Agate is a variety of Chalcedony which forms in concentric layers. It forms by filling a cavity in a host rock and as a result is often found as a round nodule with colourful bands. Other names which often precede the word Agate either indicate its visual characterisitcs or its place of origin, for example, Dendritic Agate which has visible crystals within the gemstone that look similar to branches or plants, quite a common form of crystallization they known as dendrites, Botswana Agate from Africa has beautiful dark and light banding and Blue Lace Agate is a delicate light blue colour with fine layers of colourless Agate within the stone.
One of the oldest of all minerals, the earliest references are in the writings of Theophrastus (c.370-285BC), it is known to have been among the world's first lapidary materials. Highly valued by ancient cultures including the Sumerians, Egyptians, Greeks and Romans who used them as talismans, for jewellery specifically rings and for utensils including bowls and vases. It is also believed to have been one of the gemstones in the High Priest's breastplate also known as the breastplate of Aaron. This was a religious garment worn by the Jewish High Priest in bibilical times.
Being graded 7 on Mohs scale of mineral hardness and also because of the wide variety of colours and markings in which Agate can be found, gemstones are extremely popular for use in jewellery where they are either sliced or cut as a cabochon. It is also used in industry to make mortars and pestles to crush and mix chemicals due to its ability to resist acids.
Gemstones can be obviously translucent or appear to be opaque when in fact they're not. When held up towards the light, wavy bands of colour often become visible which makes it particularly distinctive. Cutting Agate into fine slices allows light to pass through more easily hence the bands become highly visible making the gemstone even more appealing.
In crystal healing it's a grounding gemstone excellent for cleansing which can bring emotional, physical and intellectual balance. It stabilizes energy, is in unison with the yin and yang and can bring hidden information to light. Soothing and calming, it works slowly but with great strength. Helping to overcome bitterness of the heart and healing self anger, it enables you to build courage to start over.
Associated with the star sign of Gemini, Agate is the Hebrew and Roman ancient traditional birthstone for the month of May.