Coso artifact

Discovered in 1961, the Coso artifact is, depending upon your mindset, either the proof of advanced manmade technology from before the dawn of time, or a 1920s spark plug that's been through hell.

While not a notable source of woo in itself, the Coso artifact is generally mentioned in conjunction with such pseudoarcheological discoveries as the Dendera lamp and the Baghdad battery, on the basis that multiplying together a lot of unrelated instances of a lack-of-proof somehow equals absolute proof of lost ancient technology. The find has also attracted interest from the creationist movement, perhaps bringing it more publicity and manufactured controversy than it ever merited in its own right.

Background
Three prospectors in California found the object while out looking for geodes to sell in their gift shop. It was picked up on the surface rather than excavated from a sealed context. Upon trying to split what they believed to be a geode, they encountered something that appeared to be a solid porcelain cylinder with a thin metal core. Further examination revealed that the porcelain cylinder was surrounded by a hexagonal sheath of what appeared to be copper, that other metal items resembling a washer and a nail appeared to be embedded in the find, and that the outer layer was full of shell fragments.

Investigations
In the opinion of one trained geologist, it has taken at least 500,000 years for this nodule to attain its present form—and yet, when we cut it open, we discovered a manmade object within the geode's cavity.

The trained geologist referred to in the quote remains unidentified, and appears never to have published their extraordinary findings. According to Virginia Maxey, one of the party who discovered the object while prospecting, the geologist based their estimate on the shell fragments in the outer layer of the strange deposit. It is largely upon this identification that the case for "proof of ancient technology" rests.

Further tests were done. Creationist "scientist" Ron Calais was permitted to physically examine the object and to take X-rays and photographs These images are the only remaining evidence of the object, which is now believed to be missing or destroyed. X-rays showed,

…a cylindrical structure with a metal ring at one end and a flared metal cap at the other. A threaded, screw-like area topped the assemblage.

The artifact featured in an article for the journal of the International Fortean Organization, written by R or P Willis (sources differ &mdash; they were co-founders of the magazine). Willis hazarded that the object might be a spark plug. Some accounts describe the Willis brothers dismantling and examining an ordinary spark plug for comparison, and concluding that the hexagonal portion of the Coso artifact was the rusted remains of a steel casing.

When asked to examine the X-rays of the artifact, then-President of the Spark Plug Collectors of America, Chad Windham, confidently suggested a match (allowing for the heavy corrosion) with Champion spark plugs dating to the 1920s.

Geology
One piece of the puzzle that can be addressed with real science is the geology. Is this object a geode? The discoverers of the Coso artifact were out looking for geodes that day; they believed that they had found one. However, the quote from the unidentified "geologist" called it a "nodule" and not a geode.

Geodes do not form around a nucleus. They start out as bubbles or cavities in a volcanic or sedimentary layer, and become lined with mineral deposits. The Coso artifact more closely resembles a concretion, a geological quirk which occasionally throws up woo of its own, when interestingly formed concretions are mistaken for dinosaur eggs, fossils, and manmade or extraterrestrial artifacts.

If one accepts that the core of the Coso artifact has now been correctly identified as a Champion spark plug dating to the 1920s, a more reasonable explanation is that it is merely an iron oxide nodule formed by the corrosion of the spark plug materials.

Creationists
Creationists got into a bit of a pickle over this one, as they so often do about supposed out-of-place artifacts. Basically, it was slightly-post-Flood evidence that evolutionists and geologists didn't have all the answers, until it turned out to be just a rusty spark plug, when suddenly it wasn't that important. But they haven't entirely given it up.

Because the Coso artifact was found in sedimentary rock, we must conclude that this too was deposited during the great Flood.

Other woo
"Mysterious unidentified technology from five-hundred-thousand years ago" just sounds so much better than "some corroded junk". Pseudoscientific guesses about the function of the Coso artifact range from superconductor to communications antenna to beyond-our-earth-understanding.