Geologist is the second Milestone in Phase three of No Man’s Sky Expedition Three: Cartographers. To complete it, you need to scan and discover a total of 18 types of minerals on the planet during your time exploring it. While this sounds easy, it can take you a shockingly long time to complete if you aren’t paying attention. This guide covers a few tips for completing the Milestone before it starts to block progress.

Look for question marks

Any minerals that you haven’t discovered will appear without a name as your reticule passes over them. They’ll be named “????” and have undiscovered properties. These are the minerals that you need to scan before mining. If you ever see a mineral with these qualities, it’s one that you need to scan for your collection.

Scan every rock you see

The key to completing this Milestone is scanning rocks. You need to scan every one you come across and keep an eye out for new ones everywhere you go. No matter how many times you think you’ve scanned a rock, it’s always worth pulling up your scanner one more time to double check that this one isn’t a new discovery. We found several rocks that looked the same but were all completely new to us before scanning them.

Look underwater

The bodies of water on this planet hide new rocks that don’t appear anywhere else on the planet’s surface. Swim under the surface and pull up your scanner. This allows you to swim in first person and see all the rocks around you in a new light. You’ll quickly notice any rocks you haven’t discovered as long as you’re swimming like this. Try to use the Terrain Manipulator to break into lower caves underneath bodies of water to discover even more new types of minerals. This is also a fantastic way to discover new Flora for the Botanist Milestone too.

Once you’ve discovered 18 minerals, the Milestone will trigger and complete. You can then claim the Magnetic Resonator plans, and Industrial Excavation plans as a reward from the Expedition menu.