Gems are pick ups in Onekey.
Gems will appear as a downwards facing isosceles triangle, with a circular top. They come in five colours: purple, cyan, lime green, magenta, and red. A slanted line runs down the middle of the gem.
Five gems appear in every level that can be picked up to boost the player's score. These gems are usually placed in a location that is not needed to be traversed in order to finish the level.
A gem can be collected by simply having the tribesman pass it in his path, and when it is collected, it will disappear. The collected gem will then appear coloured in on a gem counter, located in the top left corner of the game screen. Once the player completes the level, all the gems they have collected will be saved, and 1000 points will be awarded for each gem they collected.
If the tribesman dies before completing a level, the gems he has collected will be saved. Collected gems, however, can be lost if the player chooses to quit the level they are currently playing without beating it.
All gems the player has obtained over the course of the game can be viewed on the level select screen. When the player goes to replay a level, any gems that have already been collected will appear as a faded, transparent colour. It is also shown that each gem has a certain attribute, as enemies and gimmicks that act the same often have the same colour gem.
- The gems from Onekey are also have the same basic design as the gem from the Twin Shot series and the gem from the Chisel series.