In an insurance appraisal remember that the description is what makes it possible to accurately replace or compensate if a piece is lost, stolen, or damaged. When the insurance company tries to replace the ring with the same quality as what was lost, one carat and a price leaves it wide open. The result is usually an unhappy customer. Two factors are most important in determining value. Rarity and beauty.
Rarity has to do with supply and demand.
Common gems will cost less than rare ones. Beauty causes demand. All things being equal, the more beautiful gem will always command a higher price. A more intense color and a better cut will give a gem more beauty and thus a higher price. Two one carat sapphires may be very different in value.