It might be time to call in Leo again. When DiCaprio's 2006 film Blood Diamond alerted the general public to the humanitarian horrors behind their bling, suddenly everyone knew what a conflict diamond was: stones mined in shocking conditions in warring regions such as Sierra Leone and the Congo, and sold to fund more war. Six years on, we could use a reminder.
The film was set in 2000, before the implementation of the Kimberley Process Certification Scheme (KPCS) - an international governmental agreement that banned trade in conflict diamonds, allowing diamond shoppers to breathe a sigh of relief as they bought their guilt-free rocks.
Unfortunately, all that glitters is not diamond - jewellery is made from a multitude of precious materials, from gold to coloured stones, all of which have their own thorny issues. And the Kimberley Process itself has recently come under severe pressure, thanks to the agreement to designate diamonds from the Marange region of Zimbabwe as non-conflict.
Global Witness, the pioneering organisation in recognising the link between diamonds and conflict, and instigators of the KPCS, withdrew from the agreement late last year, causing serious damage to the scheme's credibility.
"The decision to endorse unlimited diamond exports from named companies in the Marange region of Zimbabwe - the scene of mass killings by the national army - has turned an international conflict prevention mechanism into a cynical corporate accreditation scheme," said the trust's founding director, Charmian Gooch, in a statement.
In other words, says Greg Valerio, one of the co-founders of the human rights and environmental organisation Fair Jewellery Action, "human-rights-abused stones are now finding their way into high-street jewellery shops."
No longer involved with Cred Jewellery, Valerio is one of the leading forces behind Fairtrade and Fairmined gold, which ensures that artisanal miners, some of the poorest and most imperilled people in the world, can live and work in safe, non-toxic conditions and are paid a fair price for their gold. He has, however, little time for the term "ethical", saying: "There's no definition, there's no criteria, there's no framework of reference."
That might partly explain the industry's reluctance to noisily jump on board the ethical train in the way that, say, fashion has. It was seven years ago that the Responsible Jewellery Council (RJC)was set up by 14 founding members, including the likes of Cartier and the Diamond Trading Company (part of diamond giants De Beers). But while smaller-scale boutique jewellers such as CRED or Ingle & Rhode have been using ethics as their major selling point, it's only since the official launch of Fairtrade and Fairmined gold and Ecological Gold (extracted without chemicals) last February that there has been a noticeable increase in the ranks of high-end established jewellers openly claiming their ethical credentials.
Yet the RJC's Chief Operations Officer, Catherine Sproule, points out: "I know of no other jewellery organisation that can make the claim that they have a completely transparent website and they have every bit of their work vetted by Global Witness and the WWF and Social Accountability International. RJC's membership has grown 50 per cent a year since 2008, even through that tough, tough time."
In a recent independent study of the validity of a number of major jewellery companies' ethical claims, Cartier and Boucheron were praised for their commitments to responsible practices, going far beyond the usual corporate social responsibility policies.
Nawal Aït-Hocine, corporate responsibility director at Cartier, explains: "We consider that we have a duty to offer our customers creations that are not only beautiful, desirable and adorned with the best quality stones and so on, but that are also made in a responsible way."
For this venerable brand, that has meant not only helping to found the RJC, but also taking an early stand on sourcing its precious materials - Burmese rubies are a no-no, as are diamonds from the Marange fields. They also buy the entire production of the Goldlake gold mine, in Honduras, a socially and environmentally responsible mine that uses no mercury or cyanide in its processes.
"That does not cover all our demand," admits Aït-Hocine, "but it is a first step and it's a way to show that practices can change and that there are other ways of exploiting gold." The rest of Cartier's gold is bought in alloy form from refiners who are members of the RJC.
Stephen Webster, the favourite jeweller of rock stars the world over and creative director of Garrard & Co, was, along with the likes of Pippa Small and Fifi Bijoux, one of the first designers to take up the Fairtrade and Fairmined gold, but he also cites supply as the reason he only currently uses it on his bridal collections.
"It's still only early days," he acknowledges, "but at least there is a supply chain, and villages and communities that know about another way are going to want to do it, because they all know that mercury kills them; they're not daft."
The consumer bears a real responsibility, too: after all, when customers started really asking about blood diamonds, the people selling them to us started to provide conflict-free stones.
"The consumer needs to ask the transparency and traceability question," says Valerio. "Where does my diamond come from? Where does my gold come from? Where do my gemstones come from? For me, the basic minimum requirement for anybody to use the term ethical should be that they have mine-to-market traceability on their products."
If the general public cares, so will retailers. The question for us, though, is what exactly are we caring about?
"It's humanitarian; it's about people on a dollar a day, and then they're working every single day in mercury - it may as well be a bath," says Webster. "Kids are playing next to the mercury pits, and people are slewing this stuff around as though it's dishwater or something. And then if that gets into the water table you've got an environmental catastrophe as well.
"Wherever there is the prospect of a bit of gold, the poorest people on the planet migrate, to make a living, and that's a reality."
Coloured gemstones are subject to similar issues, whether it is funding oppressive regimes or destroying vast tracts of valuable ecosystems. That was an issue that Fabergé highlighted earlier this year, when it revealed its Romanov necklace, remarkable not only for its considerable size and peerless craftsmanship but also for its 79 Zambian emeralds sourced from Gemfields, an ethical mining company owned by Pallinghurst - also Fabergé's owner.
Ian Harebottle, the CEO of Gemfields, argues that ethical processes, far from costing more, can actually save money for the mine. "What Gemfields is doing goes way beyond [environmental liability]. We inherited this mine, it was run by the government in Zambia for many many years, and whenever they dug they left a massive hole. We worked closely with the World Land Trust, the universities and the government, and we've been able to fill many of those holes with water and fish so what was a hole in the ground is now a lake that's providing fresh water and fish.
"We're also working with universities to go to the next level; not just making it back to how it was but back to how it should have been.
"We're leaving projects that create sustainable benefits - what's the old story? 'If you give a man a fish, you feed him for a day; if you teach him how to fish you feed him for life'. We've built four schools, two clinics, and we're involved in two farming projects, so all of the fresh produce that we eat on the mine comes from these local farmers, and all excess supply we take into the local village and sell in the market."
But do we really need to be mining so much anyway? In the tents at New York Fashion Week for the last two seasons, the jewellery company Circa has mounted prominent exhibitions. Circa is the world's largest buyer of high jewellery from the general public, and many of the pieces it buys are recycled and returned to the market as gold and gems.
The co-founder, chairman and CEO of Circa, Chris Del Gatto, makes the argument that recycling diamonds and gold can reduce the need for mining with what he calls "very, very real positive environmental consequences.
"By every analysis there's anything from $6-8 trillion [Dh22-29.3 trillion] of diamonds and jewellery that sits in the general public's hands, and it's anyone's guess what percentage of that is just sitting in a jewellery box or a safety deposit box," he says. "Because of that you have mining going on at an elevated level when the product is already sitting out there."
Ultimately, it comes down to what you want from your jewellery. If it's just sparkle you seek, you can find it in abundance, and you needn't worry your pretty little head about where it comes from. But, says Sproule, for most people, jewellery is sentimental.
"Jewellery is passed down, it's treasured, it's worn next to your skin; it's not in one season and out the next. If it'a a mother who buys a gold locket for her daughter's graduation, she wants to buy that knowing it's not associated with collateral damage. If it's going to your 13-year-old daughter, you don't want to think a 13-year-old has just made it."
Whether shoppers who are not already ethically engaged can be persuaded to think about this when they are buying is still to be proved. Harebottle says, "It's changing at the very high end, but in general if the price of the ethical gem is higher, what they do is just choose not to ask the difficult questions."
Webster is more hopeful: "The more available it is, the more normal it is, so then you get a generation of people who like Fairtrade coffee, bananas, cocoa, whatever, and it becomes their choice, if you like."
Valerio puts it more bluntly. "The consumer has just not made the connection that that beautiful piece of expensive jewellery you're buying for your fiancée or your wedding actually comes from a filthy hole in the ground that has probably impoverished communities, denuded the environment, toxified it and created all kinds of indigenous and community-based human rights issues."
Sounds like a case for DiCaprio.