Apophyllite

  • End members: Apophyllite - (KF ) Apophyllite - (KOH ), Apophyllite - (NaF )
  • Obsolete: Fluorapophyllite, Hydroxyapophyllit, natro - Apophyllite

The Apophyllitgruppe (short Apophyllite ) is a term for a group of relatively high occurrence of minerals from the mineral class of silicates and the Department of phyllosilicates. They crystallize in the tetragonal crystal system with the chemical composition (K, Na) Ca4Si8O20 (F, OH) · 8H2O given in the parentheses elements potassium and sodium or fluoride and hydroxide ions can relax in the formula each represent each other (substitution, Diadochie ) but are always in the same proportions to the other components of the mineral. The minerals are found as secondary minerals in cavities in basalt or other igneous rocks.

In pure form, Apophyllite are colorless and transparent, stages with crystals in the centimeter range are commonly found in the trade. These levels usually come from the Indian province of Poona.

Special Features

The octahedral faces { 111} often form a distinct, steep pyramid tip. The mineral shows through the elimination of water of crystallization a significant reaction before the blowpipe. It scrolls up in a characteristic manner.

Etymology and history

Apophyllite was described by C. Rinman in 1784 as one of the " zeolites " from Hellesra in Denmark. Historically Apophyllite was ( for "fish-eye stone " in Greek ), also known as fish-eye stone or Ichthyophthalmit. The name refers to the bright white gloss, similar to a cooked fish eye. In 1801 Hauy gave the name " mesotype epoinlee " for Apophyllite from Iceland and four years later the name Apophyllite ("ab " Greek ἀπό, apo and "leaf" in Greek φύλλον, phyllon ) in terms of the behavior before the blowpipe. An overview of other historical names of Dunn et. al. given.

During group name Apophyllite is not a single mineral, but for a solid solution series, the name of the end members in 1978 were re- appointed by the IMA. The Apophyllite Group consists of the following is now recognized by the IMA minerals:

  • Fluorapophyllite ( K) (formerly Fluorapophyllite, Apophyllite - (KF ) )
  • Hydroxyapophyllit ( K) (formerly Hydroxyapophyllit, Apophyllite - (KOH ) )
  • Fluorapophyllite (Na ) (formerly natro - Apophyllite, Apophyllite - (NaF ) )

Classification

In the now outdated but still in use 8th edition of the mineral classification by Strunz the Apophyllite belonged to the mineral class of " silicates and Germanates " and then to the Department of " layer silicates ( phyllosilicates ) ," where the three end members of the Apophyllite Group VIII / H. 01 were formed.

The 9th edition used since 2001 and valid by the International Mineralogical Association (IMA ) of the Strunz'schen Mineral classification assigns the Apophyllite also included in the category of " silicates and Germanates " and there in the department of " layer silicates ( phyllosilicates ) ". This division, however, is further divided according to the structure of the layers, so that the mineral is found in accordance with its construction in the subsection " Simple tetrahedral grids with 4, 5, (6) and 8 rings involved " where the three end members, in turn, the Apophyllite group 9.EA.15 form.

The mainly common in English-speaking classification of minerals according to Dana assigns the Apophyllite in the class of " silicates and Germanates " and there in the department of " layer silicate minerals " one. Here are the three Apophyllite - end members form the " Apophyllite - group " with the system no. 72.03.01 within the sub-division of " layer silicates: Two-dimensional infinite layers with other than six -membered rings: 3 -, 4 -, or 5- membered rings and 8- membered rings ."

Modifications and varieties

The three groups - end members form Msichkristallreihen. They are without complex analysis does not distinguish and does not typically occur on the ideal composition.

Education and Locations

The crystals are found as a secondary mineral in cavities in basalt or other igneous rocks. These stages are often derived from the Indian province of Poona.

Worldwide there are approximately 1000 sites previously known. The type locality of Apophyllite - ( hydroxy) is the Ore Knob Mine, Ore Knob, Ashe Co., North Carolina, USA. ( Coordinates of the Ore Knob Mine36.4 - 81.329166666667 ) The type locality of Apophyllite - (NaF ) is the Sampo mine in Japan

Morphology

Apophyllite usually form prismatic crystals with the major faces {100 }, { 111} and { 001 } subordinate. The {100 } faces often have a distinct edge parallel striations. The angle between the surface (111 ) and ( 001) is 119.5 °, between two ( 111) faces between 104 ° and 128 ° (111) and (100).

Crystal structure

The Apophyllite crystallize in the tetragonal space group P/4mnc ( Raumgruppen-Nr. 128) with the lattice parameters a = 8.965 Å; and c = 15.767 Å; and Z = 2 formula units per unit cell.

A base assembly are annular Si8O20 layers, which are composed of corner-sharing tetrahedra. The crystal water is expelled between 330 ° C and 440 ° C.

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