Sapphire
From Runescape Guides & Runescape Tips
The Uncut Sapphire is one of the many gems that can be found and cut in Runescape. For non-members, this is the lowest level gem. It can be used in crafting to make a Amulet of Magic.
To cut this gem, use a chisel on it. you need a Crafting level of 20 or greater.

