WorldGen

public class ModWorldGen implements IWorldGenerator {
    @Override
    public void generate(Random random, int chunkx, int chunkz, World world, IChunkGenerator chunkGenerator, IChunkProvider chunkProvider) {
        if(world.provider.getDimension() == 0) {
            generateOverworld(random, chunkx, chunkz, world, chunkGenerator, chunkProvider);
        }
    }

    private void generateOverworld(Random random, int chunkx, int chunkz, World world, IChunkGenerator chunkGenerator, IChunkProvider chunkProvider){
        generateOre(ModBlocks.RUBY_ORE.getDefaultState(), world, random, chunkx * 16, chunkz * 16, 16, 64, random.nextInt(7) + 4, 30);
    }

    private void generateOre(IBlockState ore, World world, Random random, int x, int z, int miny, int maxy, int size, int chances) {
        int deltay = maxy - miny;

        for(int i = 0; i < chances; i++){
            BlockPos pos = new BlockPos(x + random.nextInt(16), miny + random.nextInt(deltay), z + random.nextInt(16));

            WorldGenMinable generator = new WorldGenMinable(ore, size);
            generator.generate(world, random, pos);
        }
    }
}