CHICAGO (WLS) -- There's precious cargo in some crates, which scientists at the Field Museum have been waiting to unpack.
At first glance, they look like slabs or blocks of limestone. But a closer look reveals the fossil of a meteorite.
Fossil meteorites were donated to the Field Museum and are some of the rarest geological specimens in the world. Collection Manager Jim Holstein said these meteorites are a window to the past.
"We're talking before the dinosaurs. We're talking 470 million years ago," Holstein said.
Holstein said 470 million years ago, in outer space, something crashed into an asteroid. Some of the pieces that broke apart fell to the earth as meteorites.
"They sank down to the sea floor and became embedded in sea floor and formed limestone rock later," said Philipp Heck with the Field Museum.
In the 1980s, workers in a limestone quarry in Sweden noticed some of these fossil meteorites.
"All the quarry workers were trained to look for these fossil meteorites and they've been finding one to two a year and this collection amassed over the years," Holstein said.
But some meteorites did not fall to earth right away after that impact millions of years ago. Scientists said the Park Forest Meteorite that fell in March of 2003 dates back to that ancient collision.
As for these fossil meteorites, scientists said the excitement is just beginning. They plan to do a lot of research.
"We're also going to study whether this had an impact on earth's systems on earth's climate, the biosphere," Heck said.
Once the collection is finished being catalogued, some of the larger pieces will be put on display at the museum.