Miner's Mate (5e Equipment)
From D&D Wiki
Used most often by impatient and foolish miners, this metal spike is filled with an explosive concoction that detonates with a flame-less explosion when exposed to air. It is hammered into the surface that the user wishes to excavate, then the flat end of the spike is removed. After 1 minute the seal dissolves and the spike explodes in a 20-foot radius sphere.
All creatures in the sphere must make a DC 15 Dexterity save, taking 3d6 piercing damage on a failed save or half as much on a successful one. If the spike was hammered into an object, that object takes double damage.
Weight: 4 lb