There's about a 5% chance each refill that an ore type will change. (Insert deity of choice) forbid that you get on a streak while you mine from the faulty RNG, and have an entire mountainside change on you after a pass or two - I've seen it happen. Ore's been randomly changing for over a decade now. The only reason someone would have ore books in libraries based on color instead of amount of generic colored output, is nostalgia or laziness.
The ore type split is 50%/8x/7x/6x/5x/4x/3x/2x/** split.
50% is Iron-only.
"**" is the percentage chance for Valorite, which was originally 1x, but was raised to 2% in a publish about a decade ago. I have no way of determining if 2% still holds true, or if a later publish may have accidentally or deliberately reset it back to "1x". It was also never said at the time of the raise whether the fraction of a percentage that increased Valorite to 2% was taken from the other colored ore chance, or the Iron chance. If it came from the iron chance, that would reduce Iron to 49.389%
"x" was originally the chance of non-iron ore (50%, originally) divided by 36 (summation {1..8}), or approximately 1.389% (I believe that the original Stratics data used 1.4% as a rounded figure - not sure how many significant digits the server code goes to)
- DC vein chance is 8x, or 11.11%
- SI vein chance is 7x, or 9.72%
- Copper vein chance is 6x, or 8.33%
- Bronze vein chance is 5x, or 6.94%
- Gold vein chance is 4x, or 5.56%
- Agapite vein chance is 3x, 4.17%
- Verite vein chance is 2x, or 2.78%
- Valorite was originally 1.39%, but was reported in publish notes a decade ago, to have been raised to 2%.
So, promoting ore types Agapite & Verite to Valorite should give somewhere between 8.33% and 8.95% valorite veins, minus any digs from before both PT & GPA were used for Agapite, or either tool for Verite.
This, of course, doesn't factor in the other random factor, which is each resource square's innate chance of colored ore (which, 2006 devs to the contrary, is based on the resource square, NOT the race - but the race modifiers modify each square's chance. So that if a dungeon or mining cave spot gives 55% colored ore (of the type it is currently set) to a human, an elf gets 66% colored ore (55%x1.2)- but if the spot's Iron only, the spot will have to be promoted to DC or SI to get the color percentages). I've never seen spots change color percentage in a decade of mining - only the color types. I know several spots that were originally 70-ish% Bronze spots that gave 20-25 ore each time before ML to my human miner. Though the ore types change now, the color numbers still hold true (and my old mining partners that played elves got slightly higher percentages and maybe an extra 1-3 digs more than me). Similarly, There were Valorite spots that were lucky to give 1-2 colored ore before ML, and after the ore randomization still give about that of whatever ore is present - and the colored ore spawn chance is so low that Elf output only differs in amount of iron they get (further indicating that the percentages are being applied to a chance innate to the resource square, as a 20% additive chance increase (as opposed to multiplicative) over a flat number for every square as described by the 2006 devs should have given an elf 2x-5x what my human got at that location).