Zeolites (SiO2) are a group of hydrated aluminosilicate minerals belonging to tectosilicates, chemically they are made up of SiO4 and AlO4 structures which repel each other and form large interconnection spaces which are very open; These structures retain Na, Ca or K ions, and as water molecules linked by hydrogen bonds to the cations of the structure originated by the leaching action of hot springs on feldspars or feldspathoids.
Characteristics and physical properties of zeolite
The zeolites In general, they are composed of aluminum, silicon, sodium, calcium, magnesium, potassium and water. Physical properties provide unique aspects for a wide variety of practical applications, they present the following properties:
| Zeolites | Characteristics and physical properties |
| Class | Silicate |
| Cluster | aluminosilicates (tectosilicate) |
| Chemical formula | M2/nO.Al2O3.xSiO2.yH2O [M: is a cation of valence n; “x” is the number of aluminum atoms and takes values between 2 and 10; “y” is the number of silicon atoms and takes values between 2 and 8] |
| Origin and geological environment | They are characteristically found in low-temperature hydrothermal systems, especially in volcanic igneous rocks, but also in a wide range of other rock types, typically feldspathic. |
| Associated minerals | Apophyllite, calcite, cavansite, prehnite, epidote, quartz, pyrite, clay minerals. |
| associated rocks | Volcanic igneous rocks, sedimentary and metamorphic rocks. |
| Density | Low density and a large volume when dehydrated. |
| Hydration | High degree of hydration. |
| Stability | Very stable. |
| cation exchange | High cation exchange capacity |
| Molecular structure | uniform molecular channels |
| adsorptive property | High adsorptive capacity |
| form of identification | They boil when calcined. |
| Applications | They are usually used and sold as commercial absorbents, the coloring of liquids and gases, as a beneficiary for our body, as well as the control of contamination (pollution). This has led to the existence of a commercial production of zeolites artificial of particular characteristics. important technical applications. |
The zeolites natural are among the most common autogenous minerals in sedimentary rocks; however, it must be said that they are formed in a wide range of rocks of different origins, age and geological deposition environment, being their presence in these environments, precisely, what has constituted a direct and modern criterion for their classification.
Zeolites in thin film
One way to identify these minerals is by thin sheets, so the zeolite in natural light appears colorless, habit: tabular, fibrous, leafy, fills cavities or alters other minerals as well as a relief: moderate to low.
Origin, formation and geological environment of zeolites.
The zeolites They form in sediments or rocks, varying physical and chemical environments.
Genetically, the classification of occurrence is based on the temperature at which it is formed, since it is an important factor for the control of formation; Another significant factor is the chemistry of water in a rock with porosity where particles precipitate. zeolites.
Furthermore, the species of zeolite is influenced by the parent material in which it is formed.
There are nine genetic types in which they are classified.
High temperature zeolites caused by the geothermal gradient
| Magmatic or primary zeolites | Unique analcime that crystallizes from a magma in alkaline basic intrusive rocks, at a temperature of 600 to 640 °C and pressures of 5 to 13 Kbar |
| From contact metamorphism | It is found along contact halos caused by vulcano-plutonic complexes that were driven into a thick sequence of porous tephra, volcanic sediment, or feldspathic sandstone. |
| hydrothermal | The zeolite assemblage and zone are primarily controlled by temperature and chemical composition of the host rocks and subordinated by permeability, composition of geothermal fluids, and age of the geothermal area and host rocks. |
| by diagenesis | Corresponds to the crystallization of a mineral by alteration of pre-existing elements of the sediment through low temperature conditions (200 °C). |
Chemical Gradient Influenced Surface Zeolites
| groundwater seepage | The formation of these zeolites It is a consequence of the reaction between the box rock and the water table, made up of water of meteoric origin. |
| weathering | These are described because of the slow percolation of meteoric water through a body of rock. |
| Saline lake and alkali deposits | By dissolution of silicate minerals and by evaporation, therefore, the water becomes a basic type solution, rich in alkalis (brine) with pH 9 |
low temperature zeolites
| marine environment | These (clinoptilolite, phillipsite) are found forming layers within a seabed clay |
Zeolites forming in impact crater
| impact crater | In this type are the following varieties of zeolites : analcime, erionite and clinoptilolite; as subordinate species: chabasite, filipsite and stilbite |
Zeolite classification
They constitute the most varied and extensive mineral group of those that form the earth’s crust.
206 types of zeolites due to its structure, of which more than 40 are natural; the rest are synthetic.
The zeolites Natural rocks were formed as a result of volcanic eruptions by hydrothermal reactions of silicon-rich and alkali-rich volcanic rocks.
The basic groups of zeolite are:
- Philipsita group
- Analcite group
- natrolite group
- modernite group
- chabasite group
- faujasite group
- heulandite group
- laumontite group
You can look at the following graph to better understand its classification.
How to identify zeolites?
A table is presented to help you identify the zeolites.
| zeolite group | Identification features |
| Laumontite and Analcima Group | They have a cubic habit, with white, gray and yellowish colors. |
| Philipsita group | It contains double rings of four members connected to each other in the form of a zig-zag chain (similar to those of feldspars). White colors Pseudorhombic prismatic habit |
| chabasite group | This group of minerals contains large cavities, which can be described as octahedrons or truncated cubo-octahedrons. |
| modernite group | Structures that can be considered as sheets formed by rings of six tetrahedrons, with pairs of tetrahedrons attached in turn to these rings. |
| natrolite group | Chain-based structure and all members of this group have fibrous habits. |
| heulandite group | They present a laminar structure, which is reflected in their tabular morphology. |
Zeolite scan?
Most of the deposits zeolites they are observed in analcime-rich halos surrounding Kuroko-type mineralization in Cretaceous or younger sediments or rocks.
The thickness of the analtop alteration may be a clue to the location of deeply embedded mineral bodies. The uranium concentration is also related to the presence of heulandite-clinoptilolite zeolite in tuffaceous sandstone rocks.
Oxidized uranium in groundwater is presumed to have been fixed by adsorption on zeolite, which in some areas contains more than 0.9% uranium.
Due to the crystal size (generally less than 20 microns) they cannot be identified in the field.
X-ray diffraction analysis of bulk samples is the method generally used for their identification in sedimentary rocks; This method also allows a semi-quantitative estimate of the abundance of the species to be made. zeolites and associated minerals in the sample
Zeolite Uses
- The zeolite It has several uses in different industries:
- Food supplement to fatten fish, cattle, sometimes without excess, to soften industrial and domestic water
- Loads in the paper industry to improve print quality, gloss contribution, opacity, retention and whiteness
- lightweight aggregates under construction
- Ionic exchangers for decontaminating water purification of solid, liquid and gaseous waste
- Catalysts and Catalyst Supports Using: Methanol to Gasoline, Alkylation, C8 Aromatics Isomerization, Polymerization, Organic Synthesis, and Inorganic Chemistry
- Supports fertilizers and soil conditioners
- Acid resistant adsorbents in gas drying
- As a retainer-distributor of nitric oxide (NO) in the human organism for the stabilization of blood pressure, treatment of thrombosis (coagulation in blood vessels); as an antibiotic agent, as well as for the control of kidney diseases
- In the manufacture of soda-lime glasses
- In the manufacture of cosmetics and in the pharmaceutical industry.