Diamond dust is a material component for the greater restoration spell, and you need about 100 gp worth for one casting. This certainly can put a financial strain on the spellcasters of the party, but before we worry about the cost we need to look at how to find them. You can find diamonds in most jewelers' shops and possibly even in alchemical stores or magical shops. They are rare and expensive items though, so keep that in mind. You can also take diamonds and start shattering them with hammers and other tools. Diamonds might be the hardest metal in the world, but they sure aren’t indestructible. Diamonds are expensive but might be very easy to find in a mining town if you are looking for uncut gems. Places of magic probably have diamonds and diamond dust available due to their need to be used in spells.