Inorganic foreign objects typically enter a well due to poor construction methods. This can either be during construction or poor sealing of the well after construction is completed. While inorganic foreign objects do not often pose health risks, they can be indicative of poor construction and pathways that harmful substances may enter the well and groundwater. Below you can find examples of inorganic objects found in wells.
 
In the above video some sort of debris, possibly a pump filter, can be seen buried in sediment at the bottom of the well.
 
A lighter can be seen floating on the right side of this image.
A lighter can be seen floating on the right side of this image.
 
At the bottom of the video of this well a metal can is resting on a ledge just above the water table.