Hematite is used to bring mental organization and is very grounding and calming. It can help with original thinking, logical thinking, and mathematics, any type of thinking which requires significant mental organization. Emotionally, hematite decreases negativity. This lowering of negativity can benefit by helping balance the body/mind/spirit connection. It also is said to balance the meridians, boost self-esteem, and self-confidence.
Onyx is associated primarily with the root chakra. It assists with challenges in life, especially those caused by a drain of energy. It prevents the draining away of personal energy and can be used for protection from such. It also helps with grounding and controlling or eliminating excess or unwanted energies.