There are at least two ways to create Industrial Diamonds;
Possibly the cheapest is to Silk Touch Nikolite Ore and process it with Water Cells through an Industrial Grinder, for one tiny pile of Diamond Dust per operation. Four of these gives a full pile, and four of those compressed with an Implosion Compressor grants three Industrial Diamonds. Note that the Diamond Dust itself can take the place of Diamonds in some recipes, so it's best not to compress it unless you're sure you need to.
Alternatively, you need:
- 64 Coal / 32 Coal Ore
- 8 Flint
- 1 Obsidian, Brick Block, or Iron Block
Put 8 Coal Dust in a crafting table, surrounding flint to create a Coal Ball.
Finally, compress the Coal Chunk, and you will get a brand new Industrial Diamond.
Industrial diamonds are now deprecated. Using this recipe will instead create a normal diamond.
"As of 1.63, they are deprecated; this method will create a normal diamond, and all existing industrial diamonds can be converted to normal diamonds by placing them in a crafting table." This may vary per modpack; at least under MindCrack 8.2.0, although diamonds can indeed be crafted directly from their industrial versions, the above recipes do still produce industrial diamonds.