earth science

Staurolite

Staurolite 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 Staurolite rather than just read about it. In short: Staurolite is a reddish brown to black, mostly opaque, nesosilicate mineral with a white streak. It crystallizes in the monoclinic crystal system, has a Mohs hardness of 7 to 7.5 and the chemical formula: Fe2+2Al9O6(SiO4)4(O,OH)2.

Key takeaways

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

Reference excerpt

Staurolite is a reddish brown to black, mostly opaque, nesosilicate mineral with a white streak. It crystallizes in the monoclinic crystal system, has a Mohs hardness of 7 to 7.5 and the chemical formula: Fe2+2Al9O6(SiO4)4(O,OH)2. Magnesium, zinc and manganese substitute in the iron site and trivalent iron can substitute for aluminium.

Properties

Staurolite often occurs twinned in a characteristic cross-shape, called cruciform penetration twinning. In handsamples, macroscopically visible staurolite crystals are of prismatic shape. The mineral often forms porphyroblasts. In thin sections staurolite is commonly twinned and shows lower first order birefringence similar to quartz, with the twinning displaying optical continuity. It can be identified in metamorphic rocks by its swiss cheese appearance (with poikilitic quartz) and often mantled porphyroblastic character.

Name The name is derived from the Greek, stauros for cross and lithos for stone in reference to the common twinning.

Occurrence

Staurolite is a regional metamorphic mineral of intermediate to high grade. It occurs with almandine garnet, micas, kyanite; as well as albite, biotite, and sillimanite in gneiss and schist of regional metamorphic rocks. It is the official state mineral of the U.S. state of Georgia and is also to be found in the Lepontine Alps in Switzerland. Staurolite is most commonly found in Fannin County, Georgia. It is also found in Fairy Stone State Park in Patrick County, Virginia. The park is named for a local name for staurolite from a legend in the area. Samples are also found in Island Park, Idaho, near Henrys Lake; Taos, New Mexico; near Blanchard Dam in Minnesota; and Selbu, Norway.

Use Staurolite is one of the index minerals that are used to estimate the temperature, depth, and pressure at which a rock undergoes metamorphism.

References

External links Mineral galleries

Illustrations

Staurolite: Staurolite from Madagascar — Staurolite from Madagascar

Worked examples

Example 1 — a first encounter with Staurolite

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

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

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

Frequently asked questions

What is Staurolite in simple terms?

Why does Staurolite 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 Staurolite?

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 Staurolite.