I have said it again and again: "Nothing delivers shareholder value to gold investors quite like the exploration drill."

To remain on my short list of the greatest investments in gold, a miner needs to show me a clear road to meaningful exploration upside. IAMGOLD (IAG 6.30%) continues to show golden promise in this regard, and is effectively tracking fresh gold ounces in North America and South America alike.

In the North, the company increased total resource ounces at the Côté gold project in Ontario by 20% last week. In fewer than four months since acquiring the asset, the shareholder value gained in that $620 million transaction is already looking positively precious. Of particular significance within IAMGOLD's updated resource estimate is the nearly fourfold increase for gold ounces in the "Indicated" category, from a modest starting point of 0.93 million ounces to an eye-catching hoard of 3.56 million ounces! And with a substantial tally of 4.66 million remaining in the "Inferred" category, all indications point to further accumulation of indicated ounces as IAMGOLD continues an aggressive exploration campaign.

Further south, IAMGOLD's road to exploration upside reaches clear into Colombia. Since acquiring a stake (currently 14%) in junior explorer Tolima Gold last year, IAMGOLD has offered technical collaboration by three of the company's geologists while keeping a close eye on Tolima's progress. This week, IAMGOLD signaled considerable interest in Tolima's early stage ANCAL project, entering an option agreement to earn between 51% and 70% ownership of the project.

Exploration drilling at ANCAL is in its infancy, having just commenced with an initial 10,000-meter program in May of this year. But early indications point to ANCAL hosting gold/copper porphyry mineralization. Given the tremendous scale of some of the world's leading porphyry deposits -- featuring Freeport-McMoRan Copper & Gold's (FCX -1.96%) legendary Grassberg mine and Newmont Mining's (NEM 0.67%) Boddington mine -- it's no wonder IAMGOLD CEO Steve Letwin declared back in July that he is "optimistic in Tolima's future resource potential."

I am optimistic, too; not only in this latest early stage exploration opportunity, but in the entirety of IAMGOLD's potential to generate meaningful shareholder value through forthcoming exploration. In my view, the shares have never properly adjusted to reflect the value created by preceding exploration achievements like the miner's 467 million inferred tons of rare earth elements or the 616% increase in niobium reserves at the Niobec mine in Québec.

IAMGOLD's various exploration teams have proven their excellence in spades over the six years since I initiated my bullish CAPScall on the stock, and as a shareholder I look forward to the treasures they're bound to identify over many years to come. For several years running I have touted the extraordinary potential for organic resource expansion by the likes of Goldcorp (GG) and Yamana Gold (AUY). Increasingly, IAMGOLD looks beautifully positioned to deliver that most efficient form of shareholder value creation.