The gem stones used for the nine planets are described as below:

BLUE SAPPHIRE:
Also called Neelam and is recommended for Saturn (Shani). It is found in lighter to darker shades of blue colour. It is believed that neelam can transform a beggar into the richest of all by removing all the misfortunes. It also helps in removing the ill effects of Saturn.
YELLOW SAPPHIRE:
Also called pukhraj and is recommended for Jupiter. It is found in lighter shades of yellow. It helps in instilling leadership qualities. It signifies fortune and help in fulfillment of all the worldly desires.
RUBY:
Also called manik and is recommended for sun ( Surya). It is found in all shades of pink. It strengthens heart circulation. It imparts power and gives name and fame to the wearer. It gives a power to rule over others.
EMERALD:
Also called panna and is recommended for Mercury ( Bhudh). It is green in colour. It helps in stabilizing mental ailments or memory problems. Increases communication and presence of mind.
PEARL:
Also called moti and is recommended for Moon (Chandrama). It is found to be white in colour. It helps in controlling temper and stabilize emotions. It has direct influence on brain and heart related matters.
CAT’S EYE:
Also called Lehsuniya and is recommended for Ketu and is generally found to be grey or milky in colour. It protects the wearer from dangers and disease and helps him gain unexpected fortune.
HESSONITE:
Also called Gomedh and is recommended for Rahu and found to be brown in colour. It removes delays in life and fulfills all ambitions.
RED CORAL:
Also called moonga and in recommended for Mars( Mangal) and is found to be red in colour. It makes one more courageous, brave and energetic. It helps in curing disease like malnutrition, improves blood and helps in martial life.
DIAMOND:
Also called Heera and is recommended for Venus( Shukra). It bestows a very lavish and luxurious life and brings popularity. It inspires creativeness and imaginative powers.