Actinolite is an amphibole asbestos that saw little direct commercial use, but — like tremolite, its close mineral relative — is important because it occurs as a contaminant in other materials and as a component of some products.

What Actinolite Is

Actinolite is a calcium magnesium iron silicate, part of a continuous mineral series with tremolite (the two differ mainly in iron content). When it grows in an asbestiform habit, its fibers are straight and brittle, sharing the biological behavior of the other amphibole asbestos types.

Appearance

Actinolite is usually dark — green to gray to nearly black — reflecting its higher iron content. Its fibrous form is straight and needle-like.

Where Actinolite Is Found

Actinolite was not mined and sold as a commercial asbestos product the way chrysotile, amosite, and crocidolite were. Instead it turns up as:

  • A contaminant in vermiculite and other mined minerals
  • A minor component of some spray-applied insulation, fireproofing, and sealant products
  • An impurity in certain talc and mineral deposits
  • A naturally occurring fiber in some soils and rock formations, creating environmental exposure risk during excavation and construction

Health Risk

Actinolite is an IARC Group 1 human carcinogen. As a biopersistent amphibole, it can cause mesothelioma, lung cancer, and asbestosis in the same way as the more common amphibole types. Because it appears mainly as a contaminant, exposure often occurred through products and activities not obviously associated with asbestos.

Regulatory Status

Actinolite is one of the six regulated asbestos minerals under U.S. and international asbestos rules. As with tremolite, oversight focuses on the materials and deposits it contaminates rather than on any commercial actinolite product.

If you were diagnosed with mesothelioma, asbestosis, or another asbestos-related disease and were exposed to actinolite-containing fireproofing, insulation, or contaminated minerals, you may be entitled to compensation through asbestos trust funds and civil litigation.