Rank Up Gem Questions

Fluffy

I am getting ready to make a run at A5 exploration. I did a search and I couldn't find the answer to my RuG questions. Apologies if I didn't dig deep enough.

1. The rank up gems from Act 5 completion are a crystal that drops a class specific RuG, correct?
2. Are the gems limited for the rank they can be used for? For example, can I use one to go from R4 to R5 on the 5*?
3. What resources does the gem replace? All of them or just the catalysts?

Thanks for reading.

Crazyjack719

1.It will be a class specific random gem,
2. act 5.3 exploration has a rank 2-3 gem, act 5.4 has a rank 3-4 gem
3. The catalysts are replaced, not the gold though.

Hope this helps!