Depth is the only lever. Everything else about a Northold position — the asset, the settlement, the ownership — is identical across the three seams.
Depth
Loose ground, worked in a month. Shallow, quick, forgiving.
Coupon, struck at mint
Worked from the surface. Nothing here is buried deep enough to be difficult.
Sink to PlacerThe working seam. A quarter underground for a heavier grade.
Coupon, struck at mint
The working seam. Most of the register sits on this bench.
Sink to LodeDeep rock, half a year down. The richest assay on the sheet.
Coupon, struck at mint
Deep ground. Long shaft, heavy grade, and no quick way back up.
Sink to MantleWhat does the coupon actually pay in?
The asset you deposited. WETH pays WETH, USDC pays USDC. There is no second token and no swap at either end.
Can the rate change after I sink?
No. The coupon is written into the position at mint. Governance can open new seams at different rates, but it cannot reach into an open shaft.
What happens if I need out early?
You abandon the shaft. Principal comes back, minus nothing — the fee is taken from unclaimed coupon at the rate published on the seam. Coupon you already lifted stays yours.
Does it compound?
No. Accrual is simple interest against the principal. If you want compounding, lift the coupon and sink it again.
Matrix reference
I · PLACER · 0 – 120 m · ALLUVIUM, GRAVEL WASH
II · LODE · 120 – 600 m · QUARTZ REEF IN SCHIST
III · MANTLE · 600 – 2 400 m · ULTRAMAFIC, HOT ROCK