The conductivity ladder — with condition tags

Every number on this ladder is real, and every one carries conditions. Click a rung to see how that value was measured, on what form of the material, and what happens to it in the form you can actually buy. The ladder ranks headline numbers; the tags rank honesty.

Values are representative room-temperature figures for the stated form of each material, drawn from the peer-reviewed sources cited in the article; they are ranking anchors, not certified data for any commercial lot. In-plane and through-plane values differ for anisotropic materials, and film, ceramic and composite forms differ from single crystals — which is the entire point of the tags.