Colloids and Granitoids

Experiments with colloids can also give rise to structures which resemble those of granite and related rocks.  One can ask oneself, whether the differentiations within granite only occur through crystallization, or whether, with particular types of granite, differentiation and diffusion processes may have taken place in which water or silicic acid were involved

The left-hand picture shows a colored gel (agar) in which, during the hardening process, there were generated a combination of particle-like precipitates of pigments and lighter sections which had hardened earlier and were broken up by movement.  On the right is a granite for comparison.

kopie_von_02_kolloide_und_granitoide_01.jpg kopie_von_02_kolloide_und_granitoide_02.jpg

Further colloidal experiments
kopie_von_02_kolloide_und_granitoide_03.jpg kopie_von_02_kolloide_und_granitoide_04.jpg

The following picture shows how colloidal processes can also create forms which are similar to the strongly metamorphosed crystalline rocks known as migmatites.
Left: Dark coloring dropped into in half-hardened gel.  Right, a migmatite. 
kopie_von_02_kolloide_und_granitoide_05.jpg kopie_von_02_kolloide_und_granitoide_06.jpg

The following pictures show colloidal processes which lead to lens- and layered forms.  First, the alternating injection of white and black colloidal material into cold water leads to spherical forms.  The entire assembly is then de-watered, bringing about lens and layered forms.
kopie_von_02_kolloide_und_granitoide_07.jpg kopie_von_02_kolloide_und_granitoide_08.jpg
kopie_von_02_kolloide_und_granitoide_09.jpg kopie_von_02_kolloide_und_granitoide_10.jpg
The lens-like structure is similar to "augen" gneiss (and also some types of marble).

Left: Augengneiss, Brazil
Right: Dolomite marble, Norway (white = dolomite, red = calcite) 
kopie_von_02_kolloide_und_granitoide_11.jpg kopie_von_02_kolloide_und_granitoide_12.jpg

A variation of the experiment creates layers through rhythmic precipitation.  Here warm colloids are alternately injected into cold water; at the end the material is dried.  The final picture shows the mass in its completely dried condition.
kopie_von_02_kolloide_und_granitoide_15.jpg kopie_von_02_kolloide_und_granitoide_16.jpg
kopie_von_02_kolloide_und_granitoide_17.jpg kopie_von_02_kolloide_und_granitoide_18.jpg
kopie_von_02_kolloide_und_granitoide_19.jpg kopie_von_02_kolloide_und_granitoide_20.jpg

For comparison: left paragneiss, right migmatite
kopie_von_02_kolloide_und_granitoide_21.jpg kopie_von_02_kolloide_und_granitoide_22.jpg

What can one conclude from these experiments?  Nothing conclusive, to begin with, since many possibilities are conceivable for the origin of lens- and layered forms.  Nevertheless, it is conceivable that the simpicity of the process reflects an important aspect of certain rocks: a greater water content and a colloidal chemistry.  With the experiments, the alternating injection of white and black material is controlled arbitrarily by the experimenter.  In the case of the corresponding rock formation, a self-organizing process in the fluids or colloids may have operated to bring about the separation.