Ferrite cores are fragile. If you drop them on a hard service they may shatter as shown in the picture below:
When broken, ferrites shatter like glass and you must be careful when cleaning up as there may be sharp corners that may cause harm.
Here are the Material Safety Data Sheets for the various ferrite mixes:
Fair-Rite_Products_Corp_MSDS_31_Material_COMPONENT
Fair-Rite_Products_Corp_MSDS_43_Material_COMPONENT
Fair-Rite_Products_Corp_MSDS_52_Material_COMPONENT
Fair-Rite_Products_Corp_MSDS_61_Material_COMPONENT
Fair-Rite_Products_Corp_MSDS_75_Material_COMPONENT
Fair-Rite_Products_Corp_MSDS_77_Material_COMPONENT