Chrysotile is a serpentine ore mineral and one of 6 forms of asbestos. This mineral contains small, heat-resistant fibres around 25 nm in diameter that makes great insulation and useful as a construction material. Chrysotile asbestos has been linked to many forms of cancer and respiratory diseases and there is an ongoing effort to remove it from industrial buildings and homes. Chrysotile is abundant at the oceanic MOHO and forms at convergent plate boundaries when ultramafic rocks undergo hydrothermal metamorphism. Chrysotile is identifiable by its green colour, slippery feel, and waxy lustre.