So I had an Idea for something, Well first of all, I think for this there would be periodical meteor showers, (A.K.A Persids and Leonids.). In these situations, you are more likely to find Star Sapphires and Star Rubies. The characters could refer to this as "Fallen Stars". I find this likley for one, There is no meteor showers Sadly, And As well I feel like there should be more unique and possibly unknown gems. I as well chose the star sapphires and rubies because they are the most known in the star gems.