You don't. You can either mine it, buy it, or get it as a random event prsent.
To get uncut diamonds you can get them as a monster drop, from one of the gem stores, buy from other players, or purchase through the grand exchange.
Quests, shilo village gem rocks, monster drop and the grand exchange.
Uncut Gem - 1990 TV was released on: USA: 19 April 1990
a sapphire from an uncut sapphire by using a chisle on it, and smelt a gold bar into a sapphire necklace.
You can't. You can only obtain it by mining gems, lucky when mining ore, killing or buying.
There is a gem store to the east of Falador.
Lvl 82 Skeltons can drop uncut oynx but vary rare
To cut diamonds, use a chisel on an uncut diamond in RuneScape. Further cut diamonds can be cut into bolts for rangers.
Prices are changing alot for diamonds, but right now an uncut diamond's price is 10,600 gp.
It is not possible to obtain onyx gems easily; they can be bought in the TzHaar city from the gem and ore store, obtained as a reward from the Fight Kiln minigame, rewarded from a challenge mystery bag, looted from a Kingly impling (rare), or mining with a gem-finding scrimshaw.
As of February 08, 2013, an uncut diamond is worth 6,818 coins.
You cut every gem with a chisel.