Plume agate is a variety of chalcedony, a microcrystalline quartz, characterized by delicate, plume-like inclusions of various colors and minerals. These inclusions often resemble feathers, flowers, or flames, giving the agate a unique and visually appealing appearance. The plumes are typically composed of iron oxides, manganese oxides, or other trace minerals that were deposited during the agate's formation.
Formation of Plume Agate
Plume agate forms in hydrothermal environments, where hot, silica-rich fluids circulate through volcanic rocks. These fluids dissolve silica and other minerals and deposit them in cavities or voids in the rocks. Over time, the deposited silica accumulates and recrystallizes, forming layers of chalcedony. The plume-like inclusions are formed when trace minerals in the hydrothermal fluids mix with the silica during the recrystallization process. The coloration depends on the specific trace minerals involved.
Properties of Plume Agate
Composition: SiO₂ (Silicon Dioxide) with inclusions of iron and manganese oxides (forming the plumes) - Same as chalcedony.
Color: White, gray, milky, yellow, green, red, orange, sometimes with banded or mottled patterns due to the plumes.
Luster: Vitreous to waxy, depending on the specific type of plume agate.
Crystal System: Microcrystalline aggregate, not a true crystal system.
Hardness: 6.5-7 on the Mohs scale (slightly softer than quartz)
Cleavage: Poorly developed to conchoidal
Crystal Form: Usually botryoidal, banded, or massive.
Density: 2.60-2.65 g/cm³ (similar to density of water)
Transparency: Translucent to opaque, depending on the thickness and density of the plumes.
Fracture: Conchoidal to uneven
Solubility: Insoluble in water and common acids, slightly soluble in strong alkalis.
Fluorescence: Varies depending on the type of plume, some may exhibit weak orange or yellow fluorescence under longwave ultraviolet light.
Pleochroism: Absent, due to the non-crystalline nature of plume agate.
Refractive Index: Typically around 1.54-1.55 (similar to chalcedony)
Varieties and Types of Plume Agate
There are several different varieties of plume agate, each with its own unique characteristics and appearance. Some of the most well-known varieties include:
|Moss Plume Agate from Indonesia
Moss Agate: While not technically a true plume agate, moss agate is often included in this category due to its feathery, moss-like inclusions. The mossy patterns, often in shades of green, brown, and black, create a captivating and earthy aesthetic. Moss agate considered a type of plume agate due to its plume-like features, but not all plume agates are moss agate.
|Dendritic agate variety of plume agate
Photo: Rare Earth Mining Co.
Dendritic agate: This type showcases fern-like or tree-like inclusions of black manganese oxides, creating a mesmerizing contrast against the agate's base color.
|Fire agate variety of plume agate
Fire agate: This type of plume agate features red or orange inclusions of iron oxides, giving it a fiery appearance.
Brecciated Plume Agate
|Brecciated Plume Agate
Photo: Roy Isaac
Brecciated Plume Agate: Formed from fragments of agate and plume agate, brecciated plume agate is known for its mosaic-like appearance. The contrasting colors and textures of the fragments create a captivating and visually striking gemstone.
|Cut Plume agate. Photo: Didiek Backbone
Phantom agate: This type of plume agate features faint, ghost-like inclusions that are visible when held up to the light.
Uses of Plume Agate
Plume agate is a popular gemstone and is often used in jewelry making. It is also used for decorative purposes, such as in carvings, sculptures, and cabochons. Plume agate is believed to have various metaphysical properties, such as enhancing creativity, balance, and emotional well-being.
- Jewelry making: Plume agate is sometimes used in jewelry making, and it can be cut into cabochons, beads, and other shapes.
- Collecting: Plume agate is a popular collector's item due to its unique and beautiful appearance.
- Decorative objects: Plume agate can also be used to make decorative objects, such as paperweights, figurines, and sculptures.
|Bouquet type, plume agate, from Presidio County, Texas.
Photo: Darwin R. Dillon
Value of Plume Agate
The value of plume agate varies depending on the quality, size, and color of the stone. High-quality plume agate with vibrant colors and intricate plumes can fetch high prices in the gemstone market.
Plume Agate occurrence
Some of the most notable localities for plume agate:
Oregon: The John Day Formation in central Oregon is one of the most famous localities for plume agate. This formation is also home to other types of agate, including moss agate and fire agate.
California: Plume agate is found in several locations in California, including the Mojave Desert, the Sierra Nevada Mountains, and the Death Valley National Park.
Nevada: Nevada is home to some of the largest and most spectacular plume agate specimens in the world. These specimens are typically found in the northern part of the state, near the Nevada-Idaho border.
|Turkish plume agate
Texas: Plume agate is found in the Woodward Ranch in Alpine, Brewster County, Texas.
Colorado: Plume agate is found in several locations in Colorado, including the San Juan Mountains and the Del Norte area.
Ashcroft, British Columbia, Canada: Plume agate is found in the Ashcroft area of British Columbia.
Turkey: Plume agate is found in Turkey, particularly in the Eskişehir Province.
Iran: Plume agate is found in Iran, particularly in the Khorasan Province.
Indonesia: Plume Agate is found on the Indonesian island of Java. The agate in this region is typically characterized by its white or gray background with delicate feather-like plumes of red, brown, or black. The Plume Agate from Java is often referred to as "Indonesian Moss Agate" because of its resemblance to moss.
|Dendritic plume agate