One estimate has it that Africa has some 19 000 variations of gemstones, nearly 50% of the global gemstone turnover. Even though coloured gemstones are found mostly in Brazil, Burma and Sri Lanka, there are restrictions on the export of these. For example, although Burmese rubies are considered the best in the world, there is a trade embargo against them entering the USA.  

The mining of coloured gemstones extends across many small mines in several African countries, however, the main producing countries are in the southern and eastern regions of Africa, stretching from Namibia in the south-west, up to Ethiopia and across to Madagascar. They all lie on the same gemstone-rich region referred to as the Neoproterozoic Mozambique Belt.

One of the most lucrative mining operations in Mozambique is the Gemfields Mozambique ruby mines. These rubies are mined and sold directly to the market via auction. In June 2018, Gemfields raised a whopping $72-million for 82 parcels of rubies. This is an average price of $122 per carat!  There is a misconception that carat indicates size, but it is actually what the stone weighs. To put this into perspective, one carat is a tiny 1/5th of a gram in weight!

Africa, the proud cradle of humankind, hosts a cornucopia of precious an semi-precious metals and gemstones deep within its rich and valuable soil. It's a treasure trove of material to fashion the most creative and desirable jewellery.

Tanzania is a massive pot of jewels. Tanzania is particularly well-known for tanzanite. Other gemstones from there include the stunning rhodolite garnet, tsavorite garnet and Tanzanian spinels, which easily rival the most beautiful ruby.  Mining there is principally on a small scale which tends to be labour intensive.

The Mozambique Belt should not detract from another African country, Nigeria – the largest supplier among West African nations. Nigeria is highly regarded for its blue sapphire as well as large quantities of fine tourmaline. Aquamarine and topaz also extensively mined there.

South Africa is recognised as probably the wealthiest mineral jurisdiction in the world. The value of the local jewellery market is estimated at around R2-billion. South Africa’s most valuable mineral market, including gold and diamonds, are currently estimated to be worth just under R30-trillion.

A quick reference guide to the most sought-after gemstones from Africa

Tourmaline: This stone comes in every colour of the rainbow and can even be colourless. It is mined in Africa in Tanzania, Nigeria, Kenya, Madagascar, Mozambique and Namibia.

Tanzanite: Natural Tanzanite gemstones were first found in 1967 near Tanzania’s Kilimanjaro Airport. The gem comes in shades of yellow, green, and violet-blue.

Moonstone: Moonstone originated in Africa and has milky translucent to transparent properties. This stone is famous among gemstone lovers around the world as its properties change with shifting rays of light.

Sapphire: The stone of royalty! Sapphire is only second in hardness to the most loved and valued rock in the world: the diamond. Madagascar is a huge producer of this gem.

African amethyst: Today, the finest African amethyst gemstones come from Zambia. The natural colour of African amethyst varies from light purple to intense shades of violet and royal mauve. These gemstones are said to have healing properties.

Aquamarine: Known as the gem of the sea, aquamarine is a blue to blue-green gem. It is mined in Kenya, Nigeria, Madagascar and Zambia. These gems are available in large sizes. Their value is often dependent on clarity, depth and purity of colour rather than carat size.

Ruby: Natural ruby originates in Tanzania and is a pink to blood-red gemstone. It is highly durable and one of the few gem species whose colour reaches saturation levels. Fine quality rubies are some of the most expensive gems with prices reaching more than $100 000 per carat for especially fine specimens.

How to choose your gem

World-class gemstones are extracted from hundreds of mines across Africa and sent to laboratories for cutting, refining and colour enhancement procedures. There, the quality of the gemstone is established based on clarity and the physical attributes comparable with the benchmark items.

The four Cs of gem grading are colour, clarity, cut and carat (weight). Gemologists grade gemstones based on these properties. Gemstones are also graded by the rarity of their features. Ultimately, though, you need to purchase a gemstone that suits you personally. What’s best for you, e.g. a big stone, may not necessarily be the top grade of the gem.

The four Cs are interrelated and each factor has a range.

Colour: This can account for 50% of a gemstone's value. A stone should neither be too light nor too dark. It should be a vivid, rich colour. The three components hue, tone and saturation are used together to describe an individual gemstone and they all vary.

Clarity: This seems to be the second most important factor in evaluating gemstones. Gemstones are categorised into clarity types based on the formation process. Gemologists simply grade most coloured stones either eye-clean (no inclusions visible to the naked eye), slightly, moderately or heavily included. Eye-visible inclusions always lower a gem’s value. Coloured gems are grouped into three clarity types: Type 1 – usually eye clean; Type 2 – usually included; Type 3 – almost always included. Generally, the highest values go to stones with pure hues and strong, rich colours. With high-value gems, subtle variations make a significant difference in price. Most people won't see the difference but to an expert grader, it is clear and obvious.

Cut: This will affect the gemstone’s brilliance and sometimes the colour, hence the gemstone’s value. Gemstones become lighter as their size is reduced, which may be a good thing for darker stones, but it may make a light stone lose even more colour. A properly cut gemstone will reflect most of the light coming through the back of the stone in an even pattern, giving the stone its brilliance.

Carat: The weight of the gemstone needs to be taken into consideration. Gems are measured by carat weight (1ct = 1/5 gram). Price per carat varies among the gemstone groups. Gemstones in larger sizes are rarer and thus receive a higher price per carat.

So in order to assess the value of any gemstone, a good understanding of these factors and their variations is needed. Enlist the help of a certified gemologist or well-established jeweller.

Given the state of development in most of the producing countries, one can expect African gemstone production to increase in the coming years. But the supply from most of these mines is very limited, and one has to be an opportunistic buyer and exploit the opportunity when supply is plentiful.