Types of Agate
Banded, lacy, mossy, iridescent. Every variety explained, and what makes one stone look so unlike another.
Slice an agate open and you find a record of time: layer after layer of colour, laid down so finely that some stones hold hundreds of bands in the width of a fingernail. Agate is one of the most varied stones there is, and one of the most commonly mislabelled, so a pale blue lace agate, a green moss agate and a flash of fire agate can look like three entirely separate minerals.
This guide covers what agate is, how it forms, the main varieties you are likely to come across, and how to tell a natural colour from a dyed one. Where a stone is sold as agate but is not strictly banded, we have said so.
What Agate Is
Agate is a banded variety of chalcedony, which is itself a form of microcrystalline quartz: quartz made of crystals so small they cannot be seen without a microscope. It sits in the silicate group we describe in our guide to mineral classes, and it measures roughly 6.5 to 7 on the Mohs scale, hard enough for everyday jewellery.
Unlike jasper, which is opaque, agate is usually translucent, so light passes partway into the stone and picks out its layers. The name is thought to come from the Achates river in Sicily, where the ancient Greeks are said to have first found it, and agate has been carved into beads, seals and bowls for thousands of years.
How Agate Forms, and Why It Is Banded
Most agate begins in volcanic rock. Gas bubbles trapped in cooling lava leave small hollows, and over time silica-rich water seeps into them. The silica is deposited on the inside walls, one thin layer after another, and slowly fills the cavity. We explain the wider process in How Crystals Form.
The bands come from changes in the water over the long time it takes. A shift in temperature, in the chemistry of the fluid, or in the minerals dissolved in it leaves a visibly different layer. Iron oxides give reds, oranges and browns. Other trace elements and fine inclusions give blues, greens and greys. If the cavity is not completely filled, the centre often lines with larger quartz crystals, and that is how a geode is born.
Not every stone called agate shows bands. Some varieties have patterns made by inclusions instead, which is where moss agate and dendritic agate come in, below.
Agate in Our Range
Several varieties of agate are in our collection, each with its own look and its own long-held associations. As with all crystal meanings, these are traditional symbolic associations rather than scientific claims.
One of the gentlest-looking stones there is: pale sky blue with fine, wavering white lines, like frost on a window. It is most famously found in Namibia. Blue lace agate is traditionally associated with calm, with clear communication and with softening a tense moment.
The opposite of calm in appearance: white, cream, yellow, red and grey in tangled, swirling bands that never repeat. Crazy lace agate is typically sourced from Mexico, and it is traditionally associated with cheerfulness and a playful outlook.
The most searched-for agate of all, and technically not banded. Moss agate is clear to milky chalcedony threaded with green, and the "moss" is not moss at all. It is made of tiny inclusions of minerals such as chlorite and iron-bearing minerals, which spread through the stone in feathery, plant-like shapes. It is traditionally associated with growth, abundance and a connection to the natural world, and it has long been a gardener's stone.
Deep, warm red to red-brown, often with darker or paler bands, coloured by iron oxide. Red agate is traditionally associated with vitality, courage and steady energy, and it is a close visual cousin of carnelian.
Other Agate Varieties Worth Knowing
These are not in our range at the moment, but you will meet them in other shops and in collectors' books, so they are worth recognising.
Fine, closely spaced bands in soft greys, pinks, peaches and whites, from Botswana. The delicate banding is its signature, and it is traditionally associated with calm and with a gentle kind of resilience.
Very different from the rest: polished domes of brown chalcedony that flash with iridescent greens, golds and reds. The colour comes from extremely thin layers of iron oxide inside the stone, which bend light in the same way a soap bubble does. It is found mainly in Mexico and the south-western United States, and good fire agate is considerably rarer than banded agate.
Clear to milky stone with branching black or brown patterns that look like tiny trees or ferns. "Dendritic" comes from the Greek for tree, and the patterns are not fossils. They are minerals, usually manganese or iron oxides, that crystallised in branching shapes as water moved through the stone.
White or grey chalcedony marked with green patterns that suggest trees and branches. It is closely related to moss agate, and like moss agate it is defined by its inclusions rather than by bands.
Onyx is agate with straight, parallel bands rather than curved ones, and sardonyx is onyx with bands of reddish-brown sard alternating with white. Sardonyx is also one of August's traditional birthstones, alongside peridot, and you can see how it fits among the rest in our birthstone guide.
Natural and Dyed Agate
Agate is slightly porous, which means it takes dye very well, and dyeing is common and long established in the trade. Agate slices in vivid blue, purple, pink or bright green are almost always dyed. The same goes for much agate sold in colours that are rare in nature.
Dyed agate is still agate, but the colour is not the stone's own. Natural agate tends to show colour that follows the bands and fades or deepens with them, while dyed colour can pool in cracks and look unnaturally even. If you are buying a stone for its natural character, it is fair to ask the seller whether a piece has been dyed or treated.
Agate, Jasper and Chalcedony
All three are microcrystalline quartz. Chalcedony is the umbrella term, agate is the banded and usually translucent form, and jasper is the opaque, impurity-rich form. The lines blur in practice, and one stone can show agate-like bands next to jasper-like opaque areas. We cover the opaque side of the family in Types of Jasper.
Not sure which stone suits you? Let us help you choose, or browse our science guides to see how stones like agate come to be.
Find Your Stone The Science of CrystalsTypes of Agate, Answered
What is agate stone?
Agate is a banded, usually translucent variety of chalcedony, which is microcrystalline quartz. It forms in cavities in volcanic rock as silica-rich water deposits fine layers over a very long time, and it measures roughly 6.5 to 7 on the Mohs scale.
How do you pronounce agate?
In British English, agate is usually said "AG-it", with a hard g and the stress on the first syllable.
How many types of agate are there?
There is no fixed number, because varieties are named for their appearance, their patterns or where they come from. Commonly recognised types include blue lace, crazy lace, moss, red, Botswana, fire, dendritic, tree and sardonyx agate.
Does moss agate have real moss in it?
No. The green patterns in moss agate are tiny inclusions of minerals such as chlorite, which spread through the stone in shapes that resemble moss or plants.
Are agates crystals?
Agate is made of microscopic quartz crystals, but they are too small to see, so it looks like a solid, banded stone rather than a single crystal with visible faces. Agate geodes often have larger quartz crystals growing in the hollow at their centre.
Are agate slices dyed?
Very often. Agate is porous and takes dye easily, so slices in bright blue, purple, pink or green are almost always dyed. Natural agate usually shows soft earthy tones such as greys, browns, creams, reds and pale blues.
What is the difference between agate and jasper?
Both are microcrystalline quartz. Agate is usually translucent and banded, while jasper is opaque because of the higher proportion of other minerals within it.