This stone is associated with the planet Mercury, and is ideal for people born under the zodiac signs of Gemini and Virgo. Incidentally, the planet Mercury is believed to be representative of intelligence, memory, and high brain power. The Onyx gemstone is recommended for those who are looking to improve their public-speaking skills, their authority, confidence, sense of logic, and memory. It is attuned to the Heart Chakra. Just like every other gemstone, the Green Onyx too, is worn for a reason. More than one reason.