Ruby

Ruby is a gem added by all RedPower 2, Project Red, Blue Power and GregTech. They are used for tools, Energium Dust and ruby dust is the main source of Chrome and Aluminium.

Ruby tools are the tier between Iron and Diamond. While they have the speed of diamond, they only have 501 uses, and ruby pickaxes can't mine Obsidian.

Rubies can occasionally be found in Dungeon chests.

Fool's Ruby is a gem added by GregTech and Crazy Ores. It is visually identical to an actual Ruby, but Fool's Ruby components cannot be used in any recipes. Fool's Rubies can be differentiated from real Rubies by checking their metadata: the metadata value of all Fool's Ruby items are 10 higher than their real Ruby versions.