Business Green: A new exchange-traded fund (ETF) covering rare earth metals, many of which are crucial for the development of clean technologies such as solar panels, attracted widespread investor interest in its first day of trading last week. The Rare Earth/Strategic Metals ETF was launched by money management company Van Eck, and began trading on the New York Stock Exchange as REMX. An ETF tracks a range of stocks, but can be traded as a single stock on its own. The rare earth ETF is designed to follow…