Experimental Study On The Fading Of Iceland Spar And Its Mineralogical Characteristics

In this paper, the yellow and purple Iceland spars are heated to remove their color. The experiments show that the color of the Iceland spar can be changed when heated to a certain temperature, that is , light yellow Iceland spars will fade when heated to 360-370℃, while dark yellow Iceland spar will fade at 440-450℃, brownish yellow Iceland spar at 460-470℃ ; And the color of light purple Iceland spar can be removed when heated to 390-400℃, while the color of deep purple Iceland spar can be removed at 440-450℃ , deep reddish purple Iceland spar at 460-470℃ .On base of the u-v absorption spectrum, we find that the u-v absorption spectra of the faded Iceland spars are paralleled to the X axis, the transmittance of them are also greatly improved . The courses of the enhancement don't damage Iceland spar or change its physical properties, such as birefringence index, optic chatacter. These show that the samples measure up to their industrial standards after the heating. The experiment is successful.The study on the cause of the color shows that Mn, Pb and CO2-3 are contributed to the yellow in the Iceland spar , while the purple of the iceland is caused by Mn, Pb, CO32- and Ni . The yellow Iceland spar are thus colored : CO32- can form V center in this way , CO32-→CO3-+e; Mn forms F center, Mn2+→Mn+-e ; Pb forms F center , Pb2+→Pb+-e . These color centers can affect each other and so they can absorb the purple and blue part of the visible spectrum , and make Iceland spar yellow ; similarly, CO32- (CO32-→C03-+e) ,Mn2+(Mn2+→Mn+-e) , Pb2+(Pb2+→Pb+-e) and Ni2+(Ni2+→Ni+-e) can work together to cause Iceland spar purple . Heating can bleach these color centers, consequently, the color caused by them is removed, and iceland spars become colorless.