Gems can be slotted into weapons with the appropriate slots.
Currently gems are only cosmetic. It is planned for a future update that they will give bonuses, but specifics are - as of yet - unknown.
There are 3 shapes and 3 colors of gems currently in the game.
Not every blade has slots for every shape of gem. The first one that can hold a gem at all is the Short Sword, which can hold two round gems in the pommel.
|Blade||Round gem slots||Square gem slots||Triangle gem slots|
|more to come||...||...||...|