The headlamp you are given in Shinsekai Into the Depths is a very useful tool which you should take advantage of at every opportunity. When you press the button on your headlamp to turn it on the beam of light it emits will denote the discovery of rare minerals hidden within cavern walls when it comes into contact with them. When the beam of light from your headlamp shines on them they will by given a red outline which makes them easy to spot.
Rare minerals are hidden everywhere and whenever your headlamp points them out you need to make sure you mine them. Some of the minerals you will be able to find are particularly valuable, these include the rare brown mineral which enables you to upgrade your suit's pressure threshold, allowing you to descend deeper into the depths and green and yellow crystals you find are needed for your suit's auxiliary and weapon upgrades. It is recommended that you keep you headlamp on and only turn it off when you encounter the light sensitive carnivore creatures that are attracted by light and noise and will attack it's source.
Shinsekai: Into the Depths Trailer