David,
It seems that is the way mine is. I don't worry about it. I would take that as a good sign since one of the things that I have heard is that Amidol is to be kept dry, until one is ready to use it. Density would seem to have to come from moisture. I have noticed that mine (from Formulary) takes some time to dissolve adequately in the tray (pretty granular)...again I don't worry about it...I mix it and use it. Seems to work pretty well. Good luck.

Regards,
Donald Miller