Sonic detonators and scan hammers
Open your calldowns menu and either a plant Sonic Detonator or activate your Scan Hammer on the deposit.
Tip: Sonic Detonators yield twice the amount of resources when used on surface deposits compared to Scan Hammer. They are, however, consumables.
You get the Sonic Detonators from either drops, purchasing them off the market, or crafting. Recharable Sonic Detonators do exist.
Seismic activity (watch out!)
If you notice “seismic activity” on a particular surface deposit, dropping a sonic detonator or scan hammer on it will trigger a mini-boss fight with a modest reward.
AutoDetonator automatically selects a sonic detonator when looking towards a surface deposite (for harvesting metals).