Spinel is the magnesium aluminum member of the larger spinel group of minerals. Its hardness is 8, its specific gravity is 3.5–4.1, and it is transparent to opaque with a vitreous to dull luster. It may be colorless, but is usually various shades of red, blue, green, yellow, brown, or black.
Silver is often coated on a base metal, such as copper, brass, white metal and nickel, to give it a silvery white, smooth and shiny finish. Silver plated jewelry often radiates purity and simplicity.