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Guide to Fine Jewellery

A glimpse of the eternal to be passed down through generations – Blacklock diamonds are as unique as they are stunning

The 4Cs of Diamonds


If you want your diamond ring to scintillate with the kind of lustre that seems to emanate from the stone itself, then the cut is the most important characteristic to consider. The cut should not be confused with the 'shape' of the diamond. Diamonds can be cut into several different shapes, which are primarily a matter of style and taste, but the 'cut' determines how well the light enters the stone and is reflected back outwards to give it that mesmeric brilliance that makes diamonds so desirable. The 'cut' characteristic is graded as follows; 'excellent', 'very good', 'good', 'fair', 'poor'. The desired effect of an 'excellent' graded cut brilliant diamond is to achieve total internal reflection.

Illustration of a diamond internal reflection


A diamond's colour is another of the key characteristics, and one that also determines its value. Jewellers value diamonds based on a colour scale represented by the letters D through to X, with the very purest white diamonds at the 'D' end of the scale. These are extremely rare, and their price reflects that, but if you are buying a solitaire engagement ring from a reputable jeweller, they will be able to advise you on the different cuts of diamonds available, and how to get the best for your money. Interestingly, the colour scale starts at D because it is thought that it may be possible to find stones even whiter than 'D' colour diamonds, which of course would make them incredibly rare and valuable.

Diamond colour chart


They say that diamonds are a girl's best friend, and when you think about it, they do have some things in common. Diamonds may look beautiful on the outside, but they all have inner flaws that make a big difference to how prized they are. These flaws, or "inclusions", can be anything from small cracks known as 'feathers', to tiny 'pinpoint' inclusions that appear as minute black spots. Inclusions occur as the diamond is being formed under intense heat and pressure over thousands of years, and their size, position and number in the stone dictate the clarity of the diamond. There are also surface flaws known as "blemishes" to look out for, but essentially, the thing to be aware of is that the very best diamonds are those with fewer inner flaws - some interesting parallels could be drawn here, but that's a discussion for another time.

Diamond clarity chart


A carat is simply the unit of measurement by which the weight of a diamond is measured. There are 100 points to a carat (0.01cts = 1 point / 0.50cts = half a carat). Carat does not measure the size directly - carat is the value of the weight of the stone. It isn't difficult to figure out that the larger the diamond, the rarer and more expensive it will be, but obviously the cut, clarity and colour still play a large part in determining the price of a diamond, no matter how large it is.

Diamon carat chart

Caring for your Fine Jewellery

Caring for your jewellery is paramount to keeping it looking its best for years to come. Here at Blacklock Jewellery we are able to draw on over 175 years of experience of caring for fine jewellery so we feel we are well equipped to pass on some helpful tips.

To ensure the longevity of your jewellery, here are some of our best jewellery care tips;

Tip 1.

To clean your diamonds, sapphires and rubies, soak them in Vodka or Gin for ½ an hour then scrub with an old toothbrush. Then simply rinse with cold water. This process of cleaning should only be used on diamonds, sapphires and rubies.

Tip 2.

If the stone(s) appear to be loose, send or take them to a reputable jeweller as soon as possible to check that they are securely set.

Tip 3.

To clean precious metal, dampen a cloth with surgical spirit (not methylated spirits) and rub carefully, then dry with a cloth. Always use non-abrasive cloths.

Tip 4.

Once every six months take your jewellery to a reputable jeweller to be cleaned professionally.

Sometimes your jewellery can be damaged and lose its brilliance if not cleaned properly or stored correctly. Here are some guidelines, gleaned from experience, that should help to prevent accidental damage;

Tip 5.

Porous stones such as emeralds and opals can crack and fracture if non-alcoholic based cleaning products are used. The product enters the stone and expands whereas alcoholic based cleaning products evaporate away, so take care in choosing the right cleaning solutions. Using warm, soapy water coupled with gentle scrubbing is the safest way to clean porous stones such as emeralds and opals.

Tip 6.

Storing your jewellery correctly is also very important. Ensure that your jewellery is not left in strong sunlight for long periods, as certain coloured stones can change colour and in some cases lose colour when left in direct sunlight for long periods. Gemstones with 2 phase inclusions (those containing liquid) should never by left in sunlight or on hot surfaces as the liquid will expand and split the stone. Gold jewellery can discolour if stored with other jewellery – for ease store gold jewellery separately from other jewellery.

Tip 7.

If not cleaned properly your diamonds and gemstones will appear colourless and lifeless. Diamonds generally attract grease and can become coated in an oily film when they are immersed in dishwater. Contact with hand and body lotions also adds to the build-up of grease and dirt. Diamonds can be safely cleaned with lint-free cloths, commercial jewellery cleaning solutions, and again scrubbing with soapy water or the gin and vodka method detailed earlier!

In short, any dirt will affect the colour and brilliance of a gemstone - hindering the 'play of light' within the stone. The advice is simple; care for your jewellery and it will last you a lifetime and beyond.

From Rough to Cut

The journey of a diamond

Diamond trading goes back over a 1,000 years, many of the traditional practices have changed surprisingly little since the days when merchants transported diamonds out of India, across Arabia on their way to Europe's capital cities.

Extraction technology, sorting and grading have all been significantly improved by technology, however, one thing that remains a constant is the need for the human touch. It takes a skilled eye to assess the quality and value of a diamond and skilled hands to undertake cutting and polishing where a lifetime's experience will never be replaced by a machine.

We are often asked about what happens to a rough diamond once it is mined. The below details this journey..

There are essentially three stages for the crystal being mined to the stone being in the hands of a customer, passing through up to 8 sets of hands.

  1. At the upstream stage the diamond is mined from the ground, sorted and sold by the producer / mining organisation.
  2. At the mid-market stage the diamond is cut, polished and then sold again and finally manufactured into a piece of jewellery.
  3. At the downstream stage the jewellery is sold to the customer.

At each stage of the journey the price of the diamond increases, often due to wastage.

5 carats of rough must be mined to create 1 carat of polished goods.


When a rough stone is first mined it is categorised according to its size, shape, clarity and colour. These factors ultimately determine the style and shape of the polished diamond.

This sorting process takes place in two locations; picking and entry-level sorting takes place at the mine and then at a separate location the second level of sorting and valuation takes place before entering the mid-market phase of its journey.

From here a diamond generally follows one of two routes, which conform, to the Kimberley Process (the process which stops conflict diamonds from being traded).

They are either sold to a large mining company such as De Beers or to an independent mining organisation that sells directly to the retailer or consumer through aggregate sites and such like.


Once they leave the mine, they are sent by the diamond trader (large mining company or independent trader) to one of the major cutting centres around the world - London, New York, Antwerp, Tel Aviv and Mumbai. Each centre specialises in different type of diamond cutting. (insert Diamond icon) Mumbai cuts mainly 'smalls' (diamonds under 0.10cts), New York specialises in cutting over 2 carat diamonds and so on.

When sent they are put in a tamper proof container with a government validated Kimberley Process certificate. Without this certificate the diamonds will not be allowed to enter another country. Diamonds that do not have a Kimberley Process certificate cannot be guaranteed to be conflict free. Once in the appropriate cutting centre they will then be cut and sorted again into parcels according to the cut, colour, carat and clarity – the 4C's.

Every year the Diamond Trading Company (DTC), the marketing arm of DeBeers holds ten week long selling sessions ('sights') whereby a handful of diamond manufacturers and diamond traders are invited to purchase these 'parcels' of diamonds. These invitees are called sight holders and are in a much sort after position. There is a minimum trading account for each organisation and if this is not achieved they are not invited back.

Once the manufacturers and traders purchase the diamonds they generally sell them on to retailers such as ourselves at an industry agreed price – this is referred to as 'Rapaport'. The stage that the jewellery is manufactured into a finished article ready for sale depends on the type of retailer being sold to. There is no hard or fast rule.

The other route from mine to market is via the independent traders who sell to manufacturers or more recently directly to the consumer through aggregate websites.

Diamonds can be sold multiple times at this stage of the journey which sometimes explains differences in price from one retailer to another.

Manufacturing of the jewellery takes place in various locations depending on the type of jewellery being created. The larger retail organisations will often manufacture in Asia whilst small, independent bespoke fine jewellers like ourselves will keep production within the UK at all times.


Once manufactured the jewellery will be sent to major selling centres such as London and Paris where it will be sold. There are many types of jewellery retailer nowadays and the various selling techniques vary from bespoke orders through to mass-produced off-the-shelf items. The demand for fine jewellery is not abating.

The difference between and benefit of one route (of the stone) over the other is often hard to define. However with the arrival of the 'Independent' dealer allows for the price of the diamond to be less easily controlled and this is therefore beneficial to the consumer. It is key for any fine jewellery retailer to try and create a streamlined network of diamond supply that limits the number of hands that diamonds pass through. Developing a strong and reliable network is essential for success.

Due to our network, size and agility we are able to source the best stones at the best prices. We are able to pass on these benefits to our clients.

Going it alone

Often the hardest decision is whether to undertake the search alone or with your partner. At Blacklocks we are old romantics so we believe it is best to go it alone – the opportunity to choose and propose with a ring that you yourself have sourced, created and presented is very special, sticks in the mind and will undoubtedly earn you multiple browny points. You are starting off your life together on the right footing.

Know what you want

The setting. The cut. The colour. There are lots of things to consider when you start looking for your ideal engagement ring. Whether it's a timeless classic like a diamond and sapphire cluster (Princess Diana's ring) or something more contemporary you need to have an idea before you begin your search.

Talk to your partner's friends for the inside scoop, make a Pinterest board you can share with your boyfriend or go window shopping together so you can enjoy the process of picking the ring without the stress of a lot of overwhelming information.

The education process should involve multiple sources and conversations – however it is easy for it to become overawed. Demystify and focus on simplicity – get ideas but go with your gut instinct!!

Three helpful questions to understand;

  1. Does she wear more gold or platinum (silver)? If neither does she have a dark or lighter complexion to her skin? A darker complexion means that gold sits better on the skin whereas a lighter complexion suits platinum better.
    In most instances we would always advise on platinum as it is the most durable precious metal with the best lustre
  2. Does she like more classical or contemporary styles? A classical style would suggest that a more traditional claw setting might be appropriate. A contemporary style would suggest a setting such rub-over
  3. Is the ring finger long and elegant or short and beautiful? The longer finger suits a step / emerald cut which is rather elongated whereas a shorter finger suits a brilliant cut or similar type of cut

Diamonds or coloured stones

Diamonds are known as a girl's best friend and make for classic, beautiful engagement rings. The Queen wears a stunning three-carat diamond ring made from the stones of Prince Phillip's mother's tiara. But if you're hoping for something a bit different then a coloured precious gemstone is a great alternative option.

The choice of coloured stone must be made very carefully as the engagement ring will be worn at all times and therefore durability and hardness are key. You don't want the stone to be chipped or damaged – the softer stones such as opal should not really be considered for an engagement ring as they are not hard wearing. Emeralds, sapphires and rubies all make beautiful engagement rings and have the requisite hardness not to be damaged when worn heavily. Jackie Kennedy wore a spectacular emerald ring at a time when diamonds were very popular.

Diamonds are the purest, hardest material known to man so they always fit the bill excellently.

On trend and timeless

There is a lot to be said for a timeless, classic engagement ring. You know it will never go out of style and will be treasured forever but if you're hinting at something more contemporary consider different cuts / shapes of diamonds, different settings and styles.

In the recent past rub-over settings became more fashionable due to more minimalist styles, however the current trend is for more layered, multi-diamond styles that combine the classic with the more contemporary. The choice of diamond, cut, shape and style is key – make sure you are informed.

Consider your budget

Elizabeth Taylor was the first person to own a million dollar diamond after Richard Burton proposed with a 33-carat ring but budgets aren't usually that high!

One of the hardest things to decide upon is the ideal budget. There are several considerations; firstly this is a symbol of your love, something that should last a lifetime and beyond, secondly investing in an engagement ring of quality will ensure a successful start to your life together and thirdly breaking the bank is not sensible, spending the appropriate amount that is reasonable within your parameters is the best way to go.

We believe that 2 or 3 months salary is a good guide.

When buying

Trust is a key issue. We have been selling engagement rings for more than 175 years so our understanding of engagement is second to none. The Blacklock Promise is about values such as craft and quality but much more than that – we sell with integrity, honesty and in a fair manner. Finding the ideal engagement ring is all about these values.

A point of note, looking beyond the purchase is important – it is essential to have recourse at all times. A fine jeweller with heritage, experience and credentials offers you that. The knowledge and understanding from how to propose to life beyond marriage will be unsurpassed!

Sizing Guide


Choosing the right size for your ring is important for comfort. Rings are crafted in sizes indicated by letters A (smallest) to Z (+), of which the commonest are shown in our table here.

To size

There are several ways to determine the correct size for your ring. If it is intended as a surprise for your partner, borrow a ring from her jewellery drawer. You can then take it to a reputable high street jeweller and ask them to gauge the size — or you can send it to us to measure.

To size your ring at home, we can send a Blacklock Jewellery ring sizer to you. Simply contact us and we will send one out accordingly.

Ring Sizing Tips

  • Measure your finger ensuring a comfortable fit
  • Avoid measuring your size in the morning, or when your hands are cold; this will give you too small a size
  • The best time to measure your finger is in the warmth, later in the day. This will give you a snug fit that's just right
  • If your measurement is in-between two sizes, always go larger
  • Make sure the gauge can be removed from the finger without expanding

We will always resize a Blacklock ring free of charge if the size is not perfect.


Our necklaces are classically 16 or 18 inches long. This is the most popular length. This length allows the pendant itself fall below the neck.

These lengths can be increased upon request with additional inches added on a jump ring to allow for something more versatile – you then have the option of wearing it longer or shorter dependant on occasion.

Simply request at point of sale.


Our bracelets measure 17cm (6.5 inches). We are able to lengthen or shorten most bracelets without issue – this process is dependent on the links and general construction of the bracelet. Simply request via email or telephone at point of sale.

Our Returns policy will allow for the item to be exchanged for an alternative of a different size if required.

Sizing Chart

Anatomy of a Ring

Appreciating the anatomy of a ring will greatly help when talking technicalities.

Illustration of the anatomy of a ring

Conflict Diamonds & The Kimberley Process

'Conflict diamonds' is the term given to rough diamonds which are used by rebel groups to finance armed conflict against legitimate governments. They were first brought to the world's attention in 1998 by a non-governmental organisation called Global Witness, who had evidence that a number of diamond mines in Angola had been taken over by an insurgent group called UNITA. These rough diamonds were then smuggled out of the country and sold, with the proceeds being used to buy weapons and supplies. Civil wars in Sierra Leone and the Democratic Republic of Congo have also been funded in this way.

Peace has recently been restored in these countries, but the diamond industry has worked with the United Nations, international governments and non-government organisations to implement a scheme to prevent conflict diamonds entering the mainstream rough diamond market. This is known as the Kimberley Process Certification Scheme.

How the Kimberley Process Works

The Kimberley Process was set up in May 2000, and is an International Certification Scheme controlling the import and export of rough diamonds. It gives reassurance to consumers that they are not purchasing stones that are financing wars and human rights abuses.

Forty governments around the world participate in the Kimberley Process, and 99% of the world's trade in rough diamonds takes place in these countries. Every shipment of rough diamonds which is exported across international borders is sealed in a tamper-proof container, and is accompanied by a government-validated Kimberley Process Certificate. The certificates are resistant to forgery, uniquely numbered, and include a full description of the contents of each container. The shipment can only be exported to one of the other countries which participates in the scheme.

Regulation of the Scheme

The World Diamond Council has laid down a system of self-regulation for the diamond industry to provide assurances for consumers purchasing cut and polished diamonds, and jewellery which contains them. Through this system, diamond buyers agree to only purchase their stones from suppliers who give the following internationally recognised warranty:-

'These diamonds are purchased from legitimate sources not involved in funding conflict and in compliance with United Nations resolutions. We hereby guarantee that these diamonds are conflict-free, based on personal knowledge and/or written guarantees provided by the supplier of these diamonds.'

All of our Diamond suppliers adhere to this warranty.

A-Z of Fine Jewellery

The process by which an article is sampled, tested and marked to identify its precious metal content (see Hallmark).
The sparkle that a diamond displays, specifically the way in which white light is reflected back out of the top of the diamond.
Brilliant Cut
A round cut shaped diamond with 57 facets arranged precisely to create optimal brilliance.
One of the Four Cs, a diamond's weight is expressed in carats; the greater the carat weight, the more expensive the diamond. One carat is equivalent to 200mg or 1/5th of a gram. The word 'carat' is derived from 'carob'. In ancient India gems were weighed with carob seeds which are naturally uniform in weight. See The 4C's of diamonds.
Another of the Four Cs, clarity assesses the internal and external perfection of the stone. All but the rarest diamonds contain inclusions, which are tiny natural imperfections in the structure of the stone. They are often not visible to the naked eye but may be viewable under magnification. The clarity scale runs from 'FL' (flawless) to 'I3' (marks visible with the naked eye). See The 4C's of diamonds.
Claw Setting
Precious metal claws hold your diamond in place, ideally allowing the maximum amount of light into the diamond to enhance the beauty of your stone. The most common claw setting is a 4-claw, however 6-claw settings are prevalent.
Another of the Four Cs, indicating how much colour tint is within a diamond. A white diamond should be as colourless as possible; however, since diamonds are a natural product, most stones have a trace of tinting. The scale runs from 'D – colourless' down to 'Z – strongly coloured'. E to J tints are rarely visible to the naked eye. Higher letters indicate yellow and brown tones.
Pink, blue, red, and green diamonds are also found, but are exceedingly rare and expensive: these are called fancy coloured diamonds. They do not follow the normal price scale for diamonds and are therefore priced separately. See The 4C's of diamonds.
The top half of the diamond, from the girdle to the table facet. A well-proportioned crown means optimal fire and brilliance in the stone.
The bottom point of the diamond. Sometimes the culet is faceted to reduce the possibilities of damage to the stone, however light can escape from the bottom of the stone if it is faceted. This is one of the many factors we look at when carefully selecting our gemstones.
Cushion Cut
An antique cut in the shape of a cushion. It is a cross between an 'old mine cut' (deep cut with large facets) and a modern brilliant cut oval. It has fire and brilliance and makes the most of the diamond.
One of the Four Cs, the quality of the cut is crucial to the overall beauty of your diamond. Cutting a diamond takes time and great skill; an expert gem-cutter follows precise geometric rules to ensure optimally cut diamonds that sparkle. On a diamond certificate, cut is graded from 'poor', 'fair', 'good', 'very good' to 'excellent'. See The 4C's of diamonds.
Diamond Certificate
A document issued by one of several independent gemmological laboratories to accompany your diamond. It contains an expert gemmologist's analysis of an individual diamond's dimensions, proportions, colour, clarity, symmetry, polish and other characteristics. The certificate guarantees your diamond's quality. Sometimes considered the 5th C.
Emerald Cut
A stepped, rectangular cut with cropped corners. It produces less fire and brilliance than a brilliant cut diamond. It is a beautiful cut where you can look deep into the heart of the stone.
The flat polished surfaces of a diamond. A round brilliant diamond has 57 facets; all facets are individually named.
Another word given to 'cutting'. The process in which a diamond's facets are formed by an expert gem cutter.
A description used for diamonds of rare and desirable colours, rather than the more common yellow or brown tints. 'Fancy' diamonds exhibit a pure tint of colours such as pink or blue, and are priced outside the usual scale for white diamonds. 'Fancy' is also used to describe cuts of diamond other than brilliant.
One of the most important visual qualities. Fire is created by the quality of the cut and refers to the spectrum of coloured light reflected out of the top of the diamond from within.
An internal imperfection of a diamond (also referred to as an 'inclusion'). There are many types of flaws, from 'feathers' to 'clouds', which are documented on the certificate for each stone. Not all flaws are visible to the naked eye. For more on how flaws are graded, see Clarity.
Some diamonds exhibit a natural blue fluorescence under ultraviolet light. A much debated quality in a diamond, it can be desirable in the right quantities: fluorescence can enhance the colour of the diamond to be more white and in certain cases make it glow. It adds another layer of interest to the stone.
The outer edge of the diamond, separating the crown and pavilion of the diamond. The girdle of a diamond is characterised by its thickness and whether it is faceted or polished.
Grain Setting
Tiny beads of precious metal, precisely positioned to retain each stone.
Hallmarking, carried out by an Assay Office, involves assaying articles made of precious metal and marking them to indicate that they are of a minimum standard of purity. It is a legal requirement for all precious jewellery sold in the UK to be hallmarked. Hallmarks identify where the article was assayed (London, Birmingham, Edinburgh or Sheffield), who made it (maker's or sponsors mark), purity of the metal and usually the year of production of the article.
Illustration of Hallmarks
An example of a Blacklock hallmark – 'RHB' – the Blacklock Makers Mark, the Leopard's head signifying the item was hallmarked in London, '950' fineness indicates that the item was hallmarked as being 950 parts out of a 1,000 being pure platinum – the remaining 50 parts are alloys, the sceptre indicates that the item is platinum and the year mark gives the item a date as to when it was hallmarked (indicating the year of fabrication).
Any internal or external imperfection of a diamond, sometimes also referred to as a 'flaw'. There are many types of inclusion, from 'feathers' to 'clouds', which are documented on the certificate for each stone. Not all inclusions are visible to the naked eye. For more on how flaws are graded, please see 'Clarity'.
The precious metal part of the jewellery without the stones, encompassing the head and the shank.
The process of holding stones in the mount; also described as 'setting'.
Oval Cut
A brilliant cut diamond in the shape of an oval.
The bottom half of the diamond from the girdle down to the culet. The right proportions of the pavilion are crucial to the fire and brilliance of your diamond; too deep, too shallow and the light will leak out of the bottom of the stone making it look lifeless.
Pear Cut
A teardrop-shaped diamond with brilliant-cut diamond characteristics.
An expression of weight of a diamond. One point is equivalent to 1/100th of a carat; a 0.75-carat diamond can be said to weigh 75-points.
The smooth finish on the facets of a diamond. Certificated diamonds are graded on the quality of their polish.
Princess Cut
A square-shaped diamond with a cutting pattern designed to achieve great brilliance like that of a round brilliant cut.
The relationship between the depth, table, girdle, symmetry, and pavilion angles. Perfect proportion is the aim of the cutter. Proportion influences light refraction and reflection, and therefore the quality of the cut.
Radiant Cut
A rectangular shaped diamond with the characteristics of a brilliant cut diamond. The radiant cut was created to combine the emerald cut with a brilliant cut so that maximum fire and brilliance is exhibited.
Rub-Over Setting
A diamond set into the top of a precious metal collar with the edges pushed over to hold the stone in place.
Scintillation is the play of white and coloured flashes of light seen when the diamond is viewed in motion. Viewable with the naked eye, scintillation is the life of the diamond.
The amount of light reflected from the diamond as it moves. It is the combination of fire and brilliance.
The part of a ring which holds the head in place; the bottom and lower side of the ring.
Shape describes the outline form of the cut (round or oval, for example). The two are often used together, e.g. round brilliant cut.
The overall uniformity of a diamond's cut. Symmetry applies to the pattern of the cut, not just the outline shape. The symmetry grade can go from poor to excellent. Poor symmetry will decrease a diamond's sparkle because light leaks from the stone.
The top facet of the diamond. Its size influences the proportions, fire and brilliance of the diamond.
Tension Setting
An innovative setting by which stones are held in place using only the tension and pressure of the surrounding metal. This setting does not involve claws. Tension settings are featured in our Classic collection.
Total Internal Reflection
A measure of how well light travels into and back out of a diamond. When the facets of the stone are polished to the correct angles and ideal proportions, you achieve total internal reflection. This is found in diamonds with the highest grade of cut.