Formation and Types
How is Zeolite Formed?
Natural occurring zeolite is a crystalline mineral that has been formed from volcanic ash generally over a period of between 50 to more than 350 million years ago. During this time there were many violent volcanic eruptions ejecting millions of tonnes of ash into the air which fell on both land (to form topsoil) and into water where most was dissipated. But in the right conditions, in a few locations, natural zeolite deposits were formed.
To appreciate the uniqueness of zeolite deposits it is necessary to understand the complex formation conditions that needed to be present and the precise order in which they occurred.
These conditions and their order of occurrence are:-
1 After the eruption a thick layer of ash drifted far enough away from the eruption site so that all the heavy particles drop out and the ash looks and behaves more like snowflakes than minute rock particles;
2 The ash must be composed of amorphous silica glass (called obsidian);
3 The ash must fall, or be washed into water;
4 The water must be stationary and brackish (i.e. neither fresh nor salt water);
5 The brackish water must have had the right type of various alkaline salts;
6 The environment around the deposit must have been stable for a very long period (at least half a million years);
7 This stability allows the amorphous glass to slowly re-crystallise and absorb the salts from the surrounding water;
8 The ratio and concentrations of the various salts causes the formation of alumino-silicate crystals, a feature necessary to build the honeycomb structure of the zeolite;
9 The deposit needs to have been placed under great pressure over at least 5 - 10 million years to allow it to be compress into a hard rock;
10 Later the deposits need to have been uplifted, preferably to where it was still covered by overburden (silt) and above where any subsequent flowing surface or sub-surface water would not contaminate it.
A good example to explain the way zeolite is formed is to compare it to the formation of ice. When snow falls it is light and fluffy, filled with air pockets. As the flakes accumulate they start to compact into a substance that takes on a crystallised form but is still easily crush in one’s hand, snow. However, as the weight of snow increases, it compacts further into a solid substance, ice.
Volcanic ash is very similar. It can also fall very quickly and can cover everything on the ground in matter of hours with heavy chocking particles many meters deep. Remember the scenes of the 1991 explosion of the Mt. Pinatubo volcano in the Philippines, where the American military facilities had to be abandoned because of the tonnes of ash falling every hour. The same sort of eruption buried the towns of Pompeii and Herculaneum in Italy over 2,000 years ago in 79AD.
Where are Zeolites Located?
Zeolites are located all over the world. However they all vary in purity and density which affects their structure and their potential effectiveness even though they appear very similar in their mineral profile. The way they were deposited varies greatly from one deposit to another. For example many zeolites in North America are only about 30-50 million years old and have been deposited in small layers with other clay materials deposited in between. This is due to the fact that they were formed from many individual eruptions of short duration over a long period, whereas the Australian deposit appears to have been formed from one continuing eruption over a much longer period. That is why the Australian zeolite we use is in a seam which is over ten meters thick. [refer to the photos on the ‘why Australian zeolite’ page].
What are the Different Zeolite Types?
There are 46 naturally occurring zeolites that are known. There are more than 150 zeolite types that have been synthesised (produced artificially). Although natural zeolites form a large family most of them can be divided into three distinct types;-
The three basic types are;-
(a) The first group contain zeolites that have chain–like structures made up of needle prismatic crystals. Asbestos, mica and serpentine have similar type crystal structures.
(b) Structures resembling sheets where the crystals are flattened much like looking at a deck of cards, each card being a sheet. Clinoptilolite and mordenite are two examples of these.
(c) Structures where the crystals are more equal in dimensions, more like cubes. Chabazite is a well know zeolite of this type.
Clinoptilolite is the zeolite type we use. It is pronounced [Clin (as in pin) op (as in shop) til (till) o (as in hoe) lite (light).
Some of the other more common known zeolites are: analcime, chabazite, clinoptilolite, heulandite, mordenite, natrolite, phillipsite, and stilbite. They all have some amounts of aluminium, sodium, silicon and oxygen in their formulas.
Clinoptilolite is a sheet zeolite and sheet zeolites are considered completely safe and non-toxic because their crystals tend to be rounded. Overseas scientific research over a long period of time has indicated that they cause no internal damage if they are ingested or inhaled, see our science web site information <safety and toxicity>.
Zeolite can best be described as a chelating agent. The term chelation [key-lay-shun] means a substance (usually negatively charged) that can attract (electro-chemically bond with) toxic minerals, metals and other materials within a fluid. Being in liquid form allows the body to dispose of them naturally.
Naturally occurring zeolites are rarely pure and are often contaminated to varying degrees by other minerals, such as clays, gypsum, erionite, quartz or other zeolites. Many occur naturally as minerals and are extensively mined in many parts of the world. Others are synthetic, and are made commercially for specific industrial uses [see uses].
Synthetic zeolites are far purer than natural zeolites as they are made in the laboratory and therefore have no natural contaminants and all their cages are identical in size and shape to one another. Unfortunately their cages are smaller than natural zeolites due to the difficulty of the manufacturing process. They are manufactured to fulfil very specific roles and therefore they are not as robust and efficient in absorbing many different types of toxic contaminants that one would find in the human body. They are widely used as catalysts in the extraction of specific products and gasses for the petrochemical industry.