An impossible discovery
On February 13, 1961, three mineral prospectors were searching for geodes in the Coso Range, about 9 kilometers northeast of Olancha, California. Wallace Lane, Virginia Maxey, and Mike Mikesell gathered a number of specimens from a peak at an elevation of 1,300 meters (4,300 feet). The next day, back at their gift shop, Mikesell's diamond-edged saw blade was ruined while cutting through one of the rocks.
Inside the hard shell was not the crystalline cavity of a geode, but a solid object. It contained a central 2-millimeter-wide magnetic metal shaft surrounded by a cylinder of a hard, white material like porcelain. The outer layer of the object was encrusted with fragments of fossilized shells, along with what appeared to be a nail and a washer. An unnamed geologist reportedly examined the object and declared the nodule was at least 500,000 years old, a claim that was never formally published. This "out-of-place artifact," or OOPArt, was a minor sensation, with proponents of ancient astronauts or lost high-tech civilizations using it as proof.
A geological explanation
Decades later, investigators sought a scientific explanation. In 1999, researcher Pierre Stromberg and geologist Paul Heinrich used X-rays and historical schematics to analyze the artifact. With assistance from the Spark Plug Collectors of America, they identified the object with certainty: it was a 1920s-era Champion spark plug. This type of spark plug was common in Ford Model T and Model A engines, which would have been used in the area.
The Coso Range was a site of mining and prospecting activity in the early 20th century. The presence of discarded automotive parts from that era is entirely plausible. The rock encasing the spark plug was not a geode, which forms over immense timescales. It was a mass of iron-rich clay and sediment. Iron objects, like a steel spark plug, can rust and act as a nucleus, causing minerals in the surrounding wet clay to cement together. This process of forming a hard, rock-like concretion can occur in a matter of decades, not hundreds of thousands of years. A 2018 physical inspection of the artifact by a geologist from the University of Washington confirmed it was a 1920s Champion spark plug and found no evidence of the claimed fossil shells.