Larnite

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Larnite
General and classification
other names
  • Dicalcium silicate
  • Belite
chemical formula β-Ca 2 [SiO 4 ]
Mineral class
(and possibly department) 		Silicates and Germanates - island silicates
System no. to Strunz
and to Dana 		9.AD.05 ( 8th edition : VIII / A.05)
51.05.01.01
Crystallographic Data
Crystal system monoclinic
Crystal class ; symbol monoclinic prismatic; 2 / m
Space group P 2 1 / n (No. 14, position 2)Template: room group / 14.2
Lattice parameters a  = 5.50  Å ; b  = 6.74 Å; c  = 9.30 Å
β  = 94.6 °
Formula units Z  = 4
Twinning polysynthetic according to {100}
Physical Properties
Mohs hardness 6th
Density (g / cm 3 ) measured: 3.28 to 3.33; calculated: 3.326
Cleavage imperfect after {010}, good after {100}
colour white to gray, colorless in thin layers
Line color White
transparency transparent to translucent
shine Glass gloss
Crystal optics
Refractive indices n α  = 1.707
n β  = 1.715
n γ  = 1.730
Birefringence δ = 0.023
Optical character biaxial positive
Axis angle 2V = 74 ° (calculated)
Other properties
Chemical behavior soluble in water, gelatinizing in dilute acids

Larnite is a rarely occurring minerals from the mineral class of "silicates and germanates" with the chemical composition of β-Ca 2 [SiO 4 ] and chemical point of view, a calcium - silicate , more dicalcium silicate .

Larnite crystallizes in the monoclinic crystal system , but is usually only found in the form of ingrown , irregular grains and granular to massive mineral aggregates . Larnite also rarely develops tabular crystals . In pure form and in thin layers, Larnite crystals are colorless and transparent with a glass-like sheen on the surfaces. However, due to multiple refraction due to lattice defects or polycrystalline formation, it can also be translucent white and take on a gray color due to foreign admixtures.

Larnite (also called belite ) is known in the cement industry as an artificial product with hydraulic properties .

Etymology and history

Type locality Scawt Hill with the exposed contact zone between limestone and the basalt above

Larnite was first discovered on Scawt Hill near the town of Larne in County Antrim, Northern Ireland . It was first described in 1929 by Cecil Edgar Tilley , who named the mineral after its type locality .

classification

Already in the outdated 8th edition of the mineral classification according to Strunz , the larnite belonged to the mineral class of "silicates and germanates" and there to the department of " island silicates (nesosilicates)", where together with bredigit and calcio -olivine it belongs to the "Ca2SiO4 group" the system no. VIII / A.05 .

In the Lapis mineral directory according to Stefan Weiß, which, out of consideration for private collectors and institutional collections, is still based on this classic system of Karl Hugo Strunz , the mineral was given the system and mineral number. VIII / A.07-30 . In the “Lapis system” this corresponds to the department “ Island silicates with [SiO 4 ] groups”, where Larnite, together with Bredigit, Calcio-Olivin, Flamit and Merwinit, forms an independent but unnamed group (as of 2018).

The 9th edition of Strunz's mineral systematics, valid since 2001 and updated by the International Mineralogical Association (IMA) until 2009, also assigns larnite to the "island silicates" department. However, this is further subdivided according to the possible presence of additional anions and the crystal structure, so that the mineral is classified in the sub-section “Island silicates without additional anions; Cations in octahedral [6] and usually larger coordination “can be found, where it is the only member of the unnamed group 9.AD.05 .

The systematics of minerals according to Dana , which is mainly used in the English-speaking world , assigns larnite to the class of "silicates and Germanates" and there in the department of "island silicate minerals ". Here he is to be found as the only member in the unnamed group 51.05.01 within the sub-section “ Island silicates: SiO 4 groups only with cations in> [6] coordination ”.

Chemism

The idealized, theoretical composition of larnite Ca 2 [SiO 4 ] consists of 46.54% calcium (Ca), 16.31% silicon (Si) and 37.16% oxygen (O).

The chemical analysis of mineral samples from the Scawt Hill type locality also showed small proportions of aluminum (1.12% Al 2 O 3 ), iron (0.64% FeO) and magnesium (0.69% MgO) and carbon (0.82 % CO 2 ), which is attributed to a slight contamination of the samples with the mineral spurrite (Ca 5 [CO 3 | (SiO 4 ) 2 ]) and spinel .

Crystal structure

Larnite crystallizes monoclinically in the space group P 2 1 / n (space group no. 14, position 2) with the lattice parameters a  = 5.50  Å , b  = 6.74 Å, c  = 9.30 Å and β = 94.6 ° as well as four formula units per unit cell . Template: room group / 14.2

The crystal structure of larnite consists of Ca [8] polyhedra that are connected to one another by common surfaces and form chains parallel to [010] and [101]. These chains are shared edge with isolated SiO 4 - tetrahedra linked.

Larnite crystal structure

  • looking parallel to the a-axis

  • looking parallel to the b-axis

  • looking parallel to the c-axis

  • spatial representation in the standard crystallographic orientation

Color table: __ Ca     __ Si     __ O

properties

Larnite slowly dissolves in water to form calcium hydroxide (Ca (OH) 2 ). The resulting solution is basic and accordingly turns red litmus paper blue. The mineral is easily decomposed by diluted hydrochloric acid (HCl) without foam formation, whereby it does not dissolve but gelatinizes.

Modifications

Four temperature-dependent modifications of the compound Ca 2 [SiO 4 ] are known, two of which are recognized as minerals:

modification Crystal system Stability area Mineral name
α-Ca 2 [SiO 4 ] orthorhombic- dipyramidal stable up to 725 ° C -
β-Ca 2 [SiO 4 ] monoclinic stable from 725 to 1450 ° C Larnite
δ-Ca 2 [SiO 4 ] orthorhombic-dipyramidal metastable above 750 ° C -
γ-Ca 2 [SiO 4 ] di trigonal -scalenohedral stable above 1450 ° C Calcio-olivine

The polymorphism of the compound Ca 2 [SiO 4 ] was the first time in 1882 by Henry Le Chatelier in Portland cement - clinker investigated.

Education and Locations

At its type locality on Scawt Hill in Northern Ireland , Larnite formed in the contact area between limestone or dolomite rock and intruding diabase . The rocks in this contact zone were described by GC Gough as early as 1907, but according to Tilley his description was largely incorrect. The figures added in Gough's essay, however, were suitable for reinterpretation. There is therefore a considerable range of rock types and minerals. Mainly it concerns thereby spurrite , Larnite, Melilith ( gehlenite ) merwinite and spinel . Other sources mention perovskite and wollastonite as additional accompanying minerals from this site .

In the likewise kontaktmetamorphen mineralization of Tokatoka in Kaipara District of the North Island of New Zealand were hydrogrossular , kilchoanite , Rank Init and Scawtit added as another companion.

In the rock formation known as the "Hatrurim formation" or "Hatrurim basin" in the Israeli part of the Negev desert , which is similar to Portland cement mixed with bituminous lime, marble and impure limestone, besides larnite, spurrite and melilite, among others yet brownmillerite and mayenite discovered.

As a rare mineral formation, Larnite could only be detected at a few sites, with around 50 sites being documented so far (as of 2019). In addition to its type locality Scawt Hill, the mineral was found in Northern Ireland in the contact metamorphic rocks of the settlement of Ballycraigy, which is also close to Larne, and in the basalts ( olivine - dolerite ) near Carneal near Glenoe in County Antrim . Furthermore, Larnite in the United Kingdom is only known from the Scottish Highlands ( Ardnamurchan , Isle of Muck ) and the Council Argyll and Bute ( Isle of Mull ).

In Germany Larnite has only been on Ettringer Bellerberg and Mayener mining area (sea rim) in the district of Mayen-Koblenz and the Emmelberg in Udersdorf in Vulkaneifel discovered.

The only known site in Austria so far is a basalt quarry near Klöch in Styria.

Other locations include Denmark, France, Greenland, Italy, Jordan, Canada, Kazakhstan, Palestine, Romania, Russia, Spain, South Ossetia, Tanzania, Turkey, Ukraine, the United States and Central Africa.

literature

  • CE Tilley: On Larnite (calcium orthosilicate, a new mineral) and its associated minerals from the limestone contact-zone of Scawt Hill, Co. Antrim . In: Mineralogical Magazine . tape 22 , no. 125 , 1929, pp. 77–86 , doi : 10.1180 / minmag.1929.022.125.01 (English, rruff.info [PDF; 540 kB ; accessed on October 31, 2019]).
  • JF Schairer: New mineral names . In: The American Mineralogist . tape 14 , 1929, pp. 338–340 (English, rruff.info [PDF; 229 kB ; accessed on October 31, 2019]).
  • K. Mori, R. Kiyanagi, M. Yonemura, K. Iwase, T. Sato, K. Itoh, M. Sugiyama, T. Kamiyama, T. Fukunaga: Charge states of Ca atoms in beta-dicalcium silicate . In: Journal of Solid State Chemistry . tape 179 , no. 11 , 2006, p. 3286-3294 , doi : 10.1016 / j.jssc.2006.06.018 .

Web links

See also

Individual evidence

  1. ↑ a b c d 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.  539 (English).
  2. ↑ Richard V. Gaines, H. Catherine W. Skinner, Eugene E. Foord, Brian Mason , Abraham Rosenzweig: Dana's New Mineralogy . 8th edition. John Wiley & Sons, New York et al. 1997, ISBN 0-471-19310-0 , pp. 1053 .
  3. ↑ a b c 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 .
  4. ↑ a b c d e f g Larnite . In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America . 2001 (English, handbookofmineralogy.org [PDF; 69  kB ; accessed on October 31, 2019]).
  5. ↑ a b c d e Larnite. In: mindat.org. Hudson Institute of Mineralogy, accessed November 1, 2019 .
  6. ^ A b Helmut Schrätze , Karl-Ludwig Weiner : Mineralogie. A textbook on a systematic basis . de Gruyter, Berlin; New York 1981, ISBN 3-11-006823-0 , pp.  664-665 .
  7. ↑ Hans Jürgen Rösler : Textbook of Mineralogy . 4th revised and expanded edition. German publishing house for basic industry (VEB), Leipzig 1987, ISBN 3-342-00288-3 , p.  459 .
  8. ↑ Ernest H. Nickel, Monte C. Nichols: IMA / CNMNC List of Minerals 2009. (PDF 1703 kB) In: cnmnc.main.jp. IMA / CNMNC, January 2009, accessed October 31, 2019 .
  9. ↑ David Barthelmy: Larnite MineralData. In: webmineral.com. Accessed November 1, 2019 .
  10. ^ 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.  559 (English).
  11. ^ JF Schairer: New mineral names . In: The American Mineralogist . tape 14 , 1929, pp. 338–340 (English, rruff.info [PDF; 229 kB ; accessed on November 1, 2019]).
  12. ↑ a b CE Tilley: On Larnite (calcium orthosilicate, a new mineral) and its associated minerals from the limestone contact-zone of Scawt Hill, Co. Antrim . In: Mineralogical Magazine . tape 22 , no. 125 , 1929, pp. 77–86 , doi : 10.1180 / minmag.1929.022.125.01 (English, rruff.info [PDF; 540 kB ; accessed on October 31, 2019]).
  13. ^ A b AE Zadov, VM Gazeev, NN Pertsev, AG Gurbanov, ER Gobechiya, NA Yamnova, NV Chukanov: Discovery and investigation of a natural analog of calcio-olivine (ϒ-Ca 2 SiO 4 ) . In: Doklady Earth Sciences . 423A, no. 9 , 2008, p. 1431–1434 , doi : 10.1134 / S1028334X08090237 (English, rruff.info [PDF; 144 kB ; accessed on November 1, 2019]).
  14. ^ William Alexander Deer, R.A. Howie, J. Zussman: Larnite . In: Disilicates and ring silicates . 1986, ISBN 978-1-897799-89-5 , pp. 248-249 .
  15. ↑ type locality Scawt Hill, Larne, Co. Antrim, Ulster, Northern Ireland, UK. In: mindat.org. Hudson Institute of Mineralogy, accessed November 1, 2019 .
  16. ^ Stefan Schorn and others: Hatrurim formation. In: mineralienatlas.de. Mineral Atlas , accessed November 1, 2019 .
  17. ↑ Localities for Larnite. In: mindat.org. Hudson Institute of Mineralogy, accessed November 1, 2019 .
  18. ↑ a b List of locations for larnite in the Mineralienatlas and Mindat , accessed on November 1, 2019.