earth science

Ilsemannite

Ilsemannite 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 Ilsemannite rather than just read about it. In short: Ilsemannite is an uncommon amorphous complex heterovalent molybdenum oxide, that was first published in 1871, and has been a valid species since pre-IMA. It is a grandfathered mineral, meaning the name ilsemannite is still believed to refer to a valid species.

Key takeaways

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

Reference excerpt

Ilsemannite is an uncommon amorphous complex heterovalent molybdenum oxide, that was first published in 1871, and has been a valid species since pre-IMA. It is a grandfathered mineral, meaning the name ilsemannite is still believed to refer to a valid species. However, it is likely that specimens formed under different conditions, in different localities do not have the same composition, and may even be a mixture of compounds. Furthermore, it is hard to analyze the specimens due to them being a mixture, hence why adequate analyses are lacking of said mineral. Ilsemannite is believed to be identical to synthetic molybdic oxide.

Properties Ilsemannite is soluble in water, which at first produces a greenish blue color, which later changes to a deep molybdenum-blue. This is probably why Native Americans believed that ilsemannite colored the waters blue in the Idaho Springs area, however, this has been debunked. Ilsemannite is now believed to consist of molybdenum (66.34%) and oxygen (33.19%), having a negligible amount of hydrogen (0.46%) in it. It has an earthy, dull, clay-like texture, and it is amorphous, meaning ilsemannite does not grow crystals. It does not show any radioactive properties. In an occurrence near Ouray, Utah, researchers found ilsemannite specimens disseminated through a rock. Analyses showed that about 10% of the sample was water-soluble, and that the water-soluble portion contains iron sulfate. Back then, in 1917, researches concluded that specimens from other localities all showed that iron sulfate was present in each of them, which is why the formula of said mineral was believed to be MoO3·SO3·5H2O. A specimen from Saxony mixed with iron sulfate showed only small amounts of iron, and gave a strong sulfate reaction. Another specimen from Carinthia had the same reaction, however this specimen had only a trace of ferric iron, with no ferrous iron in it. The specimen from Cripple Creek, Colorado showed the exact same reaction. During a study, it was found out that jordisite alters to ilsemannite more readily than it does to molybdenite, probably due to its amorphous state. This, among the scarcity of jordisite in mineral deposits, could explain why ilsemannite can be discovered in molybdenum districts. When first found, the mineral is usually black-blue or black in color, and it turns to blue-green and fades when exposed to sunlight. When put in a furnace alongside cinnabar, the calcined product's color changed to a purplish pink color. Chemical analyses of the material were not obtained due to the fact that the very thin coating surrounding ilsemannite couldn't be separated from the specimens. Underneath this coating there was a black, submetallic, sectile mineral first believed to be metacinnabar, but it was later proved to be a molybdenum compound. It was obvious that ilsemannite was an alteration product of this compound. The specimen from Colorado was described to have this coating as well, only that this time it was green. It is believed that the specimen was actually either a yellow iron sulfate, or a yellow molybdite, which was colored green due to the ilsemannite solution.

Occurrences and localities Ilsemannite forms by the oxidation of molybdenum-bearing minerals, making it a secondary mineral. It is associated with gypsum, wulfenite, melanterite, halotrichite, molybdite, molybdenite, jordisite, and other oxidized uranium minerals; however, it had been found in association with cinnabar as well in 1939. In the aforementioned encounter, ilsemannite was found as veinlets and as irregular lenses or pods in association of the cinnabar specimens. These specimens were described to often stain the nearby calcites a light blue color. It has a type locality of Carinthia, and although it is an uncommon mineral, it has been described in more than a dozen of other localities since then. Despite this fact, there is still an uncertainty lingering around the chemical composition and the origin of the mineral.

References

Media related to Ilsemannite at Wikimedia Commons

Illustrations

Worked examples

Example 1 — a first encounter with Ilsemannite

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

In research: Ilsemannite 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 Ilsemannite 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: Ilsemannite is common in secondary-school and first-year university syllabi. It links to neighbouring topics Amorphous solids, Mineral County, Colorado, Molybdenum minerals, so understanding it makes those chapters shorter.
In everyday life: Look for Ilsemannite 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 Ilsemannite in 20 minutes

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

Frequently asked questions

What is Ilsemannite in simple terms?

Why does Ilsemannite 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 Ilsemannite?

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 Ilsemannite.