These nine gems, Nava-ratna in Sanskrit, correspond to the nine planets or nava grahas. Recorded in numerous Vedic scriptures, the gems are believed to have "auspicious powers which can protect one from demons, snakes, poisons, diseases, sinful reactions, and other dangers (Sri Suta Goswami, Garuda Puranam 68:17)".
For these stones to be auspicious, it is imperative that they be top quality and flawless: "A gem free from all impurities and radiating its characteristic internal luster should be looked upon as an escort of good luck; A gem which is cracked, fissured, devoid of luster, or appearing rough or sandy, should not be used at all (Agni Puranam 246:7,8)".