Geodes resemble ordinary stones from the outside, usually spherical, or elliptical in nature, and sometimes hollow, but their cavities can contain an amazing display of crystal structures and minerals.
When sawn in half they reveal their wonderful displays, and are highly sought after by rock collectors.
In 1961 a fossil encrusted geode (although this one was not hollow) was picked up in the Coso Mountains, six miles northeast of Olancha, California, near the top of a 4300′ peak overlooking the dry bed of Owens Lake by some geologists.
What was discovered after it had been cut in half, ruining a diamond saw blade in the process, is something that has caused much debate over the years, and continues to this day.
In the centre of the geode was a metal core approximately .08″ in diameter. Encircling this was what appeared to be a ceramic casing which was also surrounded by a hexagonal sleeve of wood, which had become petrified.
This was encased by the outer layer of the geode which was made up of hardened clay, pebbles, and bits of fossil shell, and two nonmagnetic metallic objects resembling a nail and a washer.
A fragment of copper still remaining between the ceramic material and the petrified wood indicates that possibly the two may have been separated by a copper sleeve.
X-rays of the objects were taken and examined by Paul Willis, then editor of INFO Journal who noticed a startling similarity between it and a modern spark plug.
An unnamed geologist in the original report of the find came up with an age estimate of 500,000 years based on the fossils contained in the matrix.