A dense essence block is a raw material used in the Runecrafting skill to make blood runes and soul runes. A dense essence block can be used on the dark altar (requires 100% favour with the Arceuus House) found north-west of the dense runestone mines to infest them with dark power, turning them into dark essence blocks. These dark essence blocks can be crushed with a chisel to turn into dark essence fragments. These dark essence fragments can then be used for runecrafting blood and soul runes.
Another use for these blocks (though not recommended) is giving them to Clerris to get house favour. This method of gaining favour only grants 0.1% per block donated, versus 2.5% per book or 5% per manuscript donated in the library. However, this method does remove the constant running required for the other methods and could be of use to people with lower Agility levels.
Players cannot get the rock golem pet while mining dense essence blocks.
Players will always get one dense essence block every nine ticks, regardless of the used pickaxe. Having a high Mining level is advantageous when mining the essence; The higher their level, the slower it depletes.