Agate is a chalcedony, a compact, microcrystalline form of quartz (made of silica). They are found in pockets of rock, most commonly in lava rock but also in metamorphic rock. They are formed when vapor vesicles (pockets) become filled with silica deposits. Agate may often have bits of quartz crystal or amethyst in it and may have a geode inside if you break it open. Agate also has characteristic banding which is visible when it is cut or broken open.
The rock was named by Theophrastus, a Greek philosopher, who collected agates from the Achates River in the 3rd or 4th century BCE.
Today most agate comes from deposits in Uruguay and Brazil.
Agate is rated 7.0 on Moh’s hardness scale.
Magic and Folklore
Agate rings were popular among Persian magi and were used in jewelry in Babylon.
The stone is purported to have the power to cure poison, especially from bites and stings, soothe the mind, prevent the spread of disease, calm rough weather, promote eloquence, help ensure the good will of others and grant victory. Placed on the head of a sleeper, agate induces fantastic dreams. It is also used in charms for love, mental clarity and good luck in card games.
Agate is the stone for the 12th and 14th anniversaries and is an unofficial birthmonth stone for May and June. It is associated with Gemini, Taurus, Virgo, Libra and Capricorn and also with the planet Mercury.
Agate is both hard and beautiful. It is used extensively in jewelry and also for mortars and pestles. It has also been used to make leather burnishing tools.
Agate comes in many colors. Blue, green and brown are most often seen.
Blue Lace Agate – Bands of translucent blue and white
Brecciated Agate – Agate that has broken but been cemented together with quartz
Eye Agate – The banded rings look like an eye
Fire Agate– Iridescent with red inclusions
Fortification Agate or Dry Head agate – the bands look like the corners of an old fortress
Moss Agate or Tree Agate – a Dendritic Agate- Rather than the usual stripes, the inclusions look blotchy, like moss growing on a rock
Onyx – Black and white banded agate
Petrified Wood– When a piece of wood is trapped inside a lava flow and decays and the space it has left is replaced by agate, you get this!
Sardonyx – Reddish brown and white banded agate.
Scenic Agate – another dentritic agate. The inclusions form a pattern suggesting a landscape.
Snakeskin Agate– Has a snakeskin like pattern