I've heard that from other users.
I think the earth ones are the most common.

Well, to me it's not the element. E.g., I have found 7 Fire Cloaks, but only 2 Fire Staffs. O.o

Oh,really?
That is really weird.
maybe your knuffel have cloaks magnet? hihih

I sometimes believe my knuffel also behave strange,like they find a typical element many times,even if the digging is actually random.

Well, I have 9 Darkness Hats, but only two staffs. But it's not that they're generally not good at finding staffs, as I have 9 Earth staffs. That's weird...

It really is weird.
But i think it must be more than just a coincidence!
I still wonder how these digging items are shared,depending on your own diggings,stats,etc or based on how many go to users
like... let's say,once every 200 diggings,you get to find a digging item.
or once 1000 diggings in all the kingdom,the 1001st one gets an item.

Well, when you dig, your probability to find a digging item is just as high as finding a rare material.

oh i see
so it has nothing to do with what other users find...

Yes, indeed. It mostly depends on your stats. ^^

oh i see.
and for example how often do you find a digging item?

Uhm, one or two per day, usually. Sometimes, none, sometimes more than that. I always post an update in my personal quest thread.

Within the last two digging days, I've found 3.