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 of the miners and gold prospectors. After the initial publication, the author continuously added new stories to the collection, such as the so-called "mountain fairy tales" in 1942, "Stories of Germans" () in 1943, a series of stories about Russian steel-makers and coiners in 1944–1945, "Stories of Lenin" () in 1944–1945, and others. Every edition of the collection ended with the dictionary of unusual words and concepts. "The Watchhouse on Dumna Mountain" () was Bazhov's essay which served as an introduction to the first edition of "The Malachite Box". It contained some information about the life, industry and culture at