Agate

Agate is a banded variety of chalcedony, the microcrystalline form of quartz (silicon dioxide). The name is normally reserved for stones that show distinct banding or patterns, while plain, evenly coloured material is simply called chalcedony.

Most agate forms inside cavities in volcanic rock such as basalt and andesite. Silica-rich water seeps into the gas bubbles left in the cooling lava and gradually deposits layer upon layer of chalcedony, with traces of iron and other minerals giving each band its colour. The centre is often filled with crystalline quartz or left hollow, as in a geode. Exactly how the banding forms is still debated, and agate has never been successfully made in a laboratory.

The name is said to come from the River Achates (now the Dirillo) in Sicily, where the Greek philosopher Theophrastus recorded the stone in the 4th century BC. Agate is one of the oldest materials used by people: it was worked into tools in the Stone Age, made into jewellery by the Sumerians around 2500 BC, and used for seals and cameos by the Greeks and Romans. The town of Idar-Oberstein in Germany has been a centre of agate cutting since the Middle Ages.

Because agate is porous, it takes dye very well, and much of the brightly coloured agate on the market (blues, pinks, purples and vivid greens) has been dyed. Many traditional dyeing methods were developed at Idar-Oberstein in the early 1800s. Dyed agate is perfectly good for beads and jewellery, but the colours of some modern dyes can fade with strong sunlight or heat.

There are many named varieties, including blue lace agate, crazy lace agate, moss agate, fire agate, Botswana agate, fortification agate and onyx (agate with straight, parallel bands).

Agate at a glance

Caring for agate

Agate is fairly hard (6.5 – 7 on the Mohs scale) and has no cleavage, so it is durable enough for everyday jewellery. Clean it with warm soapy water and a soft brush or cloth, then rinse and dry. Avoid ultrasonic and steam cleaners, and keep it away from bleach and other household chemicals, which can attack dyes. Because many agates are dyed, avoid prolonged strong sunlight and high heat, which can fade the colour. Store separately from harder stones, such as sapphire and diamond, which can scratch it.

In folklore

The beliefs below are traditional folklore, included for interest. They are not scientifically proven, and nothing here is medical advice.

Agate has a long history as a talisman. Ancient warriors carried it in the belief that it brought victory and kept them safe, and in the ancient world it was thought to make the wearer agreeable and persuasive. Folklore also says that agate guards against storms, cures insomnia and brings pleasant dreams. In the Middle Ages it was believed to protect against poison and to quench thirst when held in the mouth. Agate is associated with the zodiac sign Gemini.

Agate is traditionally regarded as a grounding and stabilising stone. Crystal healing lore holds that it brings emotional balance, calms the mind and builds self-confidence, and that it helps with concentration and practical thinking. It is also said to protect the wearer and to soothe and strengthen relationships. Different colours and varieties are given their own meanings: blue lace agate is associated with calm communication, and moss agate with nature, growth and new beginnings.

Related stones

Chalcedony, carnelian, onyx, sardonyx, jasper, chrysoprase, bloodstone, petrified wood. Varieties of agate include blue lace agate, crazy lace agate, moss agate, fire agate, Botswana agate, tree agate and fortification agate. Agate is also related to the crystalline quartzes such as amethyst, citrine and rock crystal.

For the technically minded

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