A Rock Formation is where players are able to obtain tephra. This is then refined at a nearby furnace into refined tephra, and then imbued at the nearby altar into imbued tephra. In order to remove Zalcano's armour, and mine her when it's removed, players must throw this imbued tephra at her.
There is a 1/127 chance that a crystal shard will be obtained while mining tephra.
There are three variants:
- The regular Rock Formation slowly gives out tephra when mined.
- The Rock Formation (Glowing) has a vastly increased rate of obtaining tephra when mined. It can give multiple at a time as well.
- The Rock Formation (Depleted) is the state of the rock formations whilst Zalcano is not present in the prison.
The Varrock platebody's effect of mining two ores at once activates when mining tephra.
When Zalcano first spawns, the rock formation in the north-east corner has the highest chance of glowing. If not north-east, it'll be south-east or north-west.
Watch out for Zalcano targeting the glowing rock with a magic attack, as this will make the rock explode, dealing ~30 damage to anyone still standing next to it. Another rock will start glowing instantly. Relocate to this one if you haven't acquired enough tephra yet.