Ruby
RUBY is the red variety of corundum, the second hardest natural mineral (9.0 on the Mohs scale of mineral hardness). Sapphire is the non-red variety of corundum and is generally thought to be blue, although it exists in nearly any other color. A very small amount of chromium gives corundum a pink color. Larger amounts produce stones that are a deep traffic light red, and are known as rubies.
The ruby is considered one of the four precious stones, together with the sapphire, the emerald, and the diamond
Chemistry: aluminum oxide ♦ Color: pink to deep red ♦ Luster: adamantine to vitreous ♦ Transparency: transparent to translucent. ♦ Crystal Form: hexagonal ♦ Cleavage: none ♦ Moh's hardness: 9 ♦ Localities: Burma, Cambodia, Sri Lanka, India, Afghanistan, Montana, other areas.