Mineral Examples of such minerals are malachite (green) and azurite (blue). In contrast, allochromatic elements in minerals are present in trace amounts as impurities. An example of such a mineral would be the ruby and sapphire varieties of the mineral corundum. The colours of pseudochromatic minerals are the result of interference of light waves. Examples include labradorite and bornite. In addition to simple body colour, minerals can have various other distinctive optical properties, such as play of colours, asterism, chatoyancy, iridescence, tarnish, and pleochroism. Several of these properties involve variability in colour. Play of colour, such as in opal, results in
The Malachite Box (18 January 1939), "Izvestia" (4 April), "Pravda" and "Industria Sotsialisma" (July). However the critics disagreed on the question of authorship. Some considered "The Malachite Box" pure folklore, others thought of it was a literary work penned by Bazhov. The author himself tried to avoid the issue, joking that "questions such as these should be left to scholars". At present Bazhov's tales are generally accepted as his own literary work based on the Urals folklore. The editor of "Izvestia" called "The Malachite Box" "a valuable contribution to the Soviet fiction" and noted that "the vividness of expression and poetic richness turn