The Silver Eagle struck in 1991, contains one ounce of silver. The current spot price of silver per ounce is $23.43. If you were to melt the coin for the value of the silver alone, you could get about $19.85.
Because this coin is a special commemorative coin, the value of the coin is usually worth more than the value of the silver it contains. Silver Eagles generally sell for around $35-$45.
As with all coins, the actual value of a 1991 Silver Dollar will depend on a number of factors, including its condition, rarity, and market demand.