It is mainly composed of chalcedony. Its chemical composition is SiO2 and it forms from silica solutions at shallow depths and low temperatures. It comes in different colors and numerous beautiful patterns, such as colorful stripes, cloud blends or moss like formation. Its most common form is a round nodule with concentric bands of different colors. Often, the stones carry small quartz crystals within them which give each stone its individual design. It is mined all over the world and is largely available in India, China, Brazil, Russia, and Madagascar.  It is relatively an inexpensive stone, except for some of the exceptionally beautiful pieces.

Agate stone has long been used in historical times to treat a number of physical disorders. Placing Agate stone on the solar plexus helps correct stomach disorders. It cleanses the lymph nodes and balances blood sugar levels. It re-energizes and rejuvenates, and is an effective post delivery recovery aid. It helps overcome weakness and debilitation due to long illness. Agate is useful in treating gum diseases, and strengthens weak gums. It is a grounding stone and stabilizes energy in the body. It preserves the extra energy in the body and provides burst of energy as and when needed by the body. Due to its energy-conservation and longevity, it was used in the breast plates of warriors in olden times to ensure their protection and success in the battle.

Agate stone is also a powerful spiritual and emotional aid. It promotes strong relationships, love and romantic fidelity. It is particularly good for those nursing grudges and bitterness over past bad experiences. It patches up broken relations, and strengthens family bonds. It develops feelings of forgiveness, diminishes hatred for the enemy, and inculcates humanitarian values. Emotionally, it improves self esteem, develops self confidence, optimism, truthfulness, and brings about inner purification and harmony.
It refreshes fatigued and tired mind. Take it along with you when going out for a walk; it helps connect you with nature and overcome tiredness, pressure, suffocation and constriction. It is also an extremely protective stone. It makes an effective gemstone for children’s amulets and protects children from falling and getting hurt. It is used in eye amulets to protect from the “evil eye”. Carrying agate stones with you while making important decisions is said to help make successful decisions.
Some of the well known varieties of agate are moss agate, eye agate, plume agate, Montana agate, black agate, blue agate, blue lace agate, fire agate, flame agate, Mexican Lace Agate, and tree agate. Moss agates are related to nature and earth, and are said to promote growth of plants and vegetables. Gardeners are recommended to wear agate stone while gardening. Flame agate is supposed to boost physical vitality and awareness. It lends clarity and precision to the thought process, particularly at times of transition and confusion.  Montana agate enhances memory and increases self confidence.
In modern times, it is used to make inexpensive jewelry, ash trays, ornamental pieces, precision instruments etc. Wearing agate bracelets is believed to bring longevity and protection. For such uses the stone may be artificially colored or chemically treated to acquire the desired shades. The porous nature of the mineral makes it absorb the applied color coating. Most of the agate stone pieces available in the market have undergone coloring.