Gem valuation is the process of determining the worth of a gemstone based on various factors. Key criteria include the Four Cs: color, clarity, cut, and carat weight. Each of these elements contributes to the overall quality and desirability of the gem, influencing its market price. Additionally, the rarity and demand for specific gemstones play a significant role in their valuation. For instance, diamonds are often more expensive than amethysts due to their scarcity and popularity. Professional appraisers use these criteria to provide accurate assessments for buyers and sellers in the gemstone market.