Thursday, 8 January 2009

Space rock

I sell a fair bit of meteorite material. Mostly it comes from a relatively small number of well-known sites. At the moment, I have examples from six meteorites localities, which is more than I would usually.

Briefly, a meteorite is a lump of stone or metal, or both, that has come from Outer Space. Where aliens live. Most meteorites that fall, over 90%, are stony ones - chondrites and further subdivisions - that are mostly composed of silicate minerals, similar to many terrestrial rocks.

Most meteorites that are found are iron, with about 6% nickel. The reason for this discrepancy is that iron meteorites are easier to detect (with metal detectors) and easier to identify. Chondrites are stones, and look like other stones with a slight sheen. There are a small percentage that are a combination of metal and mineral, too. Some pallasites contain beautiful green olivine crystals.

It's easier to find meteorites in places where anything different sticks out. A desert, an icy plain, or a small country pub, for example. In the desert, anything that's not sand is worth a second look. If I spent any amount of time in the desert, I'd be very keen to look at something that wasn't sand, and would consider walking a few hundred yards to do so. You get the idea.

When a meteorite falls - and a few hundred do each year, at least - it often breaks up before hitting the surface, and doesn't usually do as much damage as you'd think. A lot of the more commerically available material comes from sites where there was a relatively big fall, and a large scattering of material. Meteorites are usually named after the places they are found - Campo del Cielo in Argentina and Sikhote Alin in Russia provide a lot of nice iron meteorites, while a lot of chondrite stuff comes from North West Africa (and is called NWA).

The majority of meteorites are thought to date to the time of formation of the planets of this solar system, which puts them around 4.55 billion years old. They had been lazily floating around for a long time before crashing to Earth. In the film Armageddon, Bruce Willis selfishly prevents a huge lump of rock from landing on the Earth. Think what we could have done with all that rock! We could have build a nice castle.

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