earth science

Tilleyite

Tilleyite 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 Tilleyite rather than just read about it. In short: Tilleyite is a rarely occurring calcium sorosilicate mineral with formula Ca3[Si2O7]·2CaCO3 (sometimes represented as Ca5(CaCO3)2[Si2O7]). It is chemically a calcium silicate with additional carbonate ions.

Key takeaways

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

Reference excerpt

Tilleyite is a rarely occurring calcium sorosilicate mineral with formula Ca3[Si2O7]·2CaCO3 (sometimes represented as Ca5(CaCO3)2[Si2O7]). It is chemically a calcium silicate with additional carbonate ions. Tilleyite crystallizes in the monoclinic crystal system and forms only poorly developed, irregularly defined, tabular crystals and spherical grains. In its pure form it is colorless and transparent, however due to multiple refractions of light from lattice defects or polycrystalline formation, it can also appear white, with the transparency decreasing accordingly.

History Tilleyite was first described from an occurrence at the Crestmore Quarry in Riverside County, California in 1932 by Esper Larsen and Kingsley Dunham, and named after Cecil Edgar Tilley (1894–1973), a professor of geology at the University of Cambridge, in recognition of his contributions to the study of metamorphism. Its type material is held at Harvard University, and the National Museum of Natural History.

Crystal structure Tilleyite crystallizes monoclinically in the space group P21/a (space group no. 14, position 3) with the lattice parameters a = 15.11 Å; b = 10.24Å; c = 7.58 Å,and β = 105.2°, with 4 formula units per unit cell.

Formation and occurrence Tilleyite is formed by contact metamorphism in the zone between volcanics and limestones at low pressure and high temperatures. Associated minerals include calcite, fluorite, gehlenite, grossular, vesuvianite and wollastonite. More generally, it occurs at gabbro-limestone contacts, such as at Carlingford, Ireland, and on the island of Muck, Scotland.

Illustrations

Worked examples

Example 1 — a first encounter with Tilleyite

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

In research: Tilleyite 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 Tilleyite 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: Tilleyite is common in secondary-school and first-year university syllabi. It links to neighbouring topics Calcium minerals, Carbonate minerals, Minerals described in 1933, so understanding it makes those chapters shorter.
In everyday life: Look for Tilleyite 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 Tilleyite in 20 minutes

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

Frequently asked questions

What is Tilleyite in simple terms?

Why does Tilleyite 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 Tilleyite?

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 Tilleyite.