89.84 ct ULEXITE - USA

Ulexite

Ulexite is a gemstone that represents the "optical magic" of the borate family. A hydrated sodium calcium borate, it is a mineral I have always found fascinating for its unique fiber-optic properties, which have earned it the nickname "TV Stone." It typically presents as snow-white, rounded "cotton ball" aggregates or as dense, parallel fibrous masses that possess a silky to pearly luster. For the specialist, Ulexite is a prize of physical phenomena; when a polished slab is placed over a page of text, the internal fibers act like natural fiber-optic cables, projecting the image of the letters onto the top surface of the stone. It is a mineral of the arid desert basins, representing the crystalline legacy of evaporated boron-rich waters. It is a stone of "clarity and projection," offering a tactile, "fuzzy" beauty in its raw form and a mind-bending optical trick when cut.

The Heritage & Discovery

Historical Significance: Ulexite is a vital species for understanding the complex chemistry of "evaporite" minerals in closed-basin environments. Historically, it was a significant discovery for the emerging boron industry of the 19th century. In the world of fine minerals, it is celebrated for its acicular (needle-like) structure. It stands as a symbol of vision and hidden potential, bridging the gap between common desert salts and the elite world of "phenomenal" collector gems. It serves as a beautiful reminder that nature invented fiber optics eons before human engineers, hiding "projection screens" within the crust of the desert floor.

Discovery: The mineral was first described in 1850 and was named in honor of the German chemist Georg Ludwig Ulex (1811-1883), who provided the first reliable chemical analysis of the species. The type-locality is Iquique, Tarapacá Region, Chile . Scientifically, it is a sodium calcium borate. Its discovery provided mineralogists with the first clear look at a "naturally fibrous" borate, helping to map the unique structural arrangements that occur in the borax marshes of the Americas and Asia.

Important Mines: The legendary source for world-class "TV Stone" Ulexite is Death Valley and the Boron district in California, USA . I also have a high regard for the spectacular "cotton ball" specimens found in the Salinas Grandes of Argentina and the thick, fibrous veins from Bigadiç, Turkey . For the vault, I prioritize the California material for its exceptional "image-transfer" quality and the Turkish specimens for their unmatched thickness and silky luster.

Mineralogical Profile

Description: Ulexite is a hydrated sodium calcium borate that crystallizes in the triclinic system. It sits at a 2 to 2.5 on the Mohs scale , making it a very soft and delicate mineral that must be protected from moisture and abrasion. it is characterized by its silky luster and its snow-white color.

One of its most identifying traits is its fibrous habit —it consists of thousands of hair-like crystals packed together in perfect parallel alignment. It has a low refractive index ($n \approx 1.49$ to $1.52$) and is usually translucent to opaque, except when viewed along the axis of the fibers. Because it is a borate, it is often found in association with Borax, Colemanite, and Halite. When I select a piece for the collection, I look for "even" fiber density and a high-gloss polish on the ends, as these maximize the "projection" effect that makes Ulexite a standout for the systematic specialist. It is a light, sophisticated mineral that offers a unique, "optical" beauty unlike any other borate species.

Chemical Formula: NaCaB ₅ O ₆ (OH) ₆ ·5H ₂ O