Diamonds, Precious Metals & Stones

Diamond is the hardest natural mineral on Earth

If you need in depth, technical information or have any questions at all please contact us for assistance (we have a qualified diamond grader on staff).

Diamond is the hardest natural mineral on Earth. It is made solely of carbon in crystallised form and is the simplest of all gemstones in composition, as well as one of the most spectacular.

Diamonds were created millions of years ago deep within the crust of the Earth. It is amazing to look at the beautiful gem on your finger and consider how ancient it truly is. It is the ideal symbol for eternal love.

Choosing a Diamond can seem daunting but trust your own eyes; you may think you’re no expert but remember if you think a diamond looks beautiful then it is and if you think it looks a little lifeless then it probably is dull. There are reasons that some diamonds “speak to our hearts” and have life and fire that some just don’t. With diamonds it really is about quality.

At Jason McCulloch Manufacturing we have a range of the best quality diamonds in stock and we can also source anything you like, from specific grades and sizes to rarer cuts.

When you need advice or information about diamonds give us a call, we can answer your questions, we have a qualified diamond grader on staff.

Four C s; Cut, Colour, Clarity, Carat determine the quality and value of a diamond.


Why do some diamonds sparkle more than others? It is the cut, which refers to the quality of workmanship (rather than the shape of the diamond). The better the cut the bigger the sparkle.

The importance of the cut cannot be understated. Two diamonds of the exact same size and colour and clarity grade will look completely different if one is well cut to proportion and the other is a poor cut.

The proportions of a diamonds cut must be mathematically accurate to maximize brilliance and dispersion which refers to the way light is reflected and refracted within and back out of the diamond, which creates its sparkle.

A good cut will enhance a diamonds beauty, a poor cut will considerably reduce it.

Rough diamonds are not sparkly, diamonds are polished using other diamonds and powdered diamond abrasives. Polishing produces facets on each diamond to create the sparkle that we all love.

Round Brilliant Cut diamonds (RBC) have 58 facets. Many fancy shapes have a similar number of facets and are cut to similar proportions. This is referred to as an “ideal cut” because it creates the greatest amount of sparkle

It is the quality of the cut that gives a diamond its sparkle. Better cut, bigger sparkle.


Most diamonds look colourless but there are many subtle shade differences and the closer a diamond is to having no colour the rarer and more valuable it is.

The internationally accepted GIA (Gemmological Institute of America) colour grading system uses the alphabet, starting at D (the highest grade) through to Z.

Increasing yellow (or sometimes grey or brown) tone decreases the value of a diamond (because they are more common) until the yellow colour becomes so intense that they are classed as “fancy” yellow which are quite rare. Other fancy colours are pink, violet, blue, green, champagne and cognac. The colours are caused by traces of other minerals within the diamond, for example the yellow colour is caused by nitrogen.

To determine the colour grade of a diamond, the grader must determine the amount by which the colour deviates from truly colourless; to measure the amount of colour (yellow, brown, grey etc) that is present in the stone.

Comparisons must be made to stones of a known colour. Graders use a set of master stones that have been specifically graded by a recognized trade laboratory for colour comparisons only.

Diamonds are always graded for colour whilst unset. Once set into jewellery the colour can only be estimated because the stone cannot be viewed in full and will reflect some colour from the settings.


Diamonds are a natural crystal and because of this they contain tiny internal marks called inclusions (external marks are called blemishes).

When diamonds are graded for clarity the worldwide standard of 10 times magnification is used, whether by using a loupe (eyeglass) or a microscope. The fewer, and smaller the inclusions, the rarer and more valuable the diamond.

The internationally accepted clarity grading system we use in Australia is the GIA (Gemmological Institute of America). In this scale any diamond graded as an SI (slightly included or small inclusions) or higher, has no inclusions that can be seen with the naked eye.

The higher the clarity grade the rarer and more valuable the diamond.

Inclusions can be present in the form of mineral specimens, fractures, cleavages, clouds, and external marks. All diamonds have inclusions and if they are magnified enough, they can be seen. That is why the standard 10 times magnification is used worldwide. Most inclusions are not visible to the naked eye.

Inclusions do not necessarily weaken a stone and when they do not interfere with the passage of light, they do not affect its beauty. Inclusions can be considered a diamonds’ birthmarks and as such can be used to identify individual diamonds as no two diamonds have the same inclusions.

Carat Weight

Diamonds are weighed in carats. The weight of a metric carat is 0.2 grams or one fifth of a gram. The abbreviation for carat is ct.

Each carat is divided into one hundred points (just like cents in the dollar). For example, a 50point diamond is 0.50ct or half a carat.

Loose diamonds are weighed on a diamond balance (special scales for measuring extremely small weights accurately), however mounted diamonds cannot be weighed but the size can be measured, and the carat weight is then determined using a specific mathematical formula.

The value of a diamond varies dramatically with weight because the larger the diamond the rarer it is. Therefore, five diamonds of 0.20ct each (total one carat) are not as rare and valuable as two diamonds of 0.50ct each (total one carat). To give some perspective, of the millions of diamonds that are cut and polished into gems only 2% are larger than 0.20ct or one fifth of a carat.

Precious Metals & Gemstones

In our workshop studio Jason creates unique and sophisticated, handmade pieces of jewellery using the most precious metals and gemstones found in nature.

Precious metals have been used to make jewellery for many centuries. This is because they look beautiful and have properties which render them excellent for the purpose. These metals are ductile which means they can be drawn into wires and malleable which means they can be hammered or pressed permanently into shapes. Their lustre means they are ideal for making jewellery.

Sterling silver is a white coloured metal and is relatively soft. Pure silver is 99.9% pure and is generally too soft to produce functional objects therefore the silver is usually alloyed (mixed) with copper to give it strength.

Sterling silver is 92.5% silver and 7.5% copper. The hallmark for Sterling Silver is 925.

Gold is a yellow metal. Pure gold is known as 24 carat. It is too soft to make jewellery, so it is alloyed with other metals to give it strength and sometimes to change its colour.

  • 9 carat gold is 37.5% gold and can be hallmarked 375 or 9ct or 9K.
  • 14 carat gold is 58.5% gold and can be hallmarked 585 or 14ct or 14K.
  • 18 carat gold 75% gold and can be hallmarked 750 or 18ct or 18K.
  • 22 carat gold is 91.6% gold and can be hallmarked 22ct or 22K.

White gold is gold that has been alloyed with white metals to change its colour. It can have a grey or yellowish grey tone. It is usually plated with rhodium to give a very shiny white finish.

Rose gold is gold that has been alloyed using copper to give it a pink colour.

Platinum is a white metal. It is very dense and is both malleable and ductile. It is usually alloyed to 95% and does not require rhodium plating. It is rarer than gold and harder.


Gemstones have fascinated people since ancient times. In past centuries they were reserved for the ruling classes, the wealthy and powerful. Today all of us can enjoy wearing beautiful gems.

Traditionally the “precious” gems are Diamond, Sapphire, Emerald and Ruby. “Semi-precious” refers to softer stones of perceived lesser value, however today many semi-precious gems can be more valuable than “precious” gems. It all depends on how rare they are and the quality of the gem.

The variety of gems available today gives us almost unlimited choices of colours and cuts. At Jason McCulloch Manufacturing we can help you find the perfect gemstones whatever the occasion. Whether you love the traditional or need something unique we can source all types of stones.

If you have any questions give us a call or email.


JanuaryGarnetRed, also pinkish red, orange, green
MarchAquamarineLight blue
AprilDiamondWhite, also pink, yellow, champagne, cognac, black
JunePearlWhite, also cream, golden, pink, black and dyed
AugustPeridotLight green
SeptemberSapphireBlue, also yellow, pink, clear, green, black
OctoberOpalMulti colours
NovemberTopazLight blue, also yellow
DecemberTurquoiseBlue – green, various shades