What Is Quartz Used For? Sand to Wafers

Quartz is used to make container glass, foundry moulds and frac sand; to filter water and blast abrasives; to melt into the silica glass that lines semiconductor furnaces; to seed the crystal in an oscillator circuit; and to smelt into silicon metal. Those uses share a mineral and almost nothing else. What separates them is the form the quartz arrives in.

That is the answer to what quartz is used for, and the numbers behind it point in two directions at once. By tonnage, industrial sand in the United States is overwhelmingly a well-completion material: about 81% went to hydraulic-fracturing, well-packing and cementing sand in 2025, against 7% to glassmaking. By value, the same material category is worth an average of $36 a tonne, while a kilogram of cultured quartz crystal is quoted at $200. Both statements are about quartz. Neither describes the other’s business.

One mineral, four different products

Quartz is silicon dioxide. All four forms below are therefore the same chemistry, sold into different markets under names that are not interchangeable.

The USGS draws the same line in its 2026 commodity summary: it separates high-purity quartz, defined as natural quartz with total impurities below 100 parts per million (99.99%), from industrial cultured quartz crystal, which it describes as electronic-grade material that is manufactured rather than mined. Ultra-high-purity products go below 10 ppm, or 99.999%.

Bulk sand carries the tonnage

The bulk category has a published end-use split, and it is worth reading before any list of quartz applications. The USGS sand and gravel chapter puts United States industrial sand and gravel sold or used in 2025 at an estimated 120 million tonnes, valued at an estimated $4.5 billion, produced by 131 companies from 207 operations in 38 states. Production from Texas, Wisconsin, Oklahoma and Louisiana combined accounted for 77% of domestic sales and use.

The destinations, as the USGS reports them for 2025:

Read the first line twice. The tonnage answer to what quartz is used for is well completions, not glass and not semiconductors, and the USGS calls frac sand the industry’s most important driving force. It also explains the price behaviour: average value was $45.40 a tonne in 2022 and an estimated $36 in 2025, and the 2026 edition attributes the 2025 fall to an oversupply of frac sand, which it says caused some operations to decrease production or idle.

That split is a United States one. The direction of travel elsewhere follows the same logic, since frac sand demand is tied to shale activity rather than to industrial output, but the percentages are not transferable.

Glass is the first customer with a specification

Glassmaking takes 7% of the tonnage and is where quartz stops being a commodity, because iron limits what a glass furnace will accept.

The US tariff schedule makes that concrete. The line covering sand with 95% or more silica and not more than 0.6% iron oxide is HTS 2505.10.1000, and per the USGS summary it covers high-purity quartz as well. Iron affects glass colour and light transmission, so it is specified separately from total silica content.

The shared tariff line is worth pausing on, because it is easy to misread. Two products on one customs code are not two interchangeable products. The code is a trade classification; the difference between glass sand and crucible feed lives in impurity profiles, inclusion counts, particle-size distributions and the qualification a customer has already run. A 99.9% silica figure on a certificate does not tell you which of those you have.

Fused quartz and fused silica are manufactured, not mined

The highest-specification quartz products are no longer sand by the time they are sold. They are glass.

The manufacturing route decides the name, and the two routes are genuinely different. Fused quartz is made by melting natural silicon-dioxide minerals. Synthetic fused silica is made from silicon-bearing chemical precursors, which is why Heraeus, which makes both, presents them as two material classes rather than two grades of one.

What the buyer gets from either route is a property set that no crystalline mineral offers: high chemical purity and corrosion resistance, a high softening temperature and thermal resistance, low thermal expansion with resistance to thermal shock, transparency from the ultraviolet into the infrared, and high radiation resistance.

For thermal expansion, the figure University Wafer’s materials page gives is around 0.55 × 10⁻⁶ per °C, and it is a page rather than a standard, so treat it as typical for the grade described rather than as a specification. Grade selection matters more than the headline number: the same page splits fused silica into JGS1 for ultraviolet optics, JGS2 for visible and near-infrared work, and JGS3 for infrared. Three products, three transmission bands, one catalogue name.

That is what fused quartz and fused silica are used for in practice: furnace tubes and other process parts in semiconductor manufacturing, windows and lenses in optical systems, envelopes in technical lamps, and the preform and cladding work behind optical fibre. In each case the customer is buying a formed glass component, not a mineral, and the specification is written around the component’s job.

Quartz crystal is a component, not a chemical

One use of quartz does not depend on silica chemistry at all. It depends on the crystal’s piezoelectric behaviour, which turns a mechanical stress into a voltage and back.

USGS is blunt about the split: electronic applications account for most industrial use of quartz crystal; other uses include special optical applications; and virtually all quartz crystal used in electronics is cultured rather than natural. The components it names are frequency controls, frequency filters and timers, in circuits for communications equipment, computers and consumer goods.

Two details follow from that, and both matter commercially. First, this is a grown material, so supply is a factory question rather than a geology question; two companies produced cultured crystal in the United States in 2025, with output data withheld to protect proprietary information. Second, the price is quoted per kilogram, not per tonne: $200 per kilogram as grown and $500 per kilogram after sawing and grinding, on USGS 2025 estimates, against $36 a tonne for bulk sand.

Piezoelectric quartz imports into the United States came overwhelmingly from one place: China supplied 89% in 2021–24, with Denmark and Japan at 3% each.

Silicon metal is where the chemistry changes

Silicon and ferrosilicon sit inside that 1% band in the tonnage table, which is the point. By quantity, the smelting route is a rounding error next to frac sand. By what happens to the material, it is the only destination on this page where the silicon-dioxide identity disappears.

Ferrosilicon in the United States is sourced primarily from domestic quartzite, and most of it is consumed in the ferrous foundry and steel industries, according to the USGS 2026 silicon summary. Silicon metal goes mainly to aluminium alloys and to the chemical industry, particularly silicones. China accounted for almost 80% of estimated global silicon materials production in 2025.

The value gap explains why a 1% line on a tonnage table still matters. The same USGS edition puts silicon metal at 130 cents per pound in 2025, or about $2,870 a tonne. The sand chapter’s $36 a tonne is an all-uses average for industrial sand, not a feedstock price, so the two are not a margin calculation. What they do mark is a difference in the transaction: silicon metal is quoted per pound of contained silicon, industrial sand per tonne of screened product. The chain from silicon metal through chemical purification to wafer feedstock is a separate subject, covered in the high-purity silicon guide.

Crucibles take the smallest tonnage and the tightest specification

The best-known high-purity quartz application is also the one with the least room for error. Fused-quartz crucibles contain the silicon melt during crystal growth for photovoltaic and semiconductor wafers, and the USGS lists them among HPQ’s specialised end uses alongside electronics, fibre-optic cables, lamp tubing and specialty glass.

The requirement is a container that holds its shape at temperature while contributing almost nothing to the melt. That is why crucible grades are specified at impurity levels measured in parts per million rather than per cent, and why the purity definition, the layered construction and the supply geography deserve their own treatment rather than a paragraph here. The high-purity quartz guide covers them.

One market signal from the same USGS edition is worth recording: demand for HPQ used in photovoltaic cells weakened in 2024 and continued lower into 2025. Crucible demand is not a straight line extrapolated from solar installations.

Where the uses stop

Two limits are usually missing from use lists: what else can do the job, and how far a property can be pushed.

Substitution is use-specific rather than material-wide, and the USGS substitutes section makes the distinction cleanly. Glassmaking, foundry and moulding sands have alternatives in chromite, olivine, staurolite and zircon sands; abrasive sands give way to garnet, olivine and slags; and frac sand faces sintered bauxite and kaolin-based ceramic proppants, which cost more and are mostly used in deeper wells, plus petroleum coke in some situations. For high-purity quartz itself the position is the opposite: USGS states that no economic substitutes exist for most applications, and that cultured quartz could substitute but is not commonly used because of the price.

Cost appears in the chapter for one family only: sintered bauxite and kaolin-based ceramic proppants are described as costlier and as mostly used in deeper wells, against a sand category averaging $36 a tonne across all uses. For the glassmaking, moulding and abrasive families the chapter says only that the listed materials can be used.

The direction reverses again on the electronics side. Silicon is increasingly used in place of quartz crystal in frequency-control oscillators, and materials with larger piezoelectric coupling, including langasite, lithium niobate and lithium tantalate, have been studied and used. So “can something else do this job?” has no general answer even within one mineral; it has an answer per form and per use.

The second limit is temperature. Quartz glass resists thermal shock, but a maximum service temperature is a property of a specific grade and forming process, not of the word quartz. Ask for the rating with the grade attached, and do not accept a materials-table value as a substitute for the supplier’s own datasheet.

Reading a quartz offer

The practical test is whether an offer names the form before it names the price. Five questions sort most enquiries:

• Which form is being quoted — bulk sand, refined sand, fused glass, or grown crystal? The units alone usually tell you: sand is priced per tonne and crystal per kilogram, a factor of 1,000 that no certificate needs to state.
• Which impurities, at what level — iron for glass, total ppm for high-purity quartz, and inclusions, which chemistry figures do not capture.
• Which application has it qualified — a foundry sand and a crucible feed can both be described as high-purity quartz sand by a seller who has not asked what you are making.
• Which site produces it — a mine, a processing plant and a glass works are three different addresses, and a deposit announcement does not establish any of them.
• What the price basis includes — grading, packaging, and whether freight is quoted to your plant or to a port.

A supplier who can answer those five has a product. One who answers with a purity percentage alone has a claim.

The other material guides are collected under industrial materials.

Methodology

This page uses four USGS commodity summaries (quartz, silicon and industrial sand and gravel from the 2026 edition, plus the 2023 edition of the sand chapter to check a revision), a manufacturer’s technical knowledge base, and one supplier materials page that is identified as such because the coefficient of thermal expansion figure it provides is not a standard value.

Where a figure exists in the current USGS edition, that edition is the source used, including the end-use split and the revision of earlier production estimates: the 2023 edition of the same series published 97 million tonnes for 2022, and the 2026 edition publishes 121 million tonnes for that year. Only the current values appear above.

All numbers carry their own year and basis: tonnage and use shares are 2025, the tariff line and import shares are as published in the 2026 edition, and price ranges are USGS estimates rather than transaction prices. The one comparison the page performs itself, between sand, silicon metal and crystal, uses USGS figures on both sides and states the units. No global market-share ranking, reserve ranking or demand forecast is inferred.

Sources

1. USGS, Mineral Commodity Summaries 2026 — Quartz (high-purity and industrial cultured crystal), February 2026. https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-quartz.pdf
2. USGS, Mineral Commodity Summaries 2026 — Silicon, February 2026. https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-silicon.pdf
3. USGS, Mineral Commodity Summaries 2026 — Sand and Gravel (Industrial), February 2026. https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-sand-industrial.pdf
4. Heraeus Covantics, properties of fused silica and quartz glass (manufacturer knowledge base). https://www.heraeus-covantics.com/knowlegde-base/properties
5. University Wafer, fused silica material properties, JGS1 vs JGS2 (supplier materials page). https://www.universitywafer.com/material-characteristics-fused-silica.html
6. Heraeus Covantics, making of fused silica (manufacturer production explanation). https://www.heraeus-covantics.com/knowlegde-base/making-of-fused-silica
7. USGS, Mineral Commodity Summaries 2023 — Sand and Gravel (Industrial), January 2023; used only for the superseded 2022 estimate. https://pubs.usgs.gov/periodicals/mcs2023/mcs2023-sand-industrial.pdf