SimpleOres adds 5 new ores to the base game: Copper, Tin, Mythril, Adamantium and Onyx. All except Onyx can be found in the overworld, while Onyx can be found only in the Nether. Each ore has its own unique properties, armor and tool sets, and more.
SimpleOres for Minecraft 1.14+ no longer requires the SimpleCore API.
My computer went down while I was revamping this description page, so I lost both the old text and the new text. Meh, it needed redoing anyway, and someday when I have time and inclination, I will redo this. I might even include pictures, if I'm not still really pissed off at losing my work.
The original Minecraft Forum thread is here. The original mod was by AleXndrTheGr8st, aka Skrallexy. Sinhika is the current off-and-on maintainer. The current code is licensed under LGPL 3.0, so go wild, modpack makers!