Keeping track of the Infinity Stones is no easy task. From Asgard to Midgard, from Xandar to Vormir, the stones have been hidden, their presence mainly unknown to the galaxy except to a select few until it became everyone’s top priority to stop Thanos from collecting them.
So which was the stone that caused the most chatter? We tallied up every mention of each Infinity Stone up through Avengers: Infinity War:
The first stone to appear in the MCU was the Tesseract. The Red Skull pulled it out of a church in Norway in Captain America: The First Avenger. The second stone to be seen was the Mind Stone. Encased in a shell and used by Loki to manipulate the minds of men, he created havoc and chaos in New York.
Source: IGN.com How Many Times the Infinity Stones Have Been Mentioned in the MCU