Brochantite

Brochantite (also Blanchardit ) is a rarely occurring mineral from the mineral class of " sulfates ( selenates, tellurates, chromates, molybdates, tungstates ) ". It crystallizes in the monoclinic crystal system with the chemical composition Cu4 [( OH) 6 | (SO4) ] and developed most long-prismatic to acicular crystals of several centimeters in length, but also low one, granular to massive aggregates or parallelstrahlige crusts. In the crystal surfaces shows vitreous luster, cleavage faces shine on the other hand nacreous. The color varies from light green, emerald green, teal and black green, the stroke color, however, always shows a bright green.

Special Features

Brochantite dissolves even in very dilute acids. In the glass tube heated Brochantite sulfur dioxide and water are from, where it turns black.

Furthermore Brochantite is soluble in aqueous ammonia solutions, forming a characteristic deep blue tetraamine copper (II ) complex. This process is used primarily for the cleaning of marble and limestone to the normally water-insoluble copper compounds such as Azurite, malachite and Brochantite to break away from the stone, with the progress of cleaning can be followed visually good due to the color change.

Etymology and history

Was first found in 1824 in the Brochantite " Mednorudjanskoje copper deposit " Nizhny Tagil in / Yekaterinburg ( Sverdlovsk ) in Russia and described by Armand Lévy ( 1795-1841 ), who named the mineral after Brochant André de Villiers ( 1772-1840 ).

Classification

In the old ( 8th edition ) and new classification of minerals according to Strunz ( 9th edition ) of the Brochantite belongs to the department of " water clear sulfates with foreign anions ." The new Strunz'sche Mineral classification divided here, however, precisely according to the size of the cations involved, and therefore the mineral is in accordance with the subdivision "With medium-sized cations ".

The commonly used in English-speaking classification of minerals according to Dana assigns the Brochantite in the department of " water clear sulfates with hydroxyl or halogen, and the general composition (AB ) m ( XO4 ) PZQ, where m: p> 2:1 ".

Education and Locations

Brochantite forms as a secondary mineral mainly under arid climatic conditions in the oxidation zone of copper deposits. Accompanying minerals are mainly Antlerite and malachite, with which it is often confused, but also Atacamit, azurite, calcite, Caledonit, cerussite, chrysocolla, cuprite, Cyanotrichite, Linarit and Tenorite.

Could be detected the mineral so far (as of 2009 ) to over 1100 localities, including, inter alia, in some regions of Argentina; many regions of Australia; Liege, Limburg, Luxembourg and Namur in Belgium; Cochabamba, La Paz and Potosí in Bolivia; Bulgaria; some regions of Chile; China; many regions of Germany and France; Greece; many regions of the UK; Ireland; Italy; Japan; several regions of Canada; Morocco; some regions of Mexico; Namibia; some regions of Norway; Carinthia, Salzburg, Styria, Tyrol and Vorarlberg in Austria; several regions of Peru; Poland; Portugal; some regions of Russia and Slovakia; Spain; South Africa; Bohemia and Moravia in the Czech Republic; Hungary; as well as in many regions of the United States.

Crystal structure

Brochantite crystallizes in the monoclinic space group P21 / a with lattice parameters a = 13.140 Å; b = 9.863 Å; c = 6.024 Å and 103.16 ° β =, and four formula units per unit cell.