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 the Urals. The first short version of the essay, included in the 1939 book, was titled "The Watchhouse on Dumna Mountain". In 1940 the author expanded it and renamed to "By the Old Mine" (). This version was first published in the 3rd volume of the "Uralsky Sovremennik" almanac (1940). Starting with the 3rd edition of "The Malachite Box", this essay was published in all subsequent editions. The author included the essay in every "The Malachite Box" edition for the purpose of familiarizing the reader with the unique culture of the Ural region. "Beloved Name" (alternative translation: That Dear Name)