Black Stone - Scientific Origins

Scientific Origins

The nature of the Black Stone has been much debated. It has been described variously as basalt stone, an agate, a piece of natural glass or — most popularly — a stony meteorite. Paul Partsch, the curator of the Austro-Hungarian imperial collection of minerals, published the first comprehensive history of the Black Stone in 1857 in which he favoured a meteoritic origin for the Stone. Robert Dietz and John McHone proposed in 1974 that the Black Stone was actually an agate, judging from its physical attributes and a report by an Arab geologist that the Stone contained clearly discernible diffusion banding characteristic of agates. A significant clue to its nature is provided by an account of the Stone's recovery in 951 AD after it had been stolen 21 years earlier; according to a chronicler, the Stone was identified by its ability to float in water. If this account is accurate, it would rule out the Black Stone being an agate, basalt lava or stony meteorite, though it would be compatible with it being glass or pumice.

Elsebeth Thomsen of the University of Copenhagen proposed a different hypothesis in 1980. She suggested that the Black Stone may be a glass fragment or impactite from the impact of a fragmented meteorite that fell some 6,000 years ago at Wabar, a site in the Rub' al Khali desert some 1,100 km east of Mecca. The craters at Wabar are notable for the presence of blocks of silica glass, fused by the heat of the impact and impregnated with beads of a nickel-iron alloy from the meteorite (most of which was destroyed in the impact). Some of the glass blocks are made of shiny black glass, with a white or yellow interior and gas-filled hollows, which allow them to float on water. Although scientists did not become aware of the Wabar craters until 1932, they were located near a caravan route from Oman and were very likely known to the inhabitants of the desert. The wider area was certainly well-known; in ancient Arabic poetry, Wabar or Ubar (also known as "Iram of the Pillars") was the site of a fabulous city that was destroyed by fire from the heavens because of the wickedness of its king. If the estimated age of the crater is accurate, it would have been well within the period of human habitation in Arabia and the impact itself may have been witnessed. However, a recent (2004) scientific analysis of the Wabar site suggests that the impact event happened much more recently than first thought and might have occurred only within the last 200–300 years. The meteoritic hypothesis is now seen as doubtful, and the British Natural History Museum suggests that it may be a pseudometeorite, i.e., a terrestrial rock mistakenly attributed to a meteoritic origin.