Marc Hendrickx and Associates Pty Ltd

Asbestiform amphiboles are listed as a Group 1 carcinogens by the International Agency for Research on Cancer (IARC).  They include asbestiform varieties of riebeckite (crocidolite), cummingtonite‐grunerite (amosite), tremolite, actinolite, anthophyllite, winchite and richterite. It is likely that other asbestiform amphibole varieties have similar adverse health effects. Amphiboles have a wide range of mineral habits and may show variation from columnar, fibrous and asbestiform habits, sometimes in a single specimen.

Tremolite schists in Ordovician meta-volcanics in central NSW mainly comprise fibrous tremolite-actinolite. They are associated with tremolite asbestos occurrences, and small quantities of asbestos were mined from narrow vein deposits in this area last century. When pulverised the host tremolite schist releases mineral fragments that fall into the classification range for countable mineral fibres and may be classed as asbestos, despite not having an asbestiform habit. The ambiguity in classification of this type of natural material raises significant health and safety, legal and environmental issues that require clarification.

While the health effects of amphibole asbestos fibres are well known and procedures are in place to reduce the risks, the consequences of exposure to non-asbestiform, fibrous varieties is not well studied. This group of minerals deserve more attention due to their widespread occurrence in metamorphic rocks in Australia, and their potential disturbance through mining, civil construction, forestry and farming practises. Toxicological studies for instance would improve our understanding of the risk of exposure.