earth science

Glaucophane

Glaucophane 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 Glaucophane rather than just read about it. In short: Glaucophane is a mineral and a mineral group belonging to the sodic amphibole supergroup of the double chain inosilicates, with the chemical formula Na2(Mg3Al2)Si8O22(OH)2. Glaucophane crystallizes in the monoclinic system.

Key takeaways

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

Reference excerpt

Glaucophane is a mineral and a mineral group belonging to the sodic amphibole supergroup of the double chain inosilicates, with the chemical formula Na2(Mg3Al2)Si8O22(OH)2. Glaucophane crystallizes in the monoclinic system.

Name Glaucophane is named for its typical blue color. In Greek, glaucophane means "blue appearing". As the major mineral component, it is glaucophane's color that gives the "blueschist" metamorphic rock type its name.

Characteristics The blue color is very diagnostic for this species. Glaucophane, along with the closely related mineral riebeckite, to which it forms a series with, and their intermediate crossite, are the only well known amphiboles that are commonly blue. Glaucophane forms a solid solution series with ferroglaucophane (Na2(Fe,Mg)3Al2Si8O22(OH)2). Glaucophane is the magnesium-rich endmember and ferroglaucophane is the iron-rich endmember. Ferroglaucophane is similar to glaucophane but is slightly denser and hence increased specific gravity. The two endmembers are indistinguishable in hand specimens and are strongly pleochroic. Glaucophane's hardness is 5–6 and its specific gravity is approximately 3–3.2.

Occurrence The blueschist metamorphic facies gets its name from abundant blue minerals glaucophane and lawsonite. Glaucophane generally forms in blueschist metamorphic rocks of gabbroic or basaltic composition that are rich in sodium and have experienced low temperature-high pressure metamorphism such as would occur along a subduction zone. This material has undergone intense pressure and moderate heat as it was subducted downward toward the mantle. Glaucophane is also found in eclogites that have undergone retrograde metamorphism.

There is also a rare amphibole called holmquistite, chemical formula Li2Mg3Al2Si8O22(OH)2, which occurs only in lithium-rich continental rocks. For many years, holmquistite was mistaken for glaucophane, as the two look identical in thin section.

Illustrations

Worked examples

Example 1 — a first encounter with Glaucophane

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

In research: Glaucophane 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 Glaucophane 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: Glaucophane is common in secondary-school and first-year university syllabi. It links to neighbouring topics Aluminium minerals, Amphibole group, Iron(II) minerals, so understanding it makes those chapters shorter.
In everyday life: Look for Glaucophane 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 Glaucophane in 20 minutes

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

Frequently asked questions

What is Glaucophane in simple terms?

Why does Glaucophane 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 Glaucophane?

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 Glaucophane.