Agate's most noticable properties overall are balancing yin/yang energy, courage, protection, healing, and calming. Historically it was placed in water for cooking or drinking to dispel sickness. The Metaphysical and Healing Properties Lore of any specific type of agate depend to some extent on the color of the agate, but all agates have certain things in common.
Agate is a stone of strength. It was used by the Ancients on the breastplates of armor to give warriors strength and make them victorious in battle. Energetically, it is considered to give strength in both battle and physically.
Agate enhances creativity and strengthens the intellect, making it a beneficial stone for both students and artists. It is also known as a good luck stone. As a stone of harmony, one of the things agate does is balance yin/yang energy. Agate increases energy. However, because it is a grounding stone, it does not increase energy at all times, but rather enables bursts of energy as needed. In this way, agate is a conservation stone, and enhances longevity.
Agate is a very protective stone. It is especially protective for children, and makes an excellent stone for children's amulets, medicine bags, jewelry, or just to carry around in a pocket. Agates are said to be especially useful for protecting children from falling.
Emotionally, agate gives courage, emotional strength, self-confidence, and dispels fears. It can also lessen feelings of envy by grounding the emotions. In the same way, it assists with acceptance of all things. It can be very beneficial for self-examination as well as examination of the circumstances one finds oneself in. These qualities make agate superior for easing anxiety and stress. Particularly when placed on the Solar Plexus (3rd) Chakra, it can help one to accept one's emotions, thereby helping overcome those emotions that one wants to remove.
Because of the harmonizing qualities of agate, and its emotional energies of removing and releasing resentments and bitterness, it is also considered by many to be an excellent stone for helping to heal and improve relationships.
Agate can cleanse and stabilize the aura by removing and/or transforming negative energy.
As far as relationships go, agate is a stone of marital and romantic fidelity.