earth science

Ulexite

Ulexite is a earth science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Ulexite rather than just read about it. In short: Ulexite (), sometimes called TV rock or TV stone due to its unusual optical properties, is a hydrous borate hydroxide of sodium and calcium with the chemical formula NaCaB5O6(OH)6·5H2O. The mineral occurs as silky white rounded crystalline masses or in parallel fibers.

Key takeaways

Ulexite belongs to earth science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Ulexite to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Ulexite from memory before moving on to harder problems.

Reference excerpt

Ulexite (), sometimes called TV rock or TV stone due to its unusual optical properties, is a hydrous borate hydroxide of sodium and calcium with the chemical formula NaCaB5O6(OH)6·5H2O. The mineral occurs as silky white rounded crystalline masses or in parallel fibers. Ulexite was named for the German chemist Georg Ludwig Ulex (1811–1883), who first discovered it. The natural fibers of ulexite act as optical fibers, transmitting light along their long axes by internal reflection. When a piece of ulexite is cut with flat polished faces perpendicular to the orientation of the fibers, a good-quality specimen will display an image of whatever surface is adjacent to its other side. The fiber-optic effect is the result of the polarization of light into slow and fast rays within each fiber, the internal reflection of the slow ray and the refraction of the fast ray into the slow ray of an adjacent fiber. An interesting consequence is the generation of three cones, two of which are polarized, when a laser beam obliquely illuminates the fibers. These cones can be seen when viewing a light source through the mineral. Ulexite is found in evaporite deposits, and the precipitated ulexite commonly forms a "cotton ball" tuft of acicular crystals. Ulexite is frequently found associated with colemanite, borax, meyerhofferite, hydroboracite, probertite, glauberite, trona, mirabilite, calcite, gypsum and halite. It is found principally in California and Nevada, US; Tarapacá Region in Chile, and Kazakhstan. Ulexite is also found in a vein-like bedding habit composed of closely packed fibrous crystals.

History Ulexite has been recognized as a valid mineral since 1840, after George Ludwig Ulex, for whom the mineral was named, provided the first chemical analysis of the mineral. In a footnote on p. 51, the editor claimed that Ulex's mineral actually was the same mineral that the American chemist Augustus Allen Hayes had found in Chile in 1844:

Es kann wohl keinem Zweifel unterworfen seyn, ... Boronatrocalcit umgeändert werden.

In 1857, Henry How, a professor at King's College in Windsor, Nova Scotia, discovered borate minerals in the gypsum deposits of the Lower Carboniferous evaporate deposits in the Atlantic Provinces of Canada where he noted the presence of a fibrous borate that he termed natro-boro-calcite, which was actually ulexite (Papezik and Fong, 1975). Murdoch examined the crystallography of ulexite in 1940. The crystallography was reworked in 1959 by Clark and Christ and their study also provided the first powder x-ray diffraction analysis of ulexite. In 1963 ulexite's remarkable fiber optics qualities were explained by Weichel-Moore and Potter. Their study highlighted the existence in nature of mineral structures exhibiting technologically required characteristics. Lastly, Clark and Appleman described the structure of ulexite correctly in 1964.

Chemistry Ulexite is a borate mineral because its formula (NaCaB5O6(OH)6·5H2O) contains boron and oxygen. The isolated borate polyanion [B5O6(OH)6]3− has five boron atoms, therefore placing ulexite in the pentaborate group. Ulexite is a structurally complex mineral, with a basic structure containing chains of sodium, water and hydroxide octahedra. The chains are linked together by calcium, water, hydroxide and oxygen polyhedra and massive boron units. The boron units have a formula of [B5O6(OH)6]3− and a charge of −3. They are composed of three borate tetrahedra and two borate triangular groups. Ulexite decomposes/dissolves in hot water.

Morphology Ulexite commonly forms small, rounded masses resembling cotton balls. Crystals are rare but will form fibrous, elongated crystals either oriented parallel or radial to each other. Crystals may also be acicular, resembling needles (Anthony et al., 2005). The point group of ulexite is 1, which means that the crystals show very little symmetry as there are no rotational axes or mirror planes. Ulexite is greatly elongated along [001]. The most common twinning plane is (010). Ulexite collected from the Flat Bay gypsum quarry in Newfoundland exhibits acicular "cotton balls" of crystals with a nearly square cross-section formed by the equal development of two pinacoids. The crystals are about 1–3 μm thick and 50–80 μm long, arranged in loosely packed, randomly oriented overlapping bundles (Papezik and Fong, 1975). In general, the crystals have six to eight faces with three to six terminal faces (Murdoch, 1940).

Optical properties

… excerpt ends here. Continue reading the full article.

Illustrations

Worked examples

Example 1 — a first encounter with Ulexite

Start with the simplest possible case. Write down what Ulexite claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In earth science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Ulexite before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Ulexite ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Ulexite

In research: Ulexite appears in earth science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Ulexite in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Ulexite is common in secondary-school and first-year university syllabi. It links to neighbouring topics Calcium minerals, Minerals described in 1840, Minerals in space group 2, so understanding it makes those chapters shorter.
In everyday life: Look for Ulexite outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Ulexite in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Ulexite means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Ulexite out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Ulexite in simple terms?

Why does Ulexite matter?

Because it connects several earth science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Ulexite?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Ulexite.