What causes a gem box to spawn in Clash of Clans?

Gem Boxes spawning is not related to the spawning of other obstacles. The detailed algorithm of the spawning of Gem Boxes is not public but there are some facts we know about Gem Boxes.

1. You can only have 1 Gem Box at a time
2. The Gem Box is a special obstacle
3. The Gem Box ignores the 1 tile buffer zone and will spawn in any 2x2 space inside your base.
4. The Gem Box is affected by the 40 Obstacle cap and will not spawn if the cap is exceeded.

The spawning of Gem Boxes are either completely random or controlled by an algorithm that is kept private to SuperCell. Currently there are no ways to predict when the next Gem Box will spawn.

Here are my calculations, I conducted 3 tests on 3 seperate months.

1st test: Started on Monday (1542 gems), at Thursday I reached 1577 gems and the next day I received a gem box. 2nd test: Started 1 month later on a THURSDAY (1626 gems), after 1 week on a Monday I reached 1671 gems. Later that day I got a gem box in the afternoon and ANOTHER in midnight ?. 3rd test: Started 1 month later on a Monday (cuz I was suspicious of that Monday) with 1753 gems and 3 days later I reached 1771 gems and got a gem box.

Conclusion:

1. Gem box has high chance to spawn in 2 weeks time.
2. Gem box spawn rate increase to 35% when your Gem count is 70, 170, 1700, 17000...
3. Gem box spawns in no specific order, but these "factors" could help you get more.

Thank you for reading this long essay ???

As far as I can tell there doesn't seem to be any specific pattern in which gem boxes spawns. Basically, if I am correct, it is entirely randomized.

I'm pretty sure that the minimum spawn time for a gem box is once a week, and to maximize your chances of getting one you should remove all of your obstacles. By doing this, you are freeing up space for the gem box. If the gem box wants to spawn where another obstacle is, it won't spawn at all (this applies to all obstacles on Clash of Clans).

Based my research/es, there is a probability that a particular obstacle like a bush or mushroom will be replaced to a gem box, so don't remove all of your obstacles otherwise you won't get any. Keep in mind that this is not 100% sure, at least don't remove all of your obstacles for experimenting purposes.

I think that you get a gem box once you reach around 70s gems ... 70, 170,270,.....

I saw that the more you donate and use gems the more often I got a gem box.

Gem Boxes Spawn once every month.