Apatite color

Another desirable property for a ceramic color is a high refractive index. For example, valuable pigments are based on spinels [1302-67-6] ( 2jj = 1.8) and on zircon ( 2j = 1.9), but no valuable pigments are based on apatite ( 2j = 1.6), even though the lattice of apatite is as versatile for making ionic substitutions as that of spinel. 

Apatite - [COAL] (Vol 6) - [COLORANTS FORCERAMICS] (Vol 6) - [FERTILIZERS] (Vol 10) -magnetic intensity [SEPARATION - MAGNETIC SEPARATION] (Vol 21) -uranium m [NUCLEAR REACTORS - NUCLEAR FUEL RESERVES] (Vol 17)... 

Figure 17.20. Phosphorus covariance map and fluorescence P-NEXAFS spectra collected from a coastal marine sediment (Brandes et al., 2007). Covariance map is color-coded Green represents P, blue represents Si, and red represents Na fluorescence signals. Regions 1,3, and 5 have spectra consistent with organic phosphorus or polyphosphate, while regions 2 and 4 closely match calcium phosphate, specifically the mineral apatite. See color insert.

The other components of apatite (iron, aluminum, uranium) partly pass into solution as salts and are partly precipitated with the calcium sulfate. Any carbonate present produces carbon dioxide during digestion. If sedimentary noncalcined apatite is utilized, the phosphoric acid obtained is colored black by the organic impurities. 

Emission Color of Sr-Apatite Phosphors Under 2527 X Excitation... 

Grisafe DA, Hummel FA (1970) Crystal chemistry and color in apatites containing cobalt, nickel and rare-earth ions. Am Mineral 55 1131-1145... 

Sm luminescence has been reported from natural anhydrite samples (Gaft et al. 1985, 2001a Taraschan 1978) as a broad strong band at 630 nm. Other sharp bands are reported at 688, 700 and 734 nm. Sm emission has not been reported for apatite, but the ion size and valence are amenable to the Ca sites, so ultimately it may be observed via pulsed laser techniques. Sm is present in aqueous solution only under quite reducing conditions, so this may limit concentrations. Sm does occur in fluorite, and is responsible for the strong green coloration and sensitized Eu luminescence in that mineral (Robbins 1994). However, in fluorite the Sm may be created by radiation effects which reduce bound Sm ions. Yb emission has not apparently been reported in any minerals, but has been studied in borates and oxides (Blasse and Grabmaier 1994). Its... 

UV at 248 and 278 nm, and sets of narrow bands centered at about 488 and 615 nm (Mitchell et al. 1997) yielding a brick-red emission color. Natural samples of hydroxyl-apatite and fluorapatite show similar CL bands (Gaft et al. 1999). Time-resolved emission spectra (Fig. 19) show well defined Pr emission in natural magmatic apatite at 485 and 607 nm (Gaft et al. 1999). Studies using polarized emission measurements on this sample were interpreted as representative of only Cal site occupation by Pr (Reisfeld et al. 1996). In contrast, a sedimentary apatite annealed in air showed a different Pr spectrum, with a set of bands centered at about 630 nm (Fig. 19). This spectrum was interpreted to be due to Pr in Ca2 (Reisfeld et al. 1996). Pr appears to be an efficient sensitizer for Sm, as many of its transition energies are almost identical to Sm, and in general Pr probably is more important as a sensitizer of other REE than for its own emission (Mitchell et al. 1997). 

Knutson C, Peacor DR, Kelly WC (1985) Luminescence, color and fission track zoning in apatite crystals of the Panasqueira tin-tungsten deposit, Beira-Baixa, Portugal. Am Mineral 70 829-837 Kottaisamy M, Jagannathan R, Jeyagopal P, Rao RP, Narayanan R (1994) Eu luminescence in M5(P04)3X apatites, where M is Ca, Sr and Ba, and X is F", Cf, Bf and OH". J Phys D 27 2210-2215 Lapraz D, Baumer A (1983) Thermoluminescent properties of synthetic and natural fluorapatite, Ca5(P04)3F. Phys Stat Solid A 80 353-366... 

Robbins M (1983) The collectors book of fluorescent minerals. Van Nostrand Reinhold, New York Robbins M (1994) Fluorescence Gems and Minerals Under Ultraviolet Light. Geoscience Press, Phoenix Roeder PL, MacArthur D, Ma X-P, Palmer GR, Mariano AN (1987) Cathodoluminescence and microprobe study of rare-earth elements in apatite. Am Mineral 72 801-811 Ronsbo JG (1989) Coupled substitutions involving REEs and Na and Si in apatites in alkaline rocks from the Ilimaussaq intrusion, South Greenland, and the petrological implications. Am Mineral 74 896-901 Ropp RC (1971) The emission colors of the strontium apatite phosphor system. J Electrochem Soc 118 1510-1512... 

Photoluminescence (short-wave ultraviolet, SWUV, Mid-wave ultraviolet, MWUV, and longwave ultraviolet, LWUV) of apatites from various localities with postulated major luminescent centers, based on various unpublished data. Photos taken with Canon 4 Mb digital camera equipped with UV filter and close-up capability. Exposures 0.5-10 seconds. Colors adjusted with Photoshop 6.0 to agree with observed emission in a dark room. 

Some minerals emit a bright, often colored light (e.g., fluorescence and phosphorescence) when heated below redness, that is, above SOO C. The effect can be observed only in darkness. It is caused by the relaxation of lattice defects upon heating. The lattice defects are always due to radiation dammage that the crystal undergoes since its formation. This effect is called thermoluminescence, it is often found on fluorite, quartz, calcite, apatite, zircon, and diamond. 

Szabo I., Barnab S., Volksch G., and Holand W, "Crystallization and Color of Apatite-Leucite Glass-Ceramic," Glastech. Ber. Glass Sci. TechnoL, 73 [Cl] 354—57 (2000). 

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