Washing and Sortex colour sorting

From rock to grade

1. Rock selectionOnly white vein quartz is accepted. Rock with visible iron staining or attached host rock is rejected before processing.
2. CrushingStaged crushing breaks the rock into angular grit while keeping fines under control.
3. GrindingGrit is ground to sand sizes and, for fillers, milled to flour below 45 µm.
4. WashingWater washing and scrubbing remove clay, dust and surface stains that carry iron and alumina.
5. ScreeningVibrating screens separate the material into the ordered size bands.
6. Sortex optical colour sortingHigh-resolution cameras inspect the falling grains; air jets reject any grain darker or more coloured than the set threshold.
7. Lab test and packingEach lot is tested for chemistry and grain size, then packed in 1,250 kg FIBC.

Washing

Most impurities in crushed quartz sit on the grain surface, not inside the crystal: clay, fine dust and iron-oxide films. Washing removes them before they become part of the product.

• Water washing flushes out clay and ultra-fine dust.
• Scrubbing rubs grains against each other to clean stained surfaces.
• Desliming removes the finest fraction, which carries most of the alumina.
• Drying delivers free-flowing, dry sand for packing.

The result, measured: loss on ignition only 0.18–0.21 % and low Al₂O₃ across all four grades.

Sortex optical colour sorting

AMASIS quartz is sorted on Sortex optical colour sorters, the final purity gate. They do what no screen or washer can: look at every single grain.

1. Feed: washed, screened grains fall in a thin, even curtain.
2. Inspect: high-resolution line cameras photograph each grain against a reference background, thousands of times a second.
3. Decide: software compares every grain’s colour with the white quartz standard.
4. Eject: within milliseconds, a jet of compressed air knocks out any dark, stained or off-colour grain.

The result, measured: Fe₂O₃ 100–106 ppm and whiteness 92.9–93.9 % across all four grades.

Quality control

• Lab report for every lot: SiO₂, Fe₂O₃, other oxides, whiteness and grain-size distribution.
• Samples from the production lot before order, on request.
• Independent pre-shipment inspection by Control Union, SGS or TÜV Rheinland on request.
• Extended analysis on request through an independent laboratory: Cr₂O₃, ZrO₂, heavy-mineral content and full sieve curve.

Request a quotation or sample

Tell us the grade, quantity, destination port and Incoterm, and your target limits for SiO₂, Fe₂O₃ and grain size. We reply with a quotation, the lab report of a current lot and sample availability.