This common mineral acts like a natural fiber optic cable for your eyes

Nature · Published 3 October 2026 Swipe more like this →

In short: Ulexite is a rare borate mineral that possesses a remarkable, built-in ability to transmit light. Often nicknamed TV rock, its fibrous structure allows it to project images of objects from one side to the other, mimicking the sophisticated technology used in modern synthetic fiber optics.

Ulexite is a complex hydrous borate hydroxide of sodium and calcium. Its unique optical properties stem from its internal structure: it is composed of parallel, fibrous crystals that act as natural light pipes. When a specimen is cut with flat, polished faces perpendicular to these fibers, it transmits light along its long axis through internal reflection. This phenomenon occurs because light is polarized into fast and slow rays within each fiber, with the slow rays reflecting internally while fast rays refract into adjacent fibers, effectively reproducing an image on the opposite surface.

The mineral's fibrous habit is a direct result of its atomic architecture. It contains chains of sodium, water, and hydroxide octahedra, which are cross-linked by calcium polyhedra and boron units. These chains run parallel to the c-axis, creating the elongated, needle-like crystals that give the mineral its silky appearance. While synthetic fiber optics rely on manufactured bundles of threadlike materials to transmit data, ulexite achieves this naturally. Even in situ, samples can produce a rough image, though the sharpness of the projection is directly proportional to the thickness of the fibers.

Beyond its optical curiosity, ulexite is a vital industrial resource. As one of the world's most abundant borate minerals, it is a primary source of boron, an essential element for manufacturing heat-resistant borosilicate glass, fiberglass, and fire retardants. Its chemical versatility extends to energy research, where it serves as a starting material for synthesizing sodium borohydride, a potential medium for hydrogen fuel storage. Found primarily in arid, volcanically active regions like California and Nevada, ulexite remains a fascinating intersection of geological complexity and high-tech utility.

General information, not professional advice. Spotted an error? Flag the card or see corrections and complaints.

Intellect Plus is a visual educational discovery platform for exploring fascinating facts and ideas. Brain Food, Not Brain Rot. What is Intellect Plus?

Related

• Nature’s optical illusions: minerals that shift colors through structural secrets
• The hidden geometry of the Earth's crust is built on simple carbonate triangles
• Fluorite is the world's most colorful mineral, but its true power lies in optics.
• Why the world's most mesmerizing gemstone is technically just a pile of glass spheres
• This versatile mineral is a secret weapon for greener concrete and stronger plastics
• An unconformity is a missing chapter in the Earth's long and complex geological history.
• How underwater avalanches create the deep ocean's most valuable geological structures
• The only continent where science is the primary national policy
• Why a rare iron sulfide from space is the gold standard for sulfur isotopes
• The upper mantle is a vast, malleable engine driving the movement of our continents.
• Where three worlds collide: the delicate geometry of tectonic triple junctions
• Ur: The ancient, tiny supercontinent that may have been Earth's only landmass

More in Geology · More in Nature · Latest · A–Z · All topics