On the Rent of Mines

Ricardo treats mines as a second rent case, not as a new theory. A mine earns rent when it is more productive, richer, or better situated than the worst mine that society still needs to work.

Chapter II showed rent arising from unequal land. Chapter III applies the same ladder to mines. Some mines yield rich ore near the surface. Others need more labour, deeper shafts, more drainage, or longer carriage. If demand requires the poorer mine, the market price must be high enough to repay its labour and capital.

The landlord or mine owner receives rent because their deposit is better than the marginal deposit. Rent is still a difference, not an independent cause of price.

For Ricardo, the price of metal is regulated by the mine that just pays ordinary wages and profits. If that mine cannot cover its costs, it will stop being worked. If society still needs its output, price must rise enough to keep it in operation.

more metal wanted
      ->
cheap deposits are not enough
      ->
costlier mine enters production
      ->
price covers that marginal mine
      ->
better mines receive rent

The point is identical to corn. Gold, silver, copper, or coal are not dear because rent is paid to the best mines. Rent is paid because the marginal mine is costly enough to make better mines especially profitable.

Use the lab as a mine ladder. Read "land yield" as "mine output." Grade A is a rich seam, Grade B is a workable deposit, and Grade C or D is the costly marginal mine. Raise demand until poorer deposits enter production; the superior mines then earn rent equal to their advantage over the margin.

Suppose the same labour and capital can raise different amounts of metal from three mines.

Keep the chapter in this three-step picture:

        MINE A: rich seam        rent = A - marginal output
        MINE B: ordinary seam    rent = B - marginal output
        MINE C: poor seam        rent = 0 when C is marginal
        ---------------------------------------------------
        metal price is regulated at the working margin

The diagram is intentionally the same shape as land rent. Ricardo wants mines to prove the general form of differential rent: unequal natural powers become rent only when society must use the inferior alternative too.

Mines differ from land in one visible way: deposits can be exhausted. The richest part of a mine may be worked first. Later production can require deeper shafts, harder rock, poorer ore, or more pumping. A mine that once earned a large rent may move closer to the margin as its best seams disappear.

This does not break the theory. It makes the margin move. Mine rent depends on present superiority, not on a permanent title to surplus.

Ricardo also leaves room for a special case. Some mines, especially precious-metal mines, may be so limited that their produce behaves partly like a scarcity good. If supply cannot be expanded by ordinary labour and capital, price may rise above the cost of the marginal mine for a time.

The normal chapter logic is still differential. The scarcity case simply reminds us of Chapter I: not every valuable thing is freely reproducible.

Chapter III strengthens Ricardo's general method. He is not building a theory only for farms. He is showing how any unequal natural resource can produce rent when demand pushes production to inferior grades.

That matters for later taxation chapters. A tax on rent, a tax on raw produce, and a tax on profits have different effects because rent is a surplus above the marginal cost of production.

Mine rent is differential rent applied to mineral deposits. Superior mines earn rent because inferior mines are required, not because rent itself makes metals dear.

• Mine rent comes from unequal richness, depth, drainage, or situation.
• The marginal mine is the worst mine still needed in production.
• The marginal mine pays no rent because it just covers ordinary wages and profits.
• Better mines earn rent equal to their surplus over the marginal mine.
• Exhaustion can reduce a mine's superiority and move it toward the margin.
• Scarcity can add a premium, but the normal rent rule remains marginal and differential.

A reader is ready to continue when they can translate land rent into mine rent without changing the theory.

• [ ] Can you define the marginal mine in one sentence?
• [ ] Can you explain why a rich mine earns rent only after poorer mines are needed?
• [ ] Can you calculate rent when A yields 100 ounces and C yields 50?
• [ ] Can you use the lab to treat lower "land yield" as lower mine output?
• [ ] Can you explain how exhaustion can reduce rent over time?