Fire Obsidian: The Rarest Type of Obsidian

Fire Obsidian: The Rarest and Most Expensive Type of Obsidian

Fire obsidian is a rare variety of iridescent obsidian that is found in southeast Oregon. It is characterized by its vibrant colors and patterns, which are caused by the presence of thin layers of magnetite within the glass. The colors of fire obsidian can vary widely, but they often include red, orange, yellow, green, and blue. The patterns can be concentric circles, bands, or other geometric shapes.

Fire obsidian is formed when lava cools very rapidly, preventing the formation of crystals. This results in a glassy material that is highly reflective. The magnetite layers within the fire obsidian cause light to be reflected in different ways, creating the iridescent colors and patterns.

Where to Find Fire Obsidian

Fire obsidian is found in only one location in the world, in the Steens Mountain Wilderness in southeast Oregon. The obsidian was formed about 4-5 million years ago when a rhyolite dome erupted. The dome collapsed, leaving behind a series of dikes and flows of obsidian. The fire obsidian is found in these dikes, which are typically only a few centimeters thick.

Fire Obsidian:The Rarest Type of Obsidain
Natural Fire Obsidian from Oregon

Facts About Fire Obsidian

  • The name "fire obsidian" is derived from the way the colors of the stone appear to dance and flicker like flames.
  •  Fire obsidian is often referred to as "iridescent obsidian."
  • The magnetite layers are typically only a few microns thick, which is about four times thinner than a human hair. 
  • Fire obsidian is a relatively rare stone, and it can be quite expensive. However, its beauty and rarity make it a prized possession for many people.

Properties of Fire Obsidian

  • Chemical composition: SiO2 (70-75%), FeO (10-14%), MgO (3-5%), Na2O (1-2%), K2O (0.5-1%)
  • Hardness: 5-6 on the Mohs scale
  • Specific gravity: 2.5-2.6
  • Fracture: Conchoidal
  • Luster: Vitreous
  • Color: Varies, but often includes shades of red, orange, yellow, green, and blue
  • Transparency: Translucent to opaque
  • Iridescence: Caused by thin layers of magnetite within the obsidian


Natural rough fire obsidian from Oregon
      Natural rough fire obsidian from Oregon. This is how fire obsidian looks before it is polished and cut.
Photo by: David Lineberger

Fire obsidian is a very rare gemstone, and it is only found in one location in the world. As a result, it is highly prized by collectors and jewelry makers. It is also used in some traditional cultures for ceremonial purposes.

See also:

Obsidian: Volcanic Glass
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