A guide to buying diamonds and Tanzanite

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A guide to buying diamonds and Tanzanite

All you need to know about buying jewellery in Cape Town

Last updated: 28 March 2023

With so many visitors buying diamond and Tanzanite jewellery in Cape Town, it was our team's goal to build a simple yet expert guide to buying these precious gems.  

What makes a “good” diamond? The aesthetics are important, but also significant is the value. Four “Cs” determine this, and these are the fundamentals you should know when selecting your diamond, according to South African diamond expert, Yair Shimansky.

The patented Millennium diamond ring is an original and iconic Shimansky design. The two bands represent the coming together of two lives, joined by a beautiful diamond in the middle that becomes a symbol of forever. Image: Shimansky


​​Shimansky is one of the most trusted diamond jewellery brands in South Africa. Experts in the diamond and Tanzanite industry for more than two decades, Shimansky is motivated to capture your special moments with beautiful crafted jewellery that will last a lifetime.


There are four key factors that must be taken into consideration when evaluating the worth of a diamond or Tanzanite: Cut, colour, clarity and carat. And then one more “C” – Confidence. This weighs up the ethicality of a stone’s origin and its journey. Here's what these key factors mean and how to apply them when purchasing your next diamond jewellery item.

An engagement ring is a timeless symbol of love and commitment. And for the rest of your days, your carefully chosen Shimansky Engagement Ring promises to be a constant reminder of the romance behind your unique journey together. Image: Shimansky


One of the most important C’s is the cut of a diamond. It affects how light is directed within the stone to increase (or decrease) the diamond's sparkle. Optimal proportions and symmetry result in greater light reflection, which enhances the diamond's value.

The patented one-of-a-kind My Girl diamond features a unique square cut and diamond-shaped table – the first of its kind in the world. Image: Shimansky 


The benchmark standard known as the “Ideal cut” originates from the work of the diamond designer and engineer, Marcel Tolkowsky, who calculated the optimal angle for a diamond to display its most intense fire and brilliance. Shimansky’s internationally patented cuts – Brilliant 10 and My Girl – are formulated to give the diamond more fire, brilliance and scintillation.

The cut of a diamond brings out its brilliance. This is Shimansky’s classic Victoria ring. Image: Shimansky


In terms of Tanzanite, if the cut is too shallow, the shade of violet or blue will be lighter and, therefore, less valuable. Generally, the deeper the cut, the more intense the colour and more valuable the stone. The shapes that yield the best intensity are the Cushion, Oval and Trillant cuts.


The closer a diamond is to being absolutely colourless – with no hint of yellow or brown – the more rare and valuable it is. On the other hand, a stone with a rich yellow, orange, pink, green or blue colour is very rare, and this makes it valuable. These jewels are called Fancy Diamonds, and are even more expensive than pure white ones.

Extremely rare and valuable, natural fancy yellow diamonds sparkle with the most magical golden hues. Image: Shimansky

The colour of Tanzanite is predominantly blue or violet, and the more intense this is, the more rare and valuable. What sets this gem apart from many others is the fact that it is trichroic, meaning it displays three colours – violet, blue and red – when viewed from three different angles.

One thousand times rarer than diamonds, Tanzanite is a truly unique African gemstone, with an exceptionally brilliant blue-violet colour. Image: Shimansky


Diamonds and Tanzanite may show minute traces of other minerals, which appear as natural imperfections known as inclusions. A stone is rated according to inclusions, known as the “clarity factor”, which gives an indication of how many of these marks there are. The more clear or flawless a diamond is, the more desirable and valuable.

Try for as clear a diamond as you can afford – the less flaws, the more valuable. Image: Shimansky


The carat indicates the weight of a diamond, with one carat being equal to 200mg. The larger the diamond, the higher its carat weight and the greater its price and worth. 

However, the value of a stone is not only determined by carat size, but by all of the factors above. So you may, for example, decide to buy a smaller diamond with high clarity and colour or you may opt for a bigger diamond with lower colour and clarity.

One carat is equal to 200mg, and that applies to both diamonds and Tanzanite. Image: Shimansky


Tanzanite is 1 000 times rarer than a diamond and, with only one known source to date, it’s predicted that within the next 10 to 12 years, no more gem-quality Tanzanite will be found. This is why it is possibly a good investment.


This is the confidence factor. It’s not yet an official “C” but is still a widely accepted one, and refers to the amount of confidence you have in the jeweller you’re buying from and the assurance that a diamond is as valuable as it’s claimed to be. 

The stone should be certified by an independent diamond body, like the Gemological Institute of America (GIA) or the European Gemological Laboratory (EGL), and it should come with an authentic certificate, which breaks down the 4 Cs. 

It’s important that the diamond is certified, from its history through to the value. Image: Shimansky


Shimansky, V&A Waterfront 

Shop 6259, Upper Level

Opening hours: daily 9 am - 9 pm

Shimansky, Rockwell

Corner of Prestwich and Alfred Street, Green Point, Cape Town, 8001

Opening hours: 9am - 6:30pm

Shimansky Showroom

Level 1, The Clocktower, V&A Waterfront

Opening hours: Mon-Sun, 9am – 9pm

Email: (feel free to contact them with your requests or questions before you visit)

Follow Shimansky on Instagram:



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