Tekkit uses two of PowerCrystals' mods. The first of which, Nether Ores, adds numerous ores to the Nether dimension.
You can find the official Mincraft Forum forum thread here
Pages in category "PowerCrystals' Mods"
“ The Geothermal Generator produces EU when provided with Lava Buckets or Lava Cells or when...
Geothermal Generator Mk. 2