Silicon is the chemical element, symbol Si — the semiconductor that chips are made from. Silica is a compound of silicon and oxygen, silicon dioxide, and it is what sand, quartz and glass are made of. Silicon is the element; silica is the everyday mineral. Neither is silicone, which is a synthetic polymer.
Three words, not two
- silicon — element 14, a hard grey semiconductor. Purified silicon is the basis of microchips and solar cells.
- silica — silicon dioxide, SiO₂. Sand, quartz and glass are silica.
- silicone — a synthetic polymer built on silicon–oxygen chains, used for sealants, baking moulds and medical implants.
Confusing the first and third is the commonest error: Silicon Valley is named for the semiconductor, not for the rubbery polymer.
Why silicon needs purifying
Silicon is the second most abundant element in the Earth's crust after oxygen, but virtually all of it is locked up as silica or silicates. Making chips requires refining it to extreme purity — semiconductor-grade silicon is among the purest materials manufactured at scale.
Where silica turns up
- sand and quartz — largely silica
- glass — made by melting silica, usually with soda and lime added to lower the melting point
- silica gel — the desiccant in those small "do not eat" sachets, a porous form that adsorbs moisture
The safety difference
Silica in solid form is inert, which is why glass and sand are handled freely. Fine crystalline silica dust, produced by cutting stone or concrete, is a serious respiratory hazard, which is why such work requires dust suppression and protection. Silicone and silicon are not respiratory hazards in the same way.
Frequently asked questions
What is the difference between silicon and silica?
Silicon is the chemical element; silica is silicon dioxide, the compound that sand, quartz and glass are made of.
Is silicone the same as silicon?
No. Silicone is a synthetic polymer built on silicon–oxygen chains, used for sealants and implants. Silicon is the element itself.
Is silica dangerous?
Solid silica such as glass or sand is inert. Fine crystalline silica dust from cutting stone or concrete is a serious respiratory hazard.