Dual Ore Add-on 1.17+
In real life, miners do not mine ore or other materials in whole blocks. You can't mine one block with only diamond or emerald ore in it. Therefore, the author of the Dual Ore mod decided to add a little realism to the world of Minecraft. Now in one block can be several types of ore.
New blocks will be generated below level 40. Each of them drops 2 or more ores at a time.
— Drops iron or gold.
— Drops Redstone or gold
Diamond and Emerald Ore
— Drops diamond or emerald
— Drops copper, iron, emerald, diamond, gold, or Redstone
The chance of one or the other ore appearing is the same as the chance of generation.