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Platinum (Pt)

 

Platinum has been used in jewellery making for a century. It is one of the rarest elements in the Earth’s crust, and it exhibits a remarkable resistance to corrosion. It has a hardness of 4-4.5 which means it is not easy to work with. Its metallic lustre with a whitish steel-grey colour makes it attractive to be used for jewellery. However, due to its rarity and high melting point, the price is more expensive than gold. Platinum resists oxidation in air at any temperature, and are useful in many industrial as well as decorative processes. The important sources are South Africa, USA, Canada, and Russia.

 

Gold (Au)

 

Gold is the most popular precious metal used in the jewellery industry. People are attracted by its highly bright and luxuriously golden colour. Gold maintains without oxidizing in air or water and resists attacks by individual acids, but it can be dissolved by the nitro-hydrochloric acid. It has a hardness of 2.5-3, which makes it easy enough to work with but sometimes too soft in its pure state. It is therefore often alloyed with other metals to increase the hardness for making jewellery.

 

Carat (Ct) is a term used to express the purity of gold in present. Twenty-four carats (24k) means 100 percent of gold is present. Eighteen carats (18k) or sometimes 750 appearing on a piece of gold jewellery represents that there are 18 parts out of 24 (or 75%) of pure gold. Pure gold is of a yellow-golden colour in its original state. By adding other metals such as silver, platinum, nickel, or zinc it converts the colour to pale or white gold; adding copper will result in red or pink gold, and iron gives a tint of blue. Large deposit gold mines are found in South Africa, Russia, Brazil, Canada, U.S.A., and Australia.

 

Silver (Ag)

 

Silver is one of the precious metal commonly used in making jewellery, high-valued silverware, ornaments, and currency coins for more than a thousand of years. It has a silver-whitish colour and a hardness of 2.5-3. With this hardness, it is also too soft for making jewellery suitable for everyday wear. It is therefore alloyed with other metals, usually copper, to make the silver present in 92.5%, increasing its hardness to a more suitable state for making jewellery. The greatest silver mine is known to be in Mexico; other major mines are U.S.A., Canada, Australia, Peru, Russia, and Kazakhstan.

 

In many cultures, silver has its special symbol of purity. In Christianity, it symbolises Divine Wisdom. The lore of silver is said to relate to the Moon, which in principle relates to the female. It is also believed that silver is associated with the dignity of kingship. However no matter what symbolization it holds, you may choose to wear it simply just for its beauty and pleasure.

 

Diamond

 

Diamond is known to be the hardest mineral and the most valued gemstone. It has a hardness of 10, with adamantine lustre and brilliance colour dispersion (known as fire) when carefully faceted in the right proportions. Its chemical composition is pure carbon and the extreme hardness is a result of the atoms being bonded and compacted together by high pressure and temperature in the earth’s upper mantle. The greatest mines of diamonds are found in South Africa, Canada, Russia, and Australia. Other mines are found in Angola, Borneo, Botswana, Brazil, China, Democratic Republic of Congo, India, Tanzania, United States, Zimbabwe.

 

In the jewellery industry, the value of Diamond is graded in its clarity, colour, carat, and cutting, known as ‘four Cs’.

 

Clarity – The number of inclusions found in diamond will affect its purity; the lesser the better. Grading is as follows:

 

FL to IF - no inclusions seen under loupe will be grade (FL) flawless to (IF) internal flawless

VVS1 – this means inclusions are extremely difficult to see

VVS2 – this means inclusions are very difficult to see

VS = Very Slightly Included, i.e. VS1, VS2

SI = Slightly Included, i.e. SI1, SI2

I = Imperfect, i.e. I1, I2, I3

 

Colour – Colour grading applies to white diamonds.

 

D = Exceptional white. Face up colourless.

E = Exceptional white. Face down colourless.

F= Rare white.
G; H; I; J; K; L; …… down to Z

Fancy = Fancy colour with definite colour appearance.

 

For white diamonds, D is the highest grading. However, natural fancy colour diamonds are rare and have become ever so popular in jewellery; vivid pink, canary yellow, and blue diamond prices are increasingly high in the market.

 

Carat weight – Carat refers to the weight of the stone. Larger sized diamonds are rare; heavier stones therefore have a relatively higher price per carat and are proportionately more valuable than smaller size stones.

 

Cut – There are several types of stone cutting; the common cuts for diamond are round brilliant-cut, where fire dispersion can be greatly seen; pear-shaped, heart-shaped, marquise shaped brilliant-cut, emerald-cut, baguette-cut, eight hearts and eight arrows-cut are also commonly used. Lapidaries will design which cutting and shape will give the best ‘four Cs’ to a diamond in terms of its value.

 

Sapphires & Rubies

 

Sapphires and Rubies are natural aluminium oxides of which both belong to the same mineral group-corundum. They have a hardness of 9, and therefore they’re very hard gemstones among other colour gemstones except Diamond. Sapphires are found naturally in wide range of colours, such as blue, green, yellow, orange, pink, white and black; except red which is known as Ruby. Both sapphire and Ruby have high vitreous lustre. The cuttings for Sapphires and Rubies are similar to Diamond, brilliant-cut are commonly used for good quality and clear stones; however, stones with long parallel inclusions when cut in cabochon shape could result in the stone to appearing to have a six-rayed star in the centre when direct light shine above. Good quality sapphires and rubies (rich in body colour and red fluorescence) found from Myanmar have relatively higher prices. However, the most prized sapphires are from Kashmir, northern India. These stones have a rich blue hue with a unique velvet lustre caused by the presence of minute inclusions. Good colour sapphires are also found in Thailand, Sri Lanka, and Tanzania.

 

Coloured Gemstones such as Chrysoberyl (hardness 8.5), Spinel, Topaz, Emerald, Aquamarine, Tourmaline, Garnet, Jadeite, Peridot, Amethyst, Citrine, Smoky and Rose Quartz, Morganite, Moonstones, Opal, and Lapis Lazuli are commonly used in jewellery.

 

Organic Gemstones commonly used in jewellery are Pearls, Amber, Coral, Shell, Ivory, and Jet.

 

Pearls

 

Pearls are found in different localities in both fresh and seawater. They occur in a variety of mollusc species, with principal composition as calcium carbonate and a hardness of 3. Big sized natural marine pearls are rare and valuable. Due to the large demand of pearls in the industry, cultured marine pearls from bivalves of oyster and freshwater mussel pearls are produced as the major source of supply.

 

The process of cultured pearls in the pearl farm – at first, a tiny sphere of mother-of-pearl is implanted in the mantle of the nacre; producing mollusc by hand. The implanted oyster or mussel is then placed straight into the water, and left to grow for a few years, minimum. Clean water of a suitable temperature is one of the most important factors during the harvesting years.

 

Pearl colours vary according to their species and their growing environments. Some delicate shades vary from black to white, creamy white, grey, blue, green, yellow, pink, lavender and mauve. The value of a pearl is determined by its size, colour, shape, lustre and sheen. South-sea pearls with round in shape, large in size, high iridescent rainbow-like pearly lustre and attractive colours are sold in higher prices. Pearls come from South Pacific, northwest of Australia and Japan are also popular due to their good quality and colour. Freshwater pearls are produced in China, Europe and the United States.

 

Caring for Pearls – Pearls are extremely delicate, and they therefore should not be treated with chemical solvents, they must be kept away from perfumes, hairsprays and detergents. You may use a soft cloth, mild water or a pearl cloth for gentle cleaning after wear. Humid weather may also affect the appearance of pearls; it is suggested that pearls should be kept in individual jewellery boxes to avoid scratches.