Resource Overview History
Gems are one of the 31 rare resources. They appear as a small patch of blue, red, and green sparkling gems and can be found on the sides of mountains, rather than on flat land.

Like with all rare resources on land, Gems can be gathered by sending a Merchant from the Market to the resource location. Gems provide the following benefits:

The gather rate of rare resources can be increased in various ways, as described in the main article. Note that Knowledge Knowledge is not gathered before the Classical Age Classical Age, but the Greeks may gather Knowledge Knowledge from the beginning, making an early exploitation of Gems more useful.

The border expanding effect isn't all that significant, when compared to other methods of border expansion (e.g., Civic Civic research adds +4 each time), but it might still prove useful.