ENWhat Is Silica Sand? Properties, Specs and How It Is Processed
Silica sand defined in buyer terms, try each industry specifies, how rock becomes graded sand, and which machines the flow needs.
Silica sand is sand in which the quartz has won. Commercially the term means at least 95% silicon dioxide by mass, in a grain window of roughly 0.1–2 mm, clean enough of clay, feldspar and iron oxide to pass the buyer’s process. Everything else about the product, cessing flow, the equipment it needs, om how far above 95% a deposit sits and how much iron has to come out before it ships.
The chemistry buyers actually specify
| Application | Typical SiO2 | Typical iron (Fe2O3) limit | Typical grain window |
|---|---|---|---|
| Container and flat glass | 98.5%+ | below 0.1% | 0.1–0.6 mm |
| Foundry casting sand | 96%+ | moderate, coating-dependent | graded to the casting size |
| Water filtration | 95%+ | low | 0.5–2 mm, laid in layers |
| Sports turf infill | 90%+ | cosmetic only | 0.3–1 mm, rounded |
These are typical windows, not a standard. Every industry and every buyer writes the numbers slightly differently, and a “0.1–0.6 mm glass sand” quoted against one buyer’s sheet will fail another’s. Always quote against the buyer’s specification, never against a nominal purity.
Why iron is the whole game
Iron oxide is the expensive contaminant. In glass it tints the melt green and ruins the grade; in foundry work it drives burn-on defects at the mould face. Two facts make it the central problem of the whole business. First, the iron usually arrives as surface coatings and stain on the grains, not inside the quartz, be washed off, but only with real machinery. Second, every stage of the flow that touches steel adds a little iron back, which means the washing and attrition stages are not accessories; they are where the grade is actually made.
Quartz sand, river sand and crushed sand
Deposits decide the starting point. Weathered sandstone and dune sand arrive already graded and only need cleaning; river sand needs washing and grading; and a hard quartzite deposit needs the full crushing train before it looks like sand at all. Crushed sources also produce angular grains, which sell fine for filtration and foundry work but need VSI rounding before they satisfy buyers who specify roundness, h and turf infill both do.
From rock to graded sand: the processing flow
- Scrubbing or log washing, to strip the clay coatings off the feed
- Primary crushing of the oversize lumps the screen deck rejects
- Shaping and finishing of the coarse fraction, eduction, VSI for roundness
- Screening into the grain windows the target spec names
- Attrition scrubbing, to knock surface staining off the grains themselves
- Hydraulic classification, to cut the fines curve the screens cannot
- Dewatering and stockpiling by grade, each grade kept separate from the first pile onward
Which machines the flow needs
| Stage | Machine type | Why it is there |
|---|---|---|
| Oversize crushing | Jaw crusher | Takes the lumps the screen deck rejects; quartz is abrasive, so compression crushing keeps wear cost sane |
| Shaping the coarse fraction | VSI sand maker | Rounds crushed grains to the shape buyers specify |
| Sizing | Vibrating screen | Cuts the grain windows the spec names; wet screening where clay is heavy |
| Washing and classification | Log washer, attrition cells, cyclones | Removes clay and surface iron, hat makes or breaks the grade |
The crushing and screening stages are covered on the jaw crusher, VSI sand-making and screening plant range pages; this dry plant is the part of the flow SUHMAN builds. Washing and classification are a separate equipment family, lones, attrition cells, ually sourced from a specialist; the flows meet at the screen house.
How a deposit gets qualified before anyone quotes
A silica sand prospect is a chemistry claim, and buyers test the claim before they test the price. The routine starts with a representative sample, 5–10 kg taken across the working face, not a handful from the pile, split in the lab. Grain size distribution runs through a sieve stack from about 63 microns to 2 mm, which gives the grading curve every downstream decision depends on. Chemistry comes off an XRF or wet assay: SiO2, and above all Fe2O3, reported to two decimal places, because the difference between 0.08% and 0.12% iron is the difference between glass grade and construction grade.
Two more tests matter on specific specs. Roundness and sphericity, measured against Krumbein charts, decide foundry and turf suitability. Acid insoluble residue and clay fraction indicate how hard the washing stage will have to work, he number that quietly decides the processing plant budget. A deposit that assays well but scrubs poorly can cost more to bring to grade than a weaker deposit that washes clean.
Common questions
Can crushed quartzite be a source of silica sand?
Yes. Hard quartz deposits are crushed, shaped in a VSI and washed to the same chemistry as naturally weathered sand. The flow just costs more: every crushing stage on quartzite is heavy on wear metal, and every steel contact adds iron that the washing plant has to take back out.
Is silica sand dangerous?
The product is not; the dust is. Respirable crystalline silica is a documented occupational hazard, which is why serious processing flows favour wet methods end to end and why dry stockpiles need dust suppression. Handling graded sand as a product is routine work; cutting, sweeping or blasting dry silica dust is not.
What does glass-grade sand sell for, compared with construction sand?
Typically several times the price per tonne, because the iron specification is unforgiving and the flow to meet it is longer. That premium is what pays for the washing, attrition and classification stages construction sand never needs, mediocre deposit near the right market can outperform a better one far from it.
The grain-size vocabulary overlaps with construction aggregate, and the coarser end of a silica operation reads against the same size-to-use conventions as any quarry, ence is only how tightly the iron and fines limits are written.
