earth science

Johannite

Johannite 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 Johannite rather than just read about it. In short: Johannite is a rare uranium sulfate mineral. It crystallizes in the triclinic crystal system with the chemical composition Cu[UO2(OH)SO4]2·8H2O.

Key takeaways

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

Reference excerpt

Johannite is a rare uranium sulfate mineral. It crystallizes in the triclinic crystal system with the chemical composition Cu[UO2(OH)SO4]2·8H2O. It crystallizes in the triclinic system and develops only small prism or thin to thick tabular crystals, usually occurs as flaky or spheroidal aggregates and efflorescent coatings. Its color is emerald-green to apple-green and its streak is pale green. Johannite is a strong radioactive mineral with a calculated activity of 87,501,143 Bq/g (to the comparison: natural potassium: 31.2 Bq/g).

Etymology and history Johannite was first described in 1830 by Wilhelm Karl Ritter von Haidinger. It was named for Archduke John of Austria (1782–1859), the founder of the Landesmuseum Joanneum (Styria, Austria).

Occurrence Johannite forms as secondary mineral by oxidation from uraninite as well as different other uranium minerals. Localities include Argentina, Czech Republic, France, Gabon, Germany, Greece, Italy, Switzerland, United Kingdom and the United States. Type locality is the “Elias Mine” in Jáchymov (Czech Republic).

Crystal structure Johannite crystallizes in the triclinic crystal system in the space group P1 with the lattice parameters a = 8.92 Å, b = 9.59 Å, c = 6.84 Å; α = 110°, β = 111.98°, γ = 100.3° and one formula unit per unit cell.

References

Bibliography Palache, P.; Berman H.; Frondel, C. (1960). "Dana's System of Mineralogy, Volume II: Halides, Nitrates, Borates, Carbonates, Sulfates, Phosphates, Arsenates, Tungstates, Molybdates, Etc. (Seventh Edition)" John Wiley and Sons, Inc., New York, pp. 606–607.

Illustrations

Worked examples

Example 1 — a first encounter with Johannite

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

In research: Johannite 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 Johannite 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: Johannite is common in secondary-school and first-year university syllabi. It links to neighbouring topics Copper(II) minerals, Minerals in space group 2, Sulfate minerals, so understanding it makes those chapters shorter.
In everyday life: Look for Johannite 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 Johannite in 20 minutes

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

Frequently asked questions

What is Johannite in simple terms?

Johannite is a rare uranium sulfate mineral. It crystallizes in the triclinic crystal system with the chemical composition Cu[UO2(OH)SO4]2·8H2O.

Why does Johannite 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 Johannite?

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 Johannite.