peridot - this green gem is the only one found in meteorites. It's pretty rare on planets, but recently, there was been a rush to mine the asteroid belt. Large deposits of peridot are rumored to be there - some have found their weight in this precious gem.
This gem is precious because
- it is the only gem found in the space between
- it cannot be magically created
- it cannot be created from protomatter in the ether.
The rush on the asteroid belt is bringing all kinds of new folks to the space between planets. Larger asteroids that have an atmosphere are springing up boom towns.
Gold, platinum, and silver still have some value. It is particularly useful as currency on planets that do not have ether travel, yet.
One unique magical treasure item is the Gold of Many Faces.
Each coin in this chest is presumably from a different planet. Thousands and thousands of coins each have a different face on them. Each coin is unique.
Each coin also grants a boon or a curse to those that possess it. Regardless of effect, owning two or more coins negates their properties.
No one has assembled the entire treasure - it is scattered all over the etherverse, and more than likely, a few planes as well. It is rumored that assembling the entire treasure will grant its possessor limitless power.