Silica is a naturally occurring mineral that is a major component of most rocks, sand and soils. Silica is used to make common building materials like bricks, pavers, concrete, artificial stone products and tiles.
Opals and other gemstones can have a high percentage of crystalline silica, as can certain fossils.
Silica dust occurs naturally due to desert dust and sandstorms. It can also be created with some agriculture practices. Volcanic ash, and volcanic soil, may have a high silica content.
Any excavation or tunnelling through silica-containing material, such as shale and sandstone, can produce silica dust.
Some materials have a higher concentration of silica than others and are therefore more hazardous when dust is released due to crushing, cutting, drilling, grinding, sanding, sawing, or polishing. Here’s a breakdown of the most common materials:
| Material | Silica Content | Risk Level |
|---|---|---|
| Engineered Stone | Up to 97% | Very High Risk |
| Sandstone | 70-90% | Very High Risk |
| Granite | 25-60% | High Risk |
| Concrete, Bricks, Mortar | 20-30% | High Risk |
| Natural Stone (Marble) | <5% | Low Risk |
| Soil, Clay and Shale | 5-50% | Moderate-High |
Further information
Australian Institute of Occupational Hygienists: What materials are likely to have more than 1% silica?
Engineered stone
Engineered stone is an artificial product typically comprised of crushed natural stone such as quartz, a resin binder, and pigments. It may also be known as artificial, composite, reconstituted, manufactured, or agglomerate stone.
Depending on the product and manufacturer, engineered stone can contain less than 10% silica or up to 97% silica.
The risk of disease from processing engineered stone became evident when increasing proportions of Australian workers from the stone benchtop fabrication and installation industries developed silica-related health issues.
Consequently, on 1 July 2024, the manufacture, supply, processing and installation of engineered stone benchtops, panels and slabs was banned in all states and territories of Australia. A ban on the importation of engineered stone benchtops, panels or slabs took effect on the 1 January 2025.