Agate is the birthstone for Leos Agate is a variety of the microcrystalline quartz, called chalcedony. The name "chalcedony" comes from Calcedon or Calchedon, an ancient port on the Sea of Marmara in Asia Minor. Black Agate meaning is Self-control, decision making, intuition, protection. It is widely believed that black Agate can change your habits are erratic, either when used with faith. It is regarded as one powerful protection stone as it absorbs negative energy of people to release mental stress and promote emotional well-being. Black Agate is associated with the planet Saturn, which will bring a positive vibe for those born in the shadow of the planet Saturn. It is a stone for Leo zodiac sign. Black Agate stone will helps maintenance Leo characteristic. Black Agate meaning In the Indian tradition is said to help people to forget about their past relationships and bring people in tune with the present.