earth science

Hübnerite

Hübnerite 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 Hübnerite rather than just read about it. In short: Hübnerite or hubnerite is a mineral consisting of manganese tungsten oxide (chemical formula MnWO4). It is the manganese endmember of the manganese–iron wolframite solid solution series.

Key takeaways

Hübnerite 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 Hübnerite to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Hübnerite from memory before moving on to harder problems.

Reference excerpt

Hübnerite or hubnerite is a mineral consisting of manganese tungsten oxide (chemical formula MnWO4). It is the manganese endmember of the manganese–iron wolframite solid solution series. It forms reddish brown to black monoclinic prismatic submetallic crystals. The crystals are typically flattened and occur with fine striations. It has a high specific gravity of 7.15 and a Mohs hardness of 4.5. It is transparent to translucent with perfect cleavage. Refractive index values are nα = 2.170 – 2.200, nβ = 2.220, and nγ = 2.300 – 2.320. Typical occurrence is in association with high-temperature hydrothermal vein deposits and altered granites with greisen, granite pegmatites and in alluvial deposits. It occurs associated with cassiterite, arsenopyrite, molybdenite, tourmaline, topaz, rhodochrosite and fluorite. It was first described in 1865 for an occurrence in the Erie and Enterprise veins, Mammoth district, Nye County, Nevada, and named after the German mining engineer and metallurgist, Adolf Hübner from Freiberg, Saxony.

Introduction Hübnerite is a rare mineral from the rare family wolframite. It is considered to be one of the principle ores of tungsten. It is usually identified by the dark color, one direction of perfect cleavage and high specific gravity all serving to distinguish it from other minerals. The first recorded identification of the wolframite family was back in 1948 but it was not added as a mineral until 1951.

Composition Since hübnerite comes from a family with only two end members it would be easier to explain the composition of the wolframite family since there is not enough data on hübnerite itself. The primary formula of the wolframite series is (Fe,Mn)WO4. The predominance of either iron or manganese results in formation of one of two minerals, the compositional end-members FeWO4 (ferberite) and MnWO4 (hübnerite), respectively. Hübnerite is rarer than ferberite because of the difficulty of substituting manganese for iron. There are also other analogues, such as MgWO4. These compounds are usually referred to as "wolframites" because they share the wolframite structure, but are not naturally occurring minerals, typically being produced for industrial applications, e.g., crystal scintillators.

Structure

Hübnerite is a rare end-member of the wolframite group, and has the same crystal structure as other members of the family. The crystal structure contains distorted tetrahedral (WO4) and octahedral ((Fe, Mn)O6) units. The wolframite family represents complete solid solution between Fe2+ and Mn2+. In ferberite, the percentage of WO3 is around 76.3% whereas in hübnerite it is around 76.6%. In naturally occurring minerals the percent range falls within 20-80 percent. In the past it was thought that the wolframite structure possesses orthorhombic symmetry but in fact it possesses monoclinic symmetry. Short prismatic, flattened or wedge-shaped crystals are the common morphologies of wolframite crystals. In some rare cases the crystals occur doubly terminated. It is common for the faces to be striated parallel to the c axis. In most cases, wolframite is found embedded in quartz as subparallel crystalline masses.

Physical properties Color differences between members of the wolframite family are clear and marked. The color of hübnerite varies from yellowish brown to reddish brown. Crystal and crystalline masses of hübnerite show a variety of lusters from adamantine, submetallic to resinous luster. In thin splints, hübnerite can be either transparent or translucent. The streak is related to the color being a shade lighter. All the wolframite minerals exhibit perfect cleavage on {010}. On {100} and {102}, parting is less well-developed. Hübnerite exhibits brittle and uneven fracture. It is common for all members of the wolframite family to show simple contact twins on {100} or rarely interpenetrant twins on {001}. The hardness of hübnerite is between 4 and 4.5 and its specific gravity is between 7.12 and 7.18.

Geological occurrence

Hübnerite is a rare member of the wolframite group. Hübnerite is usually found within pegmatites and high-temperature quartz veins. Hübnerite does not occur on its own, but is typically associated with other minerals such as cassiterite, scheelite, quartz, galena, arsenopyrite, native bismuth, pyrite, and sphalerite.

History and uses Hübnerite was not the original name given to the mineral. Hübnerite is a synonym of the original name, megabasite. The name megabasite was given to the mineral by A. Breithaupt in 1852. The name hübnerite was given to the mineral by E.N. Riotte in 1865 to honor the metallurgist Adolph Hübner. Hübnerite is primarily used as a source of tungsten. Tungsten is used to harden metal in the manufacture of high-speed tools.

See also List of minerals List of minerals named after people

References

Illustrations

Worked examples

Example 1 — a first encounter with Hübnerite

Start with the simplest possible case. Write down what Hübnerite 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 Hübnerite 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 Hübnerite 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 Hübnerite

In research: Hübnerite 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 Hübnerite 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: Hübnerite is common in secondary-school and first-year university syllabi. It links to neighbouring topics Manganese(II) minerals, Minerals described in 1865, Minerals in space group 14, so understanding it makes those chapters shorter.
In everyday life: Look for Hübnerite 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 Hübnerite in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Hübnerite 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 Hübnerite out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Hübnerite in simple terms?

Hübnerite or hubnerite is a mineral consisting of manganese tungsten oxide (chemical formula MnWO4). It is the manganese endmember of the manganese–iron wolframite solid solution series.

Why does Hübnerite 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 Hübnerite?

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 Hübnerite.