Onyx stone is probably the only stone with many stories of its origin, and all these stories of its origin vary from culture to culture. According to Vedic Astrology, the Onyx gemstone is ruled by Saturn and Mars, and it is one among the many protective semi-precious gemstones. Birthstone-wise, onyx is considered to be Leo's birthstone. Onyx gemstone is available in a wide array of colors. Depending upon what the astrologer suggests, you can decide the quality, size, and color of onyx jewelry that you need to wear. As far as the day on which you should wear onyx jewelry is concerned, you should wear it on Tuesday.