Carbonado compared to carbon‑12, relative to typical diamonds). Carbonado exhibits strong luminescence (photoluminescence and cathodoluminescence) induced by nitrogen and by vacancies existing in the crystal lattice. Luminescence halos are present around radioactive inclusions, and it is suggested that the radiation damage occurred after formation of the carbonados, an observation perhaps pertinent to the radiation hypothesis listed below. The origin of carbonado is controversial. Some proposed hypotheses are as follows: None of these hypotheses for carbonado formation had come into wide acceptance in the scientific literature by 2008. Supporters of an extraterrestrial origin of carbonados propose that their material source was a
What Is and What Should Never Be What Is and What Should Never Be "What Is and What Should Never Be" is a song by English rock band Led Zeppelin. It was written by Jimmy Page and Robert Plant and was included as the second track on "Led Zeppelin II" (1969). "What is and What Should Never Be" was one of the first songs on which Page used his soon-to-become trademark Gibson Les Paul for recording. The production makes liberal use of stereo as the guitars pan back and forth between channels. Robert Plant's vocals were phased during the verses. Record producer Rick Rubin has remarked, "The