Witherite

Witherite is a rarely occurring barium carbonate mineral from the mineral class " carbonates and nitrates " (formerly known as carbonates, nitrates and borates ). It crystallizes in the orthorhombic crystal system with the chemical composition Ba [ CO3 ], and is therefore chemically seen a barium carbonate.

Witherite developed due to twinning mainly dipyramidal, pseudo-hexagonal crystals, rarely, fibrous, grape-like, massive mineral aggregates that knows either colorless or colored by impurities, may be colored gray or yellowish.

Special Features

Depending on the location may witherite under the action of UV light, X-ray fluorescence and electron occasionally and / or phosphorescent.

Before the blowpipe Witherite easily melts and turns it yellowish green flame.

Witherite is only slightly soluble in water and non-hygroscopic (water- attracting). However, it is readily soluble in hydrochloric acid and nitric acid. In dilute sulfuric acid it forms the other hand, insoluble barium sulphate (barytes ).

Etymology and history

The mineral was " Terra Ponderosa " first described in 1784 by William Withering, a British botanist and physician, as. In 1790 it was named by Abraham Gottlob Werner after Withering Witherite.

Classification

In the now outdated 8th edition of the mineral classification by Karl Hugo Strunz the Witherite still belongs to the common class of " carbonates, nitrates and borates " and then to the Department of " water clear carbonates without foreign anions ." The mineral is there. During the " Aragonitgruppe " with the other members Alstonite, Barytocalcit, Cerussite, Olekminskit, Paralstonit, strontianite and aragonite

The revision of the Strunz'schen Mineral classification in the 9th edition the one hand, the borates were moved to a separate class and on the other hand divides the now reduced class of " carbonates and nitrates " precisely on the nature of the cations involved further. The Witherite is therefore now in accordance with the subsection "B. Alkaline-earth (and other M2 ) carbonates ", where he remains a member of the " Aragonitgruppe " is, however, only contains the other members Cerussite, strontianite and aragonite. The minerals Alstonite, Barytocalcit, Olekminskit and Paralstonit were put into separate groups within the subdivision.

The commonly used in English-speaking classification of minerals according to Dana assigns the aragonite also in the class of " carbonates, nitrates and borates ," there, however, in the department of " water clear carbonates with a simple formula A CO3 ", where he also along with Cerussite, strontianite and aragonite " Aragonitgruppe ( Orthorhombic: Pmcn ) " forms.

Education and Locations

Witherite forms similar to strontianite by hydrothermal processes in low-temperature vein deposits. Accompanying minerals include barite, calcite and fluorite.

Locations include South Australia in Australia; Minas Gerais in Brazil; Chongqing, Hubei, Shaanxi and Sichuan in the People's Republic of China; Hesse, Lower Saxony and Saxony in Germany; Auvergne in France; Sardinia in Italy; Honshu in Japan; Northwest Territories, Ontario and Yukon in Canada; Katanga in the Democratic Republic of Congo; Baja California in Mexico; northern regions of the Caucasus and Siberia in Russia; Banská Bystrica, Košice and Žilina in Slovakia; Limpopo in South Africa; Moravia in the Czech Republic; as well as different regions of the UK and the USA.

Crystal structure

Witherite crystallizes in the orthorhombic crystal system, space group Pmcn with the lattice parameters a = 5.31 Å, b = 8.90 Å and c = 6.43 Å and four formula units per unit cell. It is isotypic with aragonite.

Precautions

Due to the release of barium ions in acids, and thus also in stomach acid is at Witherite mainly by accidental ingestion, the risk of adverse health effects. As a result, it may cause muscle paralysis and damage to the heart, central nervous system and gastrointestinal tract. Inhalation of Witheritstaub cause irritation to the respiratory tract. Inclusion in the body ( incorporation or ingestion) should therefore be prevented in any case and the relevant safety precautions when using Witherite be observed.