Aerinite

Aerinite
Aerinite from Estopiñán del Castillo , Spain
General and classification
other names	Aërinite Aerinite
chemical formula	(Ca, Na) 6 (Fe 3+ , Fe 2+ , Mg, Al) 4 (Al, Mg) 6 Si 12 O 36 (OH) 12 (CO 3 ) 12H 2 O (Ca 5.1 Na 0.5 ) (Fe 3+ AlFe 2+ 1.7 Mg 0.3 ) (Al 5.1 Mg 0.7 ) [Si 12 O 36 (OH) 12 H] [(CO 3 ) 1.2 (H 2 O) 12 ]
Mineral class (and possibly department)	Silicates and germanates - chain and band silicates
System no. to Strunz and to Dana	9.DB.45 68.01.03.01
Crystallographic Data
Crystal system	trigonal
Crystal class ; symbol	ditrigonal-pyramidal; 3 m
Space group	P 3 c 1 (No. 158)
Lattice parameters	a  = 16.87  Å ; c  = 5.23 Å
Formula units	Z  = 1
Physical Properties
Mohs hardness	3
Density (g / cm 3 )	2.48
Cleavage	Please complete
colour	blue, sky blue, teal
Line color	bluish white
transparency	translucent
shine	Glass gloss
Crystal optics
Refractive indices	n α  = 1.510 n β  = 1.560 n γ  = 1.580
Birefringence	δ = 0.070
Optical character	biaxial negative
Axis angle	2V = measured: 63 °; calculated: 62 °
Pleochroism	strong: X = strong blue; Y = Z = light beige

The mineral aerinite (also aërinite ) is a rarely occurring chain silicate from the mineral class of "silicates and germanates" and crystallizes in the trigonal crystal system with the chemical composition (Ca, Na) ₆ (Fe ³⁺ , Fe ²⁺ , Mg, Al) ₄ (Al, Mg) ₆ Si ₁₂ O ₃₆ (OH) ₁₂ (CO ₃ ) · 12H ₂ O.

Aerinit usually develops massive mineral aggregates and crusty coatings, more rarely small, fibrous crystals in sky-blue to blue-green color with blue-white streak color .

Etymology and history

The word aerinite is derived from the Greek ἀέρινος aerinos for sky blue based on its color.

Aerinite was first discovered at Caserras del Castillo in the Spanish municipality of Estopiñán del Castillo and described in 1876 by Arnold von Lasaulx , who noticed the mineral in the mineralogical collection of the University of Wroclaw, built up by his predecessor Martin Websky , because of its lively blue color. When he examined the mineral labeled “ Vivianite from Spain” more closely, he found that, in contrast to this, it was free of phosphoric acid. Further investigations finally made it clear that the mineral sample from Spain was a new, previously unknown mineral.

The spelling Aërinit originally chosen by Lasaulx has been discredited since 2008 because the colon above the 'e' ( Trema ) is a superfluous diacritical mark according to the origin of the word .

classification

In the outdated 8th edition of the mineral classification according to Strunz , aerinite was classified as blue calcium leptochlorite (Orcel 1922). These belonged to the "chlorite group" with the system no. VIII / E.09 within the department "Phyllosilicates". Aerinite was not listed there as an independent mineral type.

In the Lapis mineral directory according to Stefan Weiß, which, out of consideration for private collectors and institutional collections, is still based on this old form of Karl Hugo Strunz's system , the mineral was given the system and mineral number. VIII / F.32-20 . In the “Lapis system”, this also corresponds to the “Chain and band silicates” department, where Aerinit and Alamosit form the group of chain silicates with chains of twelve [Si ₁₂ O ₃₆ ] ^24- (status 2018).

The 9th edition of Strunz's mineral systematics , which has been in effect since 2001 and was updated by the International Mineralogical Association (IMA) until 2009, also classifies the Aerinit in the category of "chain and band silicates (inosilicates)". However, this is further subdivided according to the structure of the chains, so that the mineral is classified in the sub-section “Chain and band silicates with 2-periodic single chains Si ₂ O ₆ ; with additional O, OH, H ₂ O pyroxene-related minerals ”can be found, where the unnamed group 9.DB.45 is the only member .

The systematics of minerals according to Dana also assigns the aerinite to the class of "silicates and germanates", but there in the more finely divided division of "chain silicates: structures with chains of different widths". Here the mineral can be found as the only member of the unnamed group 68.01.03 within the sub-section " Chain silicates: structures with chains of different widths ".

Crystal structure

Aerinite crystallizes trigonally in the space group P 3 c 1 (space group no. 158) with the lattice parameters a  = 16.87  Å and c  = 5.23 Å ​​as well as one formula unit per unit cell .

The crystal structure is interesting in two ways. On the one hand, Aerinit is one of the few chain silicates that incorporate CO ₃ as an integral part of their structure ( Caysichit- (Y) , Ashcroftin- (Y) , Fukalith the others). On the other hand, Aerinit contains face-sharing FeO octahedra, in which the Fe cations come unusually close.

SiO ₄ chains

Two simple silicate chain of Aerinit; View perpendicular to the c-axis

The Si ⁴⁺ cations are tetrahedrally surrounded by 4 oxygen . As in the case of pyroxenes, these SiO ₄ tetrahedra are connected to single chains with a periodicity of 2 via 2 oxygen. The chains run parallel to the crystallographic c-axis.

Al (O | OH) ₆ chains

Al-octahedral chain of aerinite; View perpendicular to the c-axis

Al ³⁺ and Mg ²⁺ are octahedral surrounded by 2O ²⁻ and 4 OH ^- groups . These octahedra are linked by 2 common edges to form zigzag chains that extend in the direction of the crystallographic c-axis.

FeO ₆ chains

Fe octahedral chain of aerinite; View perpendicular to the c-axis

The Fe ²⁺ and Fe ³⁺ cations are octahedral surrounded by six oxygens. These octahedra are connected to chains via two faces in the direction of the c-axis. Neighboring Fe cations of different charge in the chain exchange electrons through the shared octahedral surface of their coordination polyhedra and form a delocalized electron system via the Fe cations of an octahedron chain. This absorbs light in the yellow wavelength range and thus colors the Aerinite blue. The alignment of the face-sharing Fe octahedron chains and thus the delocalized Fe electron system parallel to the c-axis is responsible for the strong directional dependence of the color of the aerinite (pleochroism).

Fe octahedron chain surrounded by Si tetrahedron chains: view along the c-axis

Each Fe octahedron chain is connected to three Si tetrahedron chains, with the oxygen at the corners of the Fe octahedron also belonging to the tips of the coordination tetrahedra of the silicate chains.

Channels with H ₂ O and CO ₃

H ₂ O and CO ₃ in channels of the Aerinit; View along the c-axis

In each case 6 silicate tetrahedron chains are connected via 6 Al octahedron chains to form large, 12-sided channels that run through the aerinite structure parallel to the c-axis. The Ca ²⁺ cations are located on the Al octahedra on the inside of the channels and form weak ionic bonds with the oxygen of two H ₂ O molecules towards the center of the channel . The planar CO ₃ groups lie in the center of the channels with their plane perpendicular to the c-axis. The oxygen of the CO ₃ groups are connected to three H ₂ O molecules via strong hydrogen bonds , which in turn are connected to the inner wall of the channels via the Ca ²⁺ ions.

Structure of aerinite; View along the c-axis

Each of the H ₂ O-CO ₃ channels is connected to 6 other H ₂ O-CO ₃ channels via the Al octahedron chains and to 6 Fe octahedron chains via the silicate tetrahedron chains.

properties

Quartz colored bluish due to aerinite inclusions from Andalusia, Spain

Aerinit is one of the pigments and is z. B. able, as an inclusion (inclusion) in quartz, to color it bluish.

Education and Locations

Aerinite formed hydrothermally at a relatively low temperature, inter alia in Zeolite - facies . Accompanying minerals include prehnite , scolezite and mesolite .

So far (as of 2011), Aerinit has been found at fewer than 20 sites worldwide. In addition to its type locality Estopiñán del Castillo (Aragón), the mineral was also found in Spain in Olvera and Antequera in Andalusia, near Tartareu in the Catalan municipality of Les Avellanes i Santa Linya ( Lleida province ) and near Albatera , Los Serranos , Los Vives (near Orihuela , Alicante Province) and Los Arenales ( Castellón Province ) can be found in Valencia.

Other sites are Saint-Pandelon in the French department of Landes and Millington in the US township of Bernards (New Jersey).

use

Because of its intense color, aerinite found limited regional use as a blue pigment for wall paintings. The use of aerinite for sacred frescoes is typical in northern Spain ( Catalonia , Aragon ) and Albania during the Middle Ages (11th to 16th centuries). He gives the wall paintings of the Catalan Romanesque their characteristic blue and green tones.

Outside of northern Spain, the use of aerinite could only be proven for medieval frescoes in two places in France (Monastery of Moissac , 12th century and Collegiate Church of Saint-Nicolas, Nogaro , 11th century). This is taken as an indication of the exchange of artists and material across the Pyrenees during the Middle Ages.

See also

• List of minerals

literature

• A. von Lasaulx: Mineralogical-Krystallographische Notes - XI. Aërinite, a new mineral . In: New Yearbook for Mineralogy . tape 175 , 1876, pp. 352–358 ( rruff.info [PDF; 289 kB ; accessed on February 1, 2020]).
• Jordi Rius, Erik Elkaim, Xavier Torrelles: Structure determination of the blue mineral pigment aerinite from synchrotron powder diffraction data. The solution of an old riddle . In: European Journal of Mineralogy . tape 16 , no. 1 , 2004, p. 127-134 , doi : 10.1127 / 0935-1221 / 2004 / 0016-0127 (English).
• Jordi Rius, Anna Crespi, Anna Roig, Joan Carles Melgarejo: Crystal-structure refinement of Fe ³⁺ -rich aerinite from synchrotron powder diffraction and Mössbauer data . In: European Journal of Mineralogy . tape 21 , 2009, p. 233-240 , doi : 10.1127 / 0935-1221 / 2009 / 0021-1895 (English).
• Floréal Daniel, B. Laborde, Aurélie Mounier, E. Coulon: Pigment aerinite as a sign of artist circulation through Pyreneas in the medival period . In: Conference: Actes du V Congresso Nazionale di Archeometria, "Scienza e Beni Culturali", Syracuse . 2008, p. 307–316 ( available online at researchgate.net [accessed February 2, 2020]).
• Jordi Ibáñez-Insa, Núria Oriols, Josep J. Elvira, Soledad Álvarez, Felicià Plana: Heat Alteration of the Blue Pigment Aerinite: Application to Sixena's Romanesque Frescoes . In: Macla. Revista de la Sociedad Española de Mineralogía . tape 16 , p. 46–47 ( [1] [PDF; 256 kB ; accessed on February 2, 2020]).

Web links

Commons : Aerinite  - collection of images, videos and audio files

Wiktionary: Aerinit  - explanations of meanings, word origins, synonyms, translations

• Mineral Atlas: Aerinit (Wiki)
• Aerinite search results. In: rruff.info. Database of Raman spectroscopy, X-ray diffraction and chemistry of minerals (RRUFF), accessed February 1, 2020 . 
• American-Mineralogist-Crystal-Structure-Database - Aerinite. In: rruff.geo.arizona.edu. Retrieved February 1, 2020 . 

Individual evidence

1. ↑ ^{a b} Stefan Weiß: The large Lapis mineral directory. All minerals from A - Z and their properties. Status 03/2018 . 7th, completely revised and supplemented edition. Weise, Munich 2018, ISBN 978-3-921656-83-9 .
2. ^ ^{A b} Karl Hugo Strunz , Christel Tennyson : Mineralogical tables . 8th edition. Academic publishing company Geest & Portig KG, Leipzig 1982, p.  449, 501 .
3. ↑ ^{a b} Malcolm Back, William D. Birch, Michel Blondieau and others: The New IMA List of Minerals - A Work in Progress - Updated: January 2020. (PDF 1729 kB) In: cnmnc.main.jp. IMA / CNMNC, Marco Pasero, January 2020, accessed February 1, 2020 .  
4. ↑ David Barthelmy: Aerinite MineralData. In: webmineral.com. Accessed February 2, 2020 .  
5. ^ ^{A b c} Hugo Strunz , Ernest H. Nickel : Strunz Mineralogical Tables. Chemical-structural Mineral Classification System . 9th edition. E. Schweizerbart'sche Verlagbuchhandlung (Nägele and Obermiller), Stuttgart 2001, ISBN 3-510-65188-X , p.  623 (English).
6. ↑ ^{a b c d e f} Aerinite. In: mindat.org. Hudson Institute of Mineralogy, accessed February 2, 2020 .  
7. ↑ Ernst AJ Burke: Tidying up Mineral Names: an IMA-CNMNC Scheme for Suffixes, Hyphens and Diacritical mark . In: Mineralogical Record . tape 39 , no. 2 , 2008 ( cnmnc.main.jp [PDF; 2.4 MB ; accessed on February 1, 2020]).
8. ↑ Ernest H. Nickel, Monte C. Nichols: IMA / CNMNC List of Minerals 2009. (PDF 1816 kB) In: cnmnc.main.jp. IMA / CNMNC, January 2009, accessed February 2, 2020 .  
9. ↑ Mineralienatlas: chain and band silicates
10. ↑ Jordi Rius, Erik Elkaim, Xavier Torrelles: Structure determination of the blue mineral pigment aerinite from synchrotron powder diffraction data . In: European Journal of Mineralogy . tape 16 , no. 1 , 2004, p. 127-134 , doi : 10.1127 / 0935-1221 / 2004 / 0016-0127 (English).
11. ↑ ^{a b} F. Daniel et al. 2008: Pigment aerinite as a sign of artist circulation through Pyreneas in the medival period
12. ↑ IBÁÑEZ-INSA et al. 2012: Heat Alteration of the Blue Pigment Aerinite: Application to Sixena's Romanesque Frescoes