I will improve Paul Frank’s statement slightly:

  1. Scarcity
  2. Universal Utility.
  3. Non-perishability
  4. Volume and weight to value ratio (and therefore transportability)
  5. Nearly universal convertibility.
  6. Functional unit of account, store of value, and medium of exchange. Very few goods meet this criteria. Silver and gold are pretty much the only goods that do meet this criteria.

https://www.quora.com/Why-is-gold-or-silver-precious-in-the-first-place-I-would-say-that-rice-is-precious