Just a dark gray metal. Here are the 0.5 inch cubes. https://www.amazon.com/dp/B0759ZTQ4R They are $20 for the ones with letter etched on them which is for some reason 15 cheaper than the plain ones so I recommend an etched one, it's soooo good to fidget with and roll around in your fingers. If you like it, I'd buy the 1 inch one next, it's $79. It's 4 times as heavy as the half inch, but you can still carry it around. The 1.5 inch is 27 of the half inch ones and you can't bring it around and it's easier to get hurt with it.

One of my favorite YouTubers, William Osman bought a 4 inch cube a few weeks ago, my friend sent me the video immediately, he knows I love tungsten. https://youtu.be/9O551__3ppM