earth science

Mineral hydration

Mineral hydration 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 Mineral hydration rather than just read about it. In short: In inorganic chemistry, mineral hydration is a reaction which adds water to the crystal structure of a mineral, usually creating a new mineral, commonly called a hydrate. In geological terms, the process of mineral hydration is known as retrograde alteration and is a process occurring in retrograde metamorphism.

Key takeaways

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

Reference excerpt

In inorganic chemistry, mineral hydration is a reaction which adds water to the crystal structure of a mineral, usually creating a new mineral, commonly called a hydrate. In geological terms, the process of mineral hydration is known as retrograde alteration and is a process occurring in retrograde metamorphism. It commonly accompanies metasomatism and is often a feature of wall rock alteration around ore bodies. Hydration of minerals occurs generally in concert with hydrothermal circulation, which may be driven by tectonic or igneous activity.

Processes There are two main ways in which minerals hydrate. One is conversion of an oxide to a double hydroxide, as with the hydration of calcium oxide—CaO—to calcium hydroxide—Ca(OH)2. The other is with the incorporation of water molecules directly into the crystalline structure of a new mineral, as with the hydration of feldspars to clay minerals, garnet to chlorite, or kyanite to muscovite. Mineral hydration is also a process in the regolith that results in conversion of silicate minerals into clay minerals. Some mineral structures, for example, montmorillonite, are capable of including a variable amount of water without significant change to the mineral structure. Hydration is the mechanism by which hydraulic binders such as Portland cement develop strength. A hydraulic binder is a material that can set and harden submerged in water by forming insoluble products in a hydration reaction. The term hydraulicity or hydraulic activity is indicative of the chemical affinity of the hydration reaction.

Examples of hydrated minerals Examples of hydrated minerals include:

silicates (SiO4−4, SiO2) phyllosilicates, clay minerals "commonly found on Earth as weathering products of rocks or in hydrothermal systems" chlorite muscovite non-silicates oxides (O2−, Al2O3, Fe2O3, etc.) and oxy-hydroxides brucite, Mg(OH)2 goethite, FeO(OH) carbonates (CO2−3, etc.) hydromagnesite, Mg5(CO3)4(OH)2·4H2O ikaite, CaCO3·6H2O, the unstable hexahydrate form of calcium carbonate hydroxylated minerals saponite talc hydroxysulfides (mixed sulfides-hydroxides) tochilinite, a hydroxysulfide or hydrated sulfide mineral of iron(II) and magnesium of chemical formula: (Fe2+)5.4(Mg,Fe2+)5S6(OH)10, also written 6 Fe0.9S · 5 (Mg,Fe2+)(OH)2, in IMA notation valleriite, an uncommon sulfide-hydroxide mineral of iron(II) and copper of chemical formula: (Fe2+,Cu)4(Mg,Al)3S4(OH,O)6, or 4 (Fe,Cu)S · 3 (Mg,Al)(OH)2

See also Clay-water interaction Hydration reaction Iron(III) oxide-hydroxide Ferrihydrite

References

Worked examples

Example 1 — a first encounter with Mineral hydration

Start with the simplest possible case. Write down what Mineral hydration 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 Mineral hydration 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 Mineral hydration 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 Mineral hydration

In research: Mineral hydration 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 Mineral hydration 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: Mineral hydration is common in secondary-school and first-year university syllabi. It links to neighbouring topics Hydrate minerals, Inorganic reactions, Metamorphic petrology, so understanding it makes those chapters shorter.
In everyday life: Look for Mineral hydration 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.

Affiliate

Preply — study more efficiently by working with a personal tutor. 50% off.

How to study Mineral hydration in 20 minutes

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

Frequently asked questions

What is Mineral hydration in simple terms?

Why does Mineral hydration 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 Mineral hydration?

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 Mineral hydration.