Satin spar is a fibrous, translucent variety of gypsum (calcium sulfate dihydrate – CaSO₄·2H₂O) distinguished by its parallel fibrous crystal growth and characteristic silky, satin-like luster.
It commonly forms in veins within evaporite deposits and is visually and structurally distinct from:
• Selenite – transparent, crystalline plates
• Alabaster – massive, fine-grained gypsum
Satin spar is used primarily for decorative, ornamental, and lighting applications and has no structural or metallurgical role.
Chemical Composition
| Component | Typical Content |
|---|---|
| Calcium Sulfate Dihydrate (CaSO₄·2H₂O) | 96 – 99% |
| Water of Crystallization | ~20.9% |
| Silica (SiO₂) | <0.5% |
| Carbonates | Trace |
| Iron Oxides / Organic Matter | Trace |
✔ High chemical purity
✔ Minimal insoluble residue
Key Physical Properties
| Property | Typical Value |
|---|---|
| Crystal System | Monoclinic |
| Crystal Habit | Fibrous, columnar |
| Density | 2.2 – 2.35 g/cm³ |
| Color | White, cream, pale grey |
| Luster | Silky, satin |
| Transparency | Translucent |
| Mohs Hardness | ~2 |
| Cleavage | Perfect (parallel to fibers) |
| Dehydration Temperature | ~100 – 150 °C |
⚠ Soft and easily scratched
⚠ Fibrous structure gives directional behavior
Key Mechanical Properties
| Property | Typical Range |
|---|---|
| Compressive Strength | 20 – 45 MPa |
| Tensile Strength | 3 – 8 MPa (parallel to fibers) |
| Flexural Strength | Low |
| Impact Resistance | Poor |
| Abrasion Resistance | Very Low |
| Elastic Modulus | ~6 – 14 GPa |
⚠ Stronger along fiber direction
⚠ Very fragile across fibers
Strengthening & Metallurgical Behavior
Strengthening behavior:
Satin spar’s fibrous structure provides anisotropic strength.
Mechanical performance may be improved by:
• Resin impregnation
• Preserving fiber alignment
• Laminated mounting
Metallurgical behavior:
🚫 No metallurgical application. Satin spar dehydrates at low temperature and
converts to:
• Plaster of Paris
• Anhydrite
Key Characteristics
✔ Satin-like silky luster
✔ Directional light reflection
✔ Fibrous crystal texture
✔ Easy cleavage into rods or slabs
✔ Moisture-sensitive
✔ Non-structural
Refining & Processing Properties
Extraction:
• Hand quarrying from veins
• Minimal blasting
• Selective extraction to preserve fibers
Processing:
• Cutting along fiber axis
• Shaping and trimming
• Light polishing
• Optional surface sealing
Thermal processing:
• Limited to specialty plaster production
• Low-temperature dehydration only
Available Forms
✔ Natural satin spar rods
✔ Polished sticks and slabs
✔ Decorative panels
✔ Carved ornaments
✔ Beads and cabochons
✔ Ground powder (limited use)
Applications
Decorative & Aesthetic:
• Interior décor elements
• Lamps and light diffusers
• Sculptural accents
• Ornamental stones
Industrial (Limited):
• Specialty plaster
• Teaching mineral structures
• Crystal growth demonstrations
Commercial Decorative Use:
• Display stones
• Interior wellness décor
• Architectural accents
Advantages of Satin Spar Gypsum
✔ Unique silky visual effect
✔ Excellent light diffusion
✔ Easy to shape
✔ Low processing cost
✔ Naturally fibrous texture
Why Choose Satin Spar Gypsum
Satin spar gypsum is the preferred decorative gypsum variety where visual appeal, light diffusion, and silky texture are required. It offers a distinctive aesthetic not found in selenite or alabaster and is ideal for indoor ornamental and lighting applications.
Comparison of Gypsum Varieties
| Feature | Selenite | Satin Spar | Alabaster |
|---|---|---|---|
| Structure | Crystalline | Fibrous | Massive |
| Transparency | High | Moderate | Low – Moderate |
| Luster | Glassy | Silky | Dull |
| Carvability | Limited | Moderate | Excellent |
| Decorative Use | Panels | Lamps | Sculptures |