Remainder Interest
The future ownership interest that vests in the remainderman when a life estate ends, giving them full title to the minerals at the life tenant's death.
A remainder interest is the future ownership right held by the remainderman, the person who takes full title to property once a life estate ends. The remainderman owns a real, presently existing interest, but the right to possess and use it, and to collect the income, does not begin until the life tenant dies.
For minerals, this split matters in practice. During the life estate the remainderman typically cannot collect royalty checks, and a buyer of just the remainder is purchasing an asset they cannot monetize until the life tenant passes. Selling or leasing the full mineral interest usually requires both the life tenant and the remaindermen to sign.
Because the remainder vests at death, the remainderman's tax cost basis in the minerals is generally set to fair-market value as of that date, a feature known as stepped-up basis. This is general information, not legal or tax advice.