Phosphorus was discovered in 1669 by Hennig Brand The word phosphorus originates from the two Greek words phos , meaning light, and phoros , meaning bearer, due to the phosphorescent nature of white phosphorus Phosphorus is the tenth most abundant element on Earth and tends to be concentrated in igneous rocks It is an incompatible element in common rock-forming minerals, and hence is susceptible to concentration via fractionation in geochemical processes It reaches its highest abundance in sedimentary rocks: the major constituents of phosphorite are the minerals of the apatite group Phosphorus is the second most abundant inorganic element in our bodies (after Ca); it makes up about 1% of our body weight, occurring primarily in bones and teeth Phosphorus (atomic number 15) is a non-metal in group VA of the periodic table, and has the ground-state electronic configuration 1 s 2 2 s 2 2 p 6 3 s 2 3 p x1 3 p y1 3 p z1 or [Ne]3 s 23 p 3 There are three orbitals occupied with only one electron each in the third energy level (the M shell) Phosphorus participates in essentially covalent bonds; electron gain to form P3− from P requires considerable energy (on the order of 1450 kJ mol−1) Loss of electrons is also difficult due to the high ionization potentials of P (the sum of the first three ionization potentials is 604 eV)

Here we use bond-valence theory (Brown 1981) and its developments (Hawthorne 1985a, 1994, 1997) to consider structure topology and hierarchical classification of crystal structures, and we point out that bond-valence theory can be considered as a simple form of molecular-orbital theory (Burdett and Hawthorne 1993; Hawthorne 1994, 1997)

The variation of P-ϕ (ϕ: O2−, …

The Crystal Chemistry of the Phosphate Minerals

The geochemistry of the alkali metals

Beryllium is one of the most widespread rare elements in granitic pegmatites. These rocks have been historically the sole industrial source of this metal (e.g., Norton et al. 1958), and they still contribute a significant proportion of the global output of beryllium ores. Hand-cobbed beryl constitutes a substantial proportion of beryllium ore concentrates in Africa, Asia and South America, although non-pegmatitic, rhyolite-related bertrandite ores are virtually the single source in North America (Petkof 1975).

The mineralogy of beryllium in granitic pegmatites is strongly diversified, but very “imbalanced” in terms of numbers of species per mineral class on one hand and of the paragenetic role, distribution and abundances on the other. Only a very few Be minerals form at the magmatic stage of pegmatite consolidation, with beryl absolutely dominant among them. Phosphates constitute most of the late subsolidus phases, with silicates a close second, but the number of the phosphate occurrences is very low and volumes are negligible. A few oxide, hydroxide and borate minerals complement the spectrum. So far, no other mineral classes are represented, although the occurrence of some arsenates is considered possible.

Part of the reason for the pattern above is the crystal-chemical behavior of Be, one of the classic amphoteric elements, which acts as a cation in acidic environments but participates in complex anions under alkaline conditions. Thus beryllo(alumino)silicates and beryllo-phosphates of alkali and alkaline-earth cations are widespread, in contrast to silicates or phosphates of beryllium with no other cations, or Al only. Be2+ is always tetrahedrally coordinated with oxygen (BeO4)6−, or with oxygen and hydroxyl (BeO3OH)5−.

The divalent charge on Be renders substitutions for other tetrahedrally coordinated oxycomplex-forming cations, such as Si, Al or P, difficult. It is possible only by charge-balancing via additional alkali or alkaline-earth …

Mineralogy of Beryllium in Granitic Pegmatites

We introduce a crystal-chemical approach to the composition and occurrence of vanadium minerals. Here, the structure of a mineral is divided into two parts: the structural unit with bonds of higher bond-valence, and the interstitial complex, [ [m] M + a [n] M 2+ b [l] M 3+ c (H 2 O) d (H 2 O) e (OH) f ] (a+2b+3c−f)+ , which connects the structural units to form a continuous structure. Average coordination numbers of oxygen in structural units of vanadium minerals are in the range [2.75] to [4]. There are characteristic ranges of average O-coordination numbers for specific structural units, and these values can be used to calculate the range of Lewis basicities of structural units in vanadium minerals. The characteristic Lewis basicities explain why some interstitial cations occur, and some do not occur, with a specific structural unit. Furthermore, the maximum and minimum number of interstitial transformer (H 2 O) groups can be predicted. The occurrence of different states of hydration in vanadium minerals is rationalized via bond-valence theory. Here, Lewis basicities and effective Lewis acidities of structural components in vanadium minerals can explain detailed structural changes during dehydration. The average basicity of a structural unit is independent of the average O-coordination number, and can be compared to structural units in minerals with different interstitial cations and hydration states. With increasing polymerization, there is a decrease in the average basicity of the structural unit. Examination of the conditions of crystallization of vanadate minerals and synthetic phases shows that the average basicity of the structural unit correlates with the pH of the environment of crystallization. The average basicity of aqueous species in a solution correlates linearly with the pH at the maximum concentration of the species in solution.

A crystal-chemical approach to the composition and occurrence of vanadium minerals

Beryllium is a quintessential upper crustal element, being enriched in the upper crust by a factor of 30 relative to primitive mantle, 2.1 vs. 0.07 ppm. Most of the 112 minerals with Be as an essential element are found in granitic pegmatites and alkalic rocks or in hydrothermal deposits associated with volcanic and shallow-level plutonic rocks and skarns. Because of the extensive differentiation needed to enrich rocks sufficiently in beryllium for beryllium minerals to form, these minerals are relative latecomers in the geologic record: the oldest known is beryl in pegmatites associated with the Sinceni pluton, Swaziland (3000 Ma). In general, beryllium mineral diversity reflects the diversity in the chemical elements available for incorporation in the minerals and increases with the passage of geologic time. Furthermore, the increase is episodic; that is, steep increases at specific times are separated by longer time intervals with little or no increase in diversity. Nonetheless, a closer examination of the record suggests that at about 1700 Ma, the rate of increase in diversity decreases and eventually levels off at ~35 species formed in a given 50 Ma time interval between 1125 and 475 Ma, then increases to 39 species at 125 Ma (except for four spikes), before dropping off to ~30 species for the last 100 Ma. These features appear to reflect several trends at work: (1) diversifications at 2475, 1775, and 525 Ma, which are associated with highly fractionated rare-element granitic pegmatites and with skarns at Langban and similar deposits in the Bergslagen ore region of central Sweden, and which are inferred to correspond to the collisional phases of the supercontinents Kenorland, Nuna, and Gondwana, respectively; (2) diversification at 1175 Ma due to the rich assemblage of beryllium minerals in the Ilimaussaq peralkaline complex, Gardar Province, West Greenland, in an extensional environment; (3) diversification at 275 Ma, which is largely attributable to granitic pegmatites (Appalachian Mountains, U.S.A., and Urals, Russia) and the Larvik alkalic complex, Norway, but nonetheless related to continental collision; and (4) limited exhumation of environments where beryllium minerals could have formed in the last 100 Ma. That the maximum diversity of Be minerals in any one geologic environment could be finite is suggested by the marked slowing of the increase in the number of species formed in a given 50 Ma time interval, whereas the drop off at 100 Ma could be due to 100 Myr being too short a time interval to exhume the deep-seated occurrences where many Be minerals had formed. The relative roles of chance vs. necessity in complex evolving systems has been a matter of considerable debate, one equally applicable to what extent the temporal distribution of beryllium minerals is a matter of contingency. On the one hand, the appearance of the most abundant Be minerals, such as beryl and phenakite, early in the history of Be mineralization appears to be a deterministic aspect since these minerals only require the abundant cations Al and Si and crystallize at relatively low concentrations of Be in aqueous solution or granitic magmas. On the other hand, it could be argued that the very existence of most other Be minerals, as well as the temporal sequence of their appearance, is a matter of chance since 55 of the 112 approved Be minerals are known from a single locality and many of these phases require an unusual combination of relatively rare elements. Consequently, we cannot exclude the possibility that other equally rare and thus contingent potential Be minerals await discovery in as yet unexposed subsurface deposits on Earth, and we suggest that details of Be mineral evolution on other Earth-like planets could differ significantly from those on Earth.

Marie Louise Lindberg

Papers

Tavorite and barbosalite, two new phosphate minerals from Minas Gerais, Brazil

Manganoan lipscombite from the sapucaia pegmatite mine, Minas Gerais, Brazil; first occurence of lipscombite in nature

Frondelite and the frondelite-rockbridgeite series

The Beryllium content of roscherite from the Sapucaia pegmatite mine, Minas Gerais, Brazil, and from other localities

Arrojadite, hühnerkobelite, and graftonite