This stage alone can run for years. Most prospects never clear the bar; a deposit has to be big enough, and rich enough, that digging it up costs less than the gold it yields. In practice, that filter is tough to clear. As a result, the gap between a geologist's first good sample and a working mine has stretched over time: S&P Global Market Intelligence's research puts the current average at roughly 16 to 18 years for mines that started production in the 2020s, up from under 13 years two decades earlier (S&P Global Market Intelligence). Crews build roads, power lines, water systems, and a processing plant before extraction even starts. That is why so much money goes into the ground before any gold comes out of it.

What's the Difference Between Open-Pit and Underground Gold Mining?

Once a deposit is confirmed, the mining method depends on depth.

Open-pit mining works when gold-bearing rock sits close to the surface. Crews dig huge benched pits in stages and haul the ore out by truck. Many of the world's largest gold mines use this method, including big sites in Nevada and Western Australia. It lets them process huge volumes of lower-grade ore at scale (USGS).

Underground mining works when the ore body runs deep. Shafts and tunnels follow the vein. Crews bring ore to the surface in smaller, higher-grade loads. In general, it costs more per ton. Even so, it pays off when the gold sits too deep to justify stripping away everything above it.

A third method, placer mining, recovers gold that already washed out of its source rock. That gold settles in riverbeds or gravel over time. This is the oldest form of gold mining in human history. It still supplies a real share of output today, especially through small-scale operations (USGS).

How Is Gold Separated from the Rock That Contains It?

Raw ore is not gold. It is rock with gold locked inside it, often just a few grams per ton. Getting from one to the other takes several steps.

Crushing and grinding. Crushers break the ore down first. Rotating mills then grind it into fine powder. Mills use steel balls, or sometimes just the ore's own weight. The goal is simple: expose as much gold surface as possible, so it can be reached in the next step (Britannica).

Leaching. Workers mix the ground ore, now a slurry, with a weak sodium cyanide solution. Concentrations run just 0.01% to 0.05% cyanide, or 100 to 500 parts per million (International Cyanide Management Institute). Cyanide is one of the few chemicals that dissolves gold in water; miners have used it this way since 1887. The cyanide bonds to gold atoms and forms a soluble complex. That pulls the metal out of the rock and into solution.

How Do Workers Recover and Secure the Gold Safely?

Adsorption and recovery. Crews pass the gold-laden solution through activated carbon which adsorbs the gold-cyanide complex out of the liquid. Workers call this step carbon-in-leach, or carbon-in-pulp. Next, an elution step strips the gold back off the carbon. Refiners then pull the gold out of solution two ways. Electrowinning uses an electric current to plate gold onto a cathode. The older Merrill-Crowe method uses zinc to make the gold settle out (Britannica).

Cyanide carries real danger at high strength. That is why the mining industry follows the International Cyanide Management Code. This voluntary rulebook, set up in 2002, covers how cyanide gets made, moved, stored, and used at mine sites. It focuses hard on worker safety and watching the environment (International Cyanide Management Institute). The industry has issued more than 1,000 certifications under the Code since 2006.

How Is Gold Refined Into Pure Bullion?

What comes out of recovery is not bullion yet. It is a rough mix called doré. Doré typically runs 60% to 90% gold, with silver and trace metals making up the rest (USGS). A refinery turns doré into certified bullion.

Two methods dominate the industry.

The Miller process, patented in 1867, blows chlorine gas through melted doré. Nearly every impurity reacts with the chlorine gas. Each one forms a slag on top, or boils off, while the gold itself resists the reaction. The result is gold at about 99.5% purity. It is fast, and it is cheap (Britannica).

The Wohlwill process, built in 1874, uses electricity instead of gas. A casting of impure gold acts as one electrode in an acid bath. A current dissolves gold off that electrode. Nearly pure gold then plates onto the other electrode, while other metals stay behind in the liquid. This method runs slower. It also ties up more cash in the process. But it pushes purity up to roughly 99.99%. That is the standard that electronics makers, and the finest bullion, both demand (Britannica).

For the most part, refiners pick a method based on where the gold is headed. Large bullion bound for bank vaults or central bank reserves often goes through the Miller process first. If a buyer wants higher purity still, it then goes through Wohlwill electrolysis.

What Makes a Gold Bar Officially "Good Delivery" Bullion?

Not every refined bar earns equal trust. The London Bullion Market Association keeps a Good Delivery List. Only refiners on that list may produce bars the institutional market fully accepts. The bars must weigh 350 to 430 troy ounces and reach a minimum purity of 99.5%. In addition, the refiner must pass LBMA's own tests for assaying and sourcing (LBMA).

In short, this rule exists for a simple reason. Gold bars all look alike once stamped and stacked. Good Delivery status is the market's way of proving that the metal inside a bar matches its markings. A trained, accredited outside party checks that, rather than forcing buyers to have to take it on faith.

How Much Gold Is Mined Each Year, and Where Does It Come From?

Global mine output hit an estimated 3,300 tons in 2025. That is up modestly from 3,280 tons the year before (USGS). Four countries led the way: Russia, Australia, Canada, and the United States. Together, they produced 41% of that total (USGS). Inside the US, Nevada alone produced roughly 64% of domestic output. Alaska supplied most of the rest (USGS).

That slow, steady growth rate tells its own story. Deposits that are both large and cheap to reach keep getting rarer. Mine grades have trended lower for decades, since the easiest ore gets mined out first. Every new mine still needs that same decade-and-a-half-plus runway from discovery to production, and that runway has been getting longer, not shorter, over the past 20 years. For this reason, supply simply cannot move fast when demand shifts. By comparison, a central bank can expand a currency's supply with a single policy vote.

Is Gold Mining Regulated for Safety and the Environment?

Modern, large-scale gold mining sits inside a dense web of industry rules. Standards still vary a lot by country, and by the type of operation.

The World Gold Council's Responsible Gold Mining Principles, launched in 2019, set clear rules for the whole life of a mine. These rules cover environmental, social, and governance issues. Every member company of the World Gold Council must follow them, including the central banks and institutions covered in GoldSilver's reporting on central bank gold reserves. Those members represent roughly a quarter to a third of the world's annual gold mine output, by most current industry estimates (World Gold Council; Mining Weekly). Companies must publicly report how well they follow the rules. An independent outside party must check the report too.

Separately, the International Cyanide Management Code governs the one chemical at the center of the leaching step. It covers how cyanide gets made, moved, stored, and used on-site. It covers worker safety, emergency plans, and how a mine shuts down a cyanide facility for good (International Cyanide Management Institute).

Both frameworks are voluntary; international law does not force anyone to follow them. Enforcement depends on whether countries, companies, and buyers choose to require it. Small-scale and artisanal mining supplies a real share of global output, especially across parts of Africa, South America, and Southeast Asia. Many of these operations sit entirely outside these formal rules. That gap keeps supply-chain tracing an active industry focus.

Why Does the Difficulty of Mining Gold Matter to Its Value as Sound Money?

Consider everything above: the years-long search, the tons of rock per ounce, the chemistry, the certification. All of it exists for one reason. Nobody can manufacture gold. Someone has to find it, dig it up, and purify it at real physical cost, every single time.

That limit is not an inconvenience. It's the mechanism. Money and currency are not the same thing. Currency is just a medium of exchange. Sound money stores value precisely because no government, and no central bank, can create it by decision (sound-money-thesis). A central bank can expand a currency's supply with a policy vote. Nobody can vote gold into existence. Every ounce in circulation stands for real capital, real labor, and real time spent pulling it from the earth. That is exactly why the annual supply figure moves by low single digits most years, instead of swinging wildly with a policy announcement.

Gold's industrial use also stays strikingly small next to other metals, a dynamic closely tied to how the gold-silver ratio behaves, since silver's much larger industrial role moves it differently. Roughly 90% of annual demand ties to investment, central bank reserves, and jewelry, not factory use (gold-monetary-mechanics knowledge base). That detail matters; it means gold's price moves mostly on its role as a monetary asset and a store of value, not on factory demand that rises and falls with the industrial cycle. Gold's scarcity is not a marketing claim. It's geology. And geology does not bend to a press release.