Calcite luminescent

In nature, RE and Mn " can substitute for Ca, becoming luminescence centers in the crystallographic environment. Most calcite luminescence is attributed to Mn ", while Mn " hides rare earth emission, and so far their luminescence in calcite is rather poorly characterized (Blasse and Aguilar 1984 Pedone et al. 1990). The lines of Sm " and Dy " have been confidently established using a hot cathode cathodolu-minescence method (Haberman et al. 1996). Besides that, luminescence of Pb " (Tarashchan 1978) and radiation-induced are known (Kasyanenko and... 

Organic acid fluorescence. In a similar manner to trace constituents, such as Mg, Sr and P, concentrations of organic acids present in speleothem calcite are sufficient to observe variation at temporal scales of less than annual in some cases (e.g.. Baker et al. 1993, Shopov et al. 1994). Organic acids (humic and fulvic) are formed in the soil by humification, and transported to the cave void by percolating waters where they are entrapped in precipitating carbonates. Under certain circumstances, where precipitation patterns are strongly seasonal and the nature of vadose percolation is such that seasonal mixing is incomplete, bands with different luminescent intensities can be differentiated after excitation with UV radiation. In other cases, bands are not observable but secular... 

Fig. 4.13. a-d Laser-induced time-resolved luminescence spectra of calcite demonstrating Ce +, Eu +, Tm +, Nd " and centers... 

Two types of Ce centers in calcite were detected by steady-state spectroscopy (Kasyanenko and Matveeva 1987). The first one has two bands at 340 and 370 nm and is connected with electron-hole pair Ce -COj". The second one has a maximum at 380 nm and was ascribed to a complex center with Ce and OH or H2O as charge compensators. Such a center becomes stronger after ionizing irradiation and disappears after thermal treatment. The typical example of Ce luminescence in the time-resolved liuninescence of calcite consists of a narrow band at 357 nm with very short decay time of 30 ns, which is very characteristic for Ce " (Fig. 4.13a). It was found that Ce " excitation bands occurs also in the Mn " " excitation spectrum, demonstrating that energy transfer from Ce to Mn " occurs (Blasse and Aguilar 1984). 

Steady-state luminescence of Eu " was found in CL spectra (Haberman et al. 1996). Eigure 4.13c represents laser-induced time-resolved luminescence of calcite under 266 nm. Luminescence lines of Eu are seen. Hypersensitive... 

Characteristic bands of Mn + well studied by steady-state luminescent spectroscopy (Tarashchan 1978 Gorobets and Rogojine 2001) have been found in time-resolved luminescence spectra of calcite (Fig. 4.14a), fluorite (Fig. 4.10d), datolite (Fig. 4.16d), wollastonite (two bands at 555 and 603 nm Fig. 4.42a,c), and spodumen (Fig. 4.61a). 

Fig. 5.48. Laser-induced luminescence of Mn bearing minerals (1-helvine 2-severgenite 3-Mn-mUarite 4-triplite 5-rodonite 6-rhodochrosite 7-Mn-calcite 8-Mn-curchatovite 9- Mn-tantalite 10-dgimboite 11-Mn-apatite) and its connection with crystallochemical structure a-rhodonite fo-rhodochrosite c-Mn-apatite d-carpholite (MnAl2(Si206)(0H)4 (Gaftetal. 1981)...

Tarashchan (1978) already ascribed the UV liuninescence band at 325 nm with an excitation band at 237 nm in pink calcite to Pb +. A decay time of 120 ns measured in our sample is consistent with such interpretation. Such a UV band was unique in the calcite collection at our disposal and ICP-MS analyses of its impurities have been done (Table 4.7). It was found that Pb concentration in Franklin, NJ calcite of 450 ppm is approximately 50 times higher than in pink calcite, taken for comparison sake, while its Ce content is more than 10 times lower. Those data confirm the connection of the UV band at 325 nm with the Pb luminescence center. 

The violet emission of the radiation-induced center (COs) " is well known in steady-state luminescence spectra of calcite (Tarashchan 1978 Kasyanenko, Matveeva 1987). The problem is that Ce also has emission in the UV part of the spectrum. In time-resolved luminescence spectroscopy it is possible to differentiate between these two centers because of the longer decay time of the radiation-induced center. Its luminescence peaking at 405 nm becomes dominant after a delay time of 100-200 ns while emission of Ce is already quenched (Fig. 4.14f). 

Fig, 5.66. Laser-induced time-resolved luminescence spectrum (a) and excitation spectrum (b) of radiation induced center in calcite... 

Certain similarity may be seen between this luminescence and short-Hved orange emission in calcite, which has been ascribed to radiation-induced center (Fig. 5.67). It is possible that natural irradiation may be a reason of orange luminescence in apatite also. 

Under short-waved UV lamp excitation (254 nm) visually observed luminescence of calcite is violet-blue with very long phosphorescence time of several seconds. Under long-waved UV lamp excitation (365 nm) calcite exhibits visually the same violet-blue luminescence as under 254 nm excitation, but long phosphorescence is not detected. Under short laser excitations, such as 266 and 355 nm, at 300 K calcite demonstrates intensive UV-violet emission band peaking at 415 nm with half-width of 55 nm (Fig. 5.76a). Excitation spectrum of this band is composed of short waved tail in the spectral range less... 

Fig. 5.76. Blue emission (a) and excitation (b) spectra of calcite at 300 K and luminescence spectra at lower temperatures (c-d)...

It is possible to suppose that LIBS sorting may be better than the luminescent one. It is clearly seen that the corresponding spectra of borosilicates, quartz and calcite are totally different (Fig. 8.4), which make radiometric sorting easy and confident. 

Identification of minerals is not a trivial question when dealing with natural objects. Luminescent minerals received from different mineralogists, museums and collectors are often not correctly identified. It is a potential source of serious errors, because the presence of a certain luminescence center in one mineral maybe trivial, while its luminescence in another mineral may represent a certain interest. For example, emission of Mn " is common in calcite, but its absence in scheelite is an interesting problem. Thus, when you find the band... 

Besides confidently identified centers, the possible participation of Mn and is proposed. The centers, such as Mn ", Cr, Cr +, and V are described, which are not found in minerals yet, but are known in synthetic analogs of minerals, such as apatite, barite, zircon and corundum. Besides that, the centers Ni " and Ti " are discussed as possible participants in mineral luminescence. The last part of this chapter is devoted to unidentified emission lines and bands in apatite, barite, calcite and zircon. 

Table 8.2. Trace elements influencing luminescence in calcite and dolomite in approximate order of importance. (After Machel, 1985.)...

Figure 8.27. Luminescent zoned calcite cements in the Mississippian Lake Valley Formation. A. Schematic diagram illustrating paragenesis of the zonal luminescent cements. B. Proportions of zone 1, 2, 3 and 5 cements making up total intergranular cement. (After Meyers, 1980 as modified by Moore, 1989.)...

Helderberg carbonates are extensively cemented by clear equant calcite cement that postdates marine cement and fills most of the original pores. These cements are compositionally zoned as shown by cathodoluminescence and trace element analyses. These precipitates include nonluminescent, bright and dull cements. The luminescent cement is the earliest generation of cement followed by... 

Reeder R. L, Nugent M., Tait C. D., Morris D. E., Heald S. M., Beck K. M., Hess W. P., and Lanzirotti A. (2001) Coprecipitation of Uranium(VI) with calcite XAES, micro-XAS, and luminescence characterization. Geochim. Cosmochim. Acta 65(20), 3491-3503. 

White, W.B., 1986, Luminescence in cave calcite deposits A current appraisal, Natl. Speleol. Soc. Bull. 48 40... 

Speleothems (stalagmites, stalactites, and flow-stones) are producing a tremendous range of reconstructions of different types of paleoclimatic parameters, including many quantitative records. Calcite speleothems display Inminescence, which is produced by calcinm salts of humic and fulvic acids derived from soils above the cave. The luminescence of speleothems depends exponentially on the solar insolation (if soil surface is heated directly by the Sun) or on the air temperature (if the cave is covered by forest or bush). Therefore, luminescence records represent solar insolation or temperature in the past. Luminescence of many speleothems is exhibited by annual bands much like tree rings. Distance between them is a quantitative proxy of annual precipitation in the past. 

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