Each gem is smooth and oblong, and about the length of a man's hand. They can shrink to fit into the groove on the Infinity Gauntlet, where they could formerly act in concert to grant the wearer absolute power over all of reality.
The six gems are:
Time Gem (red) - Control over the flow of time.
Space Gem (purple) - Control over space, allowing instantaneous travel across vast distances.
Power Gem (pink) - Increases physical strength and endurance.
Soul Gem (green) - Control over the soul.
Mind Gem (blue) - Allows mind control and vastly enhances the holder's intellect.
Reality Gem (orange) - Control over reality itself, creating and uncreating matter and energy.
The Infinity Gems figured prominently in three major crossovers. In chronological order, they were:
Following the Infinity Gauntlet event, the Living Tribunal declared that the Infinity Gems would no longer function as a whole, although Eternity (the incarnation of that cosmic concept) may be able to reverse the decision should he desire to. When the gems were separated, they were distributed to individual members of the Infinity Watch.
In the recent JLA/Avengers crossover, the DC Comics villain Darkseid obtained the full Gauntlet, but casually discarded it when he discovered it wouldn't work.
GEM was a very close match for the MacOS - the same on-screen layout of menu bar at the top of the screen, then windows below - the first version of the GEM Desktop had a wastepaper basket.
GEM was one of the first commercially available GUIs for both the IBM compatible market (being packaged with Amstrad's original PC series) and more successfully for the Atari ST range.
GEM Programmer toolkits were marketed with portability, both in terms of the 'C' compilers supported, as well as the M68k platform.
It was not one of the original six gems in the Marvel Universe, but was found in the Ultraverse when Loki attempted to steal the other gems from the existing holders.
Many times the gems have been discarded by these dissatisfied would-be wielders because they possessed neither the knowledge, the patience, nor the inclination towards their proper use.
A cross-over story arc featuring the Avengers and Malibu Comics' Ultraforce revealed the seventh gem, as well as the fact that the seven gems were originally extracted from the consciousness of a cosmic being known as Nemesis.