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.
The National Weather Service says there are four main categories of clouds: Cirro-form: Derived from the Latin word âcirro,â meaning âcurl of hair,â this term describes whitish, wispy clouds composed of ice crystals. They typically are the first types of clouds to appear in the sky before a storm system, the NWS says.