CIBJO is the international trade organisation of

the world jewellery industry. Its members comprise

representatives of commercial organisations

and over 70 national jewellery associations in

more than 34 countries. Established in 1926,

CIBJO educates and communicates on matters

of business responsibility by raising awareness

of consumer confidence issues, distributing

information and acting as a forum for the

worldwide industry to debate its views.

CIBJO’s ‘Code of Ethics’ is designed to give its

members overarching principles to help them

operate according to strict ethical, business

and consumer confidence guidelines. Jewellery

retailers can refer to CIBJO’s membership to

identify whether their suppliers should adhere

to the Code.

CIBJO – The WOrld JeWellery COnfederaTIOn

www.cibjo.org

DIamOnDs, COlOurED GEmstOnEs, PEarls anD PrECIOus mEtalsa COnsumEr GuIDE

Welcomea piece of jewellery is one of most inspirational, exciting and magical purchases

you can ever make. Whether the piece is for you or a loved one this guide will

take you through the basic information about diamonds, coloured gemstones,

pearls and precious metals.

the guide has been put together by the most knowledgeable experts in the

global jewellery industry. We hope that by empowering you with the knowledge

about the jewellery we sell, it will help you make the right choice.

Please enjoy your guide to: Diamonds, Coloured Gemstones, Pearls and

Precious metals.

Best wishes

Jonathan Kendall, President, marketing and Education Commission, CIBJO

Contentslearn more about diamonds 2

Introducing gemstones 9

mini guide to birthstones 11

understanding pearls 14

Overview of precious metals 18

this guide was co-ordinated and produced by andré marais, Forevermark,

De Beers Family of Companies and roland naftule, CIBJO President sector III

the project Gem materials co-ordinator

learn more about diamondsDiamonds are one of nature’s most rare and

precious gifts. their age and history, symbolism

and amazing brilliance, make them the jewel

of all jewels.

this section of the guide gives you an

understanding of diamonds. It is designed to

help you appreciate their complex charms and

to give you more information and practical

advice. then you will have total confidence

in your own choice.

First discovered in India, diamonds are now

mined in many parts of the world, including

africa, australia, Canada and russia. they can be

found in remote deserts or even the ocean beds.

amazingly, only a tiny portion of those found are

of a size and quality that can be cut, polished

and set into jewellery.

Diamonds are symbols of love, devotion, pride,

wealth and power – the ultimate gift from a loved

one, or to yourself. the decision to buy a diamond

does not come lightly. It is therefore crucial you

know what you are looking for in your diamond.

there are at least 13 factors that affect polished

diamond value but the most important factors

when determining its quality are known as the

4 Cs. these are the diamond’s carat weight,

its cut, its colour and its clarity. the key thing

to note is that no one C is more significant than

another. a particular combination of the 4 Cs can

be chosen to suit a particular budget, occasion,

design or jewellery piece. Each diamond can

be described by its particular combination of

the 4 Cs, but its unique beauty is much more

than a list of characteristics. When you choose

a diamond to own or to give, it becomes special

– regardless of its place on the 4 Cs chart.

Importantly all diamonds are beautiful and come

with a heritage of being at least 900 million

years old.

2

emeraldassCher CushIOn hearT marquIse Pear rOundOvalPrInCess TrIllIanT

COmmOn CuTTIng sTyles

COlOur

as we talk about a diamond’s colour we can

talk about two different aspects. When most

people talk about a diamond’s colour they are

actually referring to colourless or near colourless

diamonds. Colourless or near colourless

diamonds remain the most available and the

most popular with consumers. However, what

most people are unaware of is that diamonds

are found in almost every colour. Diamonds

occur – albeit very rarely – in red, blue, green

and all other colours of the rainbow and are also

known as ‘fancy colours’. Due to their rarity they

can fetch exceptional prices.

there are more than 20 subtle grades of colour,

identified in alphabetical order from D-Z.

Variations are so slight that colours must be

graded by an expert under controlled lighting

conditions and compared against a master set for

accuracy. those at the upper end of the scale will

be more expensive, as they are rarer. However,

they are difficult to discern with the naked eye.

Top Tips

• When buying a diamond, consider the setting

and the metal, as it can be used to accentuate

or de-emphasise the colour.

• Be sure to try on the diamond jewellery as the

colour may look different when worn on the body.

• If purchasing a loose diamond, place the

diamond on the top of your hand and compare

it with a similar stone mounted in jewellery.

CaraT

Carat is often mistakenly used to refer to a

diamond’s size, but it is actually a measure of

weight. One carat (equivalent to 200 milligrams)

can be divided into 100 ‘points’. a 0.75 carat

diamond may also be described as a 75-point

or ¾ carat diamond. larger diamonds are found

less frequently in nature, so they can command

a significantly higher price. For instance, a one

carat diamond will cost more than two ½ carat

diamonds of equal colour, clarity and cut.

However, your diamond is not valued by carat

weight alone. two diamonds of equal carat weight

can have very different values, depending on

cut, clarity and colour. Furthermore, a smaller

but perfectly cut diamond of whiter colour and

flawless clarity can be more valuable than a larger

stone that is less white and with more inclusions.

Whatever its carat weight, you should choose

the diamond which suits you and your budget,

the occasion and the design you like best.

Top Tips

• a diamond can appear larger or smaller than

its actual weight, depending on its cut.

• look at different designs and mountings as

they can affect the appearance of the size

of diamond.

CuT

nature determines so much about a diamond,

but it takes a master cutter to reveal the stone’s

true brilliance, fire and ultimate beauty.

regardless of size or shape, a well cut diamond

will reflect light within itself, from one mirror-like

facet to another. to spot a well cut diamond,

you are looking for three important factors –

brilliance, dispersion and scintillation. Brilliance

is the return of white light to the viewer’s eyes

from the internal and external surfaces of a

diamond. Dispersion or as it is more commonly

known ‘fire’ are the flashes of spectral colours

that come from a diamond. scintillation is the

sparkle or flashes of light you see as the diamond

or light source moves. If a diamond is cut too

deep or too shallow, light will be lost through the

side or bottom; this reduces its brilliance and,

ultimately, its value.

the cut of a diamond can also affect its visual

size. two diamonds with the same carat weight

can appear to be different sizes depending on

the shallowness or shape of its cut.

the cut at its most basic level also refers to the

shape of a diamond and is a matter of personal

taste, with the round brilliant cut the most

popular. although there are many diamond

cuts the most well-known other shapes are the

asscher, cushion, emerald, heart, pear, marquise,

oval, princess and trilliant. You might also

hear of trademarked, copyrighted or ‘branded

cuts’ which have been developed by individual

companies. a branded cut will have something

unusual or a parameter that is different than

the standard cut. shapes other than round are

referred to as fancy shapes.

Top Tips

• When choosing a diamond, hold it up to

the light and see the fire. see how the light

dances around – it should throw out a

rainbow of colours and display the diamond’s

natural brilliance.

• ask your jeweller to show you all the cuts

and shapes.

• Be sure to try on a good selection to find

the perfect one for you.

2 CTs 1.5 CTs 1.25 CTs 1 CTs 0.75 CTs 0.50 CTs 0.25 CTs 0.10 CTs

75 points 50 points 25 points 10 points

guIde TO aPPrOxImaTe CaraT sIze

heIghT Of CrOWn

gIrdle

dePTh Of PavIlIOn

WIdTh Of TaBle

Well CuT TOO deeP TOO shallOW

3 4 5

ClarITy

the clarity of a diamond is its most obvious

characteristic as no two stones are alike.

Clarity characteristics include a wide range

of features but they are generally broken down

into two basic categories: blemishes, such as

surface features like scratches and nicks, and

inclusions, which are internal features and not

easily removed.

the professional will view the diamond at

10 x magnification in a controlled environment

and decide on the clarity grade considering

four characteristics of the blemish or inclusion:

size, nature, location and number. Obviously,

as a buyer you cannot see the detail of these

blemishes, but they can affect the overall

appearance of the diamond.

Flawless diamonds are the rarest and thus, most

expensive, but ultimately, small inclusions do not

affect the beauty or the brilliance of a diamond.

Be aware of the inclusions, but don’t let them

deter you from buying a diamond you love.

Top Tips

• View and try on all ranges of clarity. some

inclusions can be hidden by a mounting and

do not detract from the diamond’s beauty.

Compare them to see if they affect the

reflection of light – you will most likely find

them equally brilliant.

• If the diamond comes with a certificate, look

to see where and how many inclusions exist.

an examPle Of a CrysTal InClusIOn

an examPle Of a feaTher InClusIOn

6

synTheTICs

‘synthetic, laboratory-created and laboratory-

grown diamonds’ refers to diamonds

that are manufactured by man. they were

first made in the 1950s in industrial quality

and have been manufactured in commercial

jewellery quantities and qualities since

the 1990s.

TreaTmenTs

a diamond that has been altered by any process

other than cutting and polishing is considered

as treated. treatments may artificially modify

the colour and/or the clarity of a diamond.

Introducing gemstonesGemstones are much more precious than most people

realise. there are many different varieties and colours

and they are a fascinating group to explore and own.

they have magical qualities that have entranced and

excited generations for thousands of years.

While we cannot go into detail about each individual

gemstone we want to provide you with an overview

of the many and varied types available today.

most gems are natural, inorganic minerals. However,

some gem minerals, such as opals or natural glass are

amorphous and some gems are organic, meaning they

come from plants or animals, such as: amber, coral

and ivory.

to be called a ‘gem’ it must possess the following

features: beauty, rarity and relative durability.

When looking to buy a gemstone, these are the

three topics to quiz the retailer on.

9

Coloured gemstone section written by the Gemological Institute of america,

Carlsbad, California. all rights reserved.

Images for this section are courtesy of the Gemological Institute of america. Faceted gems

courtesy of the Dr. Eduard J. Gubelin Gem Collection, now part of the GIa Gem Collection.

mini guide to birthstonesa popular reason for giving jewellery with a

specific gemstone is that they can also be

a person’s birthstone. Below we outline which

stones are linked to which months of the year.Alexandrite and other

chrysoberyls

Amethyst

Aquamarine Other beryls Citrine Emerald The feldspar group

The garnet group

Jade Kunzite Lapis lazuli Opal

Organic gems Peridot Unusual quartzes and chalcedony

Ruby Sapphire Spinel Tanzanite Topaz Tourmaline Turquoise Zircon JANUARY

Garnet

FEBRUARY

Amethyst

MARCH

Aquamarine

APRIL

Diamond

MAY

Emerald

JUNE

Pearl / Moonstone /

Alexandrite

JULY

Ruby

AUGUST

Peridot

SEPTEMBER

Sapphire

OCTOBER

Opal / Tourmaline

NOVEMBER

Topaz / Citrine

DECEMBER

Turquoise / Tanzanite /

Zircon

1110

the following gemstones have been included as an introduction:

Gem materials are occasionally treated to

improve their appearance. the aim of treatments

is to strengthen colour, improve clarity,

accentuate phenomena, improve lustre or

improve durability of the stone. treatments

might affect the value of a gemstone so make

sure you check with the retailer.

When buying gemstones, you might also come

across ‘simulants’. these can be artificial stones,

that imitate the appearance of gemstones

without having their chemical composition,

physical properties, or structure.

many important natural gemstones, including

ruby, sapphire, and emerald, have man-made

counterparts that are manufactured in a

laboratory. such materials are called synthetic.

In all cases your jeweller should disclose

whether they are selling a gemstone,

a simulant or a synthetic.

the faceting & fashioning of gemstones the care & cleaning of gemstonesthe objective of cutting, sculpting and polishing

transparent gemstones is to show their fine glassy

polish, transparency and translucency. there are

many classic gemstone outlines. among the best

known, are: ovals, rounds, cushions, emerald cut,

pears, marquise, squares, triangles and cabochon

style cuts. Other gem shapes, including trapezoid

and hexagonal, or those with a free-form style, are

referred to as a fancy shapes. Within these outlines,

a vast array of facets, and facet combinations are

seen in gem materials. In turn, these combinations

help dictate the color, reflection and beauty that is

observed in gems. Because so much skill is required

to successfully cut or carve gemstones, there are

a series of quality characteristics you can look for

when evaluating the quality of cut.

Overall appearance:

• Face-up: the faceted gemstone should have a

pleasing ‘face-up’ appearance. It should reveal a

homogenous, even reflectivity and color in the

gem.

• the gem shape should be proportional. If you

could imagine folding a gem in half, one half

should be a mirror reflection of the other.

Faceting detail:

• Polishing marks (fine, curved scratches that

cross an entire facet) should preferably not

be observed along the surfaces.

• Facet junctions, where the lines or corners of

one facet meet up with another, should also

be crisp, sharp and straight.

Rules-of-thumb for carved gems:

• In carved gems, proportionality is not as critical;

here the artist dictates the outcome of the gem.

• some carvings may be free form. Here the

quality and evenness of polishing is important,

especially along curved surfaces.

Gems mounted in jewelry are rare and

precious heirlooms that can be lovingly passed

from one generation to another. as with all

things of value, they do require special care

considerations. For example, while some gems

are harder or more durable than others, none

should be worn while performing rigorous

physical exercise, repetitive movements or

around heavy machinery. that is because a

hard knock could endanger any gem material.

the following care considerations are also

important:

Storage:

• a clean, dry storage container with a padded

base, such as a drawer, or a jewelry box should

be used to store gems and jewelry.

• It is best to store jewels separately – in such

a way that sharp edges of one gemstone cannot

scratch another.

• When traveling, it is best to separate jewelry

into separate boxes or plastic bags so that they

cannot rub against one another.

Cleaning:

• Whenever possible clean a gemstone with

a clean, dry cloth. lukewarm water or water-

diluted mild detergent moistened cloths may

also be used for stubborn fingerprints, soil or

stains. Densely woven microfiber cloths are

best to use, as cloth fibers are less likely to

be caught in a prong.

• Organic gems such as amber, bone, coral

and ivory are generally fairly soft and porous

relative to other gems, though most also

have excellent durability. With proper care,

these may last for generations. With all

organic materials it is best to avoid the use

of chemicals solvents to clean a gem.

• ultrasonic cleaners use high frequency

vibration capable of dislodging debris and

soil that is hard to get to in jewelry. still, it

might be a better idea to reach debris with

a soft bristle toothbrush and running water.

While most gems can be cleaned this way,

it is prudent not to submit softer or more

porous gems to ultrasonic cleaners.

1312

understanding natural pearls, cultured pearls and imitation pearlsTyPes Of Pearls

today there are four types of ‘pearl’, these are

the rare natural pearls, the rare cultured pearls

that have not been subject to treatments, the

common cultured pearls where the appearance

has been artificially modified and the common

imitation pearls.

natural pearls are accidentally formed in

the interior of a mollusc without human

intervention and may be nacreous or non-

nacreous.

Cultured pearls are also formed within

molluscs but with the intervention of man,

the overwhelming majority being nacreous.

Imitation of pearls are artificial products not

formed in molluscs but manufactured by man

to only imitate the appearance, colour and

other features of natural or cultured pearls.

It should be noted that the practice of

artificially modifying natural and cultured

pearls to remove blemishes or to improve

their appearance has existed for centuries.

However with modern processing techniques,

this practice is standard procedure today for

the vast majority of common cultured pearls.

naTural Pearls

Nacreous pearls

many historical documents show that mankind

has used nacreous natural pearls as ornaments

since long before the beginning of the Christian

era. In about 4,000 BC, the Indian Ocean,

the red sea and the arabian Gulf were famous

for being a rich source of natural pearls.

In addition, many freshwater natural pearls

were found in European countries.

after the discovery of america by Columbus,

numerous saltwater natural pearls were fished

from Venezuela, Central america and mexico.

later large quantities of natural freshwater

pearls would be found from the rivers and lakes

throughout north america. nacreous pearls may be white, grey to black but

also slightly cream to yellow. Its typical growth

leads to the succession of concentric layers of

nacre. the finest nacreous pearls show a typical

bright lustre and a vivid orient, a subtle play of

all rainbow colours.

From the 1930s the availability of new nacreous

natural pearls to the market contracted, largely

due to the discovery of oil in the arabian Gulf

and the evolution of pearl culturing.

nevertheless, fine jewellery containing these

unique products of nature continue to be

available to those who appreciate and desire

these wondrous and very special prizes. Indeed,

some important pearls now have significant

collector potential and have become the

centrepiece of displays in museums and

personal collections throughout the world.

Abalone pearls

the abalone produces some of the most

interesting and certainly the most colourful of

natural nacreous pearls. Only rarely found in

symmetrical shapes these baroque pearls lend

themselves to one of a kind designer jewelry.

much sought after as a food source, the abalone

is a gastropod widely inhabiting the Pacific,

atlantic and Indian oceans. the population is

particularly rich along the coastal areas of Japan,

north america, australia and new Zealand.

1514

One Of The fInesT examPles Of an amerICan naTural

freshWaTer Pearl neCklaCe and an equally fIne

sIngle Pearl

a unIque fIve rOW neCklaCe Of naCreOus salTWaTer

naTural Pearls

aBOve: a hOrn shaPed aBalOne Pearl

WITh a rare rOund shaPed examPle

BelOW: a lOng aBalOne BlIsTer Pearl

sTIll aTTaChed TO ITs shell

Non-Nacreous pearls

there are several wonderfully fascinating non-

nacreous pearls available in the market. these

are produced by a variety of molluscs and are

generally of natural origin. Conch pearls are

produced by a gastropod commonly known as

the ‘Queen‘ or ‘Giant conch’ (Strombus gigas)

that inhabits Caribbean waters. as with many

non-nacreous pearls, conch pearls differ from

nacreous pearls by having a tough crossed

lamellar microarchitecture that manifests

itself as a flame-like structure that appears

to move as “watered-silk” when the pearl is

moved under light. Be aware that cultured

conch pearls have recently become available

and watch out for natural and cultured conch

imitations, which are produced by cutting the

thick conch shells into beads.

Other examples of non-nacreous pearls include;

the orange to reddish brown coloured horse

conch pearl produced by Pleuroploca gigantea,

a very large gastropod inhabiting Indo-Pacific

waters. the yellow to orange melo pearl produced

by the melo volutes and found in australian

waters, the south China sea, the waters around

the Philippines, the eastern coast of Indonesia

and the adaman sea. they are often spherical

and quite large but can also be baroque. Very

fine individual melo pearls have fetched very high

prices both in the trade and at auctions

CulTured Pearls

History

Cultured pearls are clear evidence of man’s

ability to merge with nature; they result from

a special relationship between man’s ingenuity

and nature’s ability to produce items of great

beauty. since their creation cultured pearls have

gradually become one of woman’s most popular

(and affordable) items of adornment; blending

with almost any fashion or skin type necklaces

of cultured pearls are today an indispensible

item in any personal jewellery collection.

there are many examples of ancient pearl

cultivation however; the modern pearl culturing

industry probably has its origins in or just prior

to 1890 when the first spherical cultured pearl

was produced by William saville Kent. While Kent

was the first to use the ‘tissue graft’ technique

to produce his spherical cultured pearls, the

first patent for this technology was actually

issued to the Japanese researcher nishikawa

by the australian Government on 24 July 1914.

subsequently, on 26 June 1916, nishikawa

was also granted a patent by the Japanese

Government. nevertheless, due to his worldwide

promotion and distribution of Japanese cultured

pearls, it is generally acknowledged that

mikimoto was the pioneer of the modern pearl

culturing industry. since then the modern day

cultured pearl industry has developed into a

significant if not the most significant presence in

the jewellery market, worldwide.

Varieties of cultured pearls

Akoya cultured pearls are cultured in Japan,

China and Vietnam using akoya oysters (P.

fucata (martensii)). Compared with other “pearl

oysters”, the akoya oyster is rather small;

hence the size of pearl produced is less than

10mm. the most popular sizes are 6 and 7mm.

akoya cultured pearls are generally bleached

in order to produce the uniform white seen in

most necklaces.

1716

akOya CulTured Pearls

varIOusly COlOured CulTured PearlsCOnCh Pearls frOm sTrOmBus gIgas

melO Pearls frOm One Of The melO vOluTes

South-sea cultured pearls are cultivated in

the oceans off northern australia, Indonesia,

and the Philippines using silver and gold-lipped

pearl oysters (P. maxima). the largest south-

sea cultured pearls and the majority of rare

cultured pearls are produced in australia waters.

the south-sea cultured pearls of Indonesia are

generally a little smaller than the australian

cultured pearls. the majority of golden (yellow)

coloured south-sea cultured pearls are produced

in the Philippines. Common south-sea cultured

pearls may be bleached, dyed or even heated to

achieve their appearance.

Black cultured pearls are cultivated in the black-

lipped pearl oyster (P. margaritifera) mainly in the

ocean around French Polynesia (tahitian cultured

pearls), but also in the waters of Fiji and the Cook

Islands, and in Pinctada mazatlanica or Pteria

sterna. rare tahitian Black cultured pearls exist in

a variety of natural colours from grey to black and

purplish green (known as “peacock green”) as well

as other colors including “pistachio”, dark blue,

“copper” and “cherry”. Common black cultured

pearls from tahiti may be bleached and/or dyed to

produce the recent “Chocolate” coloured pearls.

Freshwater cultured pearls are cultured in

lakes and rivers mostly in China, Japan, and the

united states. a freshwater cultured pearl is not

cultivated in a pearl oyster; but in a freshwater

mussel and generally this is without a bead, that is,

the process involves only a piece of mantle tissue.

approximately 40 (larger sizes) and maybe up to

100 (smaller sizes) cultured pearls are produced

by each freshwater mussel; this compares to the

norm of culturing one cultured pearl at a time per

pearl oyster. Chinese freshwater cultured pearls are

available in their natural colours, which are usually

white, orange and purple, but are mostly dyed to

almost any colour.

Quality elements

Size

most cultured pearls produced measure between

4mm and 8mm. the akoya beaded cultured pearl

ranges from 2 to 10mm. Freshwater non-beaded

cultured pearls range from 2 to 15mm. the south-

sea beaded cultured pearl (from P. maxima) and

the tahitian black beaded cultured pearl (from P.

margaritifera) range from 7mm to over 20mm.

Shape

there are many different shapes of cultured pearls:

shapes are generally described as being: round,

semi-round, oval, drop, button, semi-baroque,

baroque, and circled.

Nacre thickness

nacre thickness (the skin of the beaded cultured

pearl) is closely related to the type of mollusc

used, and the culturing period. the thickness of

the nacre covering the bead will determine the

durability of the cultured pearl. the quality and

thickness of the nacre will determine the lustre

and whether or not it possesses ‘orient’ – the

appearance of multiple but subtle colours.

Surface

the surface of a cultured pearl is examined in

terms of the number, size, kind and location of

imperfection(s). In evaluating imperfections, first,

the number of imperfections is taken into account

– whether a pearl has a clean surface, one spot

or many spots. then the kind of imperfection is

examined to determine whether there is a dent

or a bump on the surface; imperfections are

subdivided into pits, holes, pinpoints, bumps and

wells. Even if the imperfection seems insignificant,

if it is visible to the eye, it lowers the value of

the pearl.

Lustre

lustre, above all other aspects, is often regarded

as the most important characteristic of a cultured

pearl; it is an inextricable factor in defining a

cultured pearl’s beauty. lustre describes the

reflection of light from the cultured pearl. In rare

cultured pearls, lustre is created by the quality and

the thickness of the pearl nacre alone. ‘Orient’ (the

subtle array of colours found in rare cultured pearls

when light is refracted from within translucent fine

quality nacre) has a similar relationship with the

quality and thickness of the nacre. In the common

cultured pearl the impression of a high lustre is

created through the polishing process. a pearl with

good lustre will be bright and will have a sharp

reflection of light. a pearl with low lustre will be

dull and will have little or no reflection.

Colour

the colour of rare cultured pearls is only related

to the colour of the nacre of the host mollusc.

the colour of common cultured pearls may also

be related to the colour of the host mollusc’s

nacre, or will be a function of a dye artificially

applied to the cultured pearl during a treatment

or growth process.

1918

freshWaTer CulTured Pearls

varIOus levels Of surfaCe lusTre

In akOya CulTured PearlsBlaCk-lIPPed CulTured Pearls sIlver- and gOld-lIPPed CulTured Pearls

Overview of precious metalsthe best known precious metals are silver, gold

and the platinum group. the purity is measured

using a process called assaying, which, in simple

terms, means measuring the content of gold,

silver or platinum in the metal. Once an assay

office has determined the purity, they will stamp

a hallmark on the item to certify it.

gOld

Gold’s chemical symbol, au, is short for the latin

word for gold, ‘aurum’, which literally means

‘Glowing Dawn’. Pure gold has a bright yellow

colour and is one of only two coloured metal

elements, the other being copper. all other metals

are silver or grey. White golds are gold alloys that

look white rather than yellow. the white colour is

achieved by careful choice of the alloying metals,

which bleach the deep yellow of pure gold.

Caratage

Gold jewellery is usually described in terms of

‘caratage’ (‘karatage’ in the u.s.) to indicate its gold

content. this can also be described as fineness which

refers to the parts of gold per thousand by weight.

many countries only allow certain caratages of

gold jewellery to be sold. For example, in the

united Kingdom one can make and sell 9, 14, 18

and 22 carat gold jewellery, but not 12 carat gold.

In some countries jewellery lower than 12 carats

(50% gold or 500 fineness) cannot be described

as gold. the price of gold jewellery is based, in

part, on its gold content. Consequently, most gold

jewellery worldwide is marked with its caratage or

fineness, often as part of the hallmark. see across

for the appropriate levels in different jurisdictions.

Carats / Karats Fineness Gold content (%) Comments

24 999 99.9 Gold bullion

24 990 99.0 Minimum allowed for 24K gold

22 916 91.6 Indian subcontinent

21 875 87.5 Arabic countries

19.2 800 80.0 Standard in Portugal

18 750 75.0 Standard caratage

14 585 58.5 583/58.3% in USA

10 417 41.7 Minimum in USA

9 375 37.5 UK standard

8 333 33.3 Minimum in Germany

20 21

PlaTInum

Platinum is one of the rarest of the precious

metals, found in only a few places worldwide

– principally south africa and russia. naturally

white; platinum will not fade or tarnish - keeping

its natural white colour forever. most platinum

jewellery is either 90% or 95% pure, does not

need rhodium plating and being hypoallergenic,

will not cause an allergic reaction. the density

of platinum gives it a heft and its ductile nature

allows craftsman to create the most intricate of

jewellery and its physical properties ensure that

precious gemstones are held securely. although

platinum may scratch like other precious metals,

minimal metal is lost, being merely displaced,

so a platinum piece will retain its metal weight

for generations.

The platinum group

the platinum group comprises six metallic

elements clustered together in the periodic table:

ruthenium, rhodium, palladium, osmium, iridium

and platinum. they are grouped together because

they have similar chemical properties.

Assaying

the usual method for assaying platinum is known

as inductively coupled plasma-optical emission

spectrometry. a sample of platinum is scraped from

the item to be tested, and then weighed on a highly

sensitive balance. the next stage is to dissolve the

sample in the appropriate acid matrix.

this solution is then passed through the

spectrometer, which determines the amount

of platinum present in the solution as compared

to the mass of the original sample taken.

Once the purity of the platinum is determined,

the item will be stamped with a hallmark to

certify this.

PalladIum

Palladium is one of the platinum group metals

but is considered a precious metal in its own right.

It is naturally white, which means there is no

need for rhodium plating.

It is more precious than silver and lighter than

platinum (nearly half the weight) so larger

necklaces and bracelets can be made capable

of bearing bigger gemstones with no gain in

overall weight. For the same reason palladium

is considered to be a good choice for earrings

although unlike platinum it is not hypoallergenic.

Assaying

the usual referee method for assaying palladium

is inductively coupled plasma-optical emission

spectrometry, the same as for platinum.

2322

sIlver

silver is a soft, white, lustrous transition metal

and is used in currency, ornaments and jewellery.

sterling silver is an alloy of silver containing 92.5%

pure silver and 7.5% other metals, usually copper.

Britannia silver is an alternative hallmark-quality

standard containing 95.8% silver, often used to

make silver tableware and wrought plate.

Hippocrates, the father of modern medicine,

wrote that silver had beneficial healing and anti-

disease properties, and the Phoenicians used to

store water, wine, and vinegar in silver bottles

to prevent spoiling.

Assaying

unlike gold, the usual referee method for

assaying silver is a process known as

‘potentiometric titration’.

a sample will be scraped from the item to be

assayed which weighs between 50 and 250

milligrams. the sample is then weighed using

a highly accurate balance and dissolved in

nitric acid.

In order to determine the silver content, potassium

chloride is added to the sample and the electrical

conductivity of the solution is tested until the

point that the ‘titration’ is complete and all of the

silver has become silver chloride. the amount of

potassium chloride needed to get to this point

indicates the amount of silver that was in the

original sample.

markIng and hallmarkIng PreCIOus meTals

It is impossible for anyone to know how much

precious metal there is in a piece of jewellery

simply by looking at it or touching it. the

precious metal content must be declared in

some meaningful way. all jewellery should

therefore be marked or hallmarked with a

stamp so that you know what you are buying.

Marking

as a minimum, all items of jewellery should

be stamped with a ‘fineness mark’ declaring

the content of precious metal in the alloy, and

a registered ‘responsibility mark’ indicating the

name of the trader who has first placed that

piece of jewellery on the market.

Hallmarking

some countries have independent third party

assay Offices who test precious metal jewellery

and then strike a ‘Hallmark’ on the article to

guarantee its’ fineness.

a hallmark, is a mark or series of marks struck on

items made of precious metals – platinum, gold,

silver and, in some nations, palladium. Hallmarks

are applied by an assay office and they guarantee

a certain purity or fineness of the metal.

national hallmarking systems differ from

country to country. the Vienna Convention of

1973 standardised the hallmarks, legislation

and inspection of precious metals in signatory

countries to facilitate international trade.

Because it is so widespread it is the best

example to illustrate how an independent

third party hallmarking system works.

articles which are assayed and found to be

in conformity by the qualifying office of a

member country receive a hallmark, known

as the Common Control mark, and can be

exported and immediately sold in any of the

Convention countries without further testing

the Common Control mark is a balance scales

symbol superimposed on:

Gold:

two intersecting circles

Silver:

the letter ‘m’

Platinum:

a diamond shape

Palladium:

a tent design

925

900

585

2524