It's still better than nothing.. my autocorrect changed what I wrote sorry. I meant collected from the ships at the docks.
I often get gems through the wildlife too.

It should have just appeared. At least it did with me. Is the land around it cleared? That may be affecting it's appearance..

I play on my phone and my tablet. You just have to go into your settings (in the game) and sync your accounts so that both devices are using the same account.

You need to blow it up using a powder keg (made at the blacksmith using 1 keg, 3 strings and 1 gun powder).

You can get free gems if you bought the island of the gem tree using the maps you correct thrift the games at the docks.