Discovered in 1961 in Olancha, California by rock collectors, the Coso spark plug has left a lot of people scratching their heads for a while about this strange artifact that on face value seems out of place. How could this be that a spark plug ends up in a rock? Is it a spark plug? How did a diamond tipped saw blade become damaged in cutting through clay, encrusted shells and a spark plug?
Anyway, after having taken x-rays of the object it was identified as an early 1920’s spark plug that eroded and became encrusted in the bits of soil, shells and stones around it. This process happens fairly quickly given the right circumstances.
It may look old but it’s not always the case as can be seen with the embedded 1945 coin in the image below. It also does not mean that every encrusted OOPArt is a natural occurrence of oxidation and mineral binding. In the case of the Coso spark plug artifact I am inclined to feel that the object was sufficiently identified and explained as just that – a 1920’s spark plug.