Pseudomorph
- Pseudomorphs sets by Jeff " Stretch" Young
Bayldonit after Mimetite
Mimetite
Ferberite after scheelite ( Reinit )
Scheelite
Gypsum
Plaster after glauberite
Glauberite
Goethite
Goethite after Gypsum
Gypsum
Goethite
Goethite after pyrite
Pyrite
Copper
Copper after aragonite
Aragonite
Copper
Copper after azurite
Azurite
Malachite
Malachite after Azurite ( incomplete)
Azurite
Malachite
Malachite after Cuprite
Cuprite
Quartz ( Amethyst color variety )
Quartz after Fluorite
Fluorite
Quartz
Quartz after Fluorite
Fluorite
Rhodochrosite
Rhodochrosite after Serandit
Serandit
Pseudomorph is a term from mineralogy and refers to a mineral that is not his own typical shape ( crystal system ), but has accepted the outward form of another mineral species. Pseudomorphs are formed for example by first mineral A crystallizes in a rock is dissolved away later and the cavity is filled by mineral B.
The name of a pseudomorph always follows the rule of mineral pseudomorphs B to A. A quartz which has the form of pyrite, is thus referred to as " pseudomorphs of quartz after pyrite ." A good mnemonic for the name of a pseudomorph is the lemma "That which is according to what was. "
The replacement of the original mineral not must take place by another mineral. In the case of halite pseudomorphs halite crystals were dissolved away and the cavities filled by clayey- siltiges sediment. This sediment is later then the cube-shaped outline of the cubic NaCl crystals.
Pseudomorphs can be classified as follows according to Strunz:
Paramorphosen
Paramorphosen occur at polymorphic substances, ie wherein elements or compounds which occur in several modifications. The carbon as the element can occur for example as graphite or diamond in nature. As Paramorphose is, for example, a hexagonal high - quartz called, has formed at a temperature of about 573 ° C and transforms during cooling in the stable phase at ambient conditions of the trigonal low - quartz without losing the outer shape of erstgebildeten high - quartz. Other examples of Paramorphosen are
- Calcite ( trigonal ) to aragonite ( orthorhombic )
- Acanthite (monoclinic ) to argentite ( cubic)
- Leucite (tetragonal ) to high - leucite ( cubic)
In the bracket while the respective crystal system of the mineral, which is decisive for the shape of the crystal indicated.
Demixing pseudomorphs
Demixing pseudomorphs caused by the separation of a mixed crystal. Here incurred mixed crystal is a generally segregated at high temperatures in the course of slow cooling. Are formed here exsolution lamellae in a host crystal. Thus, e.g. form, to compensate at 250 ° C solid solution with a zinc blende structure with slow cooling Gallit lamellae in the host crystal of sphalerite.
Displacement pseudomorphs
Displacement pseudomorphs form the most comprehensive group of pseudomorphs, which can be subdivided according to Strunz even further. Here, the chemical ingredient in the main crystal is changed by dispensing, recording, or replacement of parts or replace the entire fuel inventory. The following is an example is given for each of the four types of emergence displacement pseudomorphs.
The name " Glendonit " means a pseudomorphs of calcite after Ikaite. Ikaite CaCO3 · 6 H2O is formed in the near-shore sea water at temperatures near the freezing point at 0 to 4 ° C. Important for the formation of Ikaite also are soft sediments that are rich in organic material, and carbonatreiche fluids and calcium- rich seawater. If Ikaite recovered, that is, the cold sea water is removed, it changes according to Greinert and Derkachev to about 5 to 10 ° C in calcite CaCO3. Here, the bound water in the crystal lattice is released without the Ikaite loses its shape. However, this change is associated with a significant reduction in volume. It thereby formed pores in the calcite, which can be seen with a magnifying glass or under a microscope. Well known are the hedgehog - or star-shaped Glendonite from the White Sea ( Olenitsa, Russia), which are often admired on mineral shows.
An example of a Pseudomorphosenbildung by absorbing ingredients are the known soapstone pseudomorphs of John colliery at Göpfersgrün, Fichtelgebirge. Here, for example, quartz crystals ( silica) and magnesium in the form of Mg2 ions have been achieved by thermal water added through the existing dolomite MgCO3 form from which then the soapstone ( dense Talk) under a layer of kollomorphen steatite ( magnesium silicate gel formed soapstone) could.
The beautiful pseudomorphs, which are probably to be found in almost every collection of minerals originated. Under the microscope, many small - talk scales are easy to recognize, accept the macroscopically as a whole in the form of a beautiful white " quartz crystal ".
Pseudomorphs of malachite after azurite, known by Tsumeb, Namibia, resulting from the exchange of components ( anion exchange ).
The conditions in which either malachite or azurite occur were studied experimentally by Menschel and Usdowski. The decisive factor here is the CO2 gas fraction flowing past the copper-containing solutions. Corresponds to the CO2 gas fraction 0.5 vol - %, then can both azurite and malachite from the H2O - Cu2 CO2 solution form. Larger CO2 shares - according to a carbonic acid fraction greater than 0.0136 g / l - lead to the formation of azurite, malachite smaller ones. Since normal rain water usually has a relatively small share of carbonic acid, Malachite is more common than azurite.
Koritnig describes in detail how the pseudomorphic formation expires. First, a carbonated rich solution for the formation of azurite crystals provides. Then decreases the proportion of carbonic acid solution flowing past, then Azurite is no longer stable and changing, starting at structural defects of azurite crystals, malachite in order. The malachite formation takes place radialstrahlig, which can also be seen clearly in the pseudomorphs.
A replacement of the entire fuel inventory records the pseudomorphs of native copper after aragonite from Coro Coro, Bolivia, from. Copper-containing solutions displaced, on the surface starting, the aragonite crystals. Many pseudomorphs of Copper after Aragonite are only partially carried out, such as on a polished section of a divided pseudomorphs (see ) to see which shows an aragonite - core, which is surrounded by native copper.
Perimorphosen and Ausfüllungsmorphosen
Perimorphosen are crusty Umwachsungen of larger crystals. They are also known as coated pseudomorphs. Thus, for example, small quartz crystals can form around a large fluorite crystal. This is then referred to as Perimorphose of quartz according fluorite. It is immaterial whether the fluorite crystal is obtained entirely or partly or completely dissolved away was. It may also happen that the cavity of a weggelösten crystal filled by a substance other again and later the crust is dissolved away again. This pseudomorph is referred to as fill- pseudomorphs. This makes it clear that the formation of pseudomorphs as a highly complex process is often puzzling and also the genesis of many a pseudomorph scientifically does not clearly indicate.