Meanwhile, obsidian and black onyx help draw out any negativity that dwells within. "Black onyx is used for the development of emotional and physical strength and stamina, especially when support is needed during times of stress, confusion or grief," says Denecia Jones, author of How Crystals Shine . Similarly, obsidian can quiet an overactive mind and even give you clarity around difficult decisions, writes Yulia Van Doren in Crystals: The Modern Guide to Crystal Healing . In other words, if the negativity in your life usually stems from a tendency to worry or overthink problems beyond your control, these stones are best-suited to your needs.