I have reached out to customer support in game and am getting help with this, but I feel like preventing this for other players could be trivial.

I have fed one sentient gem to another many times to add experience, change voice, etc. I have built up a number of gems to various levels, but have yet to decide where/when I am using my acquired sparks. I just recently fed a 20k gem to my 60k gem as I work towards my next slot. and now it has 61k sentient xp. 19k sentient xp (66 lvl 29 named items) gone.

It is not clear what the cap in xp is for a sentient gem. It allows you to go over 60k without any sparks, but there is no indication if/what the hard cap is in game. This should be trivial to add, and I would consider it essential to a clear system. Just a line beneath current xp: "hard cap" or something. If the system has hard caps that can destroy progress, please make that clear.

As long as customer support is able to help me get back that sent xp, I am good. I now know to be extremely careful of the hard cap. But other people new to the sentient system, or who are first moving up into the realm of using sparks, may not know that progress can be thus lost.