Colloids and Limestone

Colloids are materials which are in a half-stable transitional condition between fluid and solid, and posess quite complex chemical and physical properties. They consist of microscopically-small substance aggregates, and are often in a sticky-creamy or gelatenous state.  They are present in the inorganic, and even more in the organic world, namely in the fluids and soft parts of all living beings from single-celled organisms up to the human being.  Cell protoplasm, milk, egg-white and blood serum are colloids.  Colloids often form the medium in which self-organization to increasingly higher levels can play out.

Here and in the following six chapters, experiments with coloidal substances are illustrated which lead to differentiations and separations with an astounding similarity to the pictures presented by certain rock types.   At first it may appear erroneous to draw conclusions based merely on similarities in form, but with reflection one can nevertheless reach the conclusion that there is more at work here than mere coincidence.  The relative simplicity of reproducing the forms present in rocks through colloidal experiments allows one to consider the possibility, that the often highly differentiated and distinctive forms of the rocks originated themselves from colloidal processes.  Certainly it would be false to think that the experiments imitate the exact origin-processes of the rocks, since these experiments are conducted with particular types of organic colloids, whereas in earlier times an entirely different type of chemistry and processes must have prevailed.  With experiments of this sort, dealing with the morphology, i.e. the external form, can only provide a stimulus to a more concentrated research.  Proof of these matters cannot be reached in this way.

The following pictures show, on the left side, experiments with colloids in a half-firm, gelatenous condition, which show shrinkage cracks with forms similar to the limesone photos on the right.  In the experiments, a colored gel (agar) was sheared, and the resulting cracks filled with a white, likewise gelatenous mass. The following pictures on the left column show that colloids, when in a half-solidified gel condition, form similar fracture-forms to certial limestone formations.  The experiments use a colored gel (agar), which is sheared by pressure and then immersed in a white, likewise gelatenous mass.

On the right, for comparison, is a deformed Cretaceous flysch limestone from Italy.

kopie_von_01_kolloide_und_kalk_01.jpg kopie_von_01_kolloide_und_kalk_02.jpg
kopie_von_01_kolloide_und_kalk_03.jpg kopie_von_01_kolloide_und_kalk_04.jpg

The origin of these rock forms is generally explained today as the result of the chemo-physical effects of extreme conditions on the limestone.  One pictures a very slow deformation of hard, water-containing limestone, accompanied by chemical and physical processes, unter the strong pressure and extension forces of the earth's interior (for example 2-3 Kilobar pressure).  For the curved white forms, the following explanations are considered: either the gray fine-grained limestone recrystallized to larger, white calcite crystals within zones of extreme conditions, or else slowly-formed fractures were filled over thousands of years with calcite carried in by pore water.  The temperatures of between one hundred to several hundred degrees Celsius did not make the rock 'soft', but only played a role chemically.  The consistence of the rock is thus not considered to be soft, but rather as hard as the ice of a glacier, which is only able to flow slowly due to great pressure.  The fiberous, flesh-like forms result, in these conceptions, in a pseudo-plastic consistency due to great pressure and long time periods.

Glacier ice, for example, can actually form standing waves similar to those in a stream (left picture).  On the right are showin strongly compressed fracture lines in kneaded glacier ice (Morteratsch glacier, Switzerland).

kopie_von_01_kolloide_und_kalk_05.jpg kopie_von_01_kolloide_und_kalk_06.jpg

Calciet lenses can also be observed where the process of origin is not finished; where recrystallization from dark limestone to coarse-crystalline, white calcite is clearly visible (strongly deformed lime-schist, Switzerland).

01_kolloide_und_kalk_06_b.jpg 01_kolloide_und_kalk_06_c.jpg

One would like to content oneself with these illuminating explanations concerning the origin of forms.  Nevertheless, one is left with a feeling of uncertainty.  How is it, for example, with the wave-formed fibers in the left picture?  (On the right a picture of dried flesh).

kopie_von_01_kolloide_und_kalk_07.jpg kopie_von_01_kolloide_und_kalk_08.jpg

It is conceivable that tectonic deformation of huge rock complexes could bring about a slow, pseudo-plastic ripping-apart or recrystallization of rocks, and form complex shear structures.  The threadlike forms in this picture are in the micro-realm, however, and cannot be so explained.

The following photos of a limestone piece from the Swiss forealps show a further example of a difficult-to-explain fracture formation.

kopie_von_01_kolloide_und_kalk_09.jpg kopie_von_01_kolloide_und_kalk_10.jpg

These fractures did not originate through a region-wide tectonic pressure.  They appear very local, and remind one of shrinkage cracks.  The object reminds one of a plant- or animal-fossil, which was petrefied in limestone.

Shrinkage-cracks in palm bark; on the right the same in negative.

kopie_von_01_kolloide_und_kalk_11.jpg 01_kolloide_und_kalk_12_300.jpg

Shrinkage cracks in the cream-skin on cocoa; on the right in negative

01_kolloide_und_kalk_13_300.jpg 01_kolloide_und_kalk_14_300.jpg

On the left again the negative picture (cracks = white), followed by pictures of flysch limestone.

01_kolloide_und_kalk_15_300.jpg 01_kolloide_und_kalk_16_300.jpg
kopie_von_01_kolloide_und_kalk_17.jpg 01_kolloide_und_kalk_17b_komp.jpg
01_kolloide_und_kalk_17c_komp.jpg 01_kolloide_und_kalk_18_300.jpg

Shrinkage cracks, or a combination of shear fractures aand shrinkage cracks, could indicate a consistency, which at the same time would explain the earlier wave-like threads:  out of a not-yet-completely hardened, strongly water-permeated, "fiberously" reacting consistency of the original limestone mass during its hardening.

In the following, further examples taken from the flysch-limestone are shown.  Note the mixture of 'fibrous' and 'blocky' cracks and breaks, as can come about in firmly-gelled material.

Left: Fracure experiments with hardened gel (agar), right metamorphic flysch

kopie_von_01_kolloide_und_kalk_19.jpg kopie_von_01_kolloide_und_kalk_20.jpg
kopie_von_01_kolloide_und_kalk_21.jpg kopie_von_01_kolloide_und_kalk_22.jpg

For comparison, present-day fracture forms in the same flysch-limestone:  the fractures run completely through; there are no half-separated locations or crumpled fragments as in the metamorphic flysch-limestone.

kopie_von_01_kolloide_und_kalk_23.jpg kopie_von_01_kolloide_und_kalk_24.jpg

Several further examples with strongly metamorphosed limestone formations.  This phenomenon can be found world-wide.

kopie_von_01_kolloide_und_kalk_25.jpg kopie_von_01_kolloide_und_kalk_26.jpg
kopie_von_01_kolloide_und_kalk_27.jpg kopie_von_01_kolloide_und_kalk_28.jpg

The conclusion to be drawn?
These limestone masses could have, during the time before and during their metamorphoses, could have contained a large percentage of water, and have had to a certain extent a 'soft' and 'fibrous' consistency, rather than having been a hardened rock.  The form of the shearing and also of the shrinkage cracks indicate such a possibility.