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The fluorite structure refers to a common motif for compounds with the formula MX 2. [1] [2] The X ions occupy the eight tetrahedral interstitial sites whereas M ions occupy the regular sites of a face-centered cubic (FCC) structure. Many compounds, notably the common mineral fluorite (CaF 2), adopt this structure.
Fluorite is normally colorless, but some varied forms found nearby look black, and are known as 'fetid fluorite' or antozonite. The minerals, containing small amounts of uranium and its daughter products, release radiation sufficiently energetic to induce oxidation of fluoride anions within the structure, to fluorine that becomes trapped inside ...
Some sources give unit cell parameters for one formula unit per unit cell (Z = 1), but some scientists consider the formula to be half the value accepted by the International Mineralogical Association (IMA), i.e. Ca 5 ((Si,S)O 4)) 3 F, with two formula units per unit cell (Z = 2). Cell parameters for natural, as opposed to synthetic, material ...
Its chemical formula is (Na,Ca) 2 Ta 2 O 6 (O,OH,F). Today [ when? ] it is a name of a group of oxide minerals of a similar stoichiometry having tantalum prevailing over titanium and niobium. The microlite group belongs to a large pyrochlore supergroup that occurs in pegmatites and constitutes an ore of tantalum.
Frankdicksonite has fluorite crystal structure with a cubic symmetry and the lattice constant a = 619.64 pm. Its Vickers hardness on the {111} cleavage crystal faces varies between 88 and 94 kg/mm 2 and is close to that of the synthetic barium fluoride (95 kg/mm 2). Its refractive index (1.475) is almost identical to that of BaF 2 (1.474).
Creedite is a calcium aluminium sulfate fluoro hydroxide mineral with formula: Ca 3 Al 2 SO 4 (F,OH) 10 ·2(H 2 O). Creedite forms colorless to white to purple monoclinic prismatic crystals. It often occurs as acicular radiating sprays of fine prisms.
The more general crystal structure describes materials of the type A 2 B 2 O 6 and A 2 B 2 O 7 where the A and B species are generally rare-earth or transition metal species; e.g. Y 2 Ti 2 O 7.The pyrochlore structure is a super structure derivative of the simple fluorite structure (AO 2 = A 4 O 8), where the A and B cations are ordered along ...
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. Fluorapatite as a mineral is the most common phosphate mineral. It occurs widely as an accessory mineral in igneous rocks and in calcium rich metamorphic rocks.