For both base and precious metals, gold production from the world's established mines is dropping, and new deposits are becoming more difficult and expensive to find. In addition, even newly discovered deposits take time to bring into production. In the meantime, demand (both jewellery and industrial) continues to grow.
There are two types of opportunities in this sector: buying mining stocks of existing gold production companies that are undervalued and/or are in a position to grow their reserves and production, and buying mining stocks of junior explorers on the verge of significant reserve/production increases through exploration discoveries.