Hopeite
- Hibbenite
- Prismatoidischer Zinkphyllit
- Stilbite duovigésimale
Hopeit is a rarely occurring mineral from the mineral class of " phosphates, arsenates and vanadates ." It crystallizes in the orthorhombic crystal system with the composition ZnZn2 [ PO4 ] 2 · 4H2O, is thus seen chemically a hydrous zinc phosphate.
Hopeit developed mostly tabular to prismatic crystals, but is also found in the form tufted, strahliger or moderate mineral aggregates or crusty coatings. Visible and unweathered crystal faces have a glass-like luster, cleavage surfaces shimmer contrast nacreous. In pure form, the mineral is colorless and transparent. Through multiple refraction due to lattice defects or multicrystalline training however, it may also appear gray white and accept by foreign admixtures a yellow to orange color. However, his stroke color is always white.
Etymology and history
Hopeit was first discovered (now La Calamine ) named in the "Old Mountain" in the Belgian province of Liège and described in 1824 by David Brewster, of the mineral after the Scottish physician and chemist Thomas Charles Hope ( 1766-1844 ).
Classification
Already in the now outdated but still in use 8th edition of the mineral classification by Strunz belonged Hopeit to the mineral class of " phosphates, arsenates and vanadates " and then to the Department of " water -containing phosphates without foreign anions ", where he along with Fahleit, Parahopeit, phosphophyllite, Radovanit and Smolianinovite the independent group VII/C.11 formed.
The 9th edition used since 2001 and valid by the International Mineralogical Association (IMA ) of the Strunz'schen Mineral classification assigns the Hopeit also in the class of " phosphates, arsenates and vanadates " and there in the department of " Phosphates without additional anions, with H2O " one. This division, however, is further divided according to the size of the cations involved, so that the mineral is found according to its composition in the subsection "With small and large / medium cations " where there is only together with Parahopeit the " Hopeit group " with system no. 8.CA.30 forms.
The mainly common in English-speaking classification of minerals according to Dana assigns the Hopeit in the class of " phosphates, arsenates and vanadates " and there in the department of " water containing phosphates, etc. " field. Here he is with Rollandit in the " Hopeit group " with the system no. " 2 × x water -containing phosphates, etc., with (A2 ) 3 ( XO4 ) ( H2O) " to find 40.03.04 within the subdivision of.
Modifications and varieties
The connection ZnZn2 [ PO4 ] 2 · 4H2O is dimorphic, ie, occurs in nature in addition to the orthorhombic crystallizing Hopeit more than triclinic crystallizing Parahopeit ago.
Education and Locations
Hopeit forms in some hydrothermal zinc deposits and complex granitic pegmatites. Encrustations occur in bone breccia in limestone caves. Accompanying minerals include Ferrisicklerit, hemimorphite, hydroxyapatite, Laueit, Leukophosphit, Robertsit, Smithsonite, Spencerit, sphalerite, Tarbuttit, Triphylin and Vanadinit.
A rare mineral formation Hopeit previously could (as of 2011) are detected only at a few localities. 20 localities are considered to be known. and its type locality " Altenberg " ( La Calamine ) is the only known locality in Belgium.
In Germany the mineral occurred among others at Kreuzberg in Pleystein and at several locations near Hagendorf / Waidhaus in Bavaria, in the pit of Fortune in Lower Saxony, in the ore mine Büsbacherberg - Brockenberg in North Rhine -Westphalia and in the pit Friedrichssegen at Frücht in Rhineland -Palatinate on.
Other localities lie including Australia, Bolivia, China, Canada, Portugal, Zambia, Spain, South Africa and the United States of America.
Crystal structure
Hopeit crystallizes in the orthorhombic space group Pnma ( Raumgruppen-Nr. 62) with the lattice parameters a = 10.62 Å; b = 18.43 Å; c = 5.02 Å and four formula units per unit cell.