BEAUTY

When we talk about beauty of gemstones .we refer to a combination of different attributes:
COLOR: The color is one of the most important factors which affect the quality and price of gemstone. Where colored gemstones are concerned the deeper the color along with transparency; it would fetch a higher price. But this is not the case of Diamond. For the diamond the colorless the diamond, the better is its price.

DURABILITY

This refers to the power of a gemstone to resist daily wear and tear. The durability of gemstones depends on following factors:
HARDNESS: The power of a mineral to resist external abrasion when a pointed fragment of another substance is drawn across it without sufficient pressure to develop cleavage is referred to as hardness. The harder the gemstone, the more durable it is. Diamond is the hardest gemstone.

RARITY

It is third and important character which a gem must possess. A gem of dark color and good transparency is rare, thus the demand is more. Rare a gemstone is, higher the demand and value. For instance emerald with light color is easily available so its price is low. But emerald with deep color and good transparency is not easily available which make then expensive.