**7.2.1. Phosphate rock deposits**

In general, phosphate rock reserves are non-metallic ores21 that can be economically pro‐ duced at the present time using existing technology. Phosphate rock resources include reserves and any other materials of interest that are not reserves. A reserve base is a portion of the resource from which future reserves may be developed. The classification applying to phosphate rocks include [23].


The most known Miocene phosphate deposits (**Table 1**) are in North Carolina, Florida, Venezuela, California, Baja California and Peru. In several cases, these emerged deposits are only the up dip limit of a larger Miocene section that extends seaward beyond the coastal plain and constitute large portions of the upper sediment regime that built the modern continen‐ tal shelves [26].


**Table 3.** Grades of apatite deposits [25].

<sup>21</sup> Ores of economic value can be classified as metallic or non-metallic according to the use of the mineral. Certain minerals may be mined and processed for more than one purpose. In one category, the mineral may be metal and non-metallic ore, e.g. bauxite used for the production of aluminum and ceramics, respectively [62].

**7.2.1. Phosphate rock deposits**

phosphate rocks include [23].

of P2O5 is listed in **Table 4**.

**Table 3.** Grades of apatite deposits [25].

**Grade P2O5 [wt.%] BLP [%] Location**

tional.

tal shelves [26].

In general, phosphate rock reserves are non-metallic ores21

352 Apatites and their Synthetic Analogues - Synthesis, Structure, Properties and Applications

duced at the present time using existing technology. Phosphate rock resources include reserves and any other materials of interest that are not reserves. A reserve base is a portion of the resource from which future reserves may be developed. The classification applying to

**• Resource** is defined as a concentration of naturally occurring phosphate material in such a form or amount for which the economic extraction of a product is currently or potentially feasible. The resources are divided into many categories depending on the amount of pertinent information available to define the amount of material potentially available and

**• Reserve base** is the part of an identified resource that meets the minimum criteria related to current mining and production practices including grade, quality, thickness and depth.

**• Reserves** are the part of the reserve base that can be economically extracted or produced at the time of the determination. They may be termed as marginal, inferred or inferred marginal reserves. This does not signify that the extraction facilities are in place or func‐

**•** The grades of apatite deposits from the economic point of view are introduced in **Table 3**. The locations of the world's phosphate deposits are shown in **Fig. 9** and the average content

The most known Miocene phosphate deposits (**Table 1**) are in North Carolina, Florida, Venezuela, California, Baja California and Peru. In several cases, these emerged deposits are only the up dip limit of a larger Miocene section that extends seaward beyond the coastal plain and constitute large portions of the upper sediment regime that built the modern continen‐

and Palabora crystalline igneous apatites

1Economic 20 40.70 Florida and Moroccan sedimentary phosphorites, Kola

2Sub-economic 5 – 20 10.93 – 40.70 Western USA phosphoria, Russia nepheline-apatites

4Non-phosphatic 0.1 – 1.0 0.22 – 2.19 Widely distributed apatite in almost all igneous rocks

21 Ores of economic value can be classified as metallic or non-metallic according to the use of the mineral. Certain minerals may be mined and processed for more than one purpose. In one category, the mineral may be metal and non-metallic

3Non-economic 1 – 5 2.19 – 10.93 Low-grade ores, phosphatic limestones

ore, e.g. bauxite used for the production of aluminum and ceramics, respectively [62].

if it is economic, marginally economic or sub-economic to exploit these resources.

that can be economically pro‐

**Fig. 9.** The overview of the world's phosphate deposits (a) [20] and the location of the major phosphate rock-producing areas of some known deposits (b) [26],[63].

Locally, these Miocene sediments are exposed on the seafloor; however, generally, they are buried below thin covers of Plio-Pleistocene and Holocene surface sediments. Thus, there is high potential for discovering new phosphate deposits within the Miocene sediments on the world's continental shelves, because [26]:



**Table 4.** Grades of apatite deposits [25].

Two important sediment relationships were developed concerning reworked phosphate in surficial sediments on the North Carolina continental shelf [26],[63]:


**Fig. 10.** The history of the discovery of the world's phosphate resources [22].

These relationships were also recognized on the shelves of northwest and southwest Africa and could represent important exploration tools for richer Tertiary22 phosphorites occurring within the shallow subsurface on many continental shelves in the world [26].

<sup>22</sup> The term Tertiary (geologic period from 66 to 2.58 ma) is no longer recognized by the International Commission on Stratigraphy.

The deposits of apatite of igneous origin occur as intrusive masses or sheets, as hydrother‐ mal veins or disseminated replacements, as marginal differentiations along or near the boundaries of intrusions or as pegmatites. Intrusive masses are the largest of these deposits. They are commonly associated with alkalic igneous rock complexes, many of which such as those in Africa, Brazil and Sweden are associated with the rift valley structures. Carbonatite, ijolite, nepheline-syenite and pyroxenite are common members of the rock assemblage. Many of these complexes have a ring like structure, with carbonatite as the central core [27].

Phosphate deposits have been discovered within the past 100 years at the rate far greater than the rate of consumption (**Fig. 10**). Since new phosphate deposits are expected to be discov‐ ered in the future, the oil exploration programs have probed most of the coastal sedimentary basins of the world during the past 20 – 30 years, and any large-scale discoveries of phos‐ phate rock would probably have occurred in conjunction with these activities [22].
