earth science

Weddellite

Weddellite 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 Weddellite rather than just read about it. In short: Weddellite (CaC2O4·2H2O) is a mineral form of hydrated calcium oxalate named for occurrences of millimeter-sized crystals found in bottom sediments of the Weddell Sea, off Antarctica. Occasionally, weddellite partially dehydrates to the monohydrate whewellite, forming excellent pseudomorphs of grainy whewellite after weddellite's short tetragonal dipyramids.

Key takeaways

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

Reference excerpt

Weddellite (CaC2O4·2H2O) is a mineral form of hydrated calcium oxalate named for occurrences of millimeter-sized crystals found in bottom sediments of the Weddell Sea, off Antarctica. Occasionally, weddellite partially dehydrates to the monohydrate whewellite, forming excellent pseudomorphs of grainy whewellite after weddellite's short tetragonal dipyramids. It was first described in 1936 but only named in 1942.

Structural properties Weddellite, or calcium oxalate dihydrate, crystallises in a tetragonal system: the classic crystal shape is the eight-face bipyramid. Using bright field microscopy, the weddellite crystals are recognised easily by their shape, reminiscent of a postal envelope. More complex shapes of weddellite are possible; the dumbbell shape is not rare and has no precise angles or sides. This form is, in reality, a microcrystalline agglomerate that takes the shape of a biconcave disc. Weddellite crystals are poorly birefringent and do not show any interference pattern under polarised light.

Biological role Whewellite (CaC2O4·1H2O) and weddellite (CaC2O4·2H2O) are the most common mineral components of renal calculi (kidney stones).

Occurrence Weddellite occurs as authigenic crystals in sea floor mud. It also has been reported in peat bearing sediments and in calcite-bearing lacustrine sediments. It occurs with whewellite, urea, phosphammite and aphthitalite. If oxalic acid is used to clean any mineral sample that contains calcium, weddellite and whewellite may be produced on the sample.

References

Illustrations

Worked examples

Example 1 — a first encounter with Weddellite

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

In research: Weddellite 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 Weddellite 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: Weddellite is common in secondary-school and first-year university syllabi. It links to neighbouring topics Calcium minerals, Dihydrate minerals, Minerals described in 1942, so understanding it makes those chapters shorter.
In everyday life: Look for Weddellite 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 Weddellite in 20 minutes

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

Frequently asked questions

What is Weddellite in simple terms?

Why does Weddellite 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 Weddellite?

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 Weddellite.