What causes bumps on eggshells (photo)?

[ChickChickChicky]

What causes the large, irregular bumps on the exterior of eggshells? Sometimes there are no lumps, sometimes only one, sometimes several. I suspect that these eggs are coming from one of my Rhode Island Reds who is approaching 2 years old (I think). She still lays nearly every day and has no other problems that I'm aware of.

 

[Fred's Hens]

It is just the processing of calcium, I believe. From time to time, chunks of calcium get deposited on some of our eggs too. It isn't a constant, so there is just no way of knowing for sure. All one can do is speculate. It doesn't seem to be serious matter.

 

[b.hromada]

It is just the processing of calcium, I believe. From time to time, chunks of calcium get deposited on some of our eggs too. It isn't a constant, so there is just no way of knowing for sure. All one can do is speculate. It doesn't seem to be serious matter.

I agree.