what is corundum

what is Corundum Corundum mineral, crystalline-alumina (Al2O3), trigonal system, ditrigonal-skalenohedral. Occurs in the form of separate or fused into groups of barrel-shaped, dipyramidal and tabular crystals of pseudohexagonal appearance, isolated impregnations and ...

what is the earth's crust

What is the Earth's crust is the Earth's shell? This is where the wheat grows .... The Earth's crust is the outer solid shell of the Earth (the geosphere), part of the lithosphere, the thickness of 5 km (under the ocean) to 75 ...

What is a trough?

What is a gutter? The gutter is: 1) An oblong groove, hollowed out in the WWC, and usually intended to drain water or to dump something. 2) An oblong groove on the ground, in the ground. 3) A long narrow depression on the ocean floor ...