Ruby

A ruby is a kind of precious stone. It is often associated with emerald, sapphire and topaz.^[1] It is usually red, but can sometimes be other colors.^[1] It is formed of aluminum and oxygen (Al₂O₃),^[1] and that means it's a kind of corundum. A small amount of chromium makes the color. They are the most popular red gemstone, and is aften linked with the birthmonth of July.

Ruby
A ruby gemstone
General
Category	Corundum variety, Oxide mineral
Formula (repeating unit)	aluminium oxide with chromium, Al2O3
Identification
Color	Red shades
Luster	Vitreous
References	[1]