E-Answer.Net

Go to DCLA diamond graders in Sydney, you can look them up on the net and give them a call, they are really nice people and extremely trustworthy and helpful. It stands for Diamond Certification Laboratory of Australia. They can grade your diamond and give you a certificate for around $100, maybe less.

You can then get a valuation from a jeweler, get a few opinions. Then you can start advertising. You can try the net or the paper. Be careful when exchanging your diamond for money, be sure to clear a cheque before you hand over the diamond or ask for cash and make sure you are not alone.

There are diamond traders that can do this for you too, they will ask for a commission in return. DCLA will explain all your options.