The secret of portfolio planning is balance. A portfolio containing several stones of high quality is generally preferable to a single stone in the bigger picture of ones long term investment strategy. This gives the portfolio flexibility because of worldwide geopolitical diversification. This being said, a gemstone portfolio can prudently be built by adding one world class gemstone at a time. If one only had the money to buy only one gemstone, a fine, world class, Pink Emerald would be a good solid choice for this single purchase as long as the purchaser's other assets were sufficiently liquid enough that they would not relying on this or any gemstone acquisition for income, sustenance or cash flow.