What kind of grease is that? So I just managed to remove the fork from the old frame I'm renovating. In the headset bearings, the grease looks odd!



See these tiny metal balls? At least it looks like that... Is that on purpose, is that debris? The races do not seem to be damaged. If I reuse the same headset, should I try to find the same type of grease, or any waterproof grease would fit?
That is old grease with debris in it, this will be shavings of the bearings and their channel.

Before re-greasing the headset you will need to degrease it to remove all of the old grease, otherwise the old grease will attack the new grease rendering it less effective. 
Then once degreased you will then need to clean out all of the degreaser (again so it doesnt attack the new grease) and dry it out. 
Then you can add the new grease, the thicker and gloopier the better