Pennsylvania law recognizes three discrete estates in land: the surface estate, the mineral estate, and the right to lateral and subjacent support (subsidence). The grantee of the mineral estate takes subject to the burden of surface support, but this can be modified or eliminated by the language of the grant or contractual obligations. Likewise, in the absence of language to the contrary, the grantee of the mineral estate takes title with the right to enter through the surface estate to access the subsurface materials.
The phrase "mineral estate" is sometimes used to generally refer to any valuable substances below the surface, but there is considerable case law construing which particular material or materials are included in specific grants. Depending on the circumstances, a reservation of "minerals" or "coal" or "gas" may or may not include other substances commonly found in and around those materials.
