This article is regularly submitted to HN, but it's good reading every time. Winning the war against the marketing of the diamond industry will be hard, but a start is to keep spreading articles like the following:
http://www.huffingtonpost.com/ira-weissman/7-reasons-why-you...
7 REASONS WHY DIAMONDS ARE A WASTE OF YOUR MONEY
I've been in the diamond business for over 10 years. I've traveled all over the world buying and selling diamonds. I've passed through most of the major airports across the United States with about a million dollars worth of diamonds in a leather wallet stuffed inside my pants. I've bought and sold diamonds in Dubai, Mumbai, Moscow, Hong Kong, Paris, Stockholm, Tel Aviv, Madrid and Barcelona. Even today I am involved on the fringe of the diamond business, running a diamond education site helping would-be buyers.
Considering my deep personal involvement in the diamond business, my opinion might surprise you -- diamonds are a terrible waste of your money.
Even if this article doesn't convince your female friends, it'll spread some awareness and cause more people to view diamond engagement rings with a bit of doubt.
When I shared it on Facebook, I got likes from only male friends and arguments from a female friend. This was slightly unusual because such topics normally get a few likes from female friends. I guess there's a serious uncertainty among my friends about throwing away the valuing of diamonds that's been strongly ensconced in the minds of wider society.
Fundamentally, a large part of the worth of diamonds comes from their cost and the sacrifice they represent. This in turn is a conspicuous signaller of value, when women show their diamonds to friends ("look how much he loves me"). So any alternative to diamond rings has to show a similar level of value/worth. We have to try to beat diamond marketers at their own game - with equally powerful anti-marketing.
I'd advocate an approach of laying the groundwork early by sharing such articles regularly, and when actually in a relationship, offering a display of value that she appreciates (e.g. memorable trip to Europe, endowment to a cause of her choice, a custom-designed gemstone) in tandem with asking her to consider other gemstones, perhaps one in her favorite color. If the ground's been softened by our combined anti-marketing campaign, she might be willing to select and customize a stone that she genuinely finds beautiful and accept your specially planned trip (maybe extend it to Asia too, to up the friends'-envy quotient).
Or at least I hope as much.