Randy uses Marineland Black Diamond (because it's good and because he runs his in a canister filter and Black Diamond is Bituminous with a larger hardness/abrasion number). Even though Lignite is the best under most circumstances, it will crumble and create dust if ran in a canister.
I would make sure you get more info from the manufacturer before you buy.
For instance,
Is it Bituminous coal, Sub-Bitumous coal, Lignite, or Anthracite coal?
Are the mesh sizes available, U.S. Standard or Tyler Standard?
What is the Iodine number? (Not really useful except to determine if it's air phase or Liquid phase)
What is the Molasses number?
What is the Methyline Blue number?
What is the Hardness (or abrasion) number. This is important if you are putting it in a canister filter or fluidized bed.
Is this produced here or is it a cheap Chinese import? (The Chinese crap will be ultra dusty. To add insult to injury, it is often made of Anthracite as opposed to Bituminous or Lignite making it pretty much worthless for our purposes).
Is it Air-phase or Liquid-phase? (I know that most people think that as long as it isn't pelletized, it's liquid-phase. That's not true. Many granulars are also air-phase. It all depends on whether it's macroporous or microporous).