thx for explanation... pretty smart mechanic.
so, when I have 200CP (not 100?) in tier 1, I have chance to cut more than 1 gem. but when I will cut that gem by tier 2 (lets say 20CP) - to fill tier 2 too, I can cut just one gem. I`m I right? now I omit sapphire and higher...
and magical tool, you mean jeweller tool? its working not only for jeweller profession?
Yes, when you have 200 CP you have a chance to cut extra gems. That is for every tier. The thing about jewellers is that you can gain crafting points by cutting the same gems, no matter which tier you are - tier 1 or tier 5, the stones are still agate, emerald, opal and topaz +1 special stone for each tier (sapphire, ruby, pearl and obsidian).
This I see as somewhat of an advantage, because you can dig such stones in all provinces (tier 2 and up). And you can cut them to level up as a stonecutter even in tier 5 ! Now, that is something that you will never find with miners for example, the chance to dig very rich iron ore, can not at all be compared to digging coal. So, I find it a bit easier perhaps to level up as a jeweller and that might be one more reason why you have no additional advantage in digging stone - because it is easier and if you could also dig extra quantities, the advantage would simply be too big.