Agate is a member of the quartz family and is commonly found across the world, including in the United States, Africa, India, China, Germany, Italy, Brazil and Mexico. Its abundance makes it relatively affordable, and it's favoured for the beautiful kaleidoscopic stripes that run through it, which look a bit like tiger stripes. Agate has an average hardness of 6.5–7 on the Mohs scale.

Declared Russia's national stone after its discovery there in 1830, alexandrite was named after the Russian Czar Alexander II, and has also influenced that country's national colours. Alexandrite is a variety of the mineral chrysoberyl, and its most valuable varieties change colour – from green in daylight to reddish purple in incandescent light. The highest quality grades of alexandrite are extremely rare and expensive. Different types of alexandrite are also found in in India, Sri Lanka, Brazil, Tanzania and Madagascar. Alexandrite is quite firm, with an average hardness of 8.5 on the Mohs scale.

Like agate, amethyst is a common and affordable member of the quartz family. Mined in Brazil, Bolivia, Uruguay, Tanzania, Zambia, Namibia and the United States, amethyst has been long believed to possess positive supernatural abilities, including the capability to suppress alcohol intoxication. Vulnerable to heat and sunlight, amethyst may lose its lovely purplish colour if it's overexposed to the sun or heat for too long. It has an average hardness of 7 on the Mohs scale.

A type of beryl mineral, aquamarine owes its name to its stunning sea-like colour, which can span different shades of aqua and blue, with greenish and yellowish tinges. The most valuable shade of aquamarine is deep blue, and it's considered by many to attract good luck. Found mostly in Brazil, Nigeria, Zambia, Mozambique, Angola and Madagascar, aquamarine has a hardness of 7.5–8 on the Mohs scale.

Plentiful and affordable, black onyx is a type of quartz that is striking in its blackness. It may also exhibit strands of white, and the sardonyx variety ranges from white, to red, to reddish brown. Mined in the United States, India, Pakistan, Brazil and Madagascar, black onyx registers an average hardness of 7 on the Mohs scale.

This honey-coloured gemstone is also a member of the quartz family, and is generally cheaper than amethyst. It can range from bright yellow to an orangey brown, and is often heat-treated to enhance its colour. Named after the French word for lemon, citrine is a bountiful stone in Brazil and Bolivia. It has an average hardness of 7 on the Mohs scale.

Coral is an organic gemstone that is rarely offered untreated on the commercial jewellery market. It forms naturally in the ocean when sea polyps secrete calcium carbonate to build their habitat. Most high-quality coral found in jewellery is sourced in Sicily or Sardinia, and requires professional divers to carefully extract coral branches from the ocean without damaging any organisms inside or marine life. Many of the world's reefs are protected and unable to produce coral harvested for commercial use. Therefore, genuine, untreated coral is highly expensive. Its colours can be red, orange, blue and white, and it registers a fragile 3.5–4 on the Mohs scale.

Emeralds are very rare and consequently highly priced, and are most valuable when they exhibit a lush green hue. A member of the beryl family, emeralds are mostly mined in Brazil, Columbia, Zambia, Zimbabwe, Madagascar and Afghanistan. Their brilliant green colour has captivated the world for centuries, and emeralds have appeared in the folklores of ancient Greeks, Egyptians, Incas, and other historic peoples, believed by many cultures to possess superhuman powers. The colour of emeralds can range from dark green to yellowish light green. Given that most emeralds contain one or more inclusions, such small imperfections generally don't devalue them, unless the inclusions are severe. While inclusion-free emeralds do exist, they are extremely rare and costly. Emeralds are fairly hard and reach 7.5–8 on the Mohs scale.

Visually similar to the rich redness of rubies in their most popular and affordable form, garnets actually come in a rainbow of colours and represent a family of stones. Their more exotic colours are often found in Russia and East Africa, while more traditional garnet colours usually originate in India, Sri Lanka, South Africa, the United States and Thailand. It's difficult to calculate an average value for garnets, given their worth is largely dependent on their rarity. Garnets have an average hardness of 7.5–8 on the Mohs scale.

There are two types of jade: jadeite and nephrite. Jadeite comes in a wider spectrum of colours than nephrite, including green, white, pink, violet, red, brown and black. While nephrite is most commonly green or greyish green, it can also be white, red and yellow. Jade is a highly revered and valuable stone in eastern cultures, and has been celebrated worldwide for many centuries. Generally, the jade stones that attract the highest values exhibit an even spread of colour with little tonal variation. While the two types of jade both register an average hardness of 6.5–7 on the Mohs scale, they are so tough that they were once used to make weapons and tools.

The bewitching deep blue of lapis lazuli has made it world famous for many thousands of years. Its name hails from Latin and Arabic words that, when combined, mean 'blue stone'. Considered a stately symbol of wisdom and truth, lapis lazuli is sometimes ground into a fine powder to make different types of artistic paints. It has a relatively soft hardness of 5–6 on the Mohs scale, and must be looked after due to its vulnerabilities.

Comparable in its beautiful whitish iridescence to a pearl, moonstone is a type of feldspar mineral, which makes it related to more than half the stones found on earth. Sri Lanka produces most of the world's moonstones, but they are also found in India, Burma, Madagascar and Mexico. While the most expensive types of moonstones are bluish and present an eye-catching sheen, moonstone can form in many colours, including yellow, green, pink, brown, multi-coloured, and colourless. The optical phenomenon that causes moonstone to seemingly glow with a bluish lustre is a type of light refraction called adularescence. Ancient Romans and Hindu communities are believed to have thought moonstone was made from pieces of moonlight, and that in its gleam could be seen a person's future. Moonstone has an average hardness of 6–6.5 on the Mohs scale.

Mined mostly in Australia, but also in the United States and Mexico, opals owe their name to the Greek word opallos, which means 'colour change'. That's because opals appear to beautifully transform their colours when they are tilted under certain light conditions. This is caused by a diffraction of light that occurs inside the stone, which produces the rainbow-like effect. Opals are mined in many appealing colours, including multi-coloured, blue, green, red, yellow, white, black, and colourless. Like many other gemstones, the mystical beauty of opals has spawned many beliefs about their supernatural powers. Opals register an average hardness of 5.5–6 on the Mohs scale.

Pearls are the most highly valued organic gemstones in the world, and are the only type that don't require cutting or human intervention to enhance their appearance. While pearls are formed by nature inside living creatures, that doesn't mean the pearls that you see on the market are entirely spontaneous: most of them are cultured pearls. Cultured pearls are created when humans deliberately introduce an irritant (such as sand or a shell) to the mouth of a mollusk, which emits the self-protective substance nacre as a result, which often produces a pearl. Most pearls are cultured in Japan, China, and countries in the South Pacific. Given their enormous range of colours, sizes and shapes, they vary greatly in their value. Some pearls are white, some are black; some are very small, some are large; some are perfect spheres, and others are asymmetrical.

Peridot's dazzling lime green colour has inspired a number of superstitious beliefs in its powers, including the ability to stave off nightmares and boost the effectiveness of medicine. A member of the olivine family, peridot is mostly found in the United States, but is also mined in China, Burma and Pakistan. Peridot is one of the few gemstones in the world that can only be found in one colour, and has a hardness of 6.5–7 on the Mohs scale.

Ruby shares its family tree with sapphire, both being types of corundum. But ruby is the only form of corundum to be coloured red, with all the other varieties belonging to sapphire. Rubies of large sizes are rare and therefore highly valuable, not least of which is due to their stunning red hue and strong constitution. The most expensive rubies are generally coloured a deep, rich red or exhibit a hint of purple. It's unsurprising that rubies' redness has made them synonymous with love, power, courage and strength. Rubies are extremely hard and register an average of 9 on the Mohs scale.

A member of the corundum family, sapphires are mostly found in blue, and owe their name to the Greek word for blue: sappheiros. Generally, the richer and more vivid the blue, the more valuable the sapphire. However, sapphires can also be formed in many other colours, apart from red (red sapphires are called rubies). Most of the world's sapphires are mined in Sri Lanka, but they are also found in the United States, Tanzania, Kenya, Burma, Kashmir, Madagascar, Vietnam, Cambodia, Laos, Thailand and Australia. Sapphires have long been believed to symbolise loyalty and harmony, and have been worn for protection for countless years. Like rubies, sapphires feature highly on the Mohs scale, with an average hardness of 9.

A gorgeously violet-coloured stone in its most recognised and popular form, tanzanite is a member of the zoisite mineral family and can also come in other bluish and purplish shades. It gets its name from the only country that produces it: Tanzania. Most of the rich violet tanzanite on the market has been treated with heat to improve its colour, and it naturally exhibits three colours when viewed from different angles (blue, purple and bronze). Often called "the gemstone of the 20th century", tanzanite wasn't actually discovered until very recently in 1967, and became a hit almost overnight. Tanzanite has an average hardness of 6.5–7 on the Mohs scale.

Topaz is a common stone that offers a rainbow of colour selections, with the most valuable being the more rare red, orange and pink stones. These types of topaz are found in Russia, Brazil and Pakistan, while China, Sri Lanka and Nigeria produce colourless topaz, which typically turns blue after undergoing irradiation enhancement. All shades of topaz are at risk of losing their colour if they are exposed to heat or the sun for extended periods of time. Topaz has a general hardness of 8 on the Mohs scale.

Its very name, which evolved from the Sinhalese term for multi-coloured (tura mali), indicates the many colours that beautiful tourmaline exhibits. No gemstone produces as wide a range of colours as tourmaline, and it's occasionally confused for different categories of gemstones, because it can look so identical to them due to its many rich colour variations. Generally, the most expensive tourmalines are bright blue and copper coloured, due to their rarity. Most of the world's tourmaline is mined in Brazil, but it can also be found in Australia, the United States, Russia, Sri Lanka, Tanzania and Madagascar. Tourmaline has a sturdy hardness of 7–7.5 on the Mohs scale.

Made famous by many ancient communities, including the Native Americans, Egyptians and Chinese, turquoise has been retrieved from the earth and celebrated in culture and tradition for centuries. It's believed that the Iranians were the first to treasure this light blue–coloured member of the copper family many thousands of years ago, wearing it on their turbans as a form of protection. Generally found in a sky or greenish­–blue colour, turquoise can sometimes contain streaks of yellow, grey, brown and black. Most of the turquoise found on the market today originates in Afghanistan, Israel, China, the United States and Mexico. Turquoise registers an average hardness of 6 on the Mohs scale.