This might be it...still trying to find the report.
Coloured diamond investment has a recession proof track record. History shows, coloured diamonds have been one of the best performing assets during periods of inflation and currency devaluation. Since formal records began in the 1970’s, prices for the highest grades of coloured diamonds have increased in value by an average of between 10-15% per year, with rarer colours and higher grades enjoying the greatest appreciation – even in times of economic instability. In addition, this appreciation has statistically been non-correlated to the stock and bond markets, an important consideration for investors seeking a diversified portfolio.
Bloomberg Tv is about to run another segment on diamond investing, similar to other commodity ETF's. ~Fusion Alternatives Investing-Diamonds are a safe haven like gold. Buying physical diamonds and storing them.