earth science

Polydymite

Polydymite 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 Polydymite rather than just read about it. In short: Polydymite, Ni2+Ni23+S4, is a supergene thiospinel sulfide mineral associated with the weathering of primary pentlandite nickel sulfide. Polydymite crystallises in the isometric system, with a hardness of 4.5 to 5.5 and a specific gravity of about 4, is dark violet gray to copper-red, often with verdigris and patina from associated copper and arsenic sulfides, and is typically in amorphous to massive infill of lower…

Key takeaways

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

Reference excerpt

Polydymite, Ni2+Ni23+S4, is a supergene thiospinel sulfide mineral associated with the weathering of primary pentlandite nickel sulfide. Polydymite crystallises in the isometric system, with a hardness of 4.5 to 5.5 and a specific gravity of about 4, is dark violet gray to copper-red, often with verdigris and patina from associated copper and arsenic sulfides, and is typically in amorphous to massive infill of lower saprolite ultramafic lithologies. Polydymite is the nickel equivalent of violarite and in many cases these two minerals are formed together, potentially in solid solution. Common contaminants of polydymite are cobalt and iron. Polydymite forms a series with linnaeite, Co+2Co+32S4.

Paragenesis Polydymite is formed by oxidisation of primary sulfide assemblages in nickel sulfide mineralisation. The process of formation involves oxidation of Ni2+ and Fe2+ which is contained within the primary pentlandite-pyrrhotite-pyrite assemblage. Continued oxidation of polydymite leads to replacement by goethite and formation of a gossaniferous boxwork, with nickel tending to remain as impurities within the goethite or hematite, or rarely as carbonate minerals.

Occurrence Polydymite is reported widely from the oxidised regolith above primary nickel sulfide ore systems worldwide. It is less common than related violarite, due to the high iron content of most primary sulfides.

Economic importance Polydymite is an important transitional ore in many nickel sulfide mines, as it has increased nickel tenor (Ni% as a total of sulfide) and occupies a position within the mineralised profile where it must be extracted to pay for development down to the more valuable primary (hypogene) mineralisation.

References

Illustrations

Worked examples

Example 1 — a first encounter with Polydymite

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

In research: Polydymite 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 Polydymite 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: Polydymite is common in secondary-school and first-year university syllabi. It links to neighbouring topics Cubic minerals, Minerals in space group 227, Nickel minerals, so understanding it makes those chapters shorter.
In everyday life: Look for Polydymite 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 Polydymite in 20 minutes

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

Frequently asked questions

What is Polydymite in simple terms?

Why does Polydymite 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 Polydymite?

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 Polydymite.