I think those “standard currencies” don’t fit into the unique setting Oort may have later. May be 100 shards become a crystal and 100 crystals a gem. Let it be more special without losing the functionality 
i can also live with that since oort stones and shards seem to kinda power everything they cant give a logical reason to. you just need some form of generally akknowledged currency or you cant have anything reminding even remotely of a stable economy
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The economy will become stable, some will barter, some will stockpile different currencies, some will travel and trade, some will place orders for goods, some will set up shops- and some will operate within an informal economy.