Diamond Plates are not currently used in any recipe, but are intermediates in crafting Dense DIamond Plates.
Diamond Plates are obtained by putting a diamond in a Compressor, which is different from the normal method of obtaining plates.
The usage of Diamond Plates is only to compress 9 of them to make a Dense Diamond Plate.
Another use of a Diamond Plate is to macerate it into Diamond Dust. See the HAYO section (below) for what you can do with this Diamond Dust...
Diamond Plates, as shown above, can be macerated into Diamond Dust, which can be Compressed back into a Diamond!
This Item has been certified to be OreDict compatible, not that you'd want to use any other mods' Diamond Plates, right? RIGHT? Yeah, thought so.