Saltpetre

Saltpetre is obtained using a spade in the Hosidius region of Zeah, just south-west of the Tithe Farms, and west of the southern-most plough farms. It spawns on 1 of 5 locations, moving when it is depleted. The region is close to a bank, which is situated just north-west of the area.

Players with a high mining level can collect 1500+ Saltpetre per hour, however players with 1 mining will only be able to get about 850. This is because when you mine Saltpetre, you have a chance of receiving two blocks, and this chance is roughly equivalent to your mining level out of 100. A higher agility level, energy potions and weight-reducing clothing are also advantageous. A spade spawn can be found just north-west of the Saltpetre mines, inside a sheep enclosure. Alternatively, the NPC Konoo can provide a player with one, found by the Saltpetre spawn.

Use
It is used with regular compost to create Sulphurous fertiliser, which can then be used to gain favor with House Hosidius by donating it to the clerk southwest of the bank. This also grants 2 Farming experience per bucket of fertiliser made.

Saltpetre is also used to make dynamite for Blast Mining.