Elastomerics Blog

Quartz is a naturally occurring mineral that’s composed of silicon and oxygen. Known by the chemical formula SiO₂, it’s used in electronics and computers, glass and concrete, and as an abrasive in sandblasting. Quartz is also needed for the silicones that are used in some gaskets, but in a form known as quartz gravel. These small, rounded pieces range in size from a few millimeters to a few centimeters and are mined around the world, especially overseas.

Silicone Production and SiME

Silicone production is a multi-step process that begins with a carbothermic reaction involving quartz gravel and carbon, typically charred wood. The metallurgical grade silicon metal (SiME) that results requires energy intensive processing, and there’s competing demand for SiME from the semiconductor, solar power, and electric vehicle industries. China produces 70% of the world’s SiME and can reduce exports to meet its own needs if internal demand rises, so the supply chain can sometimes be problematic.

Now is the time for the United States to develop enough SiME refining capacity to support the production of silicones, semiconductors, and other critical technologies. However, the Critical Materials List from U.S. Department of Energy (DOE) includes “silicon”, a term that is overly broad, instead of SiME. The United States has few producers of silicon metal, of which SiME is only a subset, and their collective capacity is limited during a time of rising demand from high-growth industries.

Industry Insights

Bill Stockwell, the Chairman and Chief Technology Officer of Stockwell Elastomerics, has advocated for SiME’s inclusion on the DOE’s Critical Materials List. In conjunction with other business leaders, he’s also worked to educate industry about why a steady supply of SiME is essential for polydimethylsiloxane (PDMS) rubber. In a November 2023 Rubber World article, he explains the process of going from quartz to silicone gasket – and everything in between. Bill also previously provided commentary on silicon metal’s importance to the silicone rubber industry.