earth science

Hauyne

Hauyne 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 Hauyne rather than just read about it. In short: Hauyne or haüyne, also called hauynite or haüynite ( ah-WEE-nyte), old name Azure spar, is a rare tectosilicate sulfate mineral with endmember formula Na3Ca(Si3Al3)O12(SO4). As much as 5 wt % K2O may be present, and also H2O and Cl.

Key takeaways

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

Reference excerpt

Hauyne or haüyne, also called hauynite or haüynite ( ah-WEE-nyte), old name Azure spar, is a rare tectosilicate sulfate mineral with endmember formula Na3Ca(Si3Al3)O12(SO4). As much as 5 wt % K2O may be present, and also H2O and Cl. It is a feldspathoid and a member of the sodalite group. Hauyne was first described in 1807 from samples discovered in Vesuvian lavas in Monte Somma, Italy, and was named in 1807 by Brunn-Neergard for the French crystallographer René Just Haüy (1743–1822). It is sometimes used as a gemstone.

Related minerals Haüyne forms a solid solution with nosean and with sodalite. Complete solid solution exists between synthetic nosean and haüyne at 600 °C, but only limited solid solution occurs in the sodalite-nosean and sodalite-haüyne systems.

Unit cell Haüyne belongs to the hexatetrahedral class of the isometric system, 43m, space group P43n. It has one formula unit per unit cell (Z = 1), which is a cube with side length of 9 Å. More accurate measurements are as follows:

a = 8.9 Å a = 9.08 to 9.13 Å a = 9.10 to 9.13 Å a = 9.11(2) Å a = 9.116 Å a = 9.13 Å

Structure All silicates have a basic structural unit that is a tetrahedron with an oxygen ion O at each apex, and a silicon ion Si in the middle, forming (SiO4)4−. In tectosilicates (framework silicates) each oxygen ion is shared between two tetrahedra, linking all the tetrahedra together to form a framework. Since each O is shared between two tetrahedra only half of it "belongs" to the Si ion in either tetrahedron, and if no other components are present then the formula is SiO2, as in quartz. Aluminium ions Al, can substitute for some of the silicon ions, forming (AlO4)5− tetrahedra. If the substitution is random the ions are said to be disordered, but in haüyne the Al and Si in the tetrahedral framework are fully ordered. Si has a charge 4+, but the charge on Al is only 3+. If all the cations (positive ions) are Si then the positive charges on the Si's exactly balance the negative charges on the O's. When Al replaces Si there is a deficiency of positive charge, and this is made up by extra positively charged ions (cations) entering the structure, somewhere in between the tetrahedra. In haüyne these extra cations are sodium Na+ and calcium Ca2+, and in addition the negatively charged sulfate group (SO4)2− is also present. In the haüyne structure the tetrahedra are linked to form six-membered rings that are stacked up in an ..ABCABC.. sequence along one direction, and rings of four tetrahedra are stacked up parallel to another direction. The resulting arrangement forms continuous channels that can accommodate a large variety of cations and anions.

Appearance

Haüyne crystallizes in the isometric system forming rare dodecahedral or pseudo-octahedral crystals that may reach 3 cm across; it also occurs as rounded grains. The crystals are transparent to translucent, with a vitreous to greasy luster. The color is usually bright blue, but it can also be white, grey, yellow, green and pink. In thin section the crystals are colorless or pale blue, and the streak is very pale blue to white.

Optical properties Haüyne is isotropic. Truly isotropic minerals have no birefringence, but haüyne is weakly birefringent when it contains inclusions. The refractive index is 1.50, and although this is quite low, similar to that of ordinary window glass, it is the largest value for minerals of the sodalite group. It may show reddish orange to purplish pink fluorescence under longwave ultraviolet light.

Physical properties Cleavage is distinct to perfect, and twinning is common, as contact, penetration and polysynthetic twins. The fracture is uneven to conchoidal, the mineral is brittle, and it has hardness 5+1⁄2 to 6, almost as hard as feldspar. All the members of the sodalite group have quite low densities, less than that of quartz; haüyne is the densest of them all, but still its specific gravity is only 2.44 to 2.50. If haüyne is placed on a glass slide and treated with nitric acid HNO3, and then the solution is allowed to evaporate slowly, monoclinic needles of gypsum form. This distinguishes haüyne from sodalite, which forms cubic crystals of chlorite under the same conditions. The mineral is not radioactive.

Geological setting and associations Haüyne occurs in phonolites and related leucite- or nepheline-rich, silica-poor, igneous rocks; less commonly in nepheline-free extrusives and metamorphic rocks (marble). Associated minerals include nepheline, leucite, titanian andradite, melilite, augite, sanidine, biotite, phlogopite and apatite.

Localities

The type locality is Lake Nemi, Alban Hills, Rome Province, Latium, Italy. Occurrences include:

Canary Islands: A pale blue mineral intermediate between haüyne and lazurite has been found in spinel dunite xenoliths from La Palma, Canary Islands. Ecuador: Phenocrysts found in alkaline extrusive rocks (tephrite), product of effusive volcanism of the Sumaco volcano, of northeast Ecuador. Germany: In ejected rocks of hornblende-haüyne-scapolite rock from the Laach lake volcanic complex, Eifel, Rhineland-Palatinate Italy: Anhedral blue to dark grey phenocrysts in leucite-melilite-bearing lava at Monte Vulture, Melfi, Basilicata, Potenza Italy: Millimetric transparent blue crystals in ejecta consisting mainly of K-feldspar and plagioclase from Albano Laziale, Roma Italy: Ejected blocks in the peperino of the Alban Hills, Rome Province, Latium, contain white octahedral haüyne associated with leucite, garnet, melilite and latiumite. US: Haüyne of metamorphic origin occurs at the Edwards Mine, St. Lawrence County, New York. US: Haüyne occurs in nepheline alnoite with melilite, phlogopite and apatite at Winnett, Petroleum County, Montana, US. US: Haüyne is common in small quantities as phenocrysts in phonolite and lamprophyre at the Cripple Creek, Colorado Mining District, Colorado, US.

See also Lapis lazuli – Metamorphic rock containing lazurite, prized for its intense blue color Lazurite – Alumino-silicate mineral whose blue colour is due to a sulfide species and not copper

References

External links JMol: https://rruff.geo.arizona.edu/AMS/viewJmol.php?id=05334 Nasti, Vincenzo (2009). "L'Olotipo della Haüyna. Il Cercapietre, Notiziario del Gruppo Mineralogico Romano, N° 1–2/" (PDF). pp. 16–43. Retrieved 2023-10-09. Nasti, Vincenzo (2019–2020). "La riscoperta del minerale di Nemi Lazialite – Haüyna" (PDF). p. 40. Retrieved 2023-10-09.

Illustrations

Hauyne: Gemmy Hauyne crystals from Mayen, Rhineland-Palatinate, Germany — Gemmy Hauyne crystals from Mayen, Rhineland-Palatinate, Germany

Worked examples

Example 1 — a first encounter with Hauyne

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

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

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

Frequently asked questions

What is Hauyne in simple terms?

Why does Hauyne 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 Hauyne?

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 Hauyne.