Copper

GregTech
Small copper ore spawns at a height of 60 to 120 with a relative frequency of 32 in the overworld, the nether, and the end. Regular copper ore spawns in several large deposits *TODO*.

Thermal Expansion
Found between layers 33 and 46 with a max vein size of eight. (Every Public FTB pack that includes Thermal Expansion will use Thermal Expansion as the main ore generation.)

IndustrialCraft 2
Found between layers 10 and 70 with a max vein size of ten.

Forestry
Found on layers above 32.

Tinker's Construct
Found between layers 4 and 64. In addition to stone ores, you may also find Copper Ore gravel, and Copper Oreberry Bushes.