Silver is far more abundant in the earth's crust and is mined in much larger quantities, so its per-gram price is a tiny fraction of gold's despite both being precious metals.
Silver also has heavy industrial demand (electronics, solar), which makes its price more volatile and tied to the economy than gold's safe-haven behavior.
To value silver, use the live spot per gram x purity (sterling is 92.5%) x weight — the same melt math as gold, just at a much lower base.
Try it: silver price per gram.