Where are the oldest rocks on Earth?

Rocks are old – but some are older than others. Discover 3 contenders for the oldest rock on Planet Earth.



See, the Jack Hills are old. Really old – and ripe for study. The landscape is like a big, creased blanket of ancient rock, formed through geological processes that took place billions of years ago.

Much of this rock contains zircon: a hard, often colourful mineral that's commonly found as tiny crystals but is rare in larger forms.

In 2014, scientists tested some of the Jack Hills zircon using radiocarbon dating. What they discovered was nothing short of groundbreaking: those tiny zircon fragments were around 4.4 billion years old.

Considering Earth is only ("only") 4.5 billion years old, that's pretty significant. You literally can't get much older – at least within terrestrial boundaries.

What does 4.4 billion years look like? Numbers that large are hard to grasp.

The Great Pyramid of Giza is very old. It was built about 4,600 years ago. The Jack Hills zircon formed around 956,522 Great Pyramids of Gizas ago. 

Amazing. Awe-inspiring. Mind-boggling. But does it count?

The oldest rock, actually: Canada's Acasta Gneiss Complex

How do we define a rock?

When does a grain of sand become gravel? How big does gravel have to get to be called a stone? And is a rock just a large stone?

Geologists have their own definition of "rock". According to Wikipedia, it's "any naturally occurring solid mass or aggregate of minerals or mineraloid matter".

Interesting. And confusing.

In any case, a tiny fragment of zircon doesn't meet many definitions of "rock", geological or otherwise.

So, let's say the zircon doesn't count. It's the oldest thing, but it's not the oldest rock. The rock surrounding the Jack Hills zircon, in fact, was a mere three billion years old.

Where should we look next?

The answer is the Acasta Gneiss Complex in Canada's Northwest Territories. Here, among the icy, rocky wastes, researchers from McGill University discovered the oldest rock on Earth.

The rock in question isn't a loose stone or boulder. It's an eight-square-mile strip of volcanic rock known as the "Nuvvuagittuq Greenstone Belt". It might be 4.28 billion years old.

We say "might be" because there's some disagreement on its precise age. Some scientists argue that, while the magma that composed the rock was extracted from Earth's mantle 4.28 billion years ago, the rock itself is closer to 3.8 billion years old.

Can we find any rocks that are older than that?

Is Earth's oldest rock on the Moon?

While the Nuvvuagittuq Greenstone Belt is often cited as Earth's oldest rock, there are a few contenders for the crown. These include the Isua Greenstone Belt on Greenland and the Napier Complex in Antarctica.

But it might be that we're looking too close to home. Earth's oldest rock may, in fact, have come from the Moon. Or, to be more precise, it came back from the Moon.

See, in the early days of 1971, three astronauts jetted off to the Moon. These three men were the crew of Apollo 14: the eighth manned lunar mission.

The astronauts returned on 9 February, carrying a batch of Moon rocks (as astronauts are wont to do).

Except they weren't all moon rocks. In 2019, scientists tested the rock samples and discovered that a fragment actually came from Earth. The clue was in its geological makeup: the rock contained feldspar, quartz and our old friend zircon. These materials are common on Earth but rarely found on the Moon.

It turned out that at some point, around four billion years ago, a large comet or asteroid collided with the young Earth. This collision coughed up a cloud of rock fragments, some of which settled on our nearest astral neighbour.

Four billion years. If the Jack Hills zircon doesn't count as a rock and the Nuvvuagittuq Greenstone Belt is only 3.8 billion years old, then that makes this Moon sample the oldest rock on Earth. Now that it's back on Earth, at least.

And you thought waiting for a connecting flight was tedious. That little fragment of rock has probably endured the lengthiest stopover in history.

Welcome home, old chum.

Love rocks? We love rocks, too. In fact, we're inspiring a whole new generation of rockers with our interactive fossil dig activities. Held on most weekends and some weekdays, these fun-packed sessions are a great way for kids to learn about history and the natural world. Want to treat a little fossil lover? It's quick and easy to book online.