From the RuneScape Wiki, the wiki for all things RuneScape

Bonemeal

Also known as?	Ground bones, crushed bones
Release date	Unknown edit
Members only?	Yes
Quest item?	Yes - Ghosts Ahoy
Tradeable?	No
Equipable?	No
Stacks?	No
High Alchemy	Cannot be alchemised
Low Alchemy	Cannot be alchemised
Destroy	Drop
Store price	Not sold
Examine	A pot of crushed [type of bones].
Weight	1 kg

Bonemeal is an item that players need during and after the Ghosts Ahoy quest. It consists of a pot filled with bones (need not be normal bones) that have been crushed in the bone grinder at the Ectofuntus.

Along with a bucket of ectoplasm, players may use a pot of bonemeal to make 5 ecto-tokens. The bones used in the bonemeal give 4 times the prayer experience when used to worship the Ectofunctus. They are sorted separately per type of bonemeal in the bank account but are all labeled Bonemeal. You can get the type via the Examine option of the pot. It show something like A pot of crushed big bones.

Trivia

On 27 January 2009 the left click empty option was replaced with use so you can no longer suffer by emptying the bonemeal accidentally.