Natural Phosphates

Phosphates, Natural

 

a class of minerals of the salts of orthophosphoric acid, H3PO4, with highly variable composition. There are about 180 phosphate minerals; middle salts, for example, xenotime, Y[PO4], and monazite, are rare. Natural phosphates are primarily complex compounds with two or more cations [for example, Ca2+, Fe2+, Fe3+, Al3+, (UO2)2+, Cu2+, Mn2+, Pb2+, and Zn2+] and additional anions (OH, Cl, F, O2–, CO32 –) or molecular water. Their composition rarely includes acid radicals, such as [SO4]2–, [SiO4]2–, and [BO3]3–. Certain natural phosphates are acid salts of the type resembling monetite, CaHPO4.

The basic crystal structure of natural phosphates consists of insular [PO4]3– tetrahedral units attached to one another by salt-forming cations. According to the nature of the spatial distribution of the attached [PO4]3– tetrahedrons and cation polyhedra, natural phosphates are classified as insular (predominant type), chain, layered, or skeletal.

Natural phosphates occur in the form of massive granular aggregates, earthy masses, oolites, concretions, and incrustations; they sometimes occur in the form of faceted crystals. The coloration is varied. Natural phosphates have a Mohs’ hardness ranging from 2 (for many aqueous natural phosphates) to 5–6 and a density ranging from 1,700 to 7,100 kg/m3.

Natural phosphates are generally disseminated in rocks. The most widely distributed minerals of practical value are apatite (also a constituent of phosphorites), torbernite, autunite, vivianite (Fe2+, Fe3+)[PO4]8H2O, monazite, xenotime, amblygonite LiAl[PO4](F,OH), and turquoise.

Natural phosphates are primarily formed in the upper part of the earth’s crust—on ocean and lake bottoms, in swamps, in soils, and in weathering crusts—as well as in the oxidation zone of many ore deposits. Some natural phosphates are of magmatic origin, for example, apatite associated with alkaline igneous rocks and monazite and xenotime associated with pegmatites and granites. A number of natural phosphates occur as accessory minerals in hydrothermal veins.

Natural phosphates are used as phosphate ores (apatite and phosphorite). Some natural phosphates have a more limited application; for example, vivianite is used as an inexpensive blue pigment and local phosphorus fertilizer, monazite as a source of rare earths and thorium, amblygonite as a lithium ore, and turquoise as an ornamental stone.

REFERENCES

Godovikov, A. A. Mineralogiia. Moscow, 1975.

G. P. BARSANOV and A. I. PEREL’MAN

References in periodicals archive ?
However, these studies do not mention the use of natural phosphates.
The viability of these sources is related to the existence of large deposits of natural phosphate, with low cost (Silva et al.
With respect to the study of phosphate fertilization using natural phosphate as a P source, the jatropha crop is not mentioned in the literature.
For field conditions, there are no conclusive results on the best dose of cattle manure and natural phosphate to promote adequate nutritional balance for jatropha.
This study aimed to evaluate the nutritional status of jatropha plants fertilized with cattle manure and natural phosphate under rainfed conditions.
1]) and 4 doses of natural phosphate (0, 250, 500 and 750 kg [ha.
The natural phosphate (from Araxa, MG) was chemically analysed in the Laboratory of Soil and Water Analysis of the Sao Paulo State University "Julio Mesquita Filho" (UNESP), at the campus of Jaboticabal-SP, and showed N [less than or equal to] 1 g [kg.
Sixteen months after applying the treatments with cattle manure and natural phosphate (August 2011), the soil was sampled under the canopy projection in the layer of 0-20 cm and showed no acidity, medium content of organic matter, high content of P and absence of exchangeable Al (Table 1).
The application of cattle manure and natural phosphate caused significant interactions on leaf contents of N, K, Ca, Mg and S (Table 2).
Leaf N contents increased quadratically in the absence of natural phosphate and linearly for the other phosphate doses (Figure 2A).
They demonstrated that the degradation of SPP by natural phosphates in freshly ground pork contributes to its ineffectiveness against L.
Other gardeners, knowing the ignorance of using artificial fertilizers, spread bags of crushed rock powders, natural phosphates and other soil amendments, relying on the natural minerals, while many older gardeners just add mulch each year and state that any tillage of their garden is unnecessary.