Archduke Joseph Diamond The Archduke Joseph Diamond was recently sold at auction for nearly US$21.5 million (A$20.7m)

This article suggesting that high-end diamonds are a "bona fide investment vehicle" recently caught my attention:

At the World Diamond Congress in Mumbai in 2012 there was extensive discussion about the investment side of diamonds, and a number of highly knowledgeable individuals discussed this in depth. Most noted was Charles Windiam, who provided a excellent insight into the investment side of our market, and wonderfully controversial to say the least... I do love when someone challenges the status quo.

I believe before we get carried away with this romantic notion of diamonds as an investment for the non diamond dealer or diamond trader, we need to pose a few questions. At what price is this consumer buying the goods? Is this purchase limited only to multi million dollar stones? And lets not pretend we are a commodity in the true sense even though amongst our trade we have fallen to this level. Simply put, you want to call this an investment like other commodities, lets have set that diamond grading standard which is internationally recognised and locked in. When the famous 4 C's parameters are massaged constantly as we have witnessed in the last few years with the majority of laboratories, with standards based on commercial considerations, we will never move to the true definition of a commodity. The pricing tools currently used are neither transparent nor accurate but merely a guide for those who have extensive knowledge. Let's not suggest to the unknowing consumer that diamonds are a good investment, unless they have a spare few million and can add a bit of value themselves like if Brad bought a 20 ct for Angelina.