The Ideal-Scope™ and Holloway Cut Adviser*(US patent 7,251,619), two of my inventions, are used around the world to check the diamond Cut quality. We sell Ideal-Scopes online, and you can use one to check the brilliance of diamonds.

If you plan to buy an expensive diamond you must come in for a two minute Ideal-Scope demonstration with good and badly cut stones.
The pale whitish ‘ring of leakage’ seen with an Ideal-Scope looks dark and dull in real life, as no light returns from the leakage area. The example diamond (photo on left) is certified by GIA with its top Cut grade, Triple Excellent, yet it fails to meet Holloway Diamonds’ Ideal Cut standards. If 10% was cut off the bottom or pavilion of this diamond, the diameter would be unchanged, yet it would appear larger due to increased brilliance. What’s more it would cost less because the carat weight is less – good for you - but bad for a cutter. Non round or fancy shaped diamonds are the most ‘cheated’ cuts because GIA are incapable of grading the Cut quality of fancy shaped diamonds.

To select fancy cut diamonds we use a tool I make for the American Gem Society called ASET™ and with software called DiamCalc™ developed by my Russian associates. Both ASET and DiamCalc are sold at



Other Related Video Tutorials



Other Related Video Tutorials

Most diamonds have a hint of yellow or brown. The rarest and most expensive colourless diamonds are D or Icy white - on a scale that goes to Z and is yellowish. (More colour than Z is graded as a ‘fancy' colour).

At Precious Metals all our diamonds are D to H and we advise you buy a diamond in that range because most people can easily detect the "off colour" in I and lower grades. However if you want the very best then we recommend icy white D to F "collection colours" as they are known in the trade.

However some people actually like the "warmth" of I ,J or K colours. But the main reason people buy a lower Colour is simply to trade up in one of the other 4 C's. For instance in Asia, low Clarity is synonymous with ‘impure' and so Colour is often traded off for a higher Clarity.

I find about half the people in a blind "Pepsi" taste test can tell the difference between a D and an H coloured diamond; at I and lower, the majority of people can see the faint tint of yellow.

Colour has a bigger impact on price as the clarity and carat weight goes up.

Glassy looking cuts like Asscher and emerald cut diamonds show more colour than ideal cut rounds; brighter cuts face up more colourless.

Now for something odd: It is easier to see the colour of a diamond in a white setting (platinum or white gold). If you have a yellowish diamond, then setting it in a rubbed over yellow gold bezel style setting can improve the apparent colour by a couple of grades.

Fluorescent diamonds with a bluish tint (about 30% of diamonds) usually appear more colourless

Carat Weight (size is not weight)

Diamonds are rare.


The rough diamond in the centre could be cut to either the sparkly 0.80ct stone on the left, or the dull drab 1.00ct stone on the right! Weight does not equal size; both diamonds have the same diameter!


Carat describes weight: 5 carats = 1.00 gram. Carat does not describe size or measurement. Weight is crucial to cost; doubling weight quadruples price. More than 90% of all diamonds are smaller in diameter size than they should be. Well cut 1.00ct round diamonds should measure more than 6.4mm, but most carat stones are smaller than 6.3mm or 6.5% bigger surface area or ‘spread’. Smaller diameter deeper diamonds sparkle less; poor light return means they look even smaller. Why is this so common?

Cutting diamonds to save weight meets consumer demand for ‘magic’ carat weights. Sparkle is sacrificed because people want 1.00ct and 2.00ct diamonds as you can see from the chart. Cutters profit at the expense of diamond beauty. GIA, the main industry gate-keeper, is powerless because measuring sparkle is too hard. I have crusaded against poor cutting practices for decades with quite a lot of success.

magic weights

Consumers pay more for ‘magic weights’. Cutters cheat to meet demand and get a higher price per carat. Cut quality and beauty suffer.


TAKEAWAY: most diamonds are cut to save weight. Diamonds of twice the weight cost 4 times more.
Carat weight costs way more than Cut quality because it's really hard to grade Cut.




Other Related Video Tutorials

After Carat weight, Clarity has the next largest impact on cost. You can save money and get a good VS or SI diamond as long as you can’t see the inclusions, they don’t dull the diamond or risk a chip or breaking (it does happen). VS and SI Clarity’s have always held their value. Some inclusions really are ‘flaws’ and the stone might break; GIA rightly grade surface reaching ‘Feathers’ harshly. Every diamond I buy is checked for transparency and durability.

 clarity compare      clarity tip

clarity inclusion

MYTH: Higher clarity diamonds sparkle more. Expertly chosen diamonds with VS and SI inclusions sparkle exactly the same way as Flawless or VVS graded diamonds of the
same cut quality. Don’t confuse rarity and beauty.


Other Related Video Tutorials


Click here to view Diamond Buying Guide (will open in a new window)

We only stock and sell the best ideal cut round and fancy shaped diamonds. Full stop.

The "4C's" quick guide on the left side bar are good for most shoppers. The 12 page Diamond Buying Guide and videos have more detail. For serious diamond lovers and engineer types, open the Advanced tab.

Holloway Diamonds focus is on diamond look and sparkle. I am well known worldwide for helping to improve the cut quality and beauty of diamonds, together with the world's leading research scientists in the field.

I have publically asked the lab directors of the world’s major labs: “Would you buy a loved one a diamond based only on its grading certificate?” None would. Not even a top colour (D) Flawless diamond; lab grading report or cert tells them if it is a nice sparkly diamond!

As a geologist with little diamond and jewellery experience when I opened Holloway Diamonds in 1976 (called Precious Metals till 2006) I couldn’t understand why most diamonds were poorly cut and lifeless and often cost more than sparkling beauties. The reason I discovered is that grading Cut and sparkle is very hard. Most diamonds are ‘Cut for Carats' not for beauty; Cut is the Cinderella of the 4 C's.

We hope you will come in, see the difference in our diamonds and buy. If not then please let me help you avoid some pitfalls, and buy a beautiful diamond.

Garry HollowayFGAA Dip DT JAA Appraiser

Graduate in gemology, diamond technology. GAA past national convener of the Diamond course and frequent jewellery trade lecturer. A ‘Cut Group’ international founder - changing the way diamonds are cut around the world.

Other Related Video Tutorials