In general the Sanskrit word for ‘gold’ hiraṇ(y)a is derived from PIE *ğhel- ‘yellow, gold’. This word is phonetically similar to Sanskrit hari ‘gold’ < *ğhel-. There is nevertheless a problem with the vowel i of hiraṇ(y)a.
As the Sanskrit word for ‘tin, lead’ nāga is itself of Hurro-Urartean origin (< nahh- ‘to flow, melt’), another possibility is to derive hiraṇ(y)a ‘gold’ from Hurrian hiyari *[hijәri] ‘gold’, hence a stem *hir-, *hīr-. This is very possibly another Sanskrit word of Anatolian origin.Best. A.