Peridot
Hardness: 6.5-7 (Mohs' scale)
Density: 3.2-4.3g/cm³
Refractive index: 1.64-1.70
Bright green stone with a yellowish sheen. In ancient Egypt it was called "sunstone". Gem-quality olivine is often called "peridot", while the name "olivine" also includes less valuable rocks.
Olivine itself is often used, for example, as a stone for sauna stoves, crushed olivine is also present in some experiments for removing carbon monoxide from the atmosphere.
The presence of this stone has also been proven on the Moon and Mars.
On Earth, it comes mainly from igneous rocks, but exceptionally it also reaches our planet in meteorites.
The ancient Egyptians mined olivine on the island of Topazior, now Zabargad, which also gave its name to topaz.
For centuries, people confused this stone with emerald; for example, the stones decorating the Shrine of the Three Kings in St. Peter's Cathedral in Cologne are an example of this mistake.
People born in August will appreciate that olivine is often attributed to them as a protective stone.