Which gemstone has the most value?

Could you please elaborate on what criteria we should use to determine which gemstone has the most value? Is it purely based on monetary worth, or should we also consider rarity, cultural significance, and overall appeal? Furthermore, are we considering all types of gemstones, including diamonds, rubies, emeralds, and sapphires, or just a select few? Lastly, could you provide some examples of gemstones that are considered highly valuable and explain why they hold such high esteem in the market?