The glue to hold the sintered carbide powder is cobalt or iron or whatever pot-metal crap they have on hand for cheap blocks. That would be where the magnetism

The glue to hold the sintered carbide powder is cobalt or iron or whatever pot-metal crap they have on hand for cheap blocks. That would be where the magnetism is coming from. If it's highly magnetic you probably have little tungsten and a lot of binder.