I just thought of a very handy way to test the ore generation in a modpack I'm coding. I thought I should share, because it's really easy to do ...
Make the ore you're testing a light source. light_source=6 or 9. Now check it out ...
Go into Freemove mode, teleport down to the depth where you're testing your oregen code.
Here's what you'll see:
You can see my test ores (the reddish lit-up areas) are fairly uncommon blobs of 6-8 blocks, as planned. They even contain ores, rarer ores with a slightly brighter glow. Good luck testing that in the dark...
Now this one:
Just hovering so many blocks away, I can see that the same ore below -2000y spawns in bigger, less common clumps, exactly as planned.
This is VERY helpful for tweaking config files that might be tweaking ore generation. I create a new world, run my mod, it creates its config file in the world folder. Quit the game, edit the config file, then teleport down into solid rock in god mode and see if things light up the way I expected them to. An immediate visual view of the ore distribution has saved me endless hours of flying through dark caves looking, and gives a real spatial feel.
When I'm happy with the result, I will turn off the light_source property. Back to the pitch blackness with all the ores where I want them.
Thought I would share. ;-)