earth science

Langite

Langite 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 Langite rather than just read about it. In short: Langite is a rare hydrated copper sulfate mineral, with hydroxyl, found almost exclusively in druses of small crystals. It is formed from the oxidation of copper sulfides, and was first described in specimens from Cornwall, United Kingdom.

Key takeaways

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

Reference excerpt

Langite is a rare hydrated copper sulfate mineral, with hydroxyl, found almost exclusively in druses of small crystals. It is formed from the oxidation of copper sulfides, and was first described in specimens from Cornwall, United Kingdom. It is dimorphous with wroewolfeite. Langite was discovered in 1864 and named after the physicist and crystallographer Viktor von Lang (1838–1921), who was Professor of Physics at the University of Vienna, Austria.

Unit cell Langite belongs to the monoclinic crystal class m, meaning that it has just one mirror plane, and no axes of rotational symmetry. The crystal is built up of identical unit cells stacked together, with no space in between. The unit cell for the monoclinic system has a base which is a rhombus, with sides a and c inclined at angle β. The third side b is perpendicular to both a and c. For langite the angle β is very close to 90°, so the unit cell is almost brick-shaped (as for the orthorhombic system). Different sources give slightly different values for the unit cell parameters, but they all fall within the ranges a = 7.118 Å to 7.137 Å, b = 6.031 Å to 6.034 Å, c = 11.209 Å to 11.217 Å, β = 90.00 to 90.02°, Z (the number of formula units per unit cell) = 2.

Physical properties Langite usually occurs as druses of small greenish-blue crystals which may be scaly or earthy. It is translucent, with a vitreous to silky luster and a blue-green streak. It has perfect cleavage perpendicular to the c crystal axis, and distinct cleavage perpendicular to b. Twinning is common, and typically repeated to give snowflake or star shaped groupings. The mineral is soft, with hardness 2.5 to 3, a little less than that of calcite. Fracture is uneven, and specific gravity is in the range 3.28 to 3.50, a little less than that of diamond.

Optical properties Langite is biaxial (−). Since it is monoclinic, it has three different refractive indices, corresponding to the three crystallographic directions. All the refractive indices are in the range 1.64 to 1.80, which is comparatively large, almost as high as garnet. Different sources give these values:

Nx = 1.641, Ny = 1.690, Nz = 1.712 Nx = 1.708, Ny = 1.760, Nz = 1.798 Nx = 1.641 to 1.654, Ny = 1.690 to 1.713, Nz = 1.705 to 1.722 Nx = 1.641, Ny = 1.690, Nz = 1.705 to 1.712 The mineral is pleochroic, with X light yellowish green, Y blue-green and Z sky blue.

Occurrence Langite is an uncommon but widespread secondary mineral in the oxidised zone of copper sulfide deposits, which may be of post-mine formation. It is associated with wroewolfeite, posnjakite, serpierite, devilline, chalcophyllite, connellite, brochantite, malachite and gypsum. There are two type localities for langite, Fowey Consols, Tywardreath, Par Area, St Austell District, and St Just, St Just District, both in Cornwall, England. The type material is conserved at the Natural History Museum, Vienna, Austria, reference A.a.4353. Other reported occurrences include:

With serpierite coating the bed of a water course affected by acid mine drainage at the Lloyd Copper Mine at Burraga, New South Wales, Australia Intergrown with ktenasite forming fibrous and botryoidal crusts and coatings less than 0.1 mm thick, at the Kintore Open Cut, Broken Hill, New South Wales, Australia Associated with a new mineral mallestigite, reported in 2004, near Carinthia, Austria, on the dump of a copper-lead-zinc mine. The mallestigite formed in fractures during weathering of primary galena and tetrahedrite. Other associated minerals were anglesite, brochantite, linarite and schultenite At Silver Gill, Caldbeck Fells, Cumbria, England, partly altered to brochantite, Cu4SO4(OH)6 As microcrystals in small vugs in prehnite-quartz vein sections at the Clark Mine, Keweenaw Peninsula, Michigan, US

References

External links

Jmol: https://rruff.geo.arizona.edu/AMS/viewJmol.php?id=09777

Illustrations

Worked examples

Example 1 — a first encounter with Langite

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

In research: Langite 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 Langite 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: Langite is common in secondary-school and first-year university syllabi. It links to neighbouring topics Copper(II) minerals, Minerals in space group 7, Monoclinic minerals, so understanding it makes those chapters shorter.
In everyday life: Look for Langite 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 Langite in 20 minutes

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

Frequently asked questions

What is Langite in simple terms?

Why does Langite 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 Langite?

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 Langite.