Crookesite
Crookesit is a rarely occurring mineral from the mineral class of " sulfides and sulfosalts " (including selenides, tellurides, arsenides, antimonides, bismuthides, Sulfarsenite, Sulfantimonite, Sulfbismuthite ). It crystallizes in the tetragonal crystal system having a chemical composition Cu7TlSe4 and is therefore a copper - thallium selenide.
Crookesit finely dispersed inclusions, granular aggregates or small veins has so far been found of lead- gray to bluish- gray in color only in the form. He is in every form opaque (opaque ) and has a metallic luster.
Etymology and history
The mineral was first discovered in the ore deposit of the pit " Skrikerum " near Valdemarsvik in the Swedish province of Östergötland County and described in 1867 by Adolf Erik Nordenskiöld. It is named after the discoverer of the chemical element thallium, Sir William Crookes.
Classification
In the now outdated but still in use 8th edition of the mineral classification by Strunz the Crookesit belonged to the department of " sulfides, selenides and tellurides with the molar ratio of metal: S, Se, Te > 1: 1", where he along with Athabascait, Bellidoit, Berzelianit, Sabatierit and Umangit the unnamed group II/B.03 formed.
The 9th edition used since 2001 and valid by the International Mineralogical Association (IMA ) of the Strunz'schen Mineral classification assigns the Crookesit also in the department of "Metal Sulfides, M: S> 1: 1 ( mainly 2: 1) " a. However, this is further subdivided according to the conditions prevailing in the interconnect metals, so that the mineral according to its composition in the subdivision " with mercury (Hg), thallium (Tl) " is to find where it is the only member of the unnamed group 2.BD .50 forms.
The mainly common in English-speaking classification of minerals according to Dana assigns the Crookesit into the class of " sulfides and sulfosalts " and there in the department of " sulfide minerals ." Here he is with Sabatierit in the unnamed group 02:04:12 within the subdivision " sulfides - tellurides and selenides, including - with the composition AmBnXp, with (m n): p = 2: 1" to find.
Education and Locations
Crookesit formed under hydrothermal conditions and usually occurs associated with other selenides as Umangit, Berzelianit, Eukairit, Klockmannit, Clausthalite and Sabatierit, but also with selenhaltigem linnaeite, calcite and quartz.
A rare mineral formation Crookesit could be detected only in a few localities, where so far (as of 2013) are about 10 localities known as. Its type locality " Skrikerum " near Valdemarsvik is the only known locality in Sweden.
In Germany they found Crookesit so far only in the pits " Brummerjan " in Zorge and " grape " in Lerbach in Lower Saxony.
In Switzerland, the mineral could ( sand or clay rock by finely divided hematite intense red colored ) are detected in Weier field near Rheinfelden in the canton of Aargau in rock samples in a study carried out by Nagra bore near Kaisten as well as in a sample hole in one " Redbed " deposit.
Other previously known localities are the " Tumiñico Mine " in the Sierra de Cacho in the Argentine province of La Rioja, the deposit " Chibukla " in Armenia, the " Sanpu " ore field in a circle Suixi ( Huaibei ) in the Chinese province of Anhui and Nové město na Moravě Petro - vice and Rožná in the Czech Kraj Highlands.
Crystal structure
Crookesit crystallized tetragonal space group I4 ( Raumgruppen-Nr. 82) with the lattice parameters a = 10.45 Å and c = 3.93 Å and two formula units per unit cell.