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 Art? in Tolstoy and his problems: essays. London: Grant Richards. pp. 66–101. Maude, Aylmer (1901b). “"What is Art?" - Tolstoy’s Theory of Art”, in Tolstoy and his problems: essays. London: Grant Richards. pp. 102–127. Noyes, George (1918). Tolstoy. London: Duffield. Pevear, Richard (1995). "Preface" in Tolstoy, Leo (1995 [1897]). "What is Art?" (Translated by Richard Pevear and Larissa Volokhonsky). London: Penguin. Simmons, Ernest (1973). "What is Art?", in Tolstoy. London: Routledge and Kegan Paul. pp. 175–189. What Is Art? What is Art? ( "Chto takoye iskusstvo?") is a book by Leo Tolstoy. It was completed in Russian in 1897 but first