Strontianite

Strontianite is a rarely occurring mineral the mineral class of " carbonates and nitrates " (formerly known as carbonates, nitrates and borates ). It crystallizes in the orthorhombic crystal system with the composition Sr [ CO3 ], and is therefore chemically seen a strontium carbonate.

Strontianite usually develops from prismatic to acicular crystals, and similar to the related aragonite by cyclic trilling formation and pseudo-hexagonal prisms. In addition, however tufted to spherical, fibrous or massive to earthy aggregates occur. On the surfaces of undamaged crystals shows a glass-like luster, fracture surfaces shimmer contrast resin or similar grease.

In its pure form strontianite is colorless and transparent. It may appear white due multicrystalline training and accept by foreign admixtures a gray, brown, greenish, yellowish or reddish color but by multiple refraction. His stroke color, however, is always white.

Special Features

Strontianite is in hydrochloric acid ( HCl) and nitric acid ( HNO3) under roaring release of carbon dioxide ( CO2) soluble. If the resulting solution was evaporated and the residue poured alcohol over it, it lights up bright red.

Before the blowpipe to inflate strontianite glowing on the flame colored carmine intensive and finally assumes a cauliflower- like shape.

Some strontianite exhibit thermoluminescence, ie produce light when heated. Show other under the action of UV light, X-ray cathode or a slight bluish fluorescence.

Etymology and history

Was first discovered in the Scottish village of Strontian strontianite and described in 1790 by Friedrich Gabriel Sulzer ( 1749-1830 ), who named the mineral after its type locality.

Classification

In the now outdated but still in use 8th edition of the mineral classification by Strunz the strontianite " water outdoors carbonates without foreign anions " belonged to the common mineral class of " carbonates, nitrates and borates " and then to the Department of where he along with Alstonite, aragonite, Barytocalcit, Cerussite, Olekminskit, Paralstonit and witherite the independent " Aragonitgruppe " was formed.

The 9th edition used since 2001 and valid by the International Mineralogical Association (IMA ) of the Strunz'schen Mineral classification assigns the strontianite in the class of " carbonates and nitrates " ( here borates form a separate class) and then in the Department of " carbonates without further anions, without H2O ". This division, however, is further subdivided according to the group membership of the cations involved, so that the mineral is found according to its composition in the subsection " alkaline-earth (and other M2 ) carbonates ", where it together with aragonite, cerussite and Witherite the " Aragonitgruppe " with the system number. 5.AB.15 forms.

The classification of minerals according to Dana assigns the strontianite as the old Strunz'sche systematics in the class of " carbonates, nitrates and borates " and there in the department of " water clear carbonates " one. Here he is with aragonite, Witherite and cerussite in existing in this system, " Aragonitgruppe ( Orthorhombic: Pmcn ) " with the system no. 14:01:03 within the sub-division of " water clear carbonates CO3 with a simple formula A " to find.

Modifications and varieties

When heated to about 920 ° C is strontianite into the hexagonal modification, however, does not occur in nature.

Usually, getting a little strontium is replaced diadoch by calcium in the chemical formula of strontianite. In the variety known as Strontiumcalcit, Calciostrontianit or Emmonit up to 13% of strontium is replaced by calcium.

Education and Locations

Strontianite formed by hydrothermal processes in volcanic rocks or by sedimentation. Accompanying minerals include barite, calcite, celestite, Harmotome, magnesite, sulfur, and various zeolites.

Locations and production in Germany

In Germany strontianite was mined mainly in the southeastern Munsterland. Between 1874 and 1900 here 650 mines were operated, the east in the area to Oelde and Beckum / Neubeckum, south to Hamm and Lippetal, west to northern churches and north Munster, Telgte and sending Horst / Warendorf were. As a final strontianitfördernde pit mine changing bag set in mountain ash in January 1945, ceased operation.

In space Ahlen - especially in the district Vorhelm - are known about 20 wells with depths up to 110 m. The largest mine was the " Alwine " south of Vorhelm. The city was Drensteinfurt with 180 mines in the capital of the Strontianitabbaus. Many street names Strontianitvilla and Strontianitspielpfad remember the short mining history of the town. In the Davert in mountain ash and north of Bockum- Hovel in the peasantry Hölter the mineral has also been lowered. As remnants of these mining activities can still be seen today Mergelaufschüttungen.

More Locations

Apart from its type locality Strontian in Scotland there is strontianite including in Huambo, Huíla and Namibe in Angola; South Australia in Australia; Cochabamba in Bolivia; Minas Gerais and São Paulo in Brazil; different regions in the People's Republic of China; Auvergne, Ile -de -France, Provence -Alpes- Côte d' Azur and Rhône -Alpes in France; Attica in Greece; Kitaa and tunu in Greenland; different regions in the UK; Tamil Nadu in India; different regions in Italy; Honshu and Shikoku in Japan; British Columbia, Ontario and Quebec in Canada; Balaka, Zomba and Phalombe in Malawi; Gelderland in the Netherlands; Bad Bleiberg, Carinthia and other regions in Austria; various regions in Russia; Medelpad and Skåne in Sweden; Grisons canton Canton of Solothurn in Switzerland; Banská Bystrica, Košice and Žilina ( Okres ) 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; and various regions in the United States.

Crystal structure

Strontianite crystallizes isotypic with aragonite in the orthorhombic crystal system, space group Pmcn ( Raumgruppen-Nr. 62) with the lattice parameters a = 5.107 Å, b = 8.414 Å and c = 6.029 Å and four formula units per unit cell.

Use

In the 1880s, strontianite ( SrCO 3 ) was used in the sugar industry as a catalyst for Restentzuckerung of molasses. In the production of sugar from sugar beets would otherwise remain still 50 % of the sweet substance back. After the so-called " Strontianitverfahren " was developed in 1871, put the strontianite degradation correctly and yet the needs of the sugar industry could hardly be met.

In 1900 the implementation of a favorable SrSO4 was discovered ( from celestite ) in the strontianite SrCO3 and began to lose importance. On top of that was the sugar ( probably because of the of sugar cane production ) on the world market so cheap, that the existing yield from the molasses was no longer profitable.