Forums → Support Forum → GC chasing shadows (PC) - strange gem combining effects

Hello. In Gemcraft chasing shadows (steam ver.) I noticed strange gem behaviour.
When I combine two gems and one is much lower grade than the other, the resulting gem has worse (sometimes MUCH worse) stats than any of two gems before combination. For some time I thought that it is effect of the complicated bloodbound mathematics (i have been using such upgrades mainly for my favourite crit - bloodbound combo). But it looked strange so I tried that on pure gems. And effects are the same.

For example I have lvl 9 orange:
value 22 920
dmg: 351 - 787
range 7.1
sps 1.72
mana leach: 22.2

when I add lvl 2 orange:
value 23 280
dmg: 351 - 787
range 7.7
sps 1.64
mana leach: 21.2

Since In GC CS ( strategy guide http://armorgames.com/page/GemCraft-Strategy-Guide ) it stays that:

If you combine a high grade gem with one of a much lower grade, you will get a gem slightly stronger than the stronger original gem. It's a good way to upgrade your strong gems a little further

I really don't know what to think about that. Is there any rule that helps to avoid degrading gem by upgrades?

EDIT: the same orange after c.a. 20 more so called "upgrades":

when I add lvl 2 orange:
value 41 280
dmg: 351 - 787
range 5.5
sps 0.73
mana leach: 12.26

So this seems really strange. After combining gems with different grade I can get really high priced trash...