User blog comment:Roranoa zoro/Eternal Flame,FT's foundin' members,Acnologia's DSE/@comment-10425110-20130714150934/@comment-7418318-20130714154512

How is it "more unspecific" or rather less specific?

Both Onyx and Obsidian are exactly ONE material. Crystal is a term that encompases dozens of materials, including sugar and salt.