By Emilia Wellesley · Published May 6, 2026 · Updated May 6, 2026
The Coso Artifact entered popular memory as a riddle: a porcelain-and-metal cylinder pried out of what its discoverers called a half-million-year-old geode in the high desert above Owens Lake. The riddle was solved decades ago. Yet the case remains a useful teaching specimen, because it shows how a single misnamed rock and one unsourced age estimate can travel through three generations of fringe literature before a careful procedural reconstruction catches up.
Direct Answer
The Coso Artifact is a 1920s Champion spark plug encased in a natural iron-oxide concretion, found near Olancha, California, on February 13, 1961. Pierre Stromberg and Paul V. Heinrich, working with the Spark Plug Collectors of America, identified it definitively in 1999 and published the analysis in 2000. The matrix is not a geode and not 500,000 years old.
What the Discoverers Found in 1961
On the morning of February 13, 1961, Wallace Lane, Virginia Maxey, and Mike Mikesell were prospecting roughly six miles northeast of Olancha, California, at about 4,300 feet of elevation, gathering specimens for the small rock-and-gift shop the three of them ran. They picked up what they thought was a geode. The next day, back at the shop, Mikesell tried to halve it on a diamond saw and ruined the blade on something the saw was not meant to cut.
When the nodule eventually opened, it revealed a slim cylinder of pale ceramic about three inches long, with a 2-millimeter shaft of bright metal running through its center. A hexagonal sleeve of greenish, oxidising copper alloy hugged one end. Small fossil shells and a couple of corroded shapes that the discoverers described as resembling a nail and a washer were lodged in the outer crust. The trio sent a description to Ronald J. Willis, then editor of the INFO Journal, the publication of the International Fortean Organization, who ran an account of the find as “Mystery in Stone” in 1969 [1]. An unnamed geologist consulted by Maxey reportedly told her the nodule “had taken at least 500,000 years to attain its present form.” That figure was never published in a peer-reviewed venue, the geologist was never named, and the dating method was never described [2].
How the Half-Million-Year Claim Took Root
A claim does not need to be examined to be repeated. Through the 1970s and 1980s the Coso Artifact circulated in books on out-of-place artifacts (OOPArts), in young-earth creationist lectures, and later in cable-television specials on ancient mysteries. Donald Chittick of the Institute for Creation Research featured it in his “Puzzle of Ancient Man” presentations, where it functioned as evidence for sophisticated antediluvian technology. Carl Baugh and J. R. Jochmans wrote it into their broader case for a vanished pre-Flood civilization. The artifact’s appeal was structural: a recognisably modern object inside a stone said to be older than Homo sapiens is exactly the sort of anomaly that, if true, would topple the established chronology of human industry [3].
The trouble was that no one with appropriate credentials had ever published a description of either the object or its supposed matrix. The original photograph and a set of crude X-rays taken by Ronald Calais, a creationist researcher who saw the artifact early, were the entire visual record in wide circulation. The object itself slipped out of public view sometime in the late 1960s and was retained by descendants of one of the original discoverers. The case rested almost entirely on a single sentence about an unnamed geologist’s estimate.
The Stromberg-Heinrich Investigation, 1999-2000
In 1999, Pierre Stromberg of the Pacific Northwest Skeptics began a methodical re-examination of the case with Paul V. Heinrich, a sedimentary geologist at Louisiana State University. Their approach was procedural rather than rhetorical: identify the object first, then ask what the matrix could be. Stromberg circulated the existing X-rays to specialists who would actually recognise the components if they belonged to a known modern technology.
On September 9, 1999, Chad Windham, then president of the Spark Plug Collectors of America, returned Stromberg’s call. Windham had viewed the X-ray photographs. His first response was suspicion, not of the artifact, but of Stromberg, whom he half-believed was a fellow collector pulling an elaborate hoax, because the identification looked obvious to a trained eye. Windham named the object as a 1920s-era Champion spark plug, of the 7/8-inch, 18-thread variety used in Ford Model T and Model A engines. Three other senior figures in the collector community, Bill Bond, founder of the SPCA museum, Mike Healy, and Vice-President Jeff Bartheld, independently confirmed the identification [4]. The hexagonal sleeve was the brass “top hat” that capped the porcelain insulator on early Champion plugs. The 2-millimeter shaft was the central electrode. The “spring or helix” visible in Calais’s X-ray was the threaded shank.
The Concretion, Not a Geode
Heinrich’s contribution was to identify the surrounding matrix. A geode is a hollow rock with crystals lining an interior cavity, formed over geological timescales. The Coso nodule was not a geode. It was an iron-oxide concretion of the kind that forms readily around rusting iron and steel objects in alkaline desert sediments. Iron in the spark plug’s threaded shank corroded; the iron oxide bound surrounding clays, sand, and shell fragments into a hard nodule. Mineral dust blown off the dry bed of Owens Lake, drained for the Los Angeles aqueduct between 1913 and 1926, accelerated the chemistry. Fossil shells from the lakebed sediment were incorporated as the concretion grew. The process can complete in decades rather than millennia [5].
There is also a plausible historical context for how a Ford-era spark plug came to be lying in the Coso Mountains. Mining operations were active in the area through the 1920s, and Ford trucks were the common workhorse. A worn plug discarded at a mine site, weathered into surrounding lakebed clay, would produce exactly the nodule that Mike Mikesell tried to cut in half on a Sunday afternoon in February 1961.
The 2018 Re-examination and Its Implications
For nearly two decades after the 2000 paper appeared in Reports of the National Center for Science Education [2], the artifact itself was unavailable for direct study. In April 2018, Stromberg located the surviving halves of the nodule in the keeping of a descendant of one of the original discoverers, who allowed an inspection on condition of family anonymity. The two halves together weighed 160 grams and measured roughly three inches in length, consistent with a 1920s Champion plug. A geologist from the University of Washington Earth and Space Sciences department independently confirmed that the matrix was a concretion, not a geode. Stromberg published the follow-up in the Skeptical Inquirer, March-April 2019, and it now sits in the Pacific Science Center’s “What Is Reality?” exhibition in Seattle [6].
No member of the spark plug collector community has ever dissented from the 1999 identification. J. R. Jochmans attempted a 2009 rebuttal arguing the object was petrified wood and the threading did not match Champion designs of the period; the rebuttal was shown to be wrong on both counts.
Why the Case Still Matters
A reader might ask, fairly, why an article should still be written about a case so thoroughly resolved. The honest answer is that the OOPArt framing has a longer half-life than its evidence. The Coso Artifact still appears in popular books, on social media threads, and in television documentaries as if the question were open. It is not. What the case offers, properly understood, is a clean worked example of how an artifact identification is supposed to go: examine the object before theorising about its age, consult specialists who would recognise the thing if it were ordinary, and let the simplest reconstruction that fits the evidence stand until something forces a revision.
For readers interested in the broader pattern, see our pillar guide to Historical and Archaeological Mysteries, where the difference between an unsolved question and an unexamined claim is the running theme.
Frequently Asked Questions
Was the Coso Artifact really 500,000 years old?
No. The age estimate came from an unnamed geologist who never published the assessment or the dating method. The matrix is an iron-oxide concretion that forms in decades, not millennia, around rusting metal in alkaline desert sediment.
Who solved the case?
Pierre Stromberg of the Pacific Northwest Skeptics and Paul V. Heinrich, a geologist at Louisiana State University, working with Chad Windham and three other officers of the Spark Plug Collectors of America. The identification was made in 1999 and published in 2000.
What kind of spark plug was it?
A 1920s Champion plug of the 7/8-inch, 18-thread variety, the standard fitting for Ford Model T and Model A engines.
What is a concretion, and why did people mistake it for a geode?
A concretion is a hard mineral mass that forms when groundwater cements sediment around a nucleus. A geode is a hollow rock with crystal-lined interior. The Coso nodule looked like a geode from the outside but had no interior cavity and no crystal lining. It was an iron-oxide concretion seeded by the rusting spark plug.
Where is the artifact now?
The two halves of the nodule are exhibited at the Pacific Science Center in Seattle, as part of its “What Is Reality?” exhibition, on loan from the family of one of the original discoverers, who has remained anonymous.
What is the INFO Journal, and what did it originally claim?
The INFO Journal was the publication of the International Fortean Organization, a society devoted to anomalous phenomena in the tradition of Charles Fort. Editor Ronald J. Willis published “Mystery in Stone” in 1969, describing the object’s appearance and the unsourced 500,000-year claim, but offering no independent dating.
How does iron-oxide concretion form so quickly?
When iron rusts in alkaline, mineral-rich sediment, the resulting iron oxides bind nearby grains of clay, sand, and shell into a hard mass. Owens Lake was drained for the Los Angeles aqueduct from 1913 to 1926, exposing fine, corrosive lakebed dust to wind. Conditions in the Coso region accelerate this kind of cementation considerably.
Why do popular sources still call the Coso Artifact a mystery?
Because the OOPArt framing was established before the resolution and is repeated by writers who have not read the 2000 paper or the 2019 follow-up. The scholarly question has been settled for over twenty years. The popular question keeps recirculating because it is a more entertaining one to keep open.
Did creationists really cite the Coso Artifact as evidence?
Yes. Donald Chittick of the Institute for Creation Research featured it in his “Puzzle of Ancient Man” lectures. Carl Baugh and J. R. Jochmans incorporated it into broader claims about pre-Flood technology. Jochmans’s 2009 attempt to rebut the spark-plug identification was shown to be incorrect.
Has any spark plug collector disputed the identification?
Not one. Bill Bond, Mike Healy, Jeff Bartheld, and Chad Windham all confirmed the 1920s Champion identification independently. The collector community has held a unanimous position on the artifact since 1999.
