How quartz is mined
One North Carolina district supplies most of the world's high-purity quartz, the raw stuff of silicon-chip crucibles.
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The short version
The purest quartz starts as pegmatite rock, dug at places like Spruce Pine in North Carolina alongside feldspar and mica. Crushing and grinding free the grains, though the rock is abrasive enough to contaminate itself with iron from the mills. Flotation and magnets remove other minerals, then strong acid and hot chlorine gas chase out the last traces of aluminum, iron and sodium.
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Dig the pegmatite
Spruce Pine pegmatite holds quartz mixed with plagioclase, microcline and muscovite, and the district is mined for all of them. Quartz from this rock formed with few inclusions, which is why it suits high-purity work.
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Crush, scrub and grind
Ore passes through a primary crusher and a scrubber, then a mill. One North Carolina evaluation ground it to 60 by 140 mesh. Quartz is so hard and abrasive that ordinary grinding gear sheds iron into the product, so specialist equipment is used.
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Float off other minerals
Flotation lifts away mica, iron minerals and feldspar. Magnetic separators then clean the remaining quartz, and the product is sized.
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Leach with strong acid
A leach in strong acid cuts iron and magnesium sharply. In one North Carolina test, aluminum, calcium, sodium and potassium stayed too high after leaching, so those elements decide the final grade.
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Chlorinate at high heat
The typical flow sheet ends in a hot chlorine atmosphere that pulls out further impurities. The gas risk is serious enough that only specialist companies run this stage. Finished quartz sand goes to makers of crucibles for chips and solar cells.
Worth repeating
- On the Mohs hardness scale, quartz sets the value of 7.
- In the 17th century Nicolas Steno found that the angles between a quartz crystal's long faces stay the same, whatever its size.
- Analysts call Spruce Pine a single point of failure for the chip industry, because roughly 70 to 90% of all high-purity quartz comes from there.
Where it goes next
Quartz feeds 4 lines directly and reaches 196 things in total.
Further down the line
Keep walking
Sources
- The challenges of producing high purity quartz
- Evaluation of quartz resources, North Carolina (GSA abstract)
- High Purity Quartz
- Spruce Pine Mining District
- Quartz
Cite this page: "How quartz is mined." Assembly Line, 2026-11-03. https://assemblyline.org/make/quartz