Finding gold when you go digging for it isn’t incredibly likely. What’s even less likely, however, is finding a meteorite. This is exactly what happened to one Australian man who thought he had a rare mineral on his hands. What he actually had is far more rare, more scientifically interesting, and more informative as to our galaxy’s history.

A treasure hunt

In 2015, a man named David Hole was searching for gold in Maryborough Regional Park (an old center of the Australian gold rush, near Melbourne) with his metal detector, hoping, as so many do, to find a bit of the rare substance. While searching, he found a large, extremely heavy red rock, and took it home, hoping that there was some gold inside.

For the next three years, he tried to crack open the rock, but it was nearly impossible for him to do so. A sledgehammer wouldn’t crack it open, a saw wouldn’t cut through it, and even acid wouldn’t put a dent in it. Having tried everything he could, Hole finally took it into the Melbourne Museum, hoping they would be able to identify it. And they did: as a rare meteorite from outer space.

What gave it away?

The meteorite’s enormous weight was one clue. Geologists at the museum explained that Earth-native rocks of this size would never be this heavy. Another clue was the strange dimpling effect all over the outside of the rock; this happens when the meteorite is entering Earth’s atmosphere, as it starts to melt due to the extreme heat, and so the dimpling is formed. Evidently, this is a pretty big giveaway for rocks that have entered our system from the outside.

Additionally, once they were finally able to cut it open (using a diamond saw—this meteorite is one tough rock), scientists could see small, crystallized droplets of metallic minerals, which are called chondrules. They also discovered that the inside of the rock has a fairly high percentage of iron, which might not mean much to the layperson, but for scientists, this classifies the meteor as an H5 ordinary chondrite. The nearly 40-lb rock is estimated to be about 4.6 billion years old.

What does it tell us?

While scientists at the museum aren’t able to nail down all of the details surrounding this meteoric masterpiece, they do have some pretty narrow guesses and quite a few tidbits of information to share with us about it. Meteors are treasure troves of information about our solar system, as many of them contain what scientists refer to as ‘stardust’, which gives us a glimpse as to how stars form in our galaxy. Other meteors contain even more information about our galaxy.

This particular meteorite, scientists are pretty certain, came from the asteroid belt between Mars and Jupiter. They think it may have crashed into another asteroid, pushing it off course, and ended up falling to Earth. While they can’t say for sure how long it’s been a resident of our planet, they’re pretty sure it’s been here for somewhere between 100 and 1,000 years.

There are a lot of things that make this meteorite as rare as it is. Firstly, it’s a huge specimen: the second-largest Australia’s ever seen. The internal composition and age of the rock also contribute to making it a pretty rare meteorite. And, in terms of numbers alone, scientists remind us that meteorites are far rarer than gold. While thousands of gold nuggets have been found in Australia, only 17 meteors have ever been found there.

That’s a pretty amazing scientific discovery from a man walking around doing his weekend hobby. Next time you see a funky-looking rock, maybe you should try taking a second look; you never know when you might actually have a meteorite on your hands.