Diamond

A Diamond is a a gem that is used in the crafting skill. The gem is obtained from cutting an uncut diamond and can be made into various pieces of jewelry.

Jewelry
For more details, see Crafting

Diamonds can be crafted into rings, necklaces and amulets. However, in RuneScape Classic, the only useful piece of jewelry is the amulet because no other pieces can be enchanted and provide no bonuses.