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.
When they are taller than that, they are called âcumulus congestusâ. The tops of cumulus clouds often resemble cauliflowers. The towering clouds that produce showers of rain, snow and/or hail are called âcumulonimbusâ (from the Latin nimbus, meaning ârainy cloudâ). The tops of these clouds are often anvil-shaped, as shown in the picture below. Cumulus clouds are manifestations of convection.