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
Malachite sunbird but highly gregarious when not breeding, forming flocks of over 1,000 birds. The call is a loud "tseep-tseep", and the male malachite sunbird has a twittering song, often accompanied by pointing its head upward and displaying his yellow pectoral tufts with his wings half open. Males also have an elaborate display flight. It was found that male birds display their pectoral tufts almost continuously throughout the night, whilst asleep, and one hypothesis is that these function as eyespots to deter nocturnal predators. Malachite sunbird The malachite sunbird ("Nectarinia famosa") is a small nectarivorous bird found from the highlands of Ethiopia