There is a definition for 'petrichor' here and a singular place for it in A.Word.A.Day but no definition at Merriam-Webster online except obliquely as the root (second) 'ichor' 2 : an ethereal fluid taking the place of blood in the veins of the ancient Greek gods.
Possibly it has to work its way into Oxford English Dictionary to be deemed a part of our lexicon. I venture it's in OED. Does anyone subscribe?
Ichor but no petrichor.
You know petrichor like you know rain, earth, air. Don't you?

