According to a W W McCormick of Abilene (Texas, USA), his grandfather Atlas Almon Mathis had worked in a coal mine at Heavener (Oklahoma, USA), where a stone block wall was found in 1928. The published account states that the discovery was made in Room 24 of Mine number 5, two miles north of the town, said to have been some two miles deep. On the day following blasting in this room, a number of cubic blocks of ‘concrete’ measuring about 305 mm (12 inches) square were found. Their six faces were all polished smooth to the point that they gave mirror-quality reflections; when broken, they proved to be filled with gravelly concrete. The room is supposed to have collapsed before any further work could be done on shoring it up. The collapse revealed an entire wall made from the same type of blocks and a similar wall was exposed some 91 to 137 m (100 to 150 yards) farther into the mine. The source claims that as soon as it learned about the discoveries, the mine company immediately ordered the workers from the shaft and forbade them to talk about what they had found. Mathis also claimed to have spoken to miners at Wilburton who had found a solid block of barrel shaped silver, with the imprints of individual staves still visible in it.
It is difficult to deal with this type of personal testimony. We don’t know who W W McCormick is or was, and there are a lot of McCormicks in Abilene: the best known is perhaps Wayne McCormick, a television newsreader. As for Atlas Mathis, we know that he had a long life (11 Oct 1892 to 15 Oct 1977) and that he was a resident of Heavener in the 1920s, so he was in the right place at the right time (I am grateful to the commenter Loyolalaw98 for pointing this out). One blogger, White Rabbit (from Missouri, USA), claims to have spoken to a grandson who was raised by Mathis (the post, hosted at Underground Ozarks’s forum, which is moderated by White Rabbit, was taken down some time after this page was first published in July 2007), but claims of this sort are not unusual in the blogosphere and must be treated with scepticism.
The story, which was first reported by Brad Steiger in Worlds before Our Own, has every appearance of a hoax. We do not have the testimony of Atlas Mathis himself, just the unsupported story related by a grandson, so it’s not even an eyewitness account. Given the alleged importance of the discovery, it shows a lack of curiosity on the part of Brad Steiger, who published Worlds before our own in 1978 and must have been researching it before Mr Mathis’s death, not to have interviewed Atlas Mathis in person. Why rely on the retelling by a grandson? The story crumbles under a lack of evidence: it is reported third hand, nobody else reported it and there is no contemporary documentation.