It's a bit of a trick question! It depends on the specific rocks. Here's why:

* Igneous rocks form directly from molten rock (magma or lava). They can be very old, some dating back to the early Earth.

* Sedimentary rocks form from the accumulation of sediments (like sand, mud, or shells) that are then cemented together. This process can happen over relatively short periods of time, but also over millions of years.

Here's the important thing: A sedimentary rock can be older than an igneous rock.

* Example: An igneous rock formed a million years ago could be eroded and broken down into sediment, which then forms a sedimentary rock that is 900,000 years old.

In general, the oldest rocks on Earth are igneous rocks. This is because sedimentary rocks are made from pre-existing rocks, meaning they cannot be older than the original rocks they were formed from.