You may have noticed that some eggshells are discolored with dark brown spots. This is known as a “speckled” egg. These dark splotches are created early in the process as the egg is traveling through the hen. As the egg passes through the oviduct (the organ that processes the yolk and adds the shell), it spins. If the egg spins too slowly as it moves along the tube, it can end up looking a little speckled.
You may also notice a bumpy egg or two in the carton you just brought home from the grocery store. The “bumps” just mean the eggshell has some texture to it rather than being completely smooth. This also occurs in the oviduct as the egg passes through the hen. There may just be some debris in the tube as the shell is being formed. Debris in the oviduct is more common in older hens or younger hens who don’t receive enough nutrients. When this happens, calcium is released which encloses the debris in the shell.