I haven't seen any posts about this on my regular sci-fi blogs, so I wondered if everyone else missed it. In the last episode of Marvel's Agents of S.H.I.E.L.D., Nick Fury gives Agent Colson a small cube and make a reference to something mental. Is this cube an Infinity Gem, specifically the "Mind Gem"?
I can think of several reasons why:
The “toolbox” contains classified SHIELD intelligence.
If it really was an Infinity Stone, then Fury would need some way to embed files into it. Human science can barely understand the Tesseract (a confirmed Infinity Stone), let alone control it in a meaningful way. Using it as a toolbox is almost certainly beyond Fury’s capabilities.
Using the Mind Gem to rebuild SHIELD is at odds with what Fury stands for.
Hypnosis and brainwashing are the tools of HYDRA, not SHIELD. Fury talks about Coulson starting from scratch, something pure. This means recruiting agents who truly believe in SHIELD’s core values; using mind control would be setting yourself up for failure later on.
(Also note that the one time when Fury saw mind control – onscreen, at least – was the Tesseract with Barton and Selvig, both of whom eventually snapped out of it. It’s not the most reliable recruitment technique.)
Fury and Coulson can hold it in their bare hands.
Of the three Infinity Stones seen so far, none can be touched by mortal hands. The power is all-consuming and deadly. If the toolbox was really an Infinity Stone, then they’d both be dead (again). And if it was inside the toolbox, you’d think Fury might mention “Oh, don’t touch the orange glowy thing, or you’ll explode”.
In the same episode, Agent Coulson told the team that the Cube contained co-ordinate of a place (where they reached in the end).
A side note: Marvel's Cinematic Universe would never introduce an Infinity Stone such way using the TV series.