I am working on making a custom ore that spawns low down, I have tools and things made out of it, but I can never find the ore in the world. I use /fill commands to see if any of the custom ore gets replaced nearby, but it never shows any blocks filling. I have searched for hours trying to find the custom ore but I can't find it naturally, only in the creative GUI. The other items all loaded perfectly fine. I have looked on forums and seen that most people don't set stone as a block that it can replace, but I have done that.
Here is a screenshot:
https://ibb.co/GsbcwpN
Those values that you have set (the average ones) are way too low. They are spawning but they are extremely rare.
Having tried to make a common block that can replace sand (an alternative clay) I gotta second what Trolmaso said. The warning that says values greater than 32 can cause problems isn't necessarily true, unless it's WAY higher, or has a custom model (which might cause lag). Try setting the rate to 24; if you still aren't ever finding the ore then you have some other issue.
those ores are very rare. try setting them so they are way more common (ex: 20 for each) then try to find them. if you can, set the values back to normal because they are spawning its just rare