Non-vanilla ores only spawn if a mod that uses them exists. All nether ores turn into their surface counterparts in a furnace - some (like redstone or coal) may need to be smacked with a pick or macerated to be made useful.
You need CoFHCore for 1.7+: CoFHCore
Minecraft Forum Thread: http://www.minecraftforum.net/topic/2016680-powercrystalsmods/
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