Capricorn’s Jewelry (Dec 22- Jan 20)

Rubies are said to bring wisdom, happiness and health to those who wear them, as well as bring good luck to gamblers and lovers.
Birthday Stones
The term "Birthday Stone" has been used as a synonym for "Birthstone", however there is also a separate list of assignment according to the day of the week you were born:
Monday: Pearl (the only organic gem)
Tuesday: Garnet
Wednesday: Cat's eye (Chatoyant Chrysoberyl)
Thursday: Emerald
Friday: Topaz
Saturday: Sapphire
Sunday: Ruby