THCA Crystalo mentioned as âcrystals,â âTHC crystals,â or âdiamonds,â may be a can-na bis concentrate that comes during a solid state. It resembles coarse sugar, the type typically used for decorating sugar cookies or glittering the tops of baked fruit pies. Crystalroduced to be freed from plant matter or terpenes, which are the distinct aromatic and flavor qualities of a can na bis cultivar, or strain.