Gold over silver resists tarnishing because the gold exterior physically blocks the oxidation process that causes it, keeping the silver base beneath it protected from the reaction.
The Perfect Gift
What makes animal motif jewelry personally resonant as a gift is that the creature is a representative of the recipient. Whether it be a spirit animal, a zodiac sign or a pet, there's a reference encoded in the piece that the wearer carries with them.
Visually Speaking
Material quality sets the lifespan and the price simultaneously for charms in fine jewelry. Constructed in gold, silver, or platinum with diamonds, colored gemstones, enamel, or engraving, a charm built to last decades is made differently from one that is not, and that difference is visible in how it holds up.