Riebeckite (including crocidolite, or blue asbestos)

Characteristics and occurrence

Crystalline riebeckite typically forms prismatic or elongated crystals in metamorphic and igneous rocks. The fibrous crocidolite version consists of fine, hair-like fibers that resist weathering and are strong and flexible. Key physical properties include a blue to blue-black color, an amphibole crystal structure, and a chemical composition approximated by Na2Fe5Si8O22(OH)2. It is less common in building materials than chrysotile (white asbestos) but can be found in some old insulation, cement, caulking, rope and gaskets.

Health risks

The fibrous form of riebeckite is classified as asbestos and is associated with severe respiratory illnesses. Inhalation of crocidolite fibers increases the risk of asbestos-related diseases such as asbestosis and malignant cancers, including mesothelioma and lung cancer. Because of its high biopersistence and needle-like fibers, many experts consider crocidolite among the more hazardous asbestos types. For general information about asbestos categories see types of asbestos. For health effects and cancer risks see cancer risks and for asbestosis information see asbestosis resources.

History and uses

During the 19th and 20th centuries crocidolite was mined and used in industrial applications that required heat resistance and strength. It appeared in filters and insulation products; one notable historical use was as a filter material in certain cigarette brands, such as Kent, which relied on an early asbestos filter design (Kent cigarette filters). Commercial mining and most uses ceased once the health hazards became clear.

Regulation, remediation, and notable facts

Because of the danger posed by airborne fibers, many countries strictly regulate removal, disposal and handling of materials containing riebeckite fibers. Professional abatement and testing are required when crocidolite is suspected in buildings. Although less prevalent in construction than chrysotile (white asbestos), its presence demands careful management to prevent exposure. Historical mining sites, such as those linked to crocidolite extraction, have been the focus of public health and cleanup efforts.

• Type: Amphibole silicate mineral
• Forms: Prismatic crystals and fibrous crocidolite
• Main concern: Respiratory disease and cancer from inhaled fibers