Gugiaite

Key takeaways

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

Reference excerpt

Gugiaite is a melilite mineral, named for the Chinese village of Gugia where it was first discovered. Its chemical formula is Ca2BeSi2O7. It occurs mostly in skarns with melanite adjacent to an alkali syenite and has no economic value. Its crystals are small tetragonal tablets with vitreous luster and perfect cleavage. It is colorless and transparent with a density of three. The mineral belongs to space group P421m and is strongly piezoelectric. Shortly after the discovery of gugiaite, it was noted that a new name was unnecessary as it could have been considered an end member of meliphanite, (Ca,Na)2Be(Si,Al)2(O,F)2 differing mainly in containing much less sodium and fluorine. Recent data have confirmed that gugiaite differs from meliphanite optically and structurally. Gugiaite is a melilite and is distinctly different from other beryllium minerals such as meliphanite and leucophanite. Gugiaite is named for its locality near the village of Gugia, China. Incongruent information exists regarding Gugia; consequently the actual location of this village within China is unclear (de Fourestier 2005). Gujia is most often referenced as being in either Jiangsu Province or Liaoning Province.

Composition Gugiaite has an ideal chemical formula of Ca2BeSi2O7 and is a member of the melilite and sorosilicate (Si2O7) groups. It is chemically similar to jeffreyite (Ca,Na)2[(Be,Al)Si2(O,OH)7], meliphanite (Ca,Na)2[Be(Si,Al)2O6(O,OH,F)], and leucophanite (Ca,Na)2[Be(Si,Al)2O6(O,F)] in that they all contain essential calcium, beryllium, and silicon. Two chemical analyses gave similar results and one is as follows: SiO2 44.90, Al2O3 2.17, Fe2O3 0.11, MnO 0.07, MgO 0.38, CaO 40.09, BeO 9.49, Na2O 0.72, K2O} 0.20, H2O− 0.36, H2O+ 0.90, F 0.25, Cl 0.18, P2O5 0.08, TiO2 trace, -O=(F,Cl)2 0.15, sum 99.94, 99.79%. Common impurities are Ti, Zr, Hf, Al, Fe, Mn, Mg, Na, K, F, Cl, and P.

Geologic occurrence Gugiaite is usually found in skarn in contact with alkaline syenite with melanite, orthoclase, aegirine, titanite, apatite, vesuvianite, and prehnite. It occurs as thin square tablets, to 3 mm, in small cavities in skarn and enclosed in melanite. Skarns are often formed at the contact zone between granite intrusions and carbonate sedimentary rocks through metasomatism. Gugiaite has also been found in a miarolitic cavity in granite. This type of cavity is crystal lined, irregular, and known for being a source of rare minerals, such as beryllium, that are not normally found in abundance in igneous rocks. While initially found in Gugia, China, its localities have expanded to include Piedmont, Italy, Ehime Prefecture, Japan, Eastern Siberian Region, Russia, and most recently Telemark, Norway.

Crystal structure Gugiaite is composed of infinite sheets of tetrahedra with Be-Si-Si linkages and interstitial Ca. As shown in Figure 1, the oxygen atom bonds to a [4]-coordinated high-valence cation, Si, to produce a discontinuous polymerization of tetrahedra linked by interstitial Ca. It is isostructural with akermanite (Ca2MgSi2O7) with Be occupying the Mg site of akermanite. X-ray studies by the Weissenberg method show gugiaite to be tetragonal, space group P421m, (space group Nr. 113), and H-M Symbol 42m. Cell dimensions are: a = b = 7.48(2) Ȧ, c = 5.044(3) Ȧ, V = 277.35 Ȧ, α = β = γ = 90◦, and Z = 2. The axial ratio is a:c = 1:0.67617. Structurally A is Ca2, T1 is BeO4, T2 is SiO4, and X is O7. The three strongest lines of the X-ray powder data for gugiaite are 2.765(10), 1.485(7), and 1.709(7).

Physical properties The crystal form of gugiaite occurs as thin tetragonal tablets mostly 2–3 mm across and 0.3–0.5 mm thick, shown in Figure 2 below. The cleavages are {010} perfect, {001} distinct, and {110} poor. It is transparent, optically uniaxial (+), and strongly piezoelectric. See Table for additional physical properties.

Significance Gugiaite does not appear to have any political significance or economic value. From a historical perspective, gugiaite was the first beryllium mineral found in skarn systems at contacts between alkaline rocks and limestones. Also, thermodynamic equilibrium studies involving gugiaite have been conducted to determine the distribution of beryllium between gaseous and solid phases as a function of temperature in attempts to deduce the processes that formed the Solar System.

References

Notes

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Illustrations

Worked examples

Example 1 — a first encounter with Gugiaite

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

In research: Gugiaite 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 Gugiaite 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: Gugiaite is common in secondary-school and first-year university syllabi. It links to neighbouring topics Beryllium, Calcium minerals, Minerals in space group 113, so understanding it makes those chapters shorter.
In everyday life: Look for Gugiaite 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.

How to study Gugiaite in 20 minutes

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

Frequently asked questions

What is Gugiaite in simple terms?

Gugiaite is a melilite mineral, named for the Chinese village of Gugia where it was first discovered. Its chemical formula is Ca2BeSi2O7.

Why does Gugiaite 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 Gugiaite?

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 Gugiaite.