According to this question about generating gems on android, gem seams are indeed available in the mobile version of Godus. I have progressed through the iOS version up to the point where the Ark has been repaired and Weyworld is available, but can't seem to find any gem seams to mine. I have unlocked and activated the gem mining card, but that did not seem to do anything.
Where are these gem seams?
Are they staring me in the face as I mine right around them without knowing what they are?