Strontianite

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Strontianite
Strontianite - USGS Mineral Specimens 1046.jpg
Colorless strontianite with a glossy resin surface
General and classification
chemical formula Sr [CO 3 ]
Mineral class
(and possibly department) 		Carbonates and nitrates (formerly carbonates, nitrates and borates)
System no. to Strunz
and to Dana 		5.AB.15 ( 8th edition : V / B.04)
01/14/03/03
Crystallographic Data
Crystal system orthorhombic
Crystal class ; symbol orthorhombic-dipyramidal; 2 / m 2 / m 2 / m
Room group (no.) Pmcn (No. 62)
Lattice parameters a  = 5.107  Å ; b  = 8.414 Å; c  = 6.029 Å Please complete the source as an individual reference!
Formula units Z  = 4 Please complete the source as an individual reference!
Twinning after {110}, contact or more often penetration twins
Physical Properties
Mohs hardness 3.5
Density (g / cm 3 ) 3.74 to 3.78
Cleavage completely after {110}, clear after {021}, indistinct after {010}
Break ; Tenacity shell-like, uneven
colour colorless, gray, brown, greenish, yellowish, reddish
Line color White
transparency transparent to translucent
shine Glass gloss, resin gloss
Crystal optics
Refractive indices n α  = 1.516 to 1.520
n β  = 1.664 to 1.667
n γ  = 1.666 to 1.668
Birefringence δ = 0.150
Optical character biaxial negative
Axis angle 2V = 7 ° (calculated: 8 ° to 12 °)
Other properties
Chemical behavior soluble in HCl or HNO 3 with release of CO 2

Strontianite is a rather seldom occurring mineral of the mineral class of " carbonates and nitrates " (formerly carbonates, nitrates and borates). It crystallizes in the orthorhombic crystal system with the composition Sr [CO 3 ], so it is chemically a strontium carbonate .

Strontianite usually develops prismatic to needle-like crystals and, similar to the related aragonite, also forms pseudo-hexagonal prisms through cyclic triplet formation . In addition, there are also tufted to spherical, fibrous or massive to earthy aggregates . The surface of undamaged crystals has a glass-like sheen , while the fracture surfaces have a resin-like or grease-like shimmer.

In its pure form, strontianite is colorless and transparent. However, it can appear white due to multiple light refraction due to its multicrystalline formation and, due to foreign admixtures, it can take on a gray, brown, greenish, yellowish or reddish color. However, its line color is always white.

Etymology and history

Strontianite was first discovered in the Scottish town of Strontian and described in 1790 by Friedrich Gabriel Sulzer (1749–1830), who named the mineral after its type of locality .

classification

In the meanwhile outdated, but still in use 8th edition of the mineral systematics according to Strunz , the strontianite belonged to the common mineral class of "carbonates, nitrates and borates " and to the department of "anhydrous carbonates without foreign anions ", where together with alstonite , aragonite , Barytocalcite , cerussite , olekminsite , paralstonite and witherite formed the independent "aragonite group".

The 9th edition of Strunz's mineral systematics , which has been in effect since 2001 and is used by the International Mineralogical Association (IMA), assigns strontianite to the class of "carbonates and nitrates" (the borates form a separate class here) and there into the department of " Carbonates without additional anions; without H 2 O “. This section is, however, further subdivided according to the group affiliation of the cations involved , so that the mineral can be found according to its composition in the sub-section "alkaline earth (and other M 2+ ) carbonates", where together with aragonite, cerussite and witherite it has the " Aragonite group "with the system no. 5.AB.15 forms.

The systematics of minerals according to Dana classifies the strontianite like the old Strunz'sche systematics in the class of "carbonates, nitrates and borates" and there in the department of "anhydrous carbonates". Here it is together with aragonite, witherite and cerussite in the "aragonite group (Orthorhombic: Pmcn)" with the system no. 01/14/03 to be found in the subsection of " Anhydrous carbonates with simple formula A + CO 3 ".

Crystal structure

Strontianite crystallizes isotypically with aragonite in the orthorhombic crystal system in the space group Pmcn (space group no. 62) with the lattice parameters a  = 5.107  Å , b  = 8.414 Å and c  = 6.029 Å as well as four formula units per unit cell .

properties

Light yellow strontianite on calcite and fluorite from the National Limestone County Quarry, Perry Township , Snyder County , Pennsylvania, USA
Same level under UV light

Strontianite is soluble in hydrochloric acid (HCl) and nitric acid (HNO 3 ) with an effervescent release of carbon dioxide (CO 2 ). If the resulting solution is evaporated and the residue is poured over with alcohol, it will flare up bright red.

Strontianite puffs up glowing in front of the soldering tube , colors the flame intensely carmine red and finally takes on a shape similar to cauliflower.

Some strontianites show thermoluminescence , which means that they produce light when heated. Others show a weak, bluish fluorescence when exposed to UV light , cathode radiation or X-rays .

Modifications and varieties

When heated to approx. 920 ° C, strontianite changes into the hexagonal modification , which, however, does not occur in nature.

Typically, in the chemical formula of the Strontianit always a little strontium by calcium diadoch replaced . In the variety known as strontium calcite , calciostrontianite or emmonite , up to 13% of the strontium is replaced by calcium.

Education and Locations

Strontianite with sulfur from the Machów opencast mine near Tarnobrzeg, Poland

Strontianite is formed by hydrothermal processes in volcanic rocks or by sedimentation . Accompanying minerals include barite , calcite , celestine , magnesite , sulfur , harmotome and various other representatives of zeolites .

Locations and extraction in Germany

In Germany , strontianite was mainly mined in the southeastern Münsterland . Between 1874 and 1900 around 650 mines were operated here, located in the area east to Oelde and Beckum / Neubeckum , south to Hamm and Lippetal , west to Nordkirchen and north to Münster , Telgte and Sendenhorst / Warendorf . The last mine to produce strontianite was the Wickensack mine in Ascheberg , which ceased operations in January 1945.

In the Ahlen area - especially in the Vorhelm district - around 20 shafts with a depth of up to 110 m are known. The largest mine was the "Alwine" south of Vorhelm. The city of Drensteinfurt was the main site of strontianite mining with 180 pits. Many street names, the strontianite villa and the strontianite play path are reminiscent of the town's brief mining history. The mineral was also mined in the Davert near Ascheberg and north of Bockum-Hövel in the Hölter farms. As remnants of these mining activities are still Mergelaufschüttungen to see.

More locations

In addition to its type locality Strontian in Scotland , Strontianite is also found in Huambo , Huíla and Namibe in Angola ; South Australia in Australia ; Department of Cochabamba in Bolivia ; Minas Gerais and São Paulo in Brazil ; various regions in the People's Republic of China ; Auvergne-Rhône-Alpes , Île-de-France and Provence-Alpes-Côte d'Azur in France ; Attica in Greece ; Kitaa and Tunu in Greenland ; different regions in the UK ; Tamil Nadu in India ; different regions in Italy ; Honshū and Shikoku in Japan ; British Columbia , Ontario and Quebec in Canada ; Balaka , Phalombe and Zomba in Malawi ; Gelderland in the Netherlands ; Bad Bleiberg , Carinthia and other regions in Austria ; different regions in Russia ; Medelpad and Skåne in Sweden ; Canton of Graubünden and Canton Solothurn in Switzerland ; Banská Bystrica , Košice and Okres Žilina in Slovakia ; Andalusia and Catalonia in Spain ; Gauteng , Limpopo and North West in South Africa ; Moravia in the Czech Republic ; Borsod-Abaúj-Zemplén in Hungary ; as well as various regions in the US .

use

In the 1880s, strontianite (SrCO 3 ) was used in the sugar industry as a catalyst to remove sugar from molasses . Otherwise, 50% of the sweet substance would still be left behind when producing sugar from sugar beet. After the so-called " strontianite process " was developed in 1871, strontianite mining really started. Nevertheless, the needs of the sugar industry could hardly be met.

Around 1900 the conversion of the cheaper SrSO 4 (from Celestine ) into SrCO 3 was discovered and the strontianite began to lose importance. On top of that, the sugar (probably because of the enormous quantities from sugar cane production ) became so cheap on the world market that the previous yield from molasses was no longer worthwhile.

See also

literature

  • Martin Gesing: Strontianite mining in the Münsterland . Sources and research on the history of the Warendorf district, Warendorf 1995, ISBN 3-920836-13-8 , p. 647 .
  • Petr Korbel, Milan Novák: Encyclopedia of Minerals . Nebel Verlag GmbH, Eggolsheim 2002, ISBN 3-89555-076-0 , p. 120 .
  • Martin Okrusch, Siegfried Matthes: Mineralogy: An introduction to special mineralogy, petrology and deposit science . 7th edition. Springer Verlag, Berlin, Heidelberg, New York 2005, ISBN 3-540-23812-3 , pp. 66 .

Web links

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

Individual evidence

  1. ↑ Webmineral - Strontianite (English).
  2. ↑ a b c Strontianite at mindat.org (English).
  3. ↑ Stefan Weiß: The large Lapis mineral directory . 4th edition. Christian Weise Verlag, Munich 2002, ISBN 3-921656-17-6 .
  4. ↑ a b c Paul Ramdohr , Hugo Strunz : Klockmanns textbook of mineralogy . 16th edition. Ferdinand Enke Verlag, Stuttgart 1978, ISBN 3-432-82986-8 , p. 575 .
  5. ↑ Hans Lüschen: The names of the stones. The mineral kingdom in the mirror of language . Ott Verlag, Thun and Munich 1968, p. 329, 381 .
  6. ↑ a b c d e A. G. Betechtin (А. Г. Бетехтин): Textbook of special mineralogy . 2nd Edition. VEB Verlag Technik, Berlin 1957, p. 364–365 (Russian: Курс минералогии - course mineralogii . Translated by Wolfgang Oestreich).
  7. ↑ John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols: Strontianite. In: Handbook of Mineralogy, Mineralogical Society of America. 2001 ( handbookofmineralogy.org PDF 65.5 kB).
  8. ↑ a b Strontianite mining in the southern Münsterland
  9. ↑ a b isa: Strontianite. The gold of the Münsterland . Theme day at the Dabbelt farm. In: Westfälischer Anzeiger . Westfälischer Anzeiger Verlagsgesellschaft (Hamm), June 24, 2012 ( wa.de [accessed October 26, 2012]).
  10. ^ Martin Gesing: The strontianite mining in the Münsterland . Sources and research on the history of the Warendorf district, Warendorf 1995, ISBN 3-920836-13-8 .
  11. ↑ MinDat - Localities for Strontianite (Eng.)