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[5] Fluorapatite crystallizes in a hexagonal crystal system. It is often combined as a solid solution with hydroxylapatite (Ca 5 (PO 4) 3 OH or Ca 10 (PO 4) 6 (OH) 2) in biological matrices. Chlorapatite (Ca 5 (PO 4) 3 Cl) is another related structure. [5] Industrially, the mineral is an important source of both phosphoric and hydrofluoric acids.
Calcium fluoride is a classic example of a crystal with a fluorite structure. Crystallographic information can be collected via x-ray diffraction, providing information on the locations of electron density within a crystal structure. Using modern software such as Olex2, [4] one can solve a crystal structure from crystallographic output files.
Fluoride is classified as a weak base since it only partially associates in solution, but concentrated fluoride is corrosive and can attack the skin. Fluoride is the simplest fluorine anion . In terms of charge and size, the fluoride ion resembles the hydroxide ion.
Fluorite (also called fluorspar) is the mineral form of calcium fluoride, CaF 2. It belongs to the halide minerals. It crystallizes in isometric cubic habit, although octahedral and more complex isometric forms are not uncommon. The Mohs scale of mineral hardness, based on scratch hardness comparison, defines value 4 as fluorite. [6]
The prevailing view in the 1940s and 1950s was that P availability was maximized near neutrality (soil pH 6.5–7.5), and decreased at higher and lower pH. [29] [30] Interactions of phosphorus with pH in the moderately to slightly acidic range (pH 5.5–6.5) are, however, far more complex than is suggested by this view. Laboratory tests ...
Halite crystals termed hopper crystals appear to be "skeletons" of the typical cubes, with the edges present and stairstep depressions on, or rather in, each crystal face. In a rapidly crystallizing environment, the edges of the cubes simply grow faster than the centers.
Naturally occurring CaF 2 is the principal source of hydrogen fluoride, a commodity chemical used to produce a wide range of materials. Calcium fluoride in the fluorite state is of significant commercial importance as a fluoride source. [11] Hydrogen fluoride is liberated from the mineral by the action of concentrated sulfuric acid: [12]
Structural and thermodynamic properties of crystal hexagonal calcium apatites, Ca 10 (PO 4) 6 (X) 2 (X= OH, F, Cl, Br), have been investigated using an all-atom Born-Huggins-Mayer potential [42] by a molecular dynamics technique. The accuracy of the model at room temperature and atmospheric pressure was checked against crystal structural data ...