The variety of gems (precious stones) found in nature is a divine gift to us. Their colours and crystalline structures have enchanted us for thousands of years.

And we jewellery professionals give them shapes and facets that enhance their brilliance and value when creatively applied to a piece of jewellery.

Although a source of enchantment and fascination, real gemstones are difficult to identify as the production of imitations and synthetics is growing rapidly, creating confusion between what is real and what is fake.

The big problem today is how to tell the difference between a real gem and a synthetic one.

The first precious stones were probably found in riverbeds.

As civilisations developed and interest in gemstones grew, specific techniques were developed to find them in nature.

Gems have been mined and traded for thousands of years.

Over the centuries, the term gemstone has come to mean a natural mineral that is desirable for its beauty, valuable for its rarity and very durable for its resistance.

This process has led to an increase in the price of these natural gems. The rarer, the more expensive.

With this great appreciation and rarity came the emergence of imitations and synthetic gemstones.

Today, it is difficult to identify natural gemstones because synthetic and imitation gemstones have perfected their production processes.

Soon after the first fakes appeared, gemology emerged – a science derived from crystallography that defines concrete parameters for evaluating and classifying gemstones.

Gemologists use equipment and tools that meet these standards and follow international grading routines.

So if you’re looking to buy a very valuable gemstone, it’s best to use the services of a gemologist.

Precious and semi-precious gemstones

The distinction between precious and semi-precious stones has never been scientifically valid. Today, all stones, both minerals and rocks, that are valued for their beauty, durability and rarity should be called gemstones.

To understand how this change came about, it is necessary to know a little about the history of gemstones. In the past, the term “precious stone” was used only for diamonds, emeralds, rubies and sapphires, known as cardinal gems because they had ecclesiastical, devotional or ceremonial uses; the other gems were called semi-precious stones.

However, this term is controversial and confusing, and devalues gems such as opal, aquamarine, chrysoberyl, amethyst or alexandrite, among other Brazilian stones of great beauty. Therefore, the distinction between precious and semi-precious stones should be avoided when using the term gemstone.

The most important Brazilian gems

Among the various Brazilian gemstones, tourmalines and various types of beryl stand out.

1. Beryl

Beryl is a silicate of beryllium and aluminium with a prismatic or columnar habit, a hexagonal base, a hardness of 7.5-8 and a specific gravity of 2.63-2.80. It has a vitreous lustre and can be transparent or translucent, with slight cleavage.

Pure beryl is colourless, but can be tinted by impurities, with the following colours: green beryl is called emerald (presence of iron or chromium), blue beryl, aquamarine (due to chromium and vanadium), pink beryl (due to manganese and iron) is called morganite, bright, clear yellow beryl or yellow-green beryl (due to manganese, iron and titanium) is called heliodorite, colourless beryl is goshenite.

The rare red beryl is known as red emerald or bixbite.

2. Tourmalines

Tourmaline minerals are boron and aluminium silicates with variable compositions due to the substitutions that can occur in their structure. The elements commonly involved in the substitutions are Fe, Mg, Na, Ca and Li. Tourmalines have a prismatic habit and vary from long, thin crystals to thick, columnar crystals with a triangular basal section, a hardness of 7-7.5 and a specific gravity between 2.9-3.2.

They are transparent to opaque, with a vitreous lustre and have well defined vertical striations that help to identify them.

Tourmalines are classified according to their colour: dravite: brown; schorlite: black; elbaite: green; rubellite: pink; indicolite: dark blue; acroite: colourless, among others.

There are bicoloured varieties, the best known of which is the watermelon tourmaline, whose colours are pink on the inside of the crystal and green on the outside. There is a very valuable type of tourmaline, the Paraíba tourmaline, which has an intense light blue colour (known in the trade as neon blue, fluorescent blue or electric blue).

Synthetic gems

Synthetic gemstones are those that are produced in a laboratory and have a counterpart in nature. These materials have the same chemical composition, crystalline structure, physical and optical properties as their natural counterparts.

The Gemological Institute of America (GIA), the largest and most respected institution for gemstone research and study, describes on its website that a synthetic gemstone is one that is produced in a laboratory but has all the chemical, optical and physical characteristics of a corresponding natural mineral, although in some cases, such as synthetic turquoise and synthetic opal, additional compounds may be present.

Artificial gems

Artificial gemstones are those that are produced in a laboratory and have no counterpart in nature, such as cubic zirconia, which is used as an imitation of diamond (JUCHEM; BRUM, 2010).

Shah (2012) distinguishes between artificial and synthetic gemstones, stating that artificial gemstones are gemstones that have no counterpart among natural stones and are entirely man-made, whereas synthetic gemstones are crystallised or recrystallised materials whose production method is entirely or partially man-made, but which have the same physical and chemical composition and optical properties as natural stones.

The Gemological Institute of America (GIA) lists cubic zirconia (zirconium oxide), yttrium-aluminium garnet (YAG), gallium-gadolinium garnet (GGG), fabulite (strontium titanate) and moissanite (silicon carbide) as the main artificial gemstones, almost all of which simulate diamonds.

Imitation gems

Imitations are imitations of natural gemstones, imitating their colour and appearance. Imitations are different from synthetic gemstones and can be distinguished from natural and synthetic gemstones by their completely different physical properties and chemical composition. Imitations are mainly made of glass, paste or rhinestones, faience, porcelain and plastics, and are moulded rather than cut.

What if the gemologist isn’t around?

There are many places where gemstones are sold. Cities such as Governador Valadares and Teóilo Otoni, in Minas Gerais, Brazil, are centres for the sale of gemstones.

However, gemstones are also sold at events and trade fairs dedicated to the jewellery market, as well as in specialist shops.

Knowing the integrity of your supplier makes it easier to buy certified gemstones, but in other situations you need at least some basic knowledge to avoid buying glass instead of gemstones.

Today, jewellery designers, jewellery writers and goldsmiths need to know the principles of gemology in order to present reliable work to their clients.

A few years ago I saw a famous jeweller buy glass instead of onyx.

The results could have been disastrous if the glass hadn’t been identified before it was set into the jewellery.

Even without such a high value, the simple fact that the piece is being sold as onyx with glass in its place could undermine the jeweller’s credibility.

For the experienced jeweller, it’s easier to identify the gemstone without more detailed analysis, but even so, fakes have reached a worrying level of quality because their value is immeasurably lower.

To avoid embarrassing situations or even professional and financial damage, in the absence of a gemologist, we can use some gemological resources to identify gems.

It’s important to note that any gemological analysis that isn’t complete has a margin of error.

Three simple and inexpensive tools can be used to identify gems: the 10x magnifying glass, the Chelsea filter and a flashlight.

Attending events, both in Brazil and abroad, can provide many opportunities to buy gems. In this situation, it is very important to know how to evaluate the gems and pay a fair price for them.

This article aims to explain the use of two basic tools that can help a lot, but we advise you to learn more about gemology or hire a gemologist.

A good gemology course can be very helpful in these situations.

Examining a gem or precious stone

Value

One of the most important aspects to consider first is the value of the gem. As with any other type of trade, gem prices vary from dealer to dealer.

Do your research before you buy. The market itself sets the price level. If you receive an offer at a price far below the market, be careful, no one can work miracles.

Price is the first factor that can establish the legitimacy of a gem.

Use of the magnifying glass

Goldsmith’s loupes are an important tool for assessing what’s inside a gem. Here we use a loupe with 10x magnification, but loupes with higher magnifications are available.

Natural gemstones will always have tiny internal defects, irregular patterns and formation marks. Be wary if a gem is completely free of these irregularities.

For example, look for bubbles in emeralds – natural emeralds don’t have air bubbles.

Whenever you carry out this type of analysis, the loupe should be held close to your eyes and the gemstone held at a distance until it is in focus. Whenever possible, analyse with the gem illuminated.

Use of the Chelsea filter

The Chelsea filter was developed in England in the early 20th century and was originally used at Chelsea University.

Its original function was to separate emeralds from green beryls.

As the Chelsea filter allowed this separation in the beryl group, they are included:

• Emeralds
• aquamarine
• Precious Beryl
• Chrysoberyl
• Spinel
• topaz
• some have green tones

At that time, only beryls coloured with chromium were considered to be emeralds, and those coloured with vanadium were considered to be another type of beryl.

Because of the high value of emeralds, it was important to distinguish them from other types of beryl using a simple and accurate test – the Chelsea filter.

At that time, chromium coloured beryl (emerald) had a reddish tinge when analysed with the Chelsea filter, whereas vanadium coloured beryl did not.

Over time it was realised that this small instrument could distinguish many other natural gemstones from imitations.

However, it is important to remember that the Chelsea filter is an additional tool and should not be used as a diagnostic tool, as this requires a more thorough gemological analysis. It works well in the situations mentioned.

How the Chelsea filter works

As the name suggests, it is a light filter.

A Chelsea filter allows only certain colours, yellow-green and red, to be transmitted, i.e. seen (it filters out the others).

Gemstones that don’t transmit yellow-green or red will be seen as a dark image.

When viewed through the Chelsea filter, a real emerald will appear yellowish or reddish.

When viewed through the Chelsea filter, a fake emerald will appear greyish.

When viewed through the Chelsea filter, a synthetic emerald will appear genuine because it also contains chromium and has all the physical and chemical properties of a natural emerald.

In synthetic emeralds, however, the red glow is more intense. More experienced gemologists can tell synthetic emeralds apart because they contain more chromium, which makes them much brighter.

If in doubt, further gemological testing will be required to make this judgement.

Synthetic Blue Spinel

Sometimes the Chelsea filter can be used to quickly determine whether a gemstone is synthetic or natural, as is the case with blue spinel.

There is no other blue gemstone with a refractive index of 1.72 that shows the red colour reaction when viewed through the Chelsea filter, only synthetic blue spinel.

The reason for this reaction is the presence of cobalt in synthetic blue spinel.

Two different processes can be used to produce synthetic spinel, but in both cases the presence of cobalt is detected by the red reaction. Detection of the cobalt layer.

In synthetic topaz, for example, cobalt produces a vivid colour and helps to make it one of the most prized gems until it is used in jewellery and the cobalt begins to flake off.

Cobalt contributes to the fact that green topaz, for example, is marketed under various names, such as Caribbean green topaz, etc.

As natural topaz does not occur in this colour, any green topaz is a cobalt coated gemstone.

If you have an unfamiliar green stone, you can easily identify it with the Chelsea filter, as no other green gemstone shows such a strong reaction with the Chelsea filter. Separating natural Tanzanite from imitation.

Tanzanite is a trichroic gem. The third colour is a golden brown to reddish brown tone.

In the picture below we can see three types of tanzanite: 1 is a natural tanzanite, 2 is a polysilicate imitation and 3 is synthetic. 2 and 3 are the most common imitations of tanzanite.

When viewed through a Chelsea filter, the reaction of the three is very different.

Note that 3 has an inert reaction. The bright red reaction of polysilicate (gem 2) is due to the agents added to obtain this imitation reaction, but you can see that the red is much brighter than the reaction of natural tanzanite (gem 1).

The same principle of luminosity occurs with alexandrites. A synthetic alexandrite will appear very bright when viewed through a Chelsea filter, while a natural alexandrite will appear less bright.

This is due to the large amount of chromium added in the laboratory process of synthetic gemstones.

The images used in this article are for illustrative purposes only and may vary greatly in colour when analysed with the Chelsea filter.

It is important to understand the principles of analysis with this filter.

We recommend that you take a gemology course to learn much more about gemstone identification.

Gemology – an almost obligatory study

Our gemstone of the month is Tourmaline, one of the most popular gemstones among jewellery designers and consumers.

But thinking a little more about those who are just starting out, studying or perfecting their jewellery design, we decided to open this section with some information on gemology.

You’ll see that gemology is an almost obligatory study for jewellery designers.

Before we talk about gemology, let’s understand what a gemstone is.

Until a few decades ago, the term “gemstone” was used to refer to diamonds, rubies, sapphires and emeralds, which were considered precious stones because they were the most commonly used in jewellery.

Today we know that there are other minerals, such as amethyst, with stones that can be worth more than an emerald.

There is the kunzita spodumena (pink stone), which can be worth more than diamonds.

Some organic materials, such as pearl and amber, have also been used in personal adornment and add value to such jewellery.

With so many materials on the jewellery market, how is it possible to determine and compare the value of these elements? How do you know if a ruby is genuine or an imitation? Gemology was born out of these needs.

Gemology is a speciality of geology that studies the physical and chemical aspects of gem materials, whether organic or inorganic in origin, used for personal adornment or decoration.

For a material to have gemological value, it must also be beautiful, rare, traditional, fashionable and durable.

Gems are substances that have aesthetic values such as colour, shape (cut) and durability, taking into account their physical and chemical characteristics and properties.

Gemology is also concerned with distinguishing between synthetic gems and their imitations, and with the various types of treatment used to enhance their appearance and value. It also studies their origin, composition and optical characteristics.

It also studies the appropriate cut (facets) for each type of stone to enhance its beauty.

The study of this science is undoubtedly indispensable for jewellers, jewellery designers, gem dealers, goldsmiths and other professionals in the sector.

The specialist in gemology is the gemologist. If you want to learn gemology, check out the website for some courses.
www.abgm.com.br
gemologia.ibgm.com.br/escola/
www.joia-e-arte.com.br/Cursos/cursoigemologia

For those interested in academic training, there is the Federal University of Espirito Santo. The UFES has an undergraduate course in gemology
www.gemologia.ufes.br.

Brazil lacks professionals with scientific training in this field.

A good guide to the study of gemology is the book “Gems of the World”.

It’s important to know that proper equipment and instruments are needed for accurate gemological analysis, but gemological knowledge can help a lot in identifying gems.

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