Ulexite

In 1956, John Marmon observed that fibrous aggregates of ulexite project an image of an object on the opposite surface of the mineral. This optical property is common for synthetic fibers, but not in minerals, giving ulexite the nickname "TV rock". According to Baur et al. (1957), this optical property is due to the reflections along twinned fibers, the most prominent twinning plane being on (010). The light is internally reflected over and over within each of the fibers that are surrounded by a medium of a lower refractive index (Garlick, 1991). This optical effect is also the result of the large spaces formed by the sodium octahedral chains in the mineral structure. Synthetic fibers used for fiber optics transmit images along a bundle of threadlike crystals the same way naturally occurring ulexite reproduces images due to the existence of different indices of refractions between fibers. Additionally, if the object is colored, all of the colors are reproduced by ulexite. Parallel surfaces of ulexite cut perpendicular to the fibers produce the best image, as distortion in the size of the projected image will occur if the surface is not parallel to the mineral. Curiously, in situ samples of ulexite are capable of producing a decent, rough image. Satin spar gypsum also exhibits this optical effect; however, the fibers are too coarse to transmit a decent image. The thickness of the fibers is proportional to the sharpness of the projected image. Ulexite also displays concentric circles of light if held up to a light source, a strange optical property first observed by G. Donald Garlick (1991). This effect can also be produced by shining a laser pointer at a slightly oblique angle through a piece of ulexite. This optical behavior is a consequence of the different refractive indices of ulexite in different directions of polarization. Microscopic analysis of ulexite also yields cones of light that clearly emerge from each grain that is thicker than 0.1 mm under the Bertrand lens. Ulexite is colorless and nonpleochroic in thin sections with low relief. Being triclinic, ulexite is optically biaxial. Interference figures yield addition on the concave side of the isogyers, causing ulexite to be biaxial positive. Ulexite has a high 2V that ranges between 73° - 78° and a maximum birefringence of up to 0.0300 (Anthony et al., 2005). According to Moore and Potter (1963), the orientation of the fibers around the c-axis is completely random based on the variations in extinctions viewed under cross polarization. Ulexite displays polysynthetic twinning parallel to the elongation, along {010} and {100} (Murdoch, 1940). In thin sections cut parallel to the fibers, ulexite grains display both length-fast and length-slow orientations in equal quantities because the intermediate axis (y) of the indicatrix is roughly parallel to the elongation of the fibers along the crystallographic c-axis (Moore and Potter, 1963).

Ulexite crystals contain three structural groups, isolated pentaborate polyanions, calcium coordinated polyhedra, and sodium coordinated octahedra that are joined together and cross-linked by hydrogen bonding. The Ca-coordination polyhedra share edges to form chains which are separate from the Na-coordination octahedral chains. There are 16 distinct hydrogen bonds that have an average distance of 2.84 Å. Boron is coordinated to four oxygens in a tetrahedra arrangement and also to three oxygens in a triangular arrangement with average distances of 1.48 and 1.37 Å, respectively. Each Ca cation is surrounded by a polyhedron of eight oxygen atoms. The average distance between calcium and oxygen is 2.48 Å. Each Na is coordinated by an octahedron of two hydroxyl oxygens and four water molecules, with an average distance of 2.42 Å (Clark and Appleman 1964). The octahedral and polyhedral chains parallel to c, the elongate direction, cause the fibrous habit of ulexite and the fiber optical properties.

Ulexite is a commercially important mineral as it is one of only three widespread mineral sources of the rare element Boron. Boron is an important element used in the production of fiberglass, and glass products like laboratory glassware and car headlights. It is also used to harden metals, and in detergents, as a fertilizer, and also as a herbicide.

Ulexite is a birthstone for the zodiac sign of Gemini.

Ulexite supposedly targets the third eye chakra, bringing more profound inner visions. Try placing it on your third eye while meditating or sleeping to witness its full power, particularly activation of telepathy. Its intense vibration may allow you to gain a better understanding of your inner self. Physically, it's said to heal impaired, double, and blurred vision.