For barium and strontium ferrites, these metals typically supplied as their carbonates, BaCO or SrCO. It is made of ferromagnetic metal such as iron, or ferrimagnetic compounds such as ferrites. Batteries require "electrolytic manganese dioxide" while ferrites require "chemical manganese dioxide". Barium ferrites are robust ceramics that are generally stable to moisture and corrosion-resistant. Hard ferrites have high coercivity, so are difficult to demagnetize. Ferrimagnetism is exhibited by ferrites and magnetic garnets. A related family of industrially useful "hexagonal ferrites" are known, also containing barium. They have a low coercivity and are called soft ferrites. It is used in the ceramic industry to make frits, ferrites, and porcelain glazes. The compounds involving are ferrites, an important class of ferromagnets. Thulium potentially has use in ferrites, ceramic magnetic materials that are used in microwave equipment. Like most of the other ceramics, ferrites are hard, brittle, and poor conductors of electricity. Because ferrites are already oxidized it can not be oxidized any further. This is one reason ferrites are so resistant to corrosion. Ferrites including iron(III) oxide and strontium carbonate display magnetic properties.