Ulexite: The Wonder Mineral

Aug 9, 2022 | MINING

Introduction to Ulexite

Ulexite, a boron mineral found in the American southwest, is recognized for its intense, pearly white color. This stone first garnered attention in 1840 and is named after the German chemist George Ludwig Ulex, who first explained its chemical composition. Ulexite is a sodium calcium borate mineral with numerous uses, aesthetically as a decorative element in jewelry and industrially as an abrasive.

Ulexite

Ulexite

Ulexite: A Boron Mineral

Ulexite is a hydrated sodium calcium borate oxide similar in composition to the colemanite mineral. Together, they are the only readily accessible sources of undissolved boron for glazes. 

Ulexite is observed in evaporite deposits and is commonly precipitated as a cotton ball. Colemanite, borax, hydroboracite, glauberite, probertite, calcite, trona, gypsum, mirabilite, and halite are its typical companion minerals. It can be seen in Canada, Turkey, China, Germany, and Argentina, but it is most prevalent in California, Boron and Nevada, the Tarapacá Region of Chile, and Kazakhstan.

The Crystal Arrangement

The hydrated sodium calcium borate oxide (NaCaB5O6(OH)6·5H2O) has three structural groups, isolated pentaborate polyanions, calcium coordinated polyhedra, and sodium coordinated octahedra which are connected and cross-linked through hydrogen bonding. It belongs to the pentaborate group as the isolated borate polyanion [B5O6(OH)6]3 comprises five boron atoms.

The edges of the Ca-coordination polyhedra connect to form chains that differ from the Na-coordination octahedral chains. They have 16 different hydrogen bonds with an average length of 2.84 Å. 

Boron is connected to four oxygen atoms in a tetrahedral arrangement with an average distance of 1.48 Å and three oxygen atoms in a triangular arrangement at an average length of 1.37 Å. 

An eight-atom polyhedron encircles each Ca2+ cation. Calcium and oxygen have an average distance of 2.48 Å. An octahedron of four water molecules and two hydroxyl oxygens coordinates each Na+, with a mean length of 2.42. 

These octahedral and polyhedral chain systems parallel to c, the enlarged direction, induce the fibrous habit and the fiber optical properties of ulexite.

Optical Properties

Ulexite, also known as TV rock, is a mineral with an optically unique property. When small fibrous granules of this mineral are observed from one side, an image of an item on the opposite surface is projected, achieved by the reflections across twinned fibers, with the most influential twinning plane (010). Each fiber contains a lower refractive index channel around which light is internally reflected many times.

Property NameDescriptions
Optical PropertiesBiaxial (+)
Refractive Indexnα = 1.491 – 1.496 nβ = 1.504 – 1.506 nγ = 1.519 – 1.520
Birefringenceδ = 0.028
2V angleMeasured: 73° to 78°
Ultraviolet fluorescenceDepending on fluorescent impurities, the mineral may fluoresce yellow, greenish-yellow, cream, or white under short waves and long waves UV

Source: Wikipedia

The optical effect is also caused by the large spaces between the sodium octahedral chains in its structure. Additionally, the crystal will reproduce all colors if the object being viewed is colored. For the most precise image, the crystal should be cut into parallel surfaces perpendicular to the fibers. Otherwise, deformation in the size and shape of the projected image may occur.

Another very unusual optical property, concentric circles of light, first observed by G. Donald Garlick in 1991, is produced when a light source (such as a laser pointer) is shone at a slightly oblique angle through a piece of the mineral. This effect is due to various refractive indices in different polarization directions that cause light to be refracted differently.

Physical Properties

Property NameDescriptions
Chemical formulaNaCa[B5O6(OH)6] · 5H2O
Molecular Weight405.23 gm
ColorColorless to white
FractureUneven
Crystal habitAcicular to fibrous
TwinningPolysynthetic on {010} and {100}
LustreVitreous, Silky
StreakWhite
DiaphaneityTransparent to opaque
Hardness2.5
Specific Gravity1.955
Crystal SystemTriclinic

Source: Wikipedia

Significance of Boron in Ulexite

Boron is a trace mineral in the lithosphere with a typical concentration of 10 ppm, but it is deficient in many parts of the world. Boron is never found in its elemental form in nature, but it does occur naturally in over 150 minerals. Tincal (also known as borax), ulexite, and colemanite are the three most significant minerals in abundance on a global commercial scale. High levels of economically beneficial boron minerals are typically found in arid areas with a volcanic history. 

Applications for Ulexite

The fact that boron compounds are used in various materials for numerous industrial uses makes the ulexite’s boron content commercially substantial. Furthermore, calcium carbonate is formed as a by-product when ulexite is absorbed in a carbonate solution. This by-product is widely used in the pulp and paper industry as a paper filler and coating that improves printability.

As more emphasis has been placed on new energy sources, hydrogen as a car fuel has come to the fore. Because of its relatively high hydrogen yield by weight for potential use in automobiles, the compound sodium borohydride (NaBH4) is presently considered an excellent hydrogen storage medium. Piskin (2009) confirms that the boron content in ulexite could be used as a boron source or starting material for synthesizing sodium borohydride (NaBH4).

Ulexite is also ideal for use to correct boron deficiency in a wide variety of plant species. When used alone or as part of a complex granular bulk blend, ulexite has many advantages over other, completely soluble forms of boron. The dissolution rate of ulexite is the most important of these. 

Apart from highly soluble borates, ulexite has a slow boron release corresponding to the gradual boron uptake plant nutrition.

Ulexite’s Higher Powers

Ulexite is considered by some to be an excellent crystal for stimulating the third eye and enhancing inner vision. It purportedly opens up a whole new world of perception, allowing one to see things they may have been blind to before. It also awakens one’s telepathic abilities through meditation or deep sleep. 

Ulexite is a powerful amplifier that operates on a high vibrational energy field to generate projections. In addition, this crystal enhances mental clarity, reduces stress, and helps users to focus more easily on tasks, thus speeding up the decision-making process.

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