earth science

Picropharmacolite

Picropharmacolite 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 Picropharmacolite rather than just read about it. In short: Picropharmacolite, Ca4Mg(AsO3OH)2(AsO4)2·11H2O, is a rare arsenate mineral. It was named in 1819 from the Greek for bitter, in allusion to its magnesium content, and its chemical similarity to pharmacolite.

Key takeaways

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

Reference excerpt

Picropharmacolite, Ca4Mg(AsO3OH)2(AsO4)2·11H2O, is a rare arsenate mineral. It was named in 1819 from the Greek for bitter, in allusion to its magnesium content, and its chemical similarity to pharmacolite. The mineral irhtemite, Ca4Mg(AsO3OH)2(AsO4)2·4H2O, has the same composition as picropharmacolite, except that it has only four water molecules per formula unit, instead of eleven. It may be formed by the dehydration of picropharmacolite.

Structure Infrared spectra show that picropharmacolite contains water molecules H2O, hydroxyl groups (OH)− co-ordinated with Mg2+ cations, and acid arsenate radicals (HAsO4)2−. There are strong structural similarities with guerinite, Ca5(AsO3OH)2(AsO4)2.9H2O which indicates a similar formula for the two minerals. X-ray diffraction methods indicate that As, Ca and Mg cations are positioned in corrugated layers parallel to the c axis, the layers being linked by hydrogen bonding only. Four independent water molecules are sandwiched between adjacent layers, and build up hydrogen-bonded chains which are also parallel to the c axis. The ratio of four Ca to one Mg remains fairly steady, and no significant Ca/Mg substitution occurs in any cation site. Hence if the formula of picropharmacolite is written as Ca4Mg(H2O)7(AsO3OH)2(AsO4)2.4H2O, it is a better representation of the structure than the more usual formula Ca4Mg(AsO3OH)2(AsO4)2.11H2O.

Morphology Picropharmacolite is usually found as small to microscopic pearly white botryoidal aggregates with a radiating foliated structure internally. Less commonly it occurs as silky fibrous aggregates or minute needle-like crystals, that are rectangular prisms elongated along the c axis.

Environment Formed as an oxidation product of arsenic-bearing sulfides in reaction with surrounding calcium-bearing rocks, and as a recent efflorescence in mine workings. Erythrite and pharmacolite are common associated minerals.

Type locality It was first described for samples from ore dumps of the Richelsdorf Smelter, Süss, Richelsdorf District, Hesse, Germany. The type material is stored at the National School of Mines, Paris, France, 95.497.

References

External links http://rruff.geo.arizona.edu/AMS/viewJmol.php?id=00824

Illustrations

Worked examples

Example 1 — a first encounter with Picropharmacolite

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

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

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

Frequently asked questions

What is Picropharmacolite in simple terms?

Why does Picropharmacolite 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 Picropharmacolite?

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 Picropharmacolite.