It is commonly called alumina, and may also be called aloxide, aloxite, or alundum depending on particular forms or applications. It commonly occurs in its crystalline polymorphic phase Î±-Al 2 O 3, in which it composes the mineral corundum, varieties of which form the precious gemstones ruby and sapphire.
rain cloud. (meteorology). Any cloud from which rain falls; a popular term having no technical denotation. 1  Facebook. 2  Twitter.
Stratocumulus clouds almost never produce rain, although they can turn into nimbostratus clouds if conditions allow. Mammatus clouds and green clouds are normally associated with severe weather, including hail or tornados. High types of clouds, above 18,000 feet, are known as cirrus clouds. Clouds above 6,500 feet to 18,000 feet are called alto clouds. Clouds below 6,500 feet are mainly the stratus clouds that may indicate rain.