Chemical formula: Mg7Si8O22(OH)2 - Mg5Fe2+2Si8O22(OH)2
Sources: Finland, U.S. and Canada
Anthophyllite can be white, gray, green, or brown. It is a non-conductor of electricity.
Its fibers are extremely thin and flat and often pointed at one end like a knife blade.
Anthophyllite is an orthorhombic amphibole and is a solid solution mineral so there is some variability in the chemical composition. Anthophyllite chemistry usually contains some Fe and the occurrence of an end member species without Fe is rare. When crystal chemistry exceeds 2 molecular units of Fe, a monoclinic crystal structure forms and the mineral species in called cummingtonite and is part of the cummingtonite-grunerite solid solution.
By Polarized Light Microscopy (PLM) anthophyllite fibers have perfect parallel extinction which helps to distinguish it from the Actinolite–Tremolite series. The refractive indices range from approx. 1.623-1.676. Anthophyllite has moderate birefringence and is a member of the amphibole double chain silicate group. Random orientation SAED of Anthophyllite shows a layerline spacing of 5.3 Å. Patterns may show preferred orientation for a zone axis pattern.
Anthophyllite may be found in a variety of materials as cleavage fragments with mean aspect ratios < 20:1. The occurrence of these fibers is usually associated with mechanical processes either in the production or in the analysis of the material.
This type of asbestos is generally not found in building materials except as a contaminant from its talc component.