Calcite, Island Spar and Aragonite CaCO

Calcite is a calcium carbonate, CaCOs, with a rhombohedral cell consisting of the large planar CO3 groups, which contain a Ca ion at the center of an equilateral 

The color of calcite can be due to its iron content, which is present as Fe , to 

to radiation damage centers, which often involve rare earth or other elements, or occasionally to other elements such as Co . The color of rhodochrosite is due to its Mn content. Most minerals with Mn in six-coordination are pale pink. Because Mn does not absorb light strongly, a mineral must have a high Mn concentration to be strongly colored by Mn (Platonov 1979). 

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 

Matveeva 1987). The natural calcite in our study consisted of 30 samples from a 

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