gypsum
Enable an AI agent to recognise gypsum, assess the condition and suitability of a particular specimen or material lot, and identify justified handling, processing or use decisions.
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.
Researched by: Codex + Grok
Purpose and description
Enable an AI agent to recognise gypsum, assess the condition and suitability of a particular specimen or material lot, and identify justified handling, processing or use decisions.
Gypsum is the monoclinic evaporite mineral and industrial calcium sulfate dihydrate (CaSO4·2H2O) produced both as a rock-forming mineral and as a process by-product, distinguished from anhydrite and hemihydrate by its two waters of crystallization.
It can be Select representative samples and request evidence that distinguishes gypsum from other mineral phases.; Compare gypsum lots against a named use specification using phase composition, impurities, moisture and particle size.; Segregate or hold material whose identity, contamination or exposure history remains unresolved.; Evaluate crushing, screening, washing or drying proposals against the required resulting material condition.; Track conversion into another calcium sulfate material and link the resulting material to its appropriate model.; Assess recovered gypsum for a specified reuse route using documented separation and qualification evidence..
Distinguishing features
Confirm calcium sulfate dihydrate identity rather than relying on a generic calcium sulfate label; gypsum has this composition, while crude material may contain other minerals. [USGS: Mineral resource of the month - gypsum](https://www.usgs.gov/publications/mineral-resource-month-gypsum)
Require phase-sensitive identification capable of distinguishing gypsum from bassanite and anhydrite; a shared calcium-and-sulfate result does not resolve mineral identity. [USGS: Spectral properties of Ca-sulfates](https://www.usgs.gov/publications/spectral-properties-ca-sulfates-gypsum-bassanite-and-anhydrite)
For material confused with limestone or chalk, require evidence distinguishing a sulfate-bearing phase from a carbonate-bearing phase rather than accepting white colour or powder texture.
For material labelled plaster or drywall, determine whether the referent is gypsum itself, a transformed binder, or a composite containing gypsum before assigning this model.
Treat clear crystals, fibrous material and massive material as identification candidates requiring mineral evidence, rather than creating separate registered things from appearance alone.
Scope
+ Identification of the gypsum mineral phase and distinction from other calcium sulfate phases
+ Gypsum specimens, granular material, powders and identifiable gypsum constituents
+ Natural, manufactured and recovered material origins and their implications for testing
+ Phase proportions, impurities, free moisture, particle form and observed condition
+ Evidence supporting handling, processing, recovery and intended-use suitability
- Geological deposits, resource estimates and mine operations
- Hemihydrate plaster and anhydrite as independently identified materials
- Wallboard, plaster assemblies and finished building-product performance
- Soil systems, crop requirements and amendment application prescriptions
- Kilns, manufacturing processes and processing equipment
- Waste-management facilities and transport operations
Characteristics
- Mineral-phase identity
- gypsum confirmed | gypsum-bearing mixture | suspected gypsum | other phase identified | unresolved Determines whether this model applies to the material or only to a constituent.
- Gypsum phase fraction
- mass %, with analytical method, uncertainty and reporting basis Separates mineral identity from bulk purity and supports comparisons between lots.
- Other calcium sulfate phases
- mass % of each identified phase, with detection limits and sample preparation Supports assessment of mixed-phase material and possible transformation.
- Source route
- natural extraction | industrial production or recovery | product recycling | mixed | unknown Directs provenance questions and the selection of impurity tests.
- Source and host association
- links to source deposit, generating process, recovered product, host material and parent lot as applicable Preserves material context without making a host object or source process part of gypsum identity.
- Non-gypsum constituents
- constituent-specific mass % or mg/kg, with method, detection limit and reporting basis Provides evidence for processing compatibility and intended-use acceptance.
- Free moisture
- mass %, with wet or dry basis and a method accounting for possible loss of structural water Supports handling and mass accounting without confusing surface water with hydration state.
- Particle-size distribution
- sieve fractions or d10, d50 and d90 in µm or mm, with method Supports decisions about screening, milling, segregation and feed consistency.
- Physical presentation
- individual crystal | massive specimen | crushed rock | granules | powder | slurry | constituent in a composite Determines how the material can be sampled, handled and assessed.
- Observed material condition
- recorded observations of wetting, caking, breakage, surface loss, foreign matter or suspected phase change Identifies reasons to segregate material or repeat testing.
- Thermal and water-exposure history
- links to dated heating, drying, wetting and storage events with known conditions Connects current measurements to events that may have altered the material.
- Intended-use qualification
- unassessed | evidence incomplete | accepted for named use | conditionally accepted | rejected for named use Prevents a general gypsum identity claim from being treated as approval for every application.
Also called
Where this came from
wikidata · CC0 1.0
Also registered as vr.tr.gypsum
Drafted structure
Bundle to layer to finding to question, as the second pass will find it: 6 bundles · 11 layers · 18 findings · 32 questions.
Gypsum identity and boundary Establish what the material is and whether gypsum names the whole referent or a constituent.
Calcium sulfate labels and gypsum-containing products can obscure the distinction between mineral identity and product identity.
Mineral phase identification
Resolve gypsum identity against competing phase interpretations.
Dihydrate identification evidence
Record the observations, analytical interpretation and limitations supporting gypsum identification.
- What evidence identifies the sampled material as gypsum rather than merely a calcium sulfate? definition
- Which method distinguishes gypsum from bassanite, anhydrite and other detected phases, and with what uncertainty? measurement
Material referent
Determine the portion of a specimen, lot or product to which this model applies.
Whole material or constituent
Separate gypsum material assertions from assertions about mixtures and finished objects.
- Does the name gypsum refer to a mineral specimen, a bulk material lot or a constituent within another object? boundary
- Which host, mixture or product model owns properties that cannot be attributed to the gypsum constituent alone? boundary
Origin and composition Connect gypsum origin and processing lineage to measured composition.
A common mineral identity does not establish equivalent impurity profiles or suitability across source routes.
Gypsum source route
Identify how the material arose and what was combined into the current lot.
Generation and recovery lineage
Record extraction, industrial generation or product-recovery evidence relevant to material assessment.
- Which deposit, generating process or recovered product supplied this gypsum, and what records substantiate that origin? provenance
- Which source lots, additives or recovered fractions were combined before the current sample was taken? provenance
Phase and impurity profile
Resolve gypsum content and accompanying constituents on an explicit analytical basis.
Composition and sampling confidence
Establish how well measured phase fractions and impurities describe the lot.
- What are the measured gypsum, other calcium sulfate and non-gypsum fractions, with methods and reporting bases? measurement
- How does sampling account for segregation, visible inclusions or variation across the gypsum lot? measurement
- Which additional constituents require testing because of this source route and proposed use? action
Physical form and water condition Characterise the gypsum's presentation, particle population and water-related condition.
Gypsum identity alone cannot determine sample representativeness, handling behaviour or the meaning of a moisture result.
Crystal and particle form
Describe intact specimens and processed particle populations at the scale relevant to the intended action.
Form and size evidence
Record morphology, particle size and aggregation without treating appearance as sufficient identification.
- Is the gypsum present as intact crystals, massive material, particles, slurry solids or an embedded constituent? definition
- What measurements describe particle size, fines and agglomerates at the scale required for sampling or processing? measurement
Free water and observed change
Separate measured free moisture from structural-water questions and record physical changes.
Moisture and condition assessment
Interpret water measurements alongside caking, wetting and specimen deterioration observations.
- What is the free-moisture content, and how does the method account for possible structural-water loss? measurement
- What evidence of caking, surface loss, breakage or water exposure requires resampling or a change in handling? action
Phase change and processing Track interventions that may alter gypsum condition, composition or mineral identity.
An agent must distinguish preparation of gypsum from conversion into a different material and verify the actual outcome.
Thermal and hydration history
Relate exposure records to evidence about current calcium sulfate phases.
Exposure-linked phase state
Record known treatment conditions and identify where phase reassessment is needed.
- What heating, drying or water-contact events occurred, with temperature, duration and environmental conditions where known? provenance
- What before-and-after phase measurements establish whether gypsum identity was retained or changed? measurement
Processing outcome and handoff
Define acceptable results of preparation or conversion and assign resulting material identity.
Intervention acceptance
Tie processing permission to an intended material outcome and a verification requirement.
- For the proposed crushing, screening, washing, drying or thermal conversion, what resulting phase composition and physical condition are required? action
- What measured outcome requires a link to a different material model rather than continued identification of the output as gypsum? boundary
- Which post-treatment checks must pass before the resulting lot is released for its intended use? action
Use qualification and recovery Determine which proposed uses and recovery routes have adequate material-specific evidence.
Gypsum identification does not establish application fitness, contaminant acceptance or equivalence between virgin and recovered feedstocks.
Application-specific acceptance
Evaluate material evidence against a named receiving process or application.
Qualified use envelope
Record the scope and conditions of an acceptance decision without importing whole-system performance claims.
- Which intended use and identified specification define acceptable gypsum content, impurities, moisture and particle size? boundary
- Which lot-specific results satisfy those requirements, and which unresolved results prevent acceptance? measurement
- What material or storage change invalidates the qualification and triggers reassessment? action
Handling and recovered feedstock
Support material-specific handling and reuse decisions from actual condition and separation evidence.
Handling and recovery readiness
Identify restrictions and required checks arising from fine particles, residual host materials or uncertain contamination.
- What handling controls are justified by the gypsum's particle form, constituent test results and applicable material documentation? action
- For recovered gypsum, what evidence establishes removal or acceptable levels of paper, coatings, adhesives and other host-material residues? measurement
- Which named receiving route can accept this lot, and what unresolved evidence requires segregation or further treatment? 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.
Kinds and varieties
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- Natural rock gypsum (massive bedded evaporite)
- Selenite (transparent crystalline gypsum)
- Satin spar (fibrous gypsum)
- Alabaster (fine massive gypsum for carving)
- FGD / synthetic gypsum from flue-gas desulfurization
- Phosphogypsum from wet-process phosphoric acid
- Recycled gypsum from construction and demolition board
- Agricultural gypsum (soil amendment grade)
- Which of these kinds and varieties hold for the sense of gypsum this model covers, and on what evidence? provenance
Identifiers and schemes
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- Wikidata - Q3962 - Item for the mineral gypsum.
- IMA-CNMNC - Gypsum (symbol Gp) - Approved mineral species; formula CaSO4·2H2O.
- CAS Registry Number - 13397-24-5 - Gypsum as a natural/commercial substance; dihydrate chemistry is also indexed as 10101-41-4.
- EC number - 231-900-3 - Calcium sulfate (covers the sulfate family rather than the dihydrate alone).
- HS / Harmonized System - 2520 - Gypsum, anhydrite, and plasters (consisting of calcined gypsum).
- Nickel-Strunz - 7.CD.40 - Sulfate class, hydrated calcium sulfate.
- Mindat mineral id - 1784 - Mineral species record for gypsum.
- Which of these identifiers and schemes hold for the sense of gypsum this model covers, and on what evidence? provenance
Standards and regulation
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- ASTM C22/C22M - Standard Specification for Gypsum (ASTM International)
- ASTM C28/C28M - Gypsum plasters (ASTM International)
- ASTM C1396/C1396M - Gypsum board (ASTM International)
- ASTM C471/C472 - chemical and physical testing of gypsum and gypsum products (ASTM International)
- EN 13279 - Gypsum binders and gypsum plasters (CEN)
- EN 520 - Gypsum plasterboards (CEN)
- 40 CFR 61 Subpart R - radon emissions and reuse limits for phosphogypsum (US EPA)
- OSHA PELs for calcium sulfate / gypsum dust: 15 mg/m3 total, 5 mg/m3 respirable (US OSHA)
- Food additive E516 calcium sulfate where food-grade sulfate, not mineral gypsum, is specified (EU / Codex practice)
- Which of these standards and regulation hold for the sense of gypsum this model covers, and on what evidence? provenance
Real-world use
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- Feedstock for gypsum wallboard (drywall / plasterboard), the dominant construction use.
- Set retarder in Portland cement clinker grinding, typically a few percent gypsum or anhydrite.
- Interior plasters, mouldings, joint compounds, and fire-rated assemblies that rely on dehydration of the dihydrate.
- Agricultural soil amendment for calcium and sulfate supply and for reclaiming sodic soils.
- Dental, orthopedic, and art plasters after calcination to hemihydrate (plaster of Paris).
- Carving stone as alabaster; optical/cleavage crystals as selenite.
- Marketed synthetic gypsum from coal-plant FGD units, often substituting for mined rock in wallboard plants.
- Which of these real-world use hold for the sense of gypsum this model covers, and on what evidence? provenance
Typical measurements
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- Combined water (loss on dehydration of the dihydrate) - 19-21 (theoretical 20.9) - mass %
- Mohs hardness - 2 - Mohs
- Specific gravity - 2.31-2.33 - g/cm3
- Aqueous solubility (near 20-25 °C) - 2.0-2.6 - g/L
- Dehydration to hemihydrate - about 100-160 - °C
- CaSO4·2H2O purity of commercial rock or FGD gypsum - 80-98 (FGD often >95) - mass %
- Ra-226 in phosphogypsum proposed for agricultural use (US EPA ceiling) - ≤10 (370 Bq/kg) - pCi/g
- Which of these typical measurements hold for the sense of gypsum this model covers, and on what evidence? provenance
Failure modes and hazards
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- Dissolution and karst collapse in gypsum terrains; settlement of foundations on gypsum soils.
- Moisture damage of paper-faced board: mould, loss of strength, and fastener pull-out.
- Fire performance of board is lost once the dihydrate is fully dehydrated and the core disintegrates.
- Excess gypsum in cement can cause flash/false set or later sulfate-related expansion.
- Phosphogypsum carries Ra-226 and radon; stacking and most building reuse are restricted.
- Wet gypsum against steel or aluminium can drive corrosion; some imported boards have off-gassed reduced sulfur compounds.
- Nuisance dust; not a high-toxicity mineral, but respirable dust is regulated.
- Under reducing conditions, sulfate from gypsum can feed hydrogen sulfide generation.
- Which of these failure modes and hazards hold for the sense of gypsum this model covers, and on what evidence? provenance
Regional variation
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- United States: 'drywall'/'sheetrock'; wallboard plants now run largely on FGD gypsum rather than mined rock.
- United Kingdom and much of Europe: 'plasterboard'; product classified under EN 520 / EN 13279 rather than ASTM C1396.
- German trade still distinguishes calcination grades (e.g. Stuckgips vs Estrichgips) even after EN harmonisation.
- Phosphogypsum practice is locally specific: large stacks in Florida, North Africa, Brazil and India, with agricultural or fill reuse allowed only under activity limits.
- Alabaster carving traditions are concentrated historically in Volterra (Italy) and parts of Spain and Egypt.
- The name plaster of Paris records the Montmartre gypsum workings; it now means hemihydrate plaster worldwide.
- Which of these regional variation hold for the sense of gypsum this model covers, and on what evidence? provenance
Neighbouring kinds and how to tell them apart
Reported by the breadth pass; each item needs checking against its source before it becomes normative.
- Anhydrite (CaSO4) - No water of crystallization: loss on heating near 100-200 °C is negligible for anhydrite (~21% for gypsum); anhydrite is harder (Mohs ~3-3.5) and denser.
- Bassanite / plaster of Paris (CaSO4·½H2O) - Combined water ~6.2% versus ~20.9%; hemihydrate sets with water to regenerate gypsum.
- Calcite / chalk (CaCO3) - Dilute HCl: calcite effervesces strongly, gypsum does not; fingernail scratches gypsum, not typical calcite.
- Halite - Halite tastes salty and is highly water-soluble; gypsum is only sparingly soluble and not salty.
- Barite (BaSO4) - Barite specific gravity ~4.5 versus ~2.3; barite is much less soluble and harder.
- Which of these neighbouring kinds and how to tell them apart hold for the sense of gypsum this model covers, and on what evidence? provenance
Sources
- Mineral Commodity Summaries: Gypsum - Industrial supply, FGD vs mined gypsum, wallboard and cement uses, typical US production practice.
- Gypsum (Q3962) - Canonical identifier, formula CaSO4·2H2O, IMA mineral status, CAS and HS crosswalks.
- ASTM C22/C22M Standard Specification for Gypsum - Product specification for gypsum as a construction raw material in North America.
- EN 13279 Gypsum binders and gypsum plasters - European classification of building gypsums and plasters by calcination and intended use.
- 40 CFR Part 61 Subpart R - National Emission Standards for Radon Emissions from Phosphogypsum Stacks - US restriction of phosphogypsum, including the 10 pCi/g Ra-226 agricultural-use limit.
What the second pass must settle
- With no registry definition recorded, should vr.tr.gypsum cover both the mineral species and commercial gypsum-rich bulk materials, and how should that boundary be expressed without inventing a purity threshold?
- Does an existing Vercy world model already own this concept, and which neighbouring entries own plaster, bassanite, anhydrite and gypsum-containing products?
- Which analytical and sample-preparation methods should be recognised for phase quantification and free-moisture measurement without materially changing the sample?
- Which source-route-specific impurity panels and application-specific acceptance criteria are supported by authoritative evidence for the intended jurisdictions?
- What evidence-based exposure or condition changes should trigger phase reassessment, renewed use qualification or rejection of recovered gypsum?