Holding gold and holding shares in a gold producer are often treated as alternative routes to the same exposure. They behave differently because a mine is a business and metal is not.
A miner's profit is a residual
A producer sells metal at the market price and pays costs that are largely fixed in the short term, so profit is the gap between the two.
Because costs do not move with the metal price, a modest change in price produces a much larger proportional change in profit.
That relationship is the source of the leverage that attracts investors to mining shares, and it operates in both directions.
Operating risk has no equivalent in bullion
A mine can flood, a mill can break, a permit can be refused and a workforce can strike, none of which affects an ounce of metal sitting in a vault.
Grade can also disappoint, meaning the ore extracted contains less metal than the resource model predicted, which reduces output without any change in the price environment.
Shares therefore carry a whole class of exposures that the metal does not, and those exposures are specific to individual companies and individual deposits.
Jurisdiction is a large part of the risk
Mines are immovable, and a producer is subject to whatever the host government decides about taxation, royalties, ownership rules and export permission.
Two companies producing identical metal at identical cost can be valued very differently because of where their deposits happen to be.
Bullion held in a stable jurisdiction is exposed to that country's rules only, and it can in principle be moved.
Cash flow works in opposite directions
Physical metal generates no income and costs money to store, so a holding slowly shrinks in value terms unless the price rises.
A profitable producer generates cash and may pay dividends, so a shareholder can receive a return without the metal price moving at all.
That difference matters most over long holding periods, when accumulated income or accumulated storage cost becomes a significant part of the result.
Equity markets add their own influence
Mining shares trade on stock exchanges, so they are affected by general equity sentiment, index flows and liquidity conditions alongside the metal price.
During broad market declines they have often fallen with equities even when the metal held its value, which weakens the diversification argument for holding them in place of bullion.
The two are related instruments rather than substitutes, and the choice between them is a choice about which risks are wanted.