The Coso Artifact
Rock hunters cut open a geode and found what looked like a machine part, supposedly half a million years old.
What was reported
On 13 February 1961, three people collecting geodes in the Coso Mountains near Olancha, California, found a rock crusted with fossil shells. When they sawed it open, they found a core of porcelain with a metal shaft through the middle, inside a six-sided casing.
Writers claimed the rock was 500,000 years old, and it became a famous 'out-of-place artefact' in books about ancient mysteries.
Explanations offered
In 1999 sceptical researchers sent X-rays of it to spark plug collectors, who identified it as a Champion spark plug from the 1920s. The 'geode' was a crust of hardened, iron-rich clay and rust that had formed around it. The original object's whereabouts are now unknown.
- When
- 13 February 1961
- Where
- Coso Range, near Olancha, California, USA
- Witnesses
- Three rock hunters
- Status
- Explained
Famous cases are real, widely reported events. Each file sets out what witnesses said and the explanations that have been offered, without taking a side.