The 1841 British edition accidentally omitted the repeated in before silver here in Ether 10:12. Elsewhere the preposition in is repeated in conjuncts involving gold and silver:
The critical text will restore the repeated preposition in here in Ether 10:12. For other cases where the repeated in has been omitted from noun phrase conjuncts, see under Mosiah 24:1.
Summary: Restore the original repeated preposition in Ether 10:12 (“and in gold and in silver”).