6 min read · Updated 23 July 2026
Silica Sand Grades Explained: Construction vs Industrial vs Glass vs Foundry vs Frac
Silica sand is graded mainly by its silica (SiO₂) purity, iron oxide (Fe₂O₃) content and grain size. Construction grade is washed building sand; industrial grade is 99%+ SiO₂ for filtration and blasting; glass grade is ultra-pure (99.5%+ SiO₂, Fe₂O₃ below 0.02%); foundry grade is refractory casting sand graded by AFS fineness; and frac grade is high-crush-strength proppant for oil and gas.
What decides a silica sand grade?
Three properties do most of the work when classifying silica sand: chemical purity (how much of the sand is SiO₂), iron content (Fe₂O₃, which colours glass and affects some processes), and the physical grain size and shape (the particle size distribution, or PSD).
Different industries weight these differently. A glassmaker cares most about low iron and high purity; a foundry cares about grain shape, fineness and refractoriness; a builder mostly needs clean, well-graded sand.
Grade-by-grade comparison
The table below summarises how the common grades differ and where each is used.
| Grade | Typical SiO₂ | Key property | Main uses |
|---|---|---|---|
| Construction | Standard | Washed, well-graded, clay-free | Concrete, mortar, plaster, asphalt |
| Industrial | 99%+ | High purity, precise grading | Water filtration, abrasive blasting, chemicals |
| Glass | 99.5%+ | Ultra-low iron (Fe₂O₃ < 0.02%) | Container, flat and specialty glass |
| Foundry | High | Refractoriness, AFS grain fineness | Metal casting (moulding and core sand) |
| Frac | High | Crush strength, sphericity | Hydraulic fracturing proppant |
Which grade do you need?
Match the grade to your process, then confirm the exact specification with your supplier before ordering.
- Building and civil work → construction grade.
- Water treatment, sandblasting or chemicals → industrial grade.
- Glass of any kind → glass grade (check the iron limit).
- Casting metal → foundry grade (specify your AFS number).
- Oil and gas fracturing → frac grade (specify mesh and crush strength).