Chemical Composition: SiO2 Cleavage: None Color: Colorless and all colors CrystalSystem: Hexagonal/trigonal Form/Habit: Cryptocrystalline Fracture: Conchoidal Gravity: 2. Hardness: 7 Luminescence: Green (long wave) / Yellowish-white (short wave) Luster: Vitreous Streak: White Transparency: Translucent to opaque
Where does Agate come from?
Agates are found all over the world. Particularly beautiful specimens have been found in Argentina, Austalia, Botswana, Brazil, Czech Republic, Germany, Hungary, India, Italy, Mexico, Morocco, Namibia, Poland, Russia, Slovakia, United Kingdom, and the United States.
What is an Agate?
Agate is a member of the Quartz family, a silicate mineral. Quartz is divided into two main groups, macrocrystalline and microcrystalline. Macrocrystalline quartz has well-formed crystals that are large enough to be seen by the naked eye, for example, Amethyst, Citrine and Smoky Quartz. Microcrystalline quartz, more commonly known as Chalcedony, has crystals so tiny they can only be seen through a microscope. Because Chalcedony is a large group of minerals, it is further subdivided into two groups, Agate and Jasper. Jaspers are most often opaque and may have spots, while Agates are usually translucent and often have stripes or organic-looking dendritic inclusions.
Agates are created after a volcanic explosion has transformed magma and lava into igneous rock. During the cooling down period, various gases form bubbles, which then become hollow spaces in the igneous rock. Agates are formed long afterwards, when silica-bearing water permeates the rocks and begins to fill the hollow spaces. Sometimes the hollow fills quickly and the resulting Agate is a solid color or has a random scattering of trace inclusions. Depending on which inclusions are added, the Agate will take on a variety of different colors, patterns and transparency levels. For example, both Moss Agate and Tree Agate are a quartz with manganese inclusions, Moss Agate tends to be translucent, while Tree Agate tends to be opaque. Fire Agate is a quartz with brownish Hematite inclusions that can appear iridescence when polished.
Banded Agates are formed more slowly, with one layer of silica-water solidifying, before another layer is deposited on top. This sequence is repeated over and over until the hollow is filled. Some of the layers will have picked up different trace elements or different quantities of the same element, resulting in bands of different colors.
How is Agate mined?
Agate is found all over the world but is not valuable enough to be the primary focus of any large-scale mining operation. It is however commonly mined in tandem with other precious metals and minerals, usually in small-scale artisanal mining environments. It may be found in it’s primary deposit still associated with the igneous rock in which it formed. Or it may be found loose and already naturally polished in rivers and on beaches. Agates are usually ball or almond-shaped nodules ranging in size from a fraction of an inch to several yards in diameter. If the Agate fills the entire hollow space left by the gas bubble, it is called an Agate Almond. If a hollow remains in the center, it is called an Agate Geode.
Agates are associated with all other quartz varieties. They are also commonly associated with Calcite, Copper and Hematite. As well as Petrified Wood and other fossils.
All Agates are natural and are typically enhanced only by tumbling, cutting, and polishing. They naturally appear in a wide variety of colors, with specific shades and patterns often used to identify a particular deposit or type. For example, Crazy Lace Agate is a multicolored agate, often including bright yellow and red, with a highly convoluted layering that is found only in Mexico.
Agates are naturally porous and have been dyed unnaturally bright colors since the Roman Era. As a loose rule, the more vivid the coloring, the more likely that it has been dyed. This is particularly true if the color is vivid and perfect, the stone is large and the price is cheap! Most dyed Agates have both bright white “hard” areas which won’t accept dye, and “soft” areas which take dye easily. Currently most of the dyed Agates on the market are actually pale gray and white Agates from Brazil. They are dyed vivid colors like hot pink or neon blue.
Varieties of Agate
There are dozens of varieties of Agates. Some of these names date back hundreds of years and may not even include the word “Agate.” For example, Sardonyx is a black, orange and white Agate. In some cases, the name indicates a specific location, such as Laguna Agate which is found near a lake (Laguna in Spanish) in Chihuahua, Mexico. In other cases, the name indicates a particular design. For example, Blue Lace Agate is named for it’s wavy bands which resemble lace. Occasionally a name is merely a matter of personal preference. For example, pink Agate from Botswana is called Apricot Agate at Moonrise Crystals, but it could just as easily be sold as “Pink Carnelian.”
Julie Abouzelof is the owner of Moonrise Crystals and an advocate for responsibly sourced gems and minerals. Her first career was in education teaching history, geology and anthropology, as well as working with special-needs students. She is now a heart-centered entrepreneur who encourages mindfulness and positive action to heal ourselves and the world. Julie lives in Hawaii with her lover and a little parrot named Darwin.