User blog comment:Scooter8pie/Alchemy and the Brown Mob/@comment-4583259-20111114070057

Right after resetting the mobs in a world that was no longer playable (see User_blog:Mrob27/Internal_Data_Format), I got a bunch of new mobs including two brown mobs. One was out in the open and I failed to trap it in a block, but the other just strolled into one of my astronaut test pits.

So I used your technique and got Snow and Silver in one go. It sure takes a long time to drill out and fill that cube! Thank you for this.