Silver and gold exist inside of many ores, if you look at the mod main page, these are the ores that have those two:

Silver "Ag" (silver, galena, chlorargyrite, petzite, electrum)
Gold "Au" (gold, petzite, porphyry, pyrite, uraniaurite)

If you're looking for pure "gold" ore, most pure ores are hard to find.