Origin of the word 'zeolite'

In 1756, the mineralogist Baron Crönstedt discovered Stilbite. This mineral gave off water during heating which gave the impression that it was boiling. Crönsted gave it the name "zeolite", from the Greek "zeo", which means "to boil", and "lithos" which means "stone". Since this initial discovery, the zeolite family has grown.

 

Natural or synthetic zeolite?

There are more than 170 zeolites but only about thirty of them are formed naturally. The others are obtained artificially in laboratories and some are produced industrially. These are known as "synthetic zeolites".

Natural zeolites originate from volcanic ash which is transformed into rock. Of the thirty or so natural zeolites, only seven are found in sufficiently large deposits to allow their commercial exploitation.

The purity and the nature of impurities varies from one deposit to another, and this affects the physico-chemical properties of each natural zeolite.

 

Zeolite or zeolitic tuff?

In the case of natural zeolites, mineralogists have adopted the practice of naming a rock according to the name of the mineral which is present in the highest concentration, on condition that this mineral represents at least 50% of the rocks composition. We therefore give the name clinoptilolite, mordenite or chabasite, for example, to rock which is composed of more than 50% of these minerals which are all from the zeolite family.

As with any natural material, the quality varies from one place to another. With zeolite, the purity is almost always different from one deposit to another, which is why we find clinoptilolite on the market ranging from 55 to 85%!

The other minerals which are present in the rock can be described as "impurities" and they are of great importance. Depending on their nature and concentration, they determine in which field of applications the rock can be used. For example, we can find two rock types from two different deposits which are both classified as identical natural zeolites, but they are not suitable for the same applications.

We use the term zeolitic tuff in the case of rock which contains less than 50% of a given zeolite. In horticultural applications for example, some improvements can be observed due to the presence of zeolite in the rock, but these tuffs are clearly inferior to a true zeolite rock.

 

Definition and structures of zeolites

Zeolites are aluminosilicates from the silicate mineral group and the tectosilicate sub group. They are not clays, which do form part of the same silicate group, but pertain to a different sub group.

Their structure is a three dimensional arrangement of SiO4 and AlO4 tetrahedra, linked by oxygen atoms. In the case of the AlO4tetrahedra, the trivalent aluminium atom is positively charged (3 +) and is surrounded by four oxygen atoms which each carry a single negative charge. The AlO4 tetrahedra therefore carries a single negative charge which must be balanced by the presence a positively charged species or cation. The empirical formula for zeolites is written as follows: M2/nO Al2O3 xSiO2 yH2O. M is the cation, of valency n, which assures the electroneutrality within the molecular structure. Typically this cation will be an alkali metal or alkali earth metal (Na+, Ca+, K+) but it can also be a heavy metal (lead, copper, nickel, cobalt, cesium…), non-metal (H+, NH4+) or an organic species. Zeolites are cation exchangers.

The layout of the SiO4 and AlO4 tetrahedra, which is similar to the cage-like structure of sodalite or pentasil, gives rise to an open cage-like configuration of channels, cavities and pores. Zeolites are therefore micro-porous minerals.

This micro-porosity gives zeolites a very large specific surface area which varies between 20 to 800 m2/g. Depending on the type of zeolite, the size and shape of the cavities range from 6,6 Å to 13 Å and the channels or pore sizes range from 2,5 to 20 Å.

 

Applications of zeolites

The physico-chemical properties of zeolites, the most complex of all minerals, determines their wide range of applications (animal nutrition, water treatment, gas adsorption, paper industry, nuclear, petrochemical, etc).

Around 300 potential applications have been cited for all types of zeolite. In the case of natural zeolites, agriculture represents about 70% of global consumption (animal bedding, animal feed additives, horticulture, soil amendment). The remaining 30 % is made up of diverse applications such as: water treatment, odour elimination, support for pesticides, gas treatment or separation, catalysis, construction materials, aquaculture, etc.

Synthetic zeolites have numerous industrial applications (catalysis, gas adsorption, nitrogen and oxygen production…), although the most important application is the global production of detergents and washing powders.

 

Which is the best zeolite for bonsai cultivation?

There are several types of natural zeolites, however, CHABASITE is by far the best because of its porosity, low density, high ion exchange capacity and water retention capacity. These are all essential characteristics for the harmonious growth of bonsai trees.

 

Are there several types of chabasite for bonsai cultivation?

No ! There are very few chabasite quarries around the world. Chabasai® comes from the only deposit which is of suitable quality for bonsai cultivation.

Some rock is falsely classified as chabasite simply because it contains a small amount of chabasite. This is the case for the ‘chabasites’ found in the south of Italy for example. In fact, these deposits barely contain 30% chabasite. Furthermore, the mechanical properties of these tuffs are relatively poor.

Other chabasites such as those found in the Americas are rich in sodium and are therefore totally unsuitable for any kind of horticultural application.

 

Is it possible to use any kind of zeolite for bonsai cultivation?

NO !!! Definitely not ! There are numerous types of natural and synthetic zeolites. Some are suitable for horticultural use but others are dangerous for vegetation. Even in the case of a single zeolite type, there can be contradictions. For example, it is possible to find chabasites which are rich in sodium which is very harmful to plants, whereas chabasai® contains practically none at all !

 

What guarantee of quality does chabasai® have?

chabasai® is a registered trademark of SOMEZ (Société Méditerranéenne des Zéolithes). Created in 1984, SOMEZ is the oldest natural zeolite specialist in Europe, and one of the oldest still in existence in the whole world. SOMEZ is considered as one of the leading specialists in natural zeolites and their applications. The company offers the largest range of natural zeolites in the world combined with the technical know-how to use these zeolites in a wide range of application areas.

The competence and quality demands of SOMEZ are widely recognised and this is a guarantee of quality. Furthermore, chabasai® has been subjected to a long technical validation process.

Particular care is taken during each stage of crushing, drying and conditioning in order to make chabasai® the most effective substrate possible for the cultivation of bonsai trees.