earth science

Ikranite

Ikranite 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 Ikranite rather than just read about it. In short: Ikranite is a member of the eudialyte group, named after the Shubinov Institute of Crystallography of the Russian Academy of Sciences. It is a cyclosilicate mineral that shows trigonal symmetry with the space group R3m, and is often seen with a pseudo-hexagonal habit.

Key takeaways

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

Reference excerpt

Ikranite is a member of the eudialyte group, named after the Shubinov Institute of Crystallography of the Russian Academy of Sciences. It is a cyclosilicate mineral that shows trigonal symmetry with the space group R3m, and is often seen with a pseudo-hexagonal habit. Ikranite appears as translucent and ranges in color from yellow to a brownish yellow. This mineral ranks a 5 on Mohs scale of mineral hardness, though it is considered brittle, exhibiting conchoidal fracture when broken.

Eudialyte group The eudialyte group currently consists of 27 known minerals (see below), all considered rare, with the exception of eudialyte. The list below also includes one of around six unnamed ("UM") species listed by Mindat. This group is growing exponentially, with 17 members having been written about since 2000, and the chemical possibility of several thousand species that have yet to be discovered. Eudialyte group members are typically found as small crystals which have a complex crystal structure that is unique in that it consists of both 3- and 9-member SiO4 tetrahedra rings. Ikranite separates itself from the other members of this group through both its physical and compositional properties. The most prominent of these characteristics is the absence of sodium in its structure, along with the replacement of divalent iron with the trivalent form. This replacement also causes the characteristic color change from the reddish color seen in eudialyte to the yellow brown of ikranite, which can be further examined in its IR spectrum.

Occurrence Ikranite was first discovered on Mount Karnasurt (Kola Peninsula) in an agpaitic pegmatite, in the form of 1–2 cm grains. It is commonly associated with microcline, nepheline, lorenzenite, murmanite, lamprophyllite, and arfvedsonite. Tetranatrolite, and halloysite can also be found with it, though they occur at a later stage.

Chemical composition

Crystal structure

The crystal structure of ikranite can be described as a framework of three- and nine- member SiO4 tetrahedra rings, connected by Ca six-membered rings and Zn (Ti, or Nb) octahedra. Layers are constructed along the c axis as Si-Zr-Si-Ca. This repetition generates 12 layers, equal to ~30Å in size. Differing types cations, anions, anionic groups, and water molecules fill any pockets within the framework. A defining feature is the location of the M(3) and M(4) vacancies in the nine-membered rings. These cavities may be occupied with Si in the M(3b) location, Zr in the M(4a), and Zr, Nb, or Ti in the (M4b), though the probability of occupancy is low. The M(2a) and M(2b) locations are also uniquely occupied in ikranite. The M(2a) vacancy is seen occupied by Fe3+ octahedra. Typically holding a five-membered polyhedra with Fe, the M(2b) position is occupied by Na cations. Ikranite also holds a significant amount of water in the space between the rings where an Na molecule is usually found. A distinctive feature is the oxonium groups that can also be found occupying Na sites. Ikranite's general formula thus becomes (Na,H3O)15(Ca,Mn,REE)6Fe3+2Zr3([ ],Zr)([ ],Si)Si24O66(O,OH)6Cl2−3H2O.

References

Further reading Chukanov, N.V., Pekov, I.V., Zadov, A.E., Korovushkin, V.V., Ekimenkova, I.A., Rastsvetaeva, R.K., Khasanov, V.V., 2003, Ikranite and Raslakite: New Eudyalite-Group Minerals from the Lovozero Massif, Kola Peninsula, Zapiski Vserossiyskogo Mineralogicheskogo Obshchestva, v. 132, p. 22–33.

Illustrations

Worked examples

Example 1 — a first encounter with Ikranite

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

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

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

Frequently asked questions

What is Ikranite in simple terms?

Why does Ikranite 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 Ikranite?

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 Ikranite.