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 underdeveloped, at that time there were no specific criteria of distinguishing literature from folklore. The question of authorship arose every time a new story was released, and is still discussed nowadays. Before the stories were released as a single volume on 28 January 1939, the issue became urgent. The publisher was concerned with the title of the book and the author's name. It was suggested to release the book as "The Tales from Grandpa Slyshko" (), as if Vasily Hmelinin was the author. It was eventually published as "The Malachite Box". Bazhov was not certain of the authorship himself. He