Sapta Ratna or Seven Jewels

The seven planets from Sun to Saturn represent the seven colours of visible light that lead to creation.

The Rig-Veda advises use of seven gemstones for capturing the rays of the sun:

Element Gem Stone Indian Name Substitute
Sun Ruby Manik Brown Tourmaline
Moon Pearl Moti  
Mars Red Coral Moonga  
Mercury Emerald Panna Berly
Jupiter Yellow Sapphire Pukhraj Citrine
Venus Diamond Heera White Sapphire
Saturn Blue Sapphire Neelam Amethyst