Liesegang Rings: 5 – Geological Quicksand

The previous post examined the entertainment biologists have enjoyed exploiting this confusion regarding the Liesegang Phenomena.

Now the fun really begins because geologists have really enjoyed misdirecting the public over Liesegang Rings while quietly ignoring the wider Liesegang Phenomena.

The geologists have had to work overtime on their obscuration routines because the Earth naturally provides some chemical environments that very closely mimic the laboratory experiments used to demonstrate the Liesegang Phenomena.

However, to get the geology into perspectives it is necessary to recap the optimal laboratory conditions that are used to demonstrate Liesegang Rings.

CLOSED CHEMICAL SYSTEM
References to Liesegang Rings experiments frequently refer to “systems” and “chemical systems” but upon closer inspection of the equipment used in the experiments it becomes apparent that they really mean a “closed chemical system” because the experiments employ test tubes [with stoppers] and Petri dishes [with lids].

Therefore, in geology the optimal environment for observing Liesegang Rings should be discrete formations with pronounced boundaries.

HOMOGENOUS REACTANT GEL
The “standard” Liesegang Ring experiments uses “a soluble electrolyte at relatively low concentration is placed in a container, to which a gel forming material is added” so that the closed chemical system ideally contains a homogenous gel [quotes from András Büki].

Therefore, in geology the optimal environment for observing Liesegang Rings should be in a discrete formation that was originally a homogenous reactant gel.

NO CONVECTION
Most sources clearly indicate that Liesegang Rings form in the absence of convection

“Liesegang rings are a phenomenon seen in many, if not most, chemical systems undergoing a precipitation reaction, under certain conditions of concentration and in the absence of convection.” [Wikipedia]

“it has been widely accepted that the role of the gel is only to prevent sedimentation of the precipitate, and convection of the electrolytes.” [András Büki]

Therefore, in geology the optimal environment for observing Liesegang Rings should be in a discrete formation that was originally a homogenous reactant gel that did not experience convection.

SECOND REACTANT “SEED”
The second reactant is ideally seeded at the top of the test tube or a the centre of the Petri dish

“After the gelation process completed, a second solution usually at substantially higher concentration is poured onto the top of the gel.” [András Büki]

Therefore, in geology the optimal environment for observing Liesegang Rings should be in a discrete formation that was originally a homogenous reactant gel with a secondary reactant “seed” that was either a) centrally placed in the gel or b) adjacent to the gel.

Agate
Initial scientific investigations into the Liesegang Phenomena frequently focussed upon quartz [in it many natural forms] because it frequently displays strong banding.

The possibility that Liesegang Rings could form in quartz was bolstered by some geologists “who believed that all quartz on earth was at one time a silica hydrogel” and this belief was reinforced when a “vein of gelatinous silica” was found when the Simplon tunnel was being excavated.

Though geology-at-large does not permit experimentation, work during the early period derived a good deal of impetus from the interests of geologists, who believed that all quartz on earth was at one time a silica hydrogel.

A vein of gelatinous silica, as yet unhardened by dehydration, was indeed reported to have been found in the course of deep excavations for the Simplon tunnel (Spezie, 1899).

Von Hahn (1925) described a similar find on the Luneburger Heide. (He asked a cardinal question designed to quicken our interest: Can you eat it?, and remarked that the substance had a ‘cool, refreshing, slightly astringent taste’, and a smell reminiscent of fruit bonbons!)

Crystals in Gels and Liesegang Rings by Heinz K. Henisch
Hardback: 1988

In 1896 the colloid chemist LIESEGANG found concentric banding similar to agate banding when he was experimenting with solutions of silver nitrate and potassium dichromate on gelatin gels.

This showed that INTERNAL RHYTHMS can build banding structures.

The appearance of Liesegang rings in agates proves that silicates had a gelatinous stage before the ripening of the agate (gelatinous silicate is commonly known as “water-glass”).

Further proof of a gelatinous, deformable precursor of the agate is deformation structures like those in the following picture.

Agate out of Juchem quarry near Idar-Oberstein, Germany – Deformation structures
Rainer Hoffmann-Rothe
http://www.horo-achate.de/seiten_englisch/index_eng.html

However, contemporary geologists seems to have long forgotten that “vein of gelatinous silica” [found in the Simplon tunnel over a hundred years ago] and Liesegang Rings.

Modern geology, apparently, has manufactured their own version of the “immaculate conception” by devising a cunning plan whereby agate rings are formed by the successive “deposition of layers”.

The formation of Agate is most often from deposition of layers of silica filling voids in volcanic vesicles or other cavities.

The layers form in stages with some of new layers providing an alternating color.

Since the cavities are irregularly and uniquely shaped, each Agate forms its own pattern based on the original cavity shape.

When a cavity is completely filled, it forms a solid mass of Agate, but often it is only partially filled, leaving a hollow void which often has crystalline Quartz growths on its innermost layer. This is the cause of Agate forming the outer lining of most geodes.

Hershel Friedman
http://www.minerals.net/mineral/agate.aspx

Geodes can form in any cavity, but the term is usually reserved for more or less rounded formations in igneous and sedimentary rocks, while the more general term “vug” is applied to cavities in fissures and veins. They can form in gas bubbles in igneous rocks, such as vesicles in basaltic lavas, or as in the American Midwest, rounded cavities in sedimentary formations.

After rock around the cavity hardens, dissolved silicates and/or carbonates are deposited on the inside surface.

Over time, this slow feed of mineral constituents from groundwater or hydrothermal solutions allows crystals to form inside the hollow chamber.

Bedrock containing geodes eventually weathers and decomposes, leaving them present at the surface if they are composed of resistant material such as quartz.

http://en.wikipedia.org/wiki/Geodes

The Laguna Agate geode [below] appears to have an entry channel [left hand side] and a restricted exit channel [right hand side] that would allow a “slow feed of mineral constituents from groundwater or hydrothermal solutions” if the geode was originally hollow.

However, the photograph clearly shows that the hollow geode was not filled by successive layers of deposition to the inner surface of the geode.

This is because the proposed first depositional band [the outer band of white agate] that is meant to have initially coated the inside of the hollow geode has evidently blocked both the entry and exit channels [with white agate] so that no more layers could have been deposited in this manner.

Section of a Laguna Agate – John Betts
http://www.johnbetts-fineminerals.com/jhbnyc/mineralmuseum/gallery.php?init=agate

Rainer Hoffmann-Rothe also states that this “theory is easy to disprove” because “one generally observes a structural diversity of adjacent agates”.

According to an old and still accepted theory, silicate rich fluids flow into the cavities caused by EXTERNAL RHYTHMS, such as fluctuation of the ground water level, leaving a thin layer of silicates as coating on the cavity wall. This process reoccurs numerous times to form the agate nodule.

This theory is easy to disprove, as agates that are close together in the same matrix should have similar banding structure.

For example at the Idar-Oberstein basalt quarries in Germany, a full agatized nodule exists close to one filled with calcite, next to a quartz geode, and finally an empty vesicle, all within a distance of one foot.

Clearly, one generally observes a structural diversity of adjacent agates.

Rainer Hoffmann-Rothe
http://www.horo-achate.de/seiten_englisch/index_eng.html

Additionally, it should be noted that silica gel is a preferred medium for growing crystals.

Although this experiment demonstrates rhythmic banding, no crystals will form because gelatin belongs to the class of ‘protective’ colloids; it prevents the direct union of particles.

Silica gel, a nonprotective colloid, is the preferred medium for growing crystals.
…
As previously mentioned, silicon is the highly reactive element that dominates the mineral kingdom. Its negative ions combine with metallic positive ions, such as those of potassium and magnesium, to form the mixtures of salts that constitute many soils, clays and rocks.

Growing Crystals in Silica Gel Mimics Natural Mineralization – C. L. Stong – 1962
http://jesseenterprises.net/amsci/1962/03/1962-03-fs.html

Sandstone
Although natural specimens of gelatinous silica [hydrogel] are rarely encountered the same cannot be said for said for sand because the hydrogel form of sand is more commonly known as quicksand.

Quicksand is a colloid hydrogel consisting of fine granular material (such as sand or silt), clay, and water.

Quicksand forms in saturated loose sand when the sand is suddenly agitated.

When water in the sand cannot escape, it creates a liquefied soil that loses strength and cannot support weight.

Quicksand can form in standing water or in upwards flowing water (as from an artesian spring).

In the case of upwards flowing water, seepage forces oppose the force of gravity and suspend the soil particles.

Given that reactants [even human beings] are prone to falling into quicksand it is easy to envisage the optimal laboratory condition [for the development of Liesegang Rings] occurring naturally when the quicksand dehydrates and starts to form sandstone.

Sandstone frequently forms discrete blocks and spherical shapes [concretions] which would appear to be ideal closed systems for the development of Liesegang Rings.

A concretion is a hard, compact mass of sedimentary rock formed by the precipitation of mineral cement within the spaces between the sediment grains.

Concretions are often ovoid or spherical in shape, although irregular shapes also occur.

The word ‘concretion’ is derived from the Latin con meaning ‘together’ and crescere meaning ‘to grow’.

Concretions form within layers of sedimentary strata that have already been deposited.

They usually form early in the burial history of the sediment, before the rest of the sediment is hardened into rock.

This concretionary cement often makes the concretion harder and more resistant to weathering than the host stratum.

http://en.wikipedia.org/wiki/Concretions

Unsurprisingly, Liesegang Rings are frequently encountered in sandstone.

This is a photograph of one of the broken spheres showing rings of an iron mineral called goethite (hydrated iron oxide). We have enough information to make an interpretation.

Recall my previous entry on the spotted sandstone. In that case a bit of rotting organic matter reduced the iron in the rock to form a green spot.

The rock spheres at this site are caused by a bit of organic material that changes the chemistry of the water in the sandstone, causing precipitation of iron minerals.

The banding is called Liesegang and you can read all about them by putting in “liesegang rings” into Google.

Paleontology with The Houston Museum of Natural Science
http://hmnspaleo.blogspot.com.es/2007/12/neal-immega-permian-pool-table.html

Liesegang rings comprised of iron oxide in sandstone from a chamber in Petra, Jordan.

Unsurprisingly, some Liesegang Rings [in sandstone] may be caused by an external reactant that causes “concretion growth from a set radius toward the centers”.

Our model proposes that concretions precipitate initially as an amorphous HFO that sets the radius and retains some original porosity.

Subsequent precipitation fills remaining pore space with younger mineral phases.

Inward digitate cement crystal growth corroborates concretion growth from a set radius toward the centers.

Internal structure is modified during late stage precipitation that diffuses reactants through semi-permeable rinds and overprints the interiors with younger cements.

Characterization of Navajo Sandstone concretions:
Mars comparison and criteria for distinguishing diagenetic origins
Sally L Pottera, Marjorie A. Chana, Erich U. Petersena, M. Darby Dyarb, Elizabeth Skluteb
University of Utah, Department of Geology and Geophysics

Earth and Planetary Science Letters – Volume 301, Issues 3–4, 15 January 2011
http://www.sciencedirect.com/science/article/pii/S0012821X1000734X

However, what is very surprising is that mainstream geology seems very keen to avoid mentioning the quicksand hydrogel.

The strange concentric and elongate structures are termed Liesegang Banding and are caused by iron-rich ground-waters passing through soft sands before they have been cemented into sandstone.

Diagenetically banded sandstones are dominated by bands of quartz cement that formed as a result of chemical compaction, quartz dissolution, and quartz precipitation during burial.

http://archives.datapages.com/data/specpubs/memoir61/ch13/0179.htm

Some sources [misguidedly] state Liesegang Rings only form after the rock is formed.

Liesegang (“LEEZ-gahng”) bands or rings are curving lines or ribbons of dark-brown iron minerals that form in sandstones and some other rocks after the rock is lithified..

http://geology.about.com/od/fossilbasics/ss/Pseudofossils_6.htm

In sedimentary rocks, Liesegang bands appear well after the sediment has become a rock (that is, it got compacted and cemented)

http://zsylvester.blogspot.com.es/2008/11/liesegang-bands-in-sandstone.html

One can charitably assume that these sources have only observed Liesegang Rings that have formed after groundwater has flowed through rock fractures – as in this photograph of granite.

Liesegang banding from groundwater flow in granite.

Note the concentration of iron oxide discoloration tends to be along fractures, sites of increased groundwater flow.

http://www.marlimillerphoto.com/G-24.html

A less charitable view might conclude that there are [at least] three questions geologists don’t want to be asked:

1) Where did the sand in the Sahara come from?

2) Where did the sand in sandstone come from?

3) Where did the water on Earth come from?

This is primarily because:

a) The Liesegang Ring evidence in sandstones strongly suggests that sandstone [primarily] formed from the hydrogel called quicksand.

b) The vast quantities of sandstone strongly suggest vast quantities of precursor quicksand.

c) The vast quantities of precursor quicksand strongly suggest vast quantities of silica rich “upwards flowing water” [Quicksand – Wikipedia] from within the Earth.

Six kilometres of sandstone and shale lie under Sydney.

In Sydney sandstone, the ripple marks from the ancient river that brought the grains of sand are distinctive and easily seen, telling geologists that the sand comes from rocks formed between 500 to 700 million years ago far to the south. This means that the highest part of the visible lines almost always faces approximately south.

It is a very porous stone and acts as a giant filter.

It is composed of very pure silica grains and a small amount of the iron mineral siderite in varying proportions, bound with a clay matrix. It oxidises to the warm yellow-brown colour that is notable in the buildings which are constructed of it.

http://en.wikipedia.org/wiki/Hawkesbury_Sandstone

Sandstone at Flint & Steel beach, Hawkesbury River, Australia

Crystal Inclusions
Studying Liesegang Phenomena in the laboratory is frequently associated with the formation of crystals.

Liesegang bands: colloidal gold (left) and copper chromate (right), with many gold and copper-chromate crystals also visible.

Salts React in a Gel to Make the Colorful Liesegang Bands – C. L. Stong – 1969
http://jesseenterprises.net/amsci/1969/06/1969-06-body.html

This associated is replicated in nature where, for example, quartz may contain crystals [and suspensions] of gold.

The piece features small, but absolutely superb, razor-sharp, highly lustrous, incredibly well formed, striated octahedral crystals of Gold which are nestled into a small vug of Quartz and are associated with minor sulfides.

Materials that are trapped inside another mineral are called inclusions.

However, geology does not associate inclusions with Liesegang Phenomena because Hutton’s law states that “fragments included in a host rock are older than the host rock itself.”

In mineralogy, an inclusion is any material that is trapped inside a mineral during its formation.
…
According to Hutton’s law of inclusions, fragments included in a host rock are older than the host rock itself.
…
Mineralogy
Inclusions are usually other minerals or rocks, but may also be water, gas or petroleum. Liquid or vapor inclusions are known as fluid inclusions. In the case of amber it is possible to find insects and plants as inclusions.

The analysis of atmospheric gas bubbles as inclusions in ice cores is an important tool in the study of climate change.

A xenolith is a pre-existing rock which has been picked up by a lava flow.

Melt inclusions form when bits of melt become trapped inside crystals as they form in the melt.

http://en.wikipedia.org/wiki/Inclusion_%28mineral%29

Unfortunately, Hutton’s Law is unlikely to be universally true for [at least] the case of gold crystals in quartz.

Herbert Freundlich, a specialist in colloidal chemistry, reports that gold crystals up to two millimeters in diameter have been grown in a gel containing sodium chloride and maintained at a temperature of 70 degrees centigrade.

He also states that the gold will deposit as a sheet at the interface between the gel and the oxalic acid, if the concentration of acid is low.

This suggests that many gold deposits in quartz could originally have been deposited in natural silica gel, because we have reason to suppose that high temperatures and an ample supply of reducing agents must have been present during eras of mineralization.

Growing Crystals in Silica Gel Mimics Natural Mineralization – C. L. Stong – 1962
http://jesseenterprises.net/amsci/1962/03/1962-03-fs.html

Luckily gemmologists are interested in inclusions [because they effect the valuation of gem stones] and enjoy photographing their collections.

Intriguing, some gem stones reveal spiral inclusions which appear to be Liesegang helices.

Kunzite spodumene with helical inclusion

Photo: Jeff Scovil
http://www.mineral-forum.com/message-board/viewtopic.php?p=30112

Aguamarine with spiral inclusions
Specimen: François Lietard Photograph: Joaquim Callén
http://www.foro-minerales.com/forum/viewtopic.php?p=49923#49923

Unfortunately, mainstream academia seems to have simply ignored these spiral inclusions.

Related Post
Researchers interested in Saharan Sand might find it worthwhile reviewing the colour coding of the volcanoes in the Canaries – especially Mount Teide.

See: https://malagabay.wordpress.com/2016/10/13/the-arabian-horizon-the-dry-deluge/

Related Post

The tubular concretions at Pobiti Kamani stand in sands and sandstones.
They probably formed in quicksand sustained by a “rising methane-bearing fluid plume”.