The stones are naturally grown artifacts of a long dead world which give the user mastery over time & space, enabling their user travel through the past, present, future, alternate timeline and adjacent realities.
Over time the planets core would become unstable causing it to explode, flinging the precious gems across space and time; one of its fragments becoming a meteor which collided with Earth causing the dinosaurs death and making room for other species.
Eventually, due to a stable time-loop, These diamonds would fall into the hands of one of Orb's henchmen as the latter's employer was busted by Spider-Man and Wolverine during a bank heist. Who would in turn be flung across different points in reality while said minion sold what little of the diamonds he could get his hands on to the drug dealer Czar.
Whom, after gaining an understanding of their power, would be approached by inter-reality television personality Mojo for his aid in orchestrating the craziest television broadcast to date featuring both Peter and Logan.
Afterwards when the two were set back on their proper coarse in reality by the Minutemen. James's older brother Dog Logan went exploring down a mine shaft that was laden with Time Diamonds all across the walls and ceilings back in Yukon, Canada; ending up in 21st century New York City. Who spent some time eating fried Wolverine while going over his younger brother's exploits.
These alien jewels have the precarious power to alternate time and/or space via thought, or can randomly displace a person throughout history and reality at random if handled improperly. When used by anyone, be they single or multiple handlers; one must have a vivid visualization and an understanding of where, when and which era they want to travel to. Otherwise they could end up anyplace between the event that wiped out the dinosaurs to the other end of reality where the Big Rip occurred and back.
The time diamonds are semi-sentient. Sharing a hive collective consciousness that interlinks them all throughout the universe and beyond. Through this oddity they have the potential to psychically or empathically communicate with each other and whomever uses them, giving their wielder an intuitive understanding of history and at which points certain events took place in it and how they occurred.
To that end they also have the tendency of sending people where they need to go instead of where they wish to be. The Diamonds also have the ability to home in on other sources, leading those who use them to large caches of it across reality. They can be weaponized by attaching them to blunt instruments or other weaponry in order to remotely transport people, places and things to any given point in eternity or finality one see's fit. Moreover they also have the power to peer beyond the veil of history, showing whomever comes across them moments or certain insights into occurrences that happened in their life.
More experienced user's can pull items, objects or people from across the timestream to their direct location. Useful as a distraction and means of attack on a superior opponent, taking elements from alternate timelines and alternate realities to fight on their behalf and just as easily send them back to whence they've came afterwards.