In calcite colored by 3-Mev electrons (${10}^5$ to ${10}^6$ rads) at -190°C, two absorption bands at 350 and 290 mμ have been observed. Samples cut parallel to the $c$ axis colored and measured with polarized light ($E_{\perp c}$ and $E_{\mathrm{II}c}$) showed that the band at 350 mμ is isotropic while that at 290 mμ is anisotropic. The former is correlated to trapped electrons and the latter to trapped holes. Both bands are stable at -190°C but decay simultaneously at room temperature, accompanied by strong luminescence with a peak at 590 mμ.

• Received 4 August 1961

DOI:https://doi.org/10.1103/PhysRev.124.1754