3,800,000,000 years ago, oxygen in the Earth's atmosphere was near zero percent. Then, over billions of years, microscopic cyanobacteria began to photosynthesize and generate breathable oxygen bit by bit.

This process is known as the Great Oxygenation Event and it is the reason we have a planet we can live on today. This changed more than just the atmosphere though—the presence of free oxygen also created bands of iron-oxide deposits which serve as physical evidence of the changing planet.

The rich colors found in banded iron formations show the process of oxygenation as it occurred over billions of years. This makes these stones important sources of information for learning about the development of our planet and how it came to support complex life.

Tiger iron, a form of banded iron, showcases the oxygenation process through its layered structure. The tiger iron in this pendant is a polished slice that originated in Western Australia. Formations in this region date back 3,020,000,000 years to the Archean Eon and were formed by the oxygen production of cyanobacteria.

The tiger iron pendants and slabs in our collection are unique in that they have layers of luminescent yellow stone between the red stripes of iron-oxide. These colorful stripes are where the material gets its nickname.

Each pendant is hand-polished and exhibits a unique set of colors in a layered pattern. The pendant ships in a hinged, black jewelry box along with an 18" silver chain. An informational card about the iron material is tucked under the box's padded insert. No two pendants are alike, and you can find all available tiger iron jewelry items as well as large banded iron specimens in the collection below.

Explore billions of years of history in this magnificent geologic wonder!

The Great Oxygenation Event marks the buildup of oxygen in the Earth's early atmosphere.  Reaching a peak 2.3 billion years ago, the evidence of the Great Oxygenation Event is found in banded iron formations found across the planet. 

We can chart the accumulation of oxygen in the atmosphere through the colors on these banded iron formations. The striking red, black, and silver lines are composed of thousands of iron oxide layers. Each layer is distinctive and the current leading theory suggests that they are the result of oxygen released in the early acidic seas by photosynthetic cyanobacteria. After more than a billion years, this process resulted in the semi-permanent oxygenation of Earth's oceans.

Even considering the scale of geological deep time, the Great Oxygenation Event was a very long-running process, perhaps spanning more than 2,000,000,000 years. There is also substantial evidence that this process ran in fits and starts in different regions of the world and was influenced by asteroid impacts and massive volcanic eruptions.

The earliest banded iron formations date to 3.8 billion years ago when the interior of the planet was still very hot, but the temperature on the iron-rich surface was not much different than it is today. The atmosphere contained little to no oxygen, but there was liquid water on the surface, even enough to form seas... and in those seas there was life.

A blue-green algae, also known as cyanobacteria, lived beneath the surface of the early seas, producing energy from photosynthesis. In turn, their photosynthetic processes created free oxygen which combined with iron carried from the surface into the sea by wind and erosion.  The oxygen and the iron combined to form iron-oxides which drifted to the bottom and accumulated in layer after layer.

The formation of iron-oxides neutralized the excess oxygen in the water, allowing the cyanobacteria to thrive, multiply, and evolve. Yet, at times, the population of the cyanobacteria exceeded the balance of iron and the seas became toxic. Such mass extinctions deprived the ocean of oxygen, resulting in new layers of iron-poor silica.

This steady process went on for over a billion years. Then, near the end of the 1.5 billion year Archean Eon, there were several spikes in iron-oxide production which coincided with evidence of rapidly increasing atmospheric oxygen.

Massive plumes grew within the mantle, creating volcanic hot spots and new continents.  Sea levels rose alongside new mountains to unprecedented levels. All of this gave life the opportunity to push forward, a "Great Oxygenation Event" which resulted in a permanently oxygenated atmosphere and a chance for life to continue beyond the sea.

From those alternating layers of iron-oxides and iron-poor silica, we find dazzling banded iron formations today. The rich reds and browns are reminders of life in its infancy on Earth and how it was able to change the very planet just through survival.

These iron formations can be found all around the world today. This particular material comes from Western Australia where some deposits are approximately 3,020,000,000 years old.