The value of a silver necklace can vary depending on several factors such as the purity of the silver, the design and craftsmanship of the necklace, and the current market price of silver.
If the necklace is made of sterling silver (which is 92.5% pure silver), its value would be calculated based on the weight of the silver used in the necklace and the current market price of silver. As of my knowledge cutoff in September 2021, the price of silver ranged from approximately $20 to $30 per ounce.
So, for example, if a silver necklace weighed 1 ounce and the current market price of silver was $25 per ounce, the necklace would be worth around $25. However, if the necklace has additional materials such as gemstones or other metals, the value may be higher due to their additional value.
It's always best to get an appraisal from a professional jeweler to determine the exact value of a silver necklace.