precious stones
The value of these four gemstones is based on their rarity, brilliance and durability.
diamond 
The hardest stone is colorless although there are also blue, yellow and pink varieties; it is the most renowned precious stone.
sapphire 
This stone can be blue, pink, orange, yellow, green, purple or even colorless; the most sought-after color is purplish-blue.
ruby 
The rarest of all precious stones is extremely hard; its color varies from a bright pinkish-red to a purplish red, which is the most sought-after color.
emerald 
Stone whose color varies from greenish-yellow to greenish-blue; an emerald’s value is based more on its color than on its purity.