If the Portal Stones came from the First Age...

[omer681]

And you need to channel to use them... So channeling was discovered in the first age? And the Portal Stones were made after the discovery?

[Luckers]

Probably in the gap between the First and Second (like the Breaking was between Second and Third, but not really counted in either).

 

There must have been some sort of cataclysm that eradicated all evidence of our society and culture, so it makes sense for the Portal Stones to be made--an attempt to flee.

[TheDecline01]

Maybe those portal stones could be one of the rare remnants to pass through turnings to turnings, thus they would be like many turnings old. That would explain why they aren't understood, and weren't even by 2nd agers. They will not be created in later ages too since there already there and we can assume safely that somehow, the ability to channel, and required to create those portal stones since they need the power to work, will disappear later in the 4th or 5th Age (or 6th or 7th).

[MikeRiley]

I don't think so because a number of the portal stones we see are already weather worn.

[Duskfire]

Probably in the gap between the First and Second (like the Breaking was between Second and Third, but not really counted in either).

 

There must have been some sort of cataclysm that eradicated all evidence of our society and culture, so it makes sense for the Portal Stones to be made--an attempt to flee.

 

Yeah that makes sense. Similar to the Ways for the Ogier. A way to travel around without worrying about any potential dangers.

[algspkr]

There is no indication of how the stones were meant to be used.  We know that they were manipulated with the One Power during the Age of Legends, but we also know that they were not fully understood then either.  It seems likely to me that using the One Power on them is like using it to replace your iPhone battery.