| 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] |
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.
