Diamonds might be very popular among bling-loving celebs, but the history of some of the precious stones isn't quite so glamorous.
Human rights groups say lots of them are what's known as conflict diamonds - diamonds with a violent past.
What is a conflict diamond?
Also known as blood diamonds, conflict diamonds come from war-torn countries, usually in Africa.
These countries include Angola, Liberia, Sierra Leone, The Democratic Republic of Congo and Cote d'Ivoire (Ivory Coast).
They have been used to pay for weapons to continue the fighting.
It's illegal to buy or sell conflict diamonds.
How big is the problem?
It's impossible to say exactly how many conflict diamonds are out there.
But, for example, we do know that recently, stones worth over £11m have been smuggled out of Cote D'Ivoire every year - and there could be lots more.
What's being done to stop the trade?
In 2000, lots of people from the diamond industry set up something called the Kimberly Process.
This is a scheme which aims to track every diamond from the place it was mined to the place it is sold, meaning illegal diamonds can't slip through.
But human rights groups say it's not being enforced well enough, meaning blood diamonds could be in our shops.
What does the diamond industry say?
It says conflict diamonds are a very small part of the world trade.
They also say legal mining is very important for the countries which do it, so avoiding diamonds would do more harm than good.
They have also started paying money to charities in Africa to try to fight problems like poverty and disease there.
Human rights groups say this is just masking the bigger problems.
What could we do?
Obviously you're not going to be buying too many diamonds yourself.
But if you know someone who is about to buy any, get them to ask the shopkeeper to prove where they come from, so you know they're not conflict diamonds.