This special Jewish Chai charm pendant is made of genuine blue Opal stone. The size is 10mm ; on the sides there is a hole where the chain is slides through. The chain is solid 14k gold. Size of necklace is 16 1/2 inch. Gematria or Jewish numerology, is one of the haggadic hermeneutical rules for interpreting the Torah by which a word or phrase is explained on the basis of numerical equivalents. According to the kabbalists, Jewish mystics, the essense of a thing is in its name since the world was created through speech. In Hebrew every letter, word and phrase equals a number. CHAI or HAY chai equals the number 18. The Hebrew spelling is het and yod, with the numerical value of eight and ten. Often Jewish people give gifts and charitable donations in increments of eighteen. CHAI MEANS LIFE! Chai is best known in the blessing Le Chai'im! meaning - To Life! A perfect gift for a loved one or a magnificent addition to your own collection.