Agate, Dendritic (USA)

Mineralolgy of Dendritic Agate

Rough Dendritic Agate, Eastern Kazakhstan Province, Kazakhstan

Mineral Family: Tectosilicate 

Chemical Composition: SiO₂
Cleavage: None
Color: Colorless Agate with various colored iron and manganese inclusions
Crystal System: Trigonal
Form/Habit: Cryptocrystalline
Fracture: None
Gravity: 2.6-2.64
Hardness: 6.5-7
Luminescence: Green (long wave) / Yellowish-white (short wave)
Luster: Vitreous
Streak: White
Transparency: Translucent, opaque

Location: Agates are found all over the world. Most Dendritic Agate is mined in Brazil, India, or the United States.

Mineral Family: Dendritic Agate is a Silicate mineral. Agate is a tiny twig on a far off branch of the crystal tree. Silicate minerals form the largest family of minerals, including more than 25% of all known minerals and 40% of all common minerals. In addition to being a major part of the Earth’s crust, Silicate minerals have also been found on the moon and in meteorites. Silicates are minerals which contain the elements Silicon (a light gray shiny metal) and Oxygen (a colorless gas). Together, these two elements form a tetrahedron – a shape similar to a pyramid – with a Silicon atom in the center and Oxygen atoms at each of the four corners. These tetrahedra connect with other chemical structures, in six different ways, to form various minerals and rocks. There are six main groups of Silicate minerals, and these main groups are further subdivided into secondary subdivisions, such as Quartz and Feldspar. Quartz is a large mineral family in its own right, and has two main subdivisions, macrocrystalline (crystals that are large enough to be seen by the naked eye, for example, Amethyst) and microcrystalline (crystals so small they can only be seen through a microscope, for example, Agate). All microcrystalline Quartz fall under the subcategory of Chalcedony, which is then further subdivided. One of these categories is Agate. Dendritic Agate is a type of agate which is colorless with inclusions of iron and manganese which can manifest in a wide variety of colors.

Formation: Dendritic Agate is created when liquid magma from a volcanic explosion cools down and transforms into igneous rocks. During this cooling down period, silica acid bubbles shift from being a gas/liquid into a solid compound. The bubble becomes a hollow space in the igneous rock and the silica acid becomes Quartz crystals. Agates are formed when thin sheets of Quartz are layered with other minerals, creating a wide variety of colors and patterns.

Mining: Agates are the primary product of numerous mines worldwide. Typically, Agates are found in their primary deposits and still have their original relationship with the host rock. 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.

Enhancements: Lab created Agates are rare, while dyed Agates are extremely common. Dendritic Agates are fully natural, enhanced only by tumbling, cutting and polishing. 

Map courtesy of TravelBlog
Photos: Dendritic Agate