SIMMONS Onyx is a stone of inner strength. It enhances one’s endurance and persistence, enabling one to carry even difficult and dreary tasks through to completion. On a mental level, it increases one’s ability to maintain focus, allowing one to learn challenging new material and use well all that one has mastered. It energetically boosts the retention of memory and encourages attention to detail. These traits make Onyx a helpful tool for students, teachers, business owners, accountants, lawyers, software and computer technicians, and all those whose work calls for high levels of focus, perseverance and discipline.
Onyx emanates the energy of self-mastery. Onyx can bring one down to Earth and keep one on task. It assists one in learning that the most important control is self-control. Those who pursue their desires by manipulating other people and things outside themselves are advised to take advantage of Onyx’s capacity to realign one’s attention to one’s own actions. Then they may find the success which has heretofore eluded them. Onyx cools and condenses excessive energies. It calms nervousness, quells anxiety, soothes hot tempers and brings reason to passion.
Simmons, Robert. The Book of Stones, Revised Edition (pp. 354-355).