> Tungsten carbide is magnetic

Pure tungsten carbide is not. You just got some magnetic contaminants in it.

This has is a good test for fake "gold" that can consist of tungsten core with a thin film of gold on top. It's pretty much impossible to get pure tungsten, so such "gold" ends up being magnetic.

I got one of those too, and it came with a manifest showing that there is about 5% of nickel in the composition so not too surprising.

I would certainly be surprised if they could manufacture a pure cube (> 99.9%) for the price they sell it at :-)

What are you using the cubes for?

The most common use for tungsten cubes is as a kind of spooky ornament. Encountering a 4 inch cube that weighs over forty pounds is pretty weird.

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.

It's probably not tungsten carbide but rather a common tungsten nickel alloy