness or indentation hardness in GPa; fracture toughness in MPa·√m; method and orientation Separates scratch resistance from resistance to cracking or impact.
- Density
- g/cm³; true, apparent or bulk density; temperature and method Supports identification and reveals effects of porosity or associated material.
- Thermal behaviour
- Conductivity in W/(m·K), expansion in K⁻¹ and transition temperatures in °C with pressure and atmosphere Supports evaluation of temperature exposure without assuming melting temperature is a service limit.
- Treatment and damage state
- Documented or detected treatments, untested treatments, cracks, chips, fillings and surface alterations Conditions processing, cleaning, identification and acceptance decisions.
- Source and lot linkage
- Specimen or lot linked to locality, producer, certificate and analytical report Keeps measurements and provenance claims attached to the material actually examined.
- Substance identity and handling classification
- Verified CAS, EC and PubChem records where applicable; dated SDS and jurisdiction-specific classification Prevents applying generic alumina records or handling assumptions to an unverified grade or mixture.
Also called
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 · 18 findings · 30 questions.
Mineral identity Establish whether the examined material contains corundum and what the identification covers.
A corundum label must distinguish crystalline phase identity from bulk alumina chemistry and commercial naming.
Phase confirmation
Connect chemical and structural evidence to the corundum identification.
Corundum phase evidence
Record the tests, reference matches and limitations supporting identification of alpha-Al2O3.
- Which diffraction or spectroscopic observations establish the corundum phase rather than another alumina phase? definition
- Does chemical analysis support the identification, and what sampling or detection limitations remain? measurement
Material boundary
Determine whether the record concerns an individual crystal, a lot or a constituent of another material.
Corundum versus containing material
Separate the corundum phase from host rock, binders, coatings, fillers and other mineral grains.
- What physical specimen or lot does this identification cover, and which portions were tested? boundary
- Which accompanying phases or added materials require separate records rather than being attributed to corundum? boundary
Composition and variety Describe chemical variation and the evidence behind optical appearance and variety names.
Purity, trace constituents and colour affect corundum's interpretation and suitability without necessarily changing its phase identity.
Purity and constituents
Distinguish lattice constituents from inclusions and external contamination.
Constituent distribution
Record assay results with their spatial distribution, analytical basis and detection limits.
- What are the measured Al2O3 purity and concentrations of relevant trace elements, including chromium, iron and titanium? measurement
- Which constituents occupy the corundum lattice, occur as inclusions or reside on the surface? boundary
Colour and variety assignment
Connect observed appearance to a qualified ruby or sapphire designation.
Variety evidence
Preserve observed colour separately from naming conventions and proposed colour mechanisms.
- What colour, zoning and optical effects are observed under specified illumination and viewing orientation? measurement
- Which convention supports the ruby or sapphire designation, especially at the pink-to-red boundary? definition
Origin and treatment Track formation history, provenance and subsequent modification.
Corundum identity alone cannot establish natural origin, geographic source or treatment status.
Formation and provenance
Separate evidence of natural or synthetic formation from claimed geographic or producer origin.
Origin claim support
Attach origin conclusions to observed growth features, analytical results and traceable records.
- What evidence supports natural, synthetic or undetermined origin for the examined corundum? provenance
- Which locality, producer or growth-method claims are documented, analytically inferred or unsupported? provenance
Modification history
Record treatment evidence and distinguish absence of detection from proof of no treatment.
Treatment assessment
Assess heating, diffusion, filling and coating individually, including the limits of available tests.
- Which treatments are documented, detected, not detected within test limits or untested? provenance
- What treatment depth or distribution must be known before recutting, polishing, cleaning or heating this material? action
Structure and performance Connect crystal or aggregate structure to measured mechanical, optical and thermal behaviour.
Reference mineral properties cannot substitute for measurements of a cracked crystal, porous aggregate or graded powder.
Microstructure and integrity
Describe orientation, grains, pores and defects relevant to material integrity.
Structural condition
Record the distribution and significance of defects at the scale relevant to the proposed use.
- What are the crystal orientation, grain-size distribution, porosity and inclusion distribution? measurement
- Which cracks, parting planes, chips or residual stresses could control failure during the proposed operation? action
Conditional material properties
Capture measured properties with conditions and distinguish reference values from specimen results.
Property evidence
Associate performance claims with methods, orientation, temperature and specimen form.
- Which density, hardness, fracture, optical and thermal properties were measured on this material rather than copied from a reference? measurement
- At what temperature, pressure, wavelength and crystal orientation do the relevant values apply? measurement
- What evidence defines an acceptable operating range for the proposed use? action
Grade and handling decisions Turn material evidence into qualified acceptance and handling decisions.
Corundum's suitability depends on grade, physical form, treatment and the requirements of the intended operation.
Application qualification
Evaluate material against explicit criteria for a named use.
Grade acceptance
Express grade as supported acceptance criteria rather than an unexplained supplier label.
- Which purity, particle-size, defect, transparency or orientation requirements define the proposed grade? definition
- Which results justify acceptance, rejection or further testing for the intended gem, abrasive, optical or ceramic use? action
Identity-linked handling
Connect substance records and handling requirements to the actual material and operation.
Applicable records and controls
Verify identifiers, classification and exposure guidance without transferring assumptions between intact crystals, powders and mixtures.
- Which CAS, EC and PubChem records apply to this corundum material, and do they identify the phase specifically or aluminium oxide more broadly? definition
- Which current SDS, GHS classification and exposure limits apply to the grade, particle fraction and jurisdiction? provenance
- What controls are required for dust, contaminants or treatment-derived constituents during the proposed handling operation? 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.
- This is recalled knowledge, without consulted sources; numerical properties depend on purity, temperature, wavelength and crystal orientation.
- Confirm the phase-specific chemical identifiers and applicable product standards before assigning a regulatory identity.
- Hazard classification and exposure limits require checking the supplied material, particle size, impurities and jurisdiction; no universal classification is asserted here.
- Which of these check these first hold for the sense of corundum this model covers, and on what evidence? provenance
Kinds and varieties
Recalled without web access and unsourced; every item is a lead to verify.
- Ruby
- Blue sapphire
- Fancy-colour sapphire
- Colourless sapphire
- Common non-gem corundum
- Synthetic corundum
- Which of these kinds and varieties hold for the sense of corundum this model covers, and on what evidence? provenance
Identifiers and schemes
Recalled without web access and unsourced; every item is a lead to verify.
- Chemical formula - Al₂O₃ - Identifies the ideal composition; the corundum crystal structure distinguishes it from other alumina phases.
- CAS Registry Number - 1344-28-1 - A general aluminium oxide identifier, not an exclusive identifier for natural corundum or a particular gem variety.
- Hermann-Mauguin space-group notation - R-3c - Space group of the ideal corundum structure.
- Which of these identifiers and schemes hold for the sense of corundum this model covers, and on what evidence? provenance
Real-world use
Recalled without web access and unsourced; every item is a lead to verify.
- Ruby and sapphire gemstones for jewellery.
- Natural and synthetic abrasive grains for grinding and polishing.
- Synthetic sapphire windows and optical components.
- Synthetic sapphire substrates for semiconductor growth.
- Chromium-doped synthetic ruby as a laser gain medium.
- Which of these real-world use hold for the sense of corundum this model covers, and on what evidence? provenance
Typical measurements
Recalled without web access and unsourced; every item is a lead to verify.
- Mohs hardness - 9 - Mohs scale
- Density near room temperature - 3.97-4.05 - g/cm³
- Melting temperature of high-purity material near atmospheric pressure - 2040-2055 - °C
- Refractive indices at visible wavelengths - 1.76-1.77 - dimensionless
- Birefringence at visible wavelengths - 0.008-0.010 - dimensionless
- Which of these typical measurements hold for the sense of corundum 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.
- High scratch hardness does not prevent brittle fracture, impact chipping or failure at existing flaws.
- Rapid or uneven heating can produce thermal stresses and cracking.
- Grinding and cutting generate airborne particulate; impurities in natural abrasive mixtures can introduce additional hazards.
- Twinning and other structural weaknesses can produce parting despite the absence of true cleavage.
- Fracture fillings and other gemstone treatments can affect durability and response to heat or chemicals.
- Which of these failure modes and hazards hold for the sense of corundum this model covers, and on what evidence? provenance
Regional variation
Recalled without web access and unsourced; every item is a lead to verify.
- The trade boundary between ruby and pink sapphire varies among markets and gemmological practices.
- Geographic deposits differ in trace elements, inclusions and typical appearance, but these differences do not create separate mineral species.
- Which of these regional variation hold for the sense of corundum 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.
- Alumina - Alumina denotes aluminium oxide more broadly; corundum specifies its alpha crystalline structure.
- Ruby - Ruby is the red gem variety of corundum, with its characteristic colour principally produced by chromium.
- Sapphire - Sapphire is gem corundum other than ruby; it is not restricted to blue material.
- Emery - Emery is a natural abrasive rock containing corundum mixed with other minerals, rather than pure corundum.
- Spinel - Gem spinel is principally MgAl₂O₄ with a cubic structure, rather than trigonal Al₂O₃.
- Silicon carbide - Silicon carbide is SiC, a chemically distinct abrasive sometimes confused with corundum through the trade name carborundum.
- Which of these neighbouring kinds and how to tell them apart hold for the sense of corundum this model covers, and on what evidence? provenance
What the second pass must settle
- Which authoritative CAS, EC and PubChem records distinguish corundum from broader aluminium oxide entries, and how should overlapping identifiers be represented?
- Which application-specific standards define acceptable corundum purity, grit size, optical quality and mechanical performance?
- Which laboratory conventions govern the ruby versus pink sapphire boundary, and how should conflicting variety assignments be retained?
- What detection limits constrain natural-origin and treatment conclusions, particularly for subtle heating, diffusion or mixed-origin material?
- Which sources establish phase stability, melting and any meaningful boiling or decomposition data under stated conditions, and which current exposure limits apply to the actual powder grade and contaminants?