Onyx is a stone recommended during times of pain and sorrow. It’s known for balancing male and female polarity and increasing hormonal balance. It’s also said to help with objectivity and making intelligent decisions. In addition, it’s believed to help strengthen one’s bones.
In addition to the generic healing properties of Onyx, specific colours and types have additional attributes:
Black Onyx is associated with our Base Chakra.
Green Onyx is associated with our Heart Chakra.
Zodiac - Gemini, Leo 
Element - Earth

Hematite grounds and protects us. It strengthens our connection with the earth, making us feel safe and secure. It endows us with courage, strength, endurance and vitality. A "stone for the mind", Hematite stimulates concentration and focus, enhancing memory and original thought. Hematite utilises the magnetic qualities of our yin-yang energies to balance the meridians within the body and to provide a stable equilibrium between the ethereal nervous system and the physical nervous system. It focuses energy and emotions for balance between the body, mind and spirit.
Chakras - Base Chakra 
Zodiac - Aries, Aquarius 
Element – Fire/Earth

Black Crystal is associated with the solar plexus chakra, and known as an excellent ground stone. Many believe it aids in relieving stress and anxiety, while calming a hyperactive mind. Crystal is also said to disperse fear and lift depression and negativity, while encouraging positive thought and action. Others associate the stone with detoxifying the digestive system, and protecting against radiation. Typical colours are Brown and Black.
Chakras - Base Chakra, Solar Plexus Chakra 
Zodiac - Scorpio, Capricorn 
Element - Earth/Air