Its green surroundings showcase a ruby from Tanzania in its unpolished beauty. Rubies, valued as precious gems, are the mineral corundum in its red form. Perhaps the country best known for its rubies was Myanmar (Burma), but the country's production has greatly decreased. Today rubies are also created synthetically in the lab.
Photograph by bildagentur-online.com, th-foto, Alamy
The igneous rock kimberlite sets off a yellow diamond from South Africa, a country known for its diamond mines. At 616 carats, one of the largest diamonds in the world—the Kimberley octahedron—is a yellow diamond.
Photograph by Eric Nathan, Alamy
Rubies shine red against black rocks. Ruby, the common name for the mineral corundum in its red form, is a precious gemstone. If the mineral has a blue colour it's known as a sapphire. Made up of the elements aluminium and oxygen, corundum also can be yellow, grey, or brown.
Photograph by Natural History Museum/Alamy
When the mineral beryl takes on a green form, we know it as an emerald. Highly valued by Mesoamerican cultures, some of the finest emeralds come from Colombia. Beryl is a beryllium-aluminium silicate, and its colour comes from small amounts of chromium.
Photograph by Peter Arnold, Inc., Alamy
Awash in yellow, a gem miner near Ratnapura, Sri Lanka, separates stones from clay-laden mud. Local industry relies on the precious and semiprecious stones found in the mines, some of which are more than 40 feet (12 meters) deep.
Photograph by John Keeble, Visual Gems, Alamy
This cut topaz gemstone shows off its striking blue colouration, but the mineral also occurs in a colourless form or with a yellow or green colour. A red topaz is a rarity. Topaz occurs in the igneous rock rhyolite.
Photograph by Natural History Museum/Alamy
A sapphire, the common name for the mineral corundum in its transparent blue form, sparkles. As seen here, some sapphires, when cut to a convex shape, exhibit a striking six-pointed star in direct sunlight. While sapphires are found in a few locations around the world, these "star" sapphires often originate in Sri Lanka.
Photograph by Doug Steley, Alamy
A polished tourmaline from India gleams. Cut in a convex form known as a cabochon, this red tourmaline could also be called a rubellite because of its red coloration. An Egyptian legend explains that tourmalines come in so many different colours because they passed through a rainbow on the journey from the Earth's centre, but scientists know that a tourmaline's chemical composition determines its colour.
Photograph by Hemis, Alamy
This diamond ring created by artisans at diamond giant De Beers exemplifies the use of gemstones in fine jewellery. Diamonds, the hardest-known natural substance, represent exquisite beauty to many but to some they also represent an exploitive industry that has fuelled African bloodshed.
Photograph by www.gerardbrown.co.uk, Alamy
The world famous Koh-i-noor diamond accentuates the grandeur of the crown of Britain's Queen Elizabeth, the Queen Mother. The platinum crown includes other precious gems, and when the Queen Mother died in 2002 the crown was removed from the Tower of London and paraded through London streets. The Koh-i-noor's earliest mention occurs in Sanskrit writings.
Photograph by Tim Graham, Alamy
