I was watching a show last night about these guys that hunt for meteorites and they talked about this huge one that was used as an anvil and now presides in the smithsonian. I found this little article on it I am sure there is much more info out there but this seems interesting check it out http://www.meteorite...cted_TUCSON.HTM
How Old Are Meteorites?
If meteorites formed from dust from the early universe, then we would expect them to be very old. Indeed, this is what we find. Scientists have used radiometric dating to measure the ages of meteorites. The results show ages of around 4,500,000,000 years--about seven hundred million years older than the oldest rocks on Earth.