Decorative / art mineral
- Process role: Natural crystalline material selected for transparency, habit and size
- Critical parameters: Visual grade; piece size; breakage; inclusions
TECHNICAL PROCUREMENT INTELLIGENCE
Gypsum - Selenite Variety (CaSO₄·2H₂O)
Crystalline Calcium Sulfate Dihydrate for Mineral, Decorative and Specification-Controlled Industrial Applications
Selenite is a transparent-to-translucent crystalline variety of gypsum (calcium sulfate dihydrate), not a selenium-containing 'selenite' chemical. For industrial procurement, the page should distinguish decorative/mineral selenite from processed gypsum and from food/pharmaceutical calcium sulfate grades. Application claims must follow the actual grade, particle size, purity and certification supplied.
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Extraction & Purification
CHEMISTRY, MANUFACTURING CONTEXT & MATERIAL BEHAVIOUR
Gypsum is CaSO₄·2H₂O. On controlled heating it loses crystal water, forming calcium sulfate hemihydrate (plaster of Paris) and, with further dehydration, anhydrite forms. This reversible hydration/dehydration chemistry underpins the setting behaviour of calcined gypsum products. Natural selenite is a crystal-habit variety of gypsum; it should not be marketed as if it were a distinct chemical composition.
PROCESS-ENGINEERING & GRADE-SELECTION CONSIDERATIONS
- Rename the product page to avoid confusion with the selenite oxyanion SeO₃²⁻ and selenium salts such as sodium selenite. This is gypsum / calcium sulfate dihydrate.
- Remove 'brown green' and 'earthy/dull' as defining selenite appearance. Pure selenite is typically colorless and transparent/translucent; natural impurities can change color.
- Do not imply that bulk natural selenite is automatically suitable for food, pharmaceutical or cosmetic use. Those markets require specific calcium sulfate grades, impurity limits and certifications.
- For industrial gypsum, define CaSO₄·2H₂O assay, free moisture, particle-size distribution, whiteness/color, insolubles and trace-element limits according to application.
- Bulk/big-bag logistics are appropriate for processed mineral grades, while decorative crystal pieces require size/visual grading and breakage-controlled packaging.
◎ Technical Specifications
| Property | Value |
|---|---|
Chemical identity |
Calcium sulfate dihydrate / gypsum |
Formula |
CaSO₄·2H₂O |
CAS |
10101-41-4 for calcium sulfate dihydrate (identity databases); food-additive specifications may reference calcium sulfate CAS 7778-18-9 |
Molar mass |
172.17 g/mol |
Crystal system |
Monoclinic |
Appearance |
Pure selenite is typically colorless and transparent/translucent; impurities can impart color Mohs hardness: 2 |
Specific gravity |
~2.30-2.33 for pure gypsum |
Thermal behaviour |
Dehydrates on heating to hemihydrate/anhydrite phases; behaviour depends on temperature and conditions |
Commercial distinction |
Natural selenite pieces/crystals ≠ industrial gypsum powder ≠ certified food/pharma calcium sulfate |
INDUSTRIAL APPLICATION MATRIX
Industrial gypsum feedstock
- Process role: Calcium sulfate dihydrate raw material
- Critical parameters: Assay; moisture; PSD; impurities; processing route
Agricultural gypsum
- Process role: Calcium and sulfate soil amendment where specification permits
- Critical parameters: Purity; fineness; neutralizing/soil program context; contaminants
Food-grade calcium sulfate
- Process role: Firming/dough-conditioning/sequestration uses under applicable food rules
- Critical parameters: Certified food grade; assay; Pb/F/Se limits; regulatory compliance
Pharma/cosmetic calcium sulfate
- Process role: Application-specific excipient/mineral use
- Critical parameters: Pharmacopeial/cosmetic grade; microbial/trace impurity requirements as applicable
QUALITY CONTROL, COA PARAMETERS & TEST FOCUS
The CaSO₄·2H₂O assay or calcium sulfate content is assessed using validated wet chemistry or XRF, as applicable, to support chemical-grade verification and process yield evaluation. Loss on drying or free moisture is determined gravimetrically to assess storage suitability, flow behavior and material balance.
Particle-size distribution is measured by sieving or laser diffraction to evaluate reactivity, handling and formulation suitability. Whiteness or color is assessed using a colorimeter or visual standard to verify decorative and formulation quality, while acid-insoluble matter is determined gravimetrically to control mineral impurities.
Trace elements are measured using ICP or AAS where specified to assess compliance with applicable food, pharmaceutical or agricultural requirements. Crystal or piece grading is performed through visual and dimensional inspection to verify decorative selenite quality.
STORAGE, HANDLING, MATERIALS COMPATIBILITY & HSE
Calcium sulfate dihydrate is generally low-hazard, but mining, crushing and powder handling can generate respirable nuisance/mineral dust. Use dust extraction, suitable respiratory protection where risk assessment requires it, eye protection and good housekeeping. Natural mineral supply should also be assessed for source-specific silica or trace impurities rather than assuming all gypsum has the same dust profile.
PACKAGING, TRANSPORT & SUPPLY PLANNING FOR GCC / MENA
Processed gypsum may be supplied in bags, big bags or bulk depending on grade and volume. Natural decorative selenite should use breakage-controlled unit packaging. Keep dry, prevent cross-contamination, and define pallet/bulk handling according to particle or piece size. Food/pharma grades require dedicated hygienic packaging and traceability.
Why Choose OGSCM?
Application-Driven Solutions
We match the right grade to your process needs.
Reliable Supply Chain
On-time delivery with strong regional & global logistics.
Quality You Can Trust
Strict quality control and batch consistency.
Expert Support
Technical & commercial support throughout your procurement journey.
Regional Presence
Serving industries across GCC and MENA with local expertise.
Frequently Asked Questions
No. Mineral selenite is a variety of gypsum, CaSO₄·2H₂O. The name can be confused with selenium oxyanions, so the page should state this clearly.
No. It is a crystalline habit/variety of gypsum with the same calcium sulfate dihydrate composition.
Not by assumption. Regulated uses require the appropriate calcium sulfate specification, impurity limits and documentation.
It loses water of crystallization, forming hemihydrate and then more dehydrated calcium sulfate phases depending on conditions.
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