MUSEUM OF NATURE

Press, Volume CVI, Issue 31316, 11 March 1967, Page 16

MUSEUM OF NATURE

ARIZONA ’S ROCK FROM THE SKY

(Contributed by the Canterbury Museum) JN 1897 a weighty specimen was unloaded from a waggon at the Canterbury Museum. This was a half-ton piece of iron —found near Canyon Diablo in Arizona a few years before that had been obtained from Ward’s Natural Science Establishment in New York in exchange for moa bones.

Its arrival must have been a major triumph for the then director, Captain F. W. Hutton.. This 10741 b specimen, two feet across, which now sits in a corner of the von Haast Hall of Geology, is only a fragment of the giant Canyon Diablo meteorite.

Some 20,000 years ago this meteorite, perhaps 200 feet across and two million tons in weight, blasted through the atmosphere and hit the flat Arizona desert with the explosive force of a 30-megaton hydrogen bomb. The explosion blew out a crater three-quarters of a mile across and 600 feet deep that is now called Meteor Crater. The rim is strewn with loose blocks of rock, some weighing as much as 4000 tons.

this in the tiny spheres of In the sandstone of the crater floor, rare forms of silica are found; forms which can be produced only at very high pressures, such as on the impact of a meteorite. Only 30 tons of meteorite fragments, a minute fraction of the supposed two-million-ton meteorite, have been found. It is now known that most of the original meteorite must have vaporised on impact; there is evidence for

iron found near the crater which are the condensed droplets of gaseous iron. Third Largest

The largest fragment so far found weighs 14001 b; the Canterbury Museum specimen is the third largest, and the largest outside the United States.

Although it is difficult, and perhaps undesirable, to attach a price to museum specimens, it is probably the most valuable single specimen in the museum. , Before it was realised that the main mass of the meteorite had been destroyed on

impact, almost a million dollars was spent on drilling into the floor of the crater. It was realised that a deposit of more than a million tons of iron would be a very rich find, particularly as the fragments analysed contained up to 7 per cent nickel, as well as cobalt and platinum. Although the hopes of the mining companies proved fruitless, their investigations yielded much useful scientific information.

The Canyon Diablo meteorite is one of four meteorites known to contain diamonds though these occur only as minute crystals.—D.R.G.