I wanted to know a bit more about how Minecraft generates ore, in order to better be able to customize my experience. Each ore generates a number of clusters of a certain size. I wanted to know how each "size" actually corresponded to the number of ore blocks generated ingame. I knew from past experiences that it wasn't a linear relationship, but nothing beyond that.

Unfortunately, ore generation settings are not something that vanilla Minecraft currently exposes to the user, so I had no choice but to resort to modding. And besides, WorldEdit makes counting blocks a million times easier than trying to do it by hand...

Long story short, I filled up a superflat world with custom-generated ore clusters (one cluster per chunk) of increasing size, starting from 1, and counted the number of ore blocks in a 40x40 chunk area. I got the following numbers:

Cluster Size    Sample 1    Sample 2    Sample 3    Sample 4
    1:            1600        1603        1595        1606
    2:            3002        2992        2971        2972
    3:            4244        4222        4254        4242
    4:            3766        3848        3877        3861
    5:            5871        5828        5615        5728
    6:            6945        7230        7096        7000

The first two samples were from separate areas in one world, whereas the third and fourth samples were from different, newly created worlds to make sure it wasn't a fluke.

Clearly there is something off here. Size 3 generates larger clusters than size 4 does. I tested all other sizes, up to 30, and these two are the only ones that look reversed. I took extra care to make sure that I absolutely, positively made no mistake in writing the config file. That was in fact the first thing I did.

After that, I then took this to the issue tracker of the mod I used to generate the ore (CoFH World), but its author assures me that all that the mod does is call vanilla functions with custom parameters. Ergo, that must mean that the above inconsistency should be reproducible in a pure vanilla client, given the tools necessary to change ore generation settings. I have checked the changelogs for 1.13 and the new 1.14 snapshots, and there are no mentiones of tweaks to the ore generation logic. So there's a pretty good chance that you'll still see this in at least one of the two.

Now, I'm aware that vanilla Minecraft doesn't even generate any ore in size 3 or size 4 clusters, but I hope this still helps you in your efforts of further improving the game!