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.
Nimbostratus clouds are associated with rain. They do not produce as much heavy rain as cumulonimbus do. Such clouds are not very high up in the sky and look like a grayish blanket. Source(s): 14 yrs. of studying meteorology. More info on clouds http://www.srh.noaa.gov/jetstream/synopt...