Agates are found across the globe and are highly valued for their beauty and diversity. Each variety showcases unique colors, patterns, and optical effects, making them fascinating for collectors and lapidarists. The wide range of appearances reflects the varying conditions in which agates form.
Agate can be identified and classified based on:
- Distinct colors
- Optical effects
- Intricate patterns
- Geographic origins
Agate Varieties by Colors
Agates come in a variety of colors, including multicolored patterns, white, gray, red, brown, pink, and yellow. Green, blue, and purple hues are rare and highly prized. Two types of highly valuable as a lapidary material:
- Carnelian Agate: Common and widely used.
- Blue and Purple Agate: Rare and highly valued as lapidary material.
Understanding Agate: Formation, Composition, and Identification
Agates by Optical Effects: Iridescence & Fluorescence
Iridescence is a rare phenomenon where the surface of some agates changes color depending on the angle of light or the viewer’s perspective. This effect is caused by microscopic structures that diffract light into different wavelengths, creating a rainbow-like display.
Fluorescence occurs when certain agates absorb ultraviolet light and emit it as visible light, causing them to glow in vivid colors such as green, blue, orange, or red. This glow can persist even after the light source is removed.
Fluorescence is unique to each specimen, with some agates from the same location displaying varying fluorescent properties—some glowing brightly while others may not fluoresce at all.
Agate Varieties by Patterns and Shapes
Agates are categorized by patterns and inclusions, often displaying multiple patterns within a single specimen.
Below are some common types of agates based on colors, optical effects, and patterns.
Carnelian Agate
Carnelian agate is a translucent variety of chalcedony. It can be banded or not. This mineral is colored by iron oxides and identified by red, orange, and brown coloration.
Locations: New Jersey, New Mexico, Oregon, and Washington in the USA; Australia, Brazil, and India.
Blue and Purple Agates
Natural blue tones in agates which is a chalcedony, are particularly rare. Usually, blue chalcedony is translucent colored by traces copper, manganese, and iron. Shades of blues varies from gray to sky-blue to violet. True blue agates are highly valuable as a lapidary material.
Locations: California, Oregon, Utah, and Washington in the USA; Australia, Botswana, India, Namibia, Malawi, and Mexico.
Iris Agate
Iris Agate isn't a specific type of agate; it's a rare visual phenomenon that can sometimes be seen in certain agates.
Iris Agate produces a rainbow or iridescent effect when the mineral is held towards a light. This effect is typically found in colorless banded nodular agates and is caused by very fine banding that diffracts light as it passes through the mineral, producing rainbow spectrum.
Locations: Oregon, California, and Montana in the USA; Argentina, Brazil, Indonesia, and Mexico.
Fire Agates
Fire Agates is a variety of chalcedony that exhibits a vibrant, iridescent play of colors, typically in shades of red, orange, and green.
This effect is caused by thin layers of iron oxide within the stone, creating a fiery, almost holographic appearance.
Locations: Arizona, California in the USA; Mexico.
Flower Agate
Flower agate is a type of agate that features distinctive patterns resembling flowers or blooms. These patterns are created by inclusions of minerals such as quartz or iron. The colors of flower agate can vary widely, often showcasing shades of pink, red, white, and orange, with a translucent to opaque appearance.
Locations: Arizona, California, and Oregon in the USA; Brazil, Madagascar, and Mexico.
Angel Wing Agate
Angel Wing Agate is a unique and visually striking type of chalcedony known for its delicate, feather-like patterns that resemble angel wings.
Angel Wing Chalcedony forms in veins or cavities of rocks. Plum agates often appear with botryoidal surfaces. Also, Angel Wing can occur in the center of a hollow thunderegg.
Locations: California, Oregon, New Mexico in the USA; Brazil and Mexico.
Banded Agate
Banded Agate, also known as Layered Agate is recognized by its parallel concentric banding and nodular shape. Some specimens occur in white, gray, yellow, or brown shades. However, at certain locations multicolored specimens with vivid red, orange, yellow, and other hues can be found.
Locations: Arizona, Michigan, Mississippi, Oregon in USA; Africa, Australia, Brazil, Germany, Madagascar, and Mexico.
Dendritic Agate
Dentritic (“tree-like” in Greek) Agate features tree-like or fern-like inclusions (dendrites) within the stone, usually in black or brown. The inclusions are typically manganese or iron oxides.
Locations: Arizona, California, Montana. Nevada, Oregon in the USA; Brazil, India, and Mexico.
Enhydro Agate
Enhydro Agate or Water Agate is featuring a tiny bubble of ancient water or air trapped inside.
Location: Found in locations where agate is present along with water.
Eye Agate
Features circular "eyes" or ring-like patterns within the stone. The eyes are formed due to concentric banding.
Location: Arizona, California, Michigan, Oregon in USA; Brazil and Mexico.
Oregon Coast Agate Hunting – The Best Beaches to Find Treasures
Dot and Orbicular Agate
Dot and orbicular agates are closely related but are not exactly the same type.
Orbicular agate features circular or orb-like patterns that can vary in size, color, and arrangement. Dot agate contains small, distinct dots or spots rather than full orbs or eyes.
Locations: Arizona, California, Oregon, Utah, and Washington in the USA; Australia, Brazil, Madagascar and Mexico.
Polka Dot Agate Mine: Discover the Hidden Gem of Central Oregon
Fortification Agate
Fortification Agate is recognized for its intricate, banded patterns that resemble the walls of a fortress, similar to an aerial view of a fort.
These patterns are formed by layers of silica that have filled cavities in the host rock, creating sharp, angular bands in various colors.
Locations: Arizona, California, Kentucky, Michigan, South Dakota, Wyoming in the USA; Argentina, Australia, Germany, and Mexico.
Lace Agate
Lace agate is a variety of agate characterized by its intricate, lace-like patterns, often with swirling, looping bands in soft colors like white, gray, blue, or pink. These delicate patterns can resemble fine lace, giving the stone a unique and elegant appearance. Mexican Lace Agate, particularly the Crazy Lace variety, is one of the most well-known, featuring vivid colors and complex designs.
Locations: Arizona, California, Colorado, and Missouri in the USA; Africa, Mexico, and Namibia.
Moss Agate
Moss agate is a type of agate that features green, brown, or black inclusions resembling moss, ferns, or other plant-like structures. These inclusions are made of minerals such as manganese or iron and are typically set against a translucent to milky white background.
Locations: Arizona, California, Nevada, Montana, Oregon, and Texas in the USA; Africa, Brazil, India, and Mexico.
Plume Agate
Plume Agate is a variety of translucent chalcedony known for its distinctive, three-dimensional contrasting mineral inclusions that resemble feathers, plants, or clouds.
Sagenitic Agate
Sagenitic agate is a variety of chalcedony known for its unique needle-like radiating patterns that can resemble a fishnet, sprays, or have star shapes. The background of sagenitic agate can vary from translucent to opaque, and it may display a range of colors.
Locations: Arizona, California, Idaho, Montana, Nevada, Oregon, and New Mexico in the USA; Brazil and Mexico.
Snakeskin Agate
Snakeskin agate is a distinctive type of agate characterized by its unique, scaly patterns that resemble the texture of snakeskin. These patterns are created by fine, overlapping bands or ridges that form a network of scales across the surface of the stone. The coloration can vary widely, including shades of brown, gray, black, and sometimes even vibrant hues.
Locations: Idaho and Oregon in the USA; Brazil, India, and Mexico.
Tube Agate
Tube agate is a variety of agate known for its distinctive tubular or cylindrical formations within the mineral. The tubes may remain hollow or filled with mineral deposits, creating striking patterns and textures. The internal tubes can vary in size and shape, and they are often surrounded by concentric bands of color or other inclusions.
Locations: Arizona, California, Idaho, Montana, Nevada, and Oregon in the USA; Argentina, Brazil, and Mexico.
Waterline Agate
Waterline or gravitationally banded agate exhibits a series of flat parallel lines, often white. The mineral was formed in the water and cases the silica instead circular line settle to the bottom of the nodule.
Locations: Found everywhere where regular agates are found.
Thundereggs
Thundereggs are a round nodule-like formation which can be filled with agate, jasper, opal, and/or quartz crystals. The color of the lumpy exterior surface varies from beige to reddish-brown or dark gray.
Various inclusions, colors, and patterns create an individual appearance for each specimen. Cutting the rough-looking nodules can surprise you by revealing truly beautiful inner content.
Locations: California, Idaho, Oregon in the USA; Australia, Canada, Germany, France, Turkey, and Mexico.
Geodes
Geodes is a round rock with a hollow center that are often lined with agate crystals or bands. The agate inside often displays a range of hues, from translucent to opaque, and can include various patterns such as banding, fortification, or druzy textures.
Locations: Arizona, California, Missouri, Montana, Nevada, Oregon, and Utah in the USA; Brazil, Mexico, and Uruguay.
Notable Agates by Locations
There are highly prized agates specifically recognized by locations.
- Holly Blue Agate - Sweet Home, Oregon
- Blue Ice Ocean Agate - Polka Dot Agate Mine, Central Oregon
- Ellensburg Blue Agate - Near Ellensburg, the state of Washington
- Turritella Agate - Green River Formation, Wyoming, USA
