China Neodymium And Ferrite Magnets Manufacturer & Supplier 
When you talk about black magnets, which kind of magnet comes to your brain? Is it a ceramic ferrite magnets? But what if I told you that it could be other materials as well?
Black magnets, that is, magnets with a black appearance, in most cases they are ferrite magnets, mainly composed of iron oxides (such as Fe₂O₃) and barium (Ba) or strontium (Sr) oxides, but there may be neodymium magnets, for example, the surface of the black epoxy-plated sintered or bonded neodymium-iron-boron which also has the appearance of black, and can also be called black magnets.
Major Black Magnets - Sintered Ceramic Ferrite
Neodymium magnets with black surface coating - Epoxy coated magnets
How to distinguish the black magnet material?
It can be judged roughly by magnetic test, appearance inspection, chemical composition analysis, density measurement and so on. Like NdFeB its base color is not black, which can be seen by scraping the coating. Magnetic force, NdFeB's magnetic force is much stronger than ferrite. Then again, density-wise, NdFeB is also quite a bit higher.
If you can't tell exactly what kind of black magnet you have, injection molded ferrite, sintered ferrite, nickel-zinc ferrite, manganese-zinc ferrite, or bonded, sintered neodymium-iron-boron with a black coating, you can contact us for help!
Comparison of related magnet materials;
Neodymium Magnets vs Ceramic Ferrite Magnets
Sintered Ferrite Magnets VS Injection Molded Ferrite Magnets