What is the Coso artifact?
The Coso artifact was found in 1961 near the Coso Mountains in California by people who ran a gem shop, while they were looking for geodes, stones with hollow, crystal-lined interiors. When they cut open a stone they brought back, they found a ceramic-like cylinder, a metal core and spring-like parts inside.
The “500,000-year-old machine” theory
The stone was covered in something like a fossil shell, said to have taken at least 500,000 years to form. X-rays showed that the parts inside closely resembled a spark plug used in car engines. It became a topic as evidence of “a mechanical civilization 500,000 years ago” or “something dropped by a time traveler,” and one of the classic examples of OOPArts.
The answer: a 1920s spark plug
In 1999, skeptical researchers showed the X-rays to spark plug collectors, who identified it as a spark plug made in the 1920s by the American Champion company, widely used in cars and other engines at the time.
The “500,000-year-old stone” is also thought to have been not a geode but soil containing rusted iron that hardened around the spark plug. Discarded parts of old cars or engines became covered in rust and mud within a few decades. Another story of machine parts found inside rock is the Cambrian “bolt”. Famous OOPArts are listed on the OOPArts page.
