BIRTHSTONE

BIRTHSTONE GUIDE: GARNET FOR THOSE BORN IN JANUARY

If you're lucky enough to be born in January then the beautiful, bright and vibrant garnet is your birthstone. A rainbow jewel of the gem world, garnet displays the greatest variety of colour of any mineral and is one of the very few untreated gems in the industry.

With a paint palette of shades, varieties and hues, garnet is also recognised for its rich history and lore and was a favoured gem of many historic eras, including royalty of the Victorian times, pharaohs of Ancient Egypt as well as Ancient Romans.

Demantoid garnet with clear horsetail inclusions. Image by Pat Daly.

Colours of garnet

Garnet is commonly seen in a striking spectrum of red, from orange rust, deep-violet to rich royal reds reminiscent of a pomegranate fruit. The term 'garnet' comes from the name "gernet", a 14th Century Middle English word meaning dark red, further deriving from the Latin 'granatum' meaning 'pomegranate'. This connection is made due to the resemblance of garnet crystals to the seeds and rich red colour of the fruit. Garnet is a term for a group of minerals found in various colours from the red Pyrope garnet to the zesty green Tsavorite garnet.

The range of garnet colours comes from trace metals such as manganese, iron or chromium. Variations in chemical composition between different species of garnet result in a range of hardness from 6.5-7.5.

Polariscope garnet peridotite. Image by Pat Daly.

Left: Spessartine garnet with feather inclusions. Right: Hessonite garnet with crystal inclusions. Images by Pat Daly.

Types of garnet

There are five main species of garnet that have the same crystal structure but slight differences in their chemical composition.

· Almandine铁铝榴石: purple to orangey reds

· Pyrope镁铝榴石: purples to orangey reds

· Spessartine锰铝榴石: oranges to yellows

· Andradite钙铁榴石: yellows to yellowish greens

· Grossularite钙铝榴石: colourless to yellow, to orangey red, to vibrant green (rare)

Where do they come from?

Garnets are commonly found in many countries worldwide, including Australia, India, Czech Republic, Myanmar, Brazil and Sri Lanka to name a few.

In the 19th Century, garnet adorned many decorative creations of jeweller Peter Carl Fabergé and was a gem highly favoured by the Russian royal family. Bohemia and Russia were documented as primary locations of sourcing garnet throughout the 19th Century whereas today, Tanzania and Namibia are prized for their abundance in garnets.

Close up of a demantoid garnet with horsetail inclusions. Image by Pat Daly.

Garnet history and Ancient Folklore

Garnet has an extensive history and rich ancient folklore that spreads across many eras. Legend has it that garnet - known as the "Gem of faith" - has powers of good health, prosperity and peace and those that wear it and do good, are further rewarded with good will. The bright and striking nature of garnet is thought to be fitting to the vibrant personalities of those born in the month of January. It is thought that individuals who wear this stone can enter the New Year with a sense of renewed purpose, hope and lasting happiness.

This gemstone has also been used as a talisman of victory and protection by those going into battle. Many warriors would wear this stone to ward off disease and poverty and would place it on their battle wounds as a catalyst for healing. Historical reference dates garnet even further back to the time of Egyptians, who utilised this stone as inlays in their jewellery and decorative carvings as a symbol of life. Garnet was also a popular choice for signet rings worn by the Ancient Romans; additionally carved into intaglios to seal important documents. Hailed for its health benefits, garnet continued to be prized amongst clergy and nobility throughout history.

Garnet from Mali. Image by Pat Daly.

Today, garnet is used in a wide range of jewellery collections and bespoke pieces such as rings, statement pendants as well as tiaras. Its array of colour and transparency make for spectacular pieces of considerable value.

One of the most famous examples of garnet jewellery to date is the Smithsonian Pyrope Hair Comb from the Victorian era. The pyrope garnets that embellish the tiara-shaped comb surrounded the central stone crest, originate from the Bohemian mines (now part of the Czech Republic). These rose-cut garnets were often mounted in gold plate or yellow gold; a popular style during the Victorian era, when this piece was fashioned.

Whether you are looking for a talisman of prosperity for 2018 or buying a gift for someone born in January, the fire and sparkle of each unique garnet gemstone will hold great emotional value and remain a piece of timeless beauty.

A malayan garnet with rutile needle inclusions. Image by Pat Daly.

BIRTHSTONES GUIDE: THE MEANING BEHIND FEBRUARY GEMSTONE AMETHYST

The February-born shall find Sincerity and peace of mind, Freedom from passion and from care, If they, the amethyst will wear. Let her an amethyst but cherish well, And strife and care can never her dwell.

February's birthstone amethyst is one of the most recognised gemstones on the market. Many are familiar with the lore and appearance of this purple gemstone...more so than the hundreds of other gemstones that are offered within our trade.

Amethyst is the purple variety of quartz and out of all of the quartz gemstones ranks at the top for desirability and value. Amethysts are pale pinkish-violet to deep reddish-purple in hue and are most often found as faceted gems, cabochons or carvings. Many rough forms are also used within jewellery including single crystals, clusters or slices of crystal-lined cavities known as geodes. The most prized amethysts are known as Russian or Siberian Amethyst, named after the fine specimens found in these localities. These have a good clarity and rich purple colouration with flashes of red.

Amethyst DreamscapeTM 53.37 ct cut by John Dyer & CO. Photo by Lydia Dyer

Historically, amethyst was kept as a talisman as it was believed to counteract the effects of alcohol. The word amethyst derives from the ancient Greek amethustos, which translates plainly to not drunk.

This mystical belief in amethyst in keeping one sober extends back to 320 BC to the poet Asclepiades of Samos, likely inspired by the wine-like colours of this gem. People believed that wearing an amethyst would save them from inebriation. The more affluent indulgers would sip from carved amethyst goblets or add powdered amethyst into their wine to keep their sobriety. This mystical power was argued as false by Pliny the Elder in the first century AD, however the belief continued for centuries to come. Inspired by the amethysts association to wine, the French poet Remy Belleau created a myth in the sixteenth century explaining how the stone came into existence.

The poem speaks of Bacchus, the Greek God of wine and beautiful maiden named Amethystos, who refused the advances of Bacchus and prayed to the Goddess Diana to keep her chaste. To protect her, Diana transformed Amethystos into white crystal quartz. In frustration, Bacchus poured his wine over the crystals, dyeing them purple forevermore.

The belief that amethyst is one of the world more precious gems can be linked back to antiquity. Amethyst was one of the twelve gemstones that were mounted in the Priestly Breastplate, cited in the Book of Exodus. It is from these twelve gemstones that the birthstones have their roots. Christianity has used amethyst historically within the Episcopal rings of Bishops and other clergy to represent abstinence from alcohol.

Within the middle ages, amethyst became a symbol of royalty and the rich purple of amethyst can be found within regal wardrobes and jewels across the world. A large domed amethyst can be found sitting atop the large Cullinan I diamond within the Imperial Sceptre with Cross in our British Crown Jewels.

The amethyst was considered a cardinal, or most precious, gem and was historically acknowledged in high regard among the diamond, ruby, emerald and sapphire. Cardinal gems held a value above all others due to their beauty and rarity. An abundant source of amethyst was found in Brazil in the eighteenth century and nowadays amethyst is widely accessible and ready to be enjoyed in all its regal beauty by gem and jewellery lovers worldwide. ■

Bentley and Skinner Amethyst Bracelet. Image courtesy of Bentley and Skinner

BIRTHSTONE GUIDE: AQUAMARINE FOR THOSE BORN IN MARCH

The blue hues common to this beautiful stone are fitting considering the Latin aquamare means ‘water of the sea’. Legends describe it as the mermaid’s stone, bringing luck to sailors and protecting them from the perils of the ocean.

Facetted Beryl from the Gem-A Archive

A member of the beryl family, including emerald, heliodor, morganite and goshenite; aquamarine is distinguished by its blue to green colour. Many aquamarines available in the gem market have been heat treated. Starting with a yellowish, greenish or bluish-green beryl, heat treatment leads to a stable blue colour. Mainly found in mines in Africa and Brazil, the March birthstone can also be mined in Australia, China, Myanmar, Pakistan, Madagascar, Russia, USA and Sri Lanka. The trace amounts of iron found in aquamarine causes the sea like colour and is what distinguishes this stone from pure colourless beryl. Aquamarine often occurs as a hexagonal-shaped long prismatic crystal, with striations and rectangular etch marks occasionally found on the prism surfaces.

Beryl Aquamarine Crystal Rectangular Etch Pits on Prism Face. Photo Credit Pat Daly.

The stone’s durability and bountiful supply make this stone a popular choice and it can be fashioned into most cuts, making it a firm favourite with many lapidaries. Although many cut aquamarines are free of inclusions, two-phase inclusions (liquid and gas filled), spiky cavities and tubes parallel to the length of the crystal that look like rain are common.

Beryl Aquamarine Feather of Two Phase Inclusions. Photo Credit Pat Daly.

Perhaps the most famous aquamarine specimen is the 10363 ct Dom Pedro, which weighs an astonishing 26 kg. To this day, it holds the honour of being the largest piece of aquamarine ever to be cut. It was specialists in Idar-Oberstein, Germany, who took on the challenge in 1992.

Discovered by three Brazilian miners in Pedra Azul, Minas Gerais in Brazil in the late 1980s, the original aquamarine was a meter-long. Accidentally dropped it fractured into three pieces and the Dom Pedro was the largest piece from the split.

In 1991, Jürgen Henn from Idar-Oberstein, visited the owner of the large aquamarine crystal. However, the crystal was not for sale and he returned to Germany. In 1992 the stone went on the market and Jürgen asked his colleague Bernd Munsteiner to look at the stone. Bernd sent his son, Tom Munsteiner and Jürgen’s son Axel Henn, to strike a deal in Brazil and bring the stone to Germany.

For a year Bernd worked on the stone, studying the crystal, drawing facet patterns, cutting, faceting and polishing. Before transforming the rough stone into the majestic obelisk, recognised and admired by many today.

The Dom Pedro Aquamarine, from Brazil. Photo Credit Don Hurlbert. Image Courtesy of Smithsonian Institution.

The Dom Pedro first went on public display in 1993 at Basel, the annual gem fair in Switzerland. Almost cut up into smaller gemstones in the late 1990s, it was rescued by Jane Mitchell and generously donated to the Smithsonian, National Museum of History, Washington DC, USA. The awe-inspiring gemstone is in the permanent collection of the museum, housed in the National Gem Collection Gallery.。

When viewed through a Chelsea colour filter aquamarine give a blue-green colour; different from the reaction of many of the other light blue gemstones. When tested with a dichroscope a blue/ green colour shows colourless and pale blue. The material is dichroic.

Quartz crystal cluster Tucson. Image courtesy of Julia Griffith.

Out of the world of gemstones, rock crystal has something extra special to offer, as there is no other containing such a wide variety of attractive inclusions.

Many may think of 'inclusions' as flaws, however, when viewing the array of possible features that can be available within this gemstone one may change this opinion.

Rutile in quartz. Image courtesy of Julia Griffith.

There is rutilated quartz, tourmalinated quartz, fluorite in quartz, hematite in quartz, gilalite in quartz, pyrite in quartz the list goes

on! These different mineral inclusions add further varieties for rock crystal whilst offering dozens of different looks.

Fluorite in quartz. Image courtesy of Julia Griffith.

As part of the quartz family, rock crystal has a hardness of 7, is reasonably durable and stable for use in jewellery. It can be fashioned as carvings, cabochons or faceted gems. An additional bonus with quartz is that it is readily available in larger sizes and at wallet-friendly prices.

Large quartz crystals at Tucson. Image courtesy of Julia Griffith.

Transparent rock crystal has been used as an imitation of diamond for centuries, due to the fact they are both colourless. Rock crystal will not be as 'firey' as diamond as it does not disperse the light to the same degree, however, a well-cut rock crystal can be very brilliant with excellent return of white light.

Faceted rock crystals are still used as diamond imitations today, particularly as 'accent stones' in jewellery. Designers may choose to surround a coloured stone with melee-sized rock crystals rather than diamonds, offering affordable price-points to the consumer whilst giving a similar look.

Quartz is a silica (SiO2) and is the most abundant mineral on Earth and therefore it is mined in many localities throughout the world. Quartz grows as long prismatic crystals with pyramidal points that can occur as single crystals, clusters and geodes - all of which can be very attractive and are commonly used as display pieces or set within jewellery. The largest single crystal recorded was from Itapore, Brazil and measured over 20 feet in length and weighed over 44 tonnes.

The industrial uses for rock crystal quartz outweigh its use in jewellery. It is used within the manufacture of glass, sand, ceramics, brick and abrasives (to name a few) and it is considered one of the world’s most useful natural materials.

Hematite in quartz. Image courtesy of Julia Griffith.

Since its successful synthesis in the 1950s, synthetic lab-grown quartz is used extensively for the majority of industrial processes and may also be found within the gem trade as fashioned stones.

Notably, quartz is used in the mechanism of quartz watches (hence the name) and anyone who sells watches will know that quartz movements keep exceptionally accurate time losing only seconds over the life-time of the battery. This is thanks to quartz’s ability to release regular electronic impulses at precise frequencies. This rare property, known as piezoelectricity, is utilised within our GPS equipment, telephones and radios as well as in the mechanism, which triggers the airbags in our cars.

It is this property, which is thought to be exploited during crystal healing as the energy held within rock crystal is thought to amplify and channel universal energy.

Quartz crystals in Tucson. Image courtesy of Julia Griffith.

As awful as I feel for ignoring true gemstone royalty with the diamond; this April we’re celebrating the rock crystal – let it reign!

BIRTHSTONE GUIDE: EMERALDS FOR THOSE BORN IN MAY

Emerald - the symbol of rebirth and bringer of good fortune and youth - is the birthstone for those born in May.

A variety of green beryl, the name emerald is derived from the Greek word smaragdus (green in Greek). The green colour of emerald is caused by traces of chromium, but vanadium may also be present in some stones.

Emeralds can be found in Colombia. Brazil, India, Pakistan, Siberia, South Africa, Zambia and Zimbabwe.

Emerald with quartz. From the Gem-A archive.

The inclusions contained in almost all natural emeralds are very useful in distinguishing natural emeralds from synthetic emeralds and other green stones. Some inclusions are common for particular localities.

LOCALITY	TYPICAL INCLUSION AND FEATURES
Colombia	Three-phase inclusions (liquid-filled cavity containing a crystal and a gas bubble)
India	Two-phase inclusions (liquid-filled cavity containign a gas bubble)
Zimbabwe	Tremolite (usually fibrous or neddle-like crystals)
Siberia	Needle-like crystals of actinolite
Many Localities	Mica flakes, pyrite and calcite, and also colour zoning

Three-phase inclusion. Image courtesy of Pat Daly.

Two-phase inclusion. Image courtesy of Pat Daly.

Needle-like inclusion. Image courtesy of Pat Daly.

Pyrite inclusion. Image courtesy of Pat Daly.

Mica inclusion. Image courtesy of Pat Daly.

Crystal inclusion. Image courtesy of Pat Daly.

Combining the typical inclusions found with an assessment of refractive index and specific gravity can give an indication of the country of origin.

BIRTHSTONE GUIDE: ALEXANDRITE FOR THOSE BORN IN JUNE

Julia Griffith FGA DGA EG, gemmology and diamond tutor at Gem-A describes the phenomenal appearances of Alexandrite, the June birthstone - 'Emerald by day, ruby by night'.

This extraordinary gemstone appears green or red dependent on the light that it is observed under – a colour change effect also known as the ‘alexandrite effect’. The rarity of this material and its chameleon-like qualities makes alexandrite one of the world’s most desirable gemstones.

Chrysoberyl Alexandrite demonstrating colour change. Image from Gem-A archive.

In 1834, alexandrite was first discovered alongside beryls within the prestigious emerald mines in the Russian Ural Mountains. It is part of the chrysoberyl family, which is separate to the beryls, being a beryllium aluminium oxide as opposed to a silicate. Chrysoberyls have good durability and a hardness of 8.5 making them perfect for use in jewellery… that is, if you can find one. Alexandrite is so rare that it has never truly been the main aim of commercial mining but instead a ‘by product’ as the likelihood of uncovering one is very slim. In Russia, just one crystal of alexandrite was found for every hundred-or-so emeralds.

In the majority of alexandrites the clarity is poor – they are commonly riddled with fractures and appear translucent to opaque. Such specimens have little value and are often unusable as gems.

Rough specimens over 5 ct in weight are also a scarcity and most alexandrites found on the market are under 1 ct. Prices for fine specimens above 1 ct will rival or surpass fine quality rubies, emeralds and diamonds making them the one of the most expensive and rare gemstones in the world.

The most important factor for alexandrite is the quality of its colour change. The most prized colour change is a strong raspberry red in incandescent light and a bright green in daylight - however such a perfect specimen is not known to exist.

The colours seen in alexandrite are caused by chromium – the same colouring element which causes the red of ruby and the green of emerald. The amount of colour change seen is often given as a percentage - with a 100% colour change from one hue to the other being the most valuable.

Alexandrite in tungsten, alpha ray. Image from Gem-A archive.Alexandrite in daylight, gamma ray. Image from Gem-A archive.

The hues seen can also vary - if they stray too far from the expected colours of alexandrite or if the amount of colour change seen is minor, the value will be significantly affected and it is debatable to whether it can be classified as an alexandrite at all.

The colour change effect is due to alexandrite transmitting green and red light equally. Incandescent and daylight light sources are richer in different wavelengths (red or blue/green respectively) and this has a direct effect on what colour the gemstone appears to the human eye.

Alexandrites are also noted for their strong pleochroism. This is an independent optical effect from colour change, in which the gem will appear different colours from different directions. In alexandrite the pleochroic colours are green, orange and purple-red.

The finest quality alexandrites are said to be from the original deposits in Russia, which were mined out in the nineteenth century. ‘Alexandrite’ was named for the Russian Tsar, Alexander II. Legend states that this rare and beautiful stone was found on the day the heir became of age on his sixteenth birthday.

The vibrant red and green colours observed also mirror the colours of the national military of Imperial Russia and alexandrite became the official stone of the Tsardom of Russia.

According to Russian legend, wearers of alexandrite reap many benefits including good luck, fortune and love. A popular belief is that alexandrite helps the wearer strive to excellence bringing concentration, discipline and self-control.

Nowadays alexandrites are mined from Brazil, Myanmar, Tanzania, India and Madagascar. Sri Lanka has also produced some fine specimens - the world’s largest faceted alexandrite hailed from this locality and is a whopping 65.7 ct! A further rarity is chatoyant or ‘cats-eye’ alexandrites, which are cut in cabochon to reveal this optical effect.

Chrysoberyl alexandrite crystal, cyclic twinning. Image from Gem-A archive.

Alexandrite has such extreme rarity that those seen on the market might not be quite what they seem. Alexandrite has been successfully synthesised in laboratories since the 1960’s and these synthetics have the same chemical, physical and optical properties of natural alexandrite and show a strong colour change - but lack rarity.

The most common simulant is synthetic colour change sapphire, which shows a greyish blue to pink colour change. At just a dollar or two per carat - it is extremely common on the market. This material has been made since 1909 so is often found in antique pieces of jewellery.

Alexandrite synthetic flux. Image from Gem-A archive.

A good colour change, good quality, transparent natural alexandrite could easily cost the consumer a five figure sum per carat and beyond in regards to price. A fine price to pay for such a spectacular and exceptional gem.

BIRTHSTONE GUIDE: RUBY FOR THOSE BORN IN JULY

Ruby the red variety of corundum occurs as bright-red, red, purplish- or brownish-red, and deep pinkish-red hues, coloured by chromium. It is the birthstone for those born in July

The toughness, stability and hardness of both natural and synthetic ruby, coupled with its red fluorescence means it is not just desirable in jewellery, but also used in watchmaking, lasers and medical instruments. Diamond is the only gemstone harder than ruby.

Barrel shaped ruby crystal. Image courtesy of Pat Daly.

The colouring element chromium in ruby, can cause fissures and cracks, so few crystals large enough to be classified as gem quality ruby are found naturally. This rarity, along with is desirable characteristics make ruby a precious and expensive purchase.

Commercial quantities of ruby are found in numerous locations including Myanmar, Pakistan, Afghanistan, Thailand, Sri Lanka, Tanzania and Vietnam. These locations have fairly distinctive inclusions to aid identification, but the inclusions are frequently seen in gemstones from other areas and may occur in stones from other localities such as Australia, Kenya, Namibia, Madagascar, India, USA, Russia, China and Nepal.

Crystal inclusions in ruby from Myanmar. Image courtesy of Pat Daly.

LOCALITY	TYPICAL INCLUSION AND FEATURES
Myanmar (Mogok district)	Commonly contain short, fine rutile needle inclusions known as silk. A variety of mineral inclusions are also seen. Inclusions may be well-formed, or corroded rounded crystals. Intersecting twining planes often seen.
Pakistan	Similar to those from Myanmar in colour but clarity is often poor, generally stones are cut as cabochons.
Afghanistan	Often contain blue patches, as well as calcite, mica and rutile inclusions. Usually found in small sizes.
Thailand	Naturally darker, brownish-red in colour. Often have irregularly-shaped fluid inclusion with dark crystals at their centres. Heat treated stones may be similar in colour to stones from Myanmar. Weak fluorescence is seen due to iron content. Intersecting twining planes often seen.
Sri Lanka	Stones contain long, coarse, rutile needles, biotite mica, pyrite, metamict zircon grains with tension hales, pronounced hexagonal colour zoning, elongate negative crystals or cavities containing fluid and/or crystals. Red and pink in colour.
Tanzania	Stones found in Longido are often of fine colour, found in a bright green chrome zoisite rock. Due to clarity stones are cut as cabochons. In the Umba valley facetable material is found showing twinning planes and apatite crystals. Morogoro is where star material is found.
Vietnam	Fine colour, good clarity, similar to Myanmar rubes. Most material contains blue patches, which can be removed or modified by heat treatment.

Dark crystal and feather inclusions in ruby from Thailand. Image courtesy of Pat Daly.

A sixteenth-century writer wrote of the July birthstone that it: "gave control of the passions, drove out evil thoughts, secured possessions to their rightful owner, reconciled quarrels, brought peace and concord and also preserved bodily strength and health." In the past many red stones with a good hardness and lustre, including ruby, spinel and garnet were referred to as ruby. As gemmological knowledge improves, the differences between these materials is more easily identified, although incorrect identification does still occur. Materials with a similar appearance today include red glass, red tourmaline, almandine pyrope garnet, red spinel, red garnet-topped doublet and corundum-corundum doublet.

BIRTHSTONE GUIDE: PERIDOT FOR THOSE BORN IN AUGUST

Lily Faber FGA, gemmology and diamond tutor at Gem-A unveils the striking tones of peridot, the August birthstone; a fitting beauty of nature to compliment the vibrant and zesty 2017 Pantone Colour of the year, 'Greenery'.

Peridot is the birthstone for August and is known for its rich, green colour. It is one of the few gems that comes in only one colour (green), and its name is thought to come from the Arabic word ‘faridot’ which translates to ‘gem'.

Peridot is a transparent gem variety of olivine. Coloured by iron, it comes in a range of greens from yellowy-green to brownish-green. It also has a slightly oily or greasy lustre, but don’t let that description put you off!

With its distinct olive-green hue that is the embodiment of long, summer days, some believe that peridot can bring happiness, luck and prosperity while calming anger, conquering fear and protecting one from evil spirits.

Formed in the earth’s mantle, this gem makes its way to the surface via volcanic eruptions and is found in ancient lava beds. Occasionally, it can also come from outer space! A special type of meteorite called a pallasite meteorite sometimes contains peridot within its iron-nickel matrix. If you slice the meteorite open, it will reveal a smattering of transparent to translucent gems.

Zabargad Island, (St. John’s Island) in the Red Sea off the coast of Egypt, is believed to be the earliest known source for peridot. Centuries ago, the Greeks called this island Topazios, which was also their name for peridot. Later, this island was mined for peridot to fill the coffers of Egyptian kings and anyone who tried to set foot on the island at that time was threatened with death.

It has been said that many of Cleopatra’s emeralds, a favourite gem of hers, were actually peridot. Strangely, the ancient Romans called peridot the ‘Evening Emerald’ because they believed that its bright green colour could only be seen at night, which is clearly not the case!

Other localities include Myanmar, Pakistan and the Peridot Mesa in the San Carlos Apache Native American Reservation in Arizona, USA.

This is a brittle stone with a hardness of 6 ½, which leaves it vulnerable to chips and scratches. Care should be taken when set in jewellery, especially rings. Perfumes, hairspray and make-up can also damage the stone, so spritz your perfume prior to draping yourself in peridots.

Common inclusions are lily pads, which consist of crystals, typically chromite, and are surrounded by curved stress cracks. Mica flakes can sometimes give a brownish tinge to the gem, and needle-like ludwigite inclusions are also seen.

Lilypad inclusions. Image by Pat Daly FGA, Gem-A.

Mica inclusions. Image by Pat Daly FGA, Gem-A.

Ludwigite and vonsenite inclusions. Image by Pat Daly FGA, Gem-A.

A characteristic feature that can help differentiate peridot from emeralds is its high birefringence of 0.036, within an RI range of 1.65 to 1.69. This causes the effect of doubling of the inclusions and facet edges. You can often see this doubling with a loupe or even with the unaided eye if the stone is big enough.

The most prized peridots are those of larger size, with a rich, ‘oily’ green colour and few inclusions.

BIRTHSTONE GUIDE: SAPPHIRE FOR SEPTEMBER

Legend describes it as a stone of purity, honesty, trust and prosperity, bringing inner peace and protection to its wearer. Sapphire - the darling gemstone of royalty and bridal jewellery - is the birthstone for those born in September.

Sapphires are a variety of the mineral corundum – an aluminium oxide in the trigonal crystal system. These stones are most commonly sourced throughout the world from Australia, Cambodia, Myanmar (Burma), Sri Lanka, Thailand as well as Africa.

When mined in their natural rough form, sapphires can appear dark and dull until their true colour shines through once polished, cut or treated. The origins of sapphires can directly affect the clarity, carat, cut and colour of the stones and therefore determines their value and popularity to the trade. Sapphires that are mined within Sri Lanka or Thailand have been considered by many to be the most valuable due to their clarity and brilliance of colour. Like any natural stone, it is the display of visible inclusions within the crystal structure that can sometimes - but not always - indicate where in the world sapphires have been mined.

Natural corundum sapphire with crystals and feather inclusions. Image ©Gem-A Pat Daly.

Measuring nine on the Mohs scale of hardness, sapphire is well known for its good durability and refractive index of 1.76 to 1.78.

The resilience of these stones makes them highly desirable not only for the consumer trade market in fine jewellery but also to industrial businesses applying them to electronics and scientific instruments. Due to its high ability to withstand scratching, sapphires have now become one of the most popular choices for engagement rings and other jewellery pieces for everyday wear.

Colour spectrum of sapphire

Traditionally, sapphires are thought of as naturally vivid blue when in fact this gemstone can occur in a wide rainbow spectrum of colours; from canary yellow, tropical orange to fuchsia pink with the only one exception being the colour red. The red variety of corundum is otherwise known as ruby.

Sapphires get their colour from different trace elements. The presence of iron and titanium is responsible for the blue tones, while traces of chromium cause pink tones. Ruby red is a result of more chromium present in the stones chemical composition.

The Padparadscha sapphire is one of the rarer colours of sapphires, displaying a combination of pink and orange. This sapphire was named after the colour of the Sri Lankan lotus flower, both symbols of natural beauty born from something ordinary.

Left: Flux healed treated corundum (crystal inclusion + healed fractures). Right: Corundum with an iridescent fracture. Images ©Gem-A Pat Daly.

Like all gemstones, Padparadscha sapphires have their own individual colouring with some stones darker in tone and others displaying lighter mediums of pink and orange. In terms of value, this type of sapphire increases in value as the saturation of colour increases. It is the gemstones that display a medium tone of pink and orange saturation that are regarded more highly due to the classification of such gems to be pastel in colour.

Padparadscha sapphires

Clarity and Inclusions

Several types of inclusions are found within sapphires, the most common being long thin mineral inclusions called needles. Long intersecting rutile inclusions are otherwise known as 'silk' and can create a soft milky transparency of some sapphires.

Generally speaking, the presence of inclusions within sapphire will make it less valuable if they are affecting the stone’s overall durability. However, in some cases like Kashmir crystals, the opposite is true.

Sapphires sourced in Kashmir, India often have a very slight milkiness caused by very small inclusions. Colour zoning and stress fractures scatter light to create an almost velvet optical effect without compromising the stone’s transparency.

The quality and appearance of stones found from certain sources worldwide can vary over time, meaning that new sources can often produce very similar stones to older established sources. This is why the clarity and presence of inclusions in a sapphire stone often suggests, not confirms its locality. The saturation of colour in star corundum vastly affects the value of the stone. Crisp and distinct visibility of a star against a vivid saturation of colour is considered to be the most valuable type of star corundum. Yet synthetic lab-made star sapphires can display a crisp star against a vivid background so it's always important to confirm with the seller if it is a natural or lab-made stone. It is these silk inclusions that can produce asterism – the star effect – in corundum. Sapphires displaying this asterism are also known as 'star sapphires' with the most famous being the star of India.

Star sapphires and star rubies can display 4,6 or 12 rays as reflections from tiny needle-like inclusions are positioned in particular directions, depending on the abundance of 'silk' or needle-like inclusions going in alternative directions.

Table showing common natural sapphire inclusions found in different localities worldwide.

LOCALITIES	COMMON NATURAL SAPPHIRE INCLUSIONS
*Myanmur* *(Burma)*	Rutile 'silk', accompanied by pinpoints of rutile. Long needles of apatite; dolomite inclusions (Mogok). Convoluted feathers, silk, hexagonal colour zoning in some stones.
*Sri Lanka* *(Ceylon)*	Crystal inclusions: particularly mica, pyrite, zirca, crystals, with haloes; healed fractures often resembling fingerprints; rutile 'silk', two-phase inclusions; apatite crystals. Graphite present as solids in two-or-three-phase inclusions. Elongated negative crystals and pyrite/pyrrhotite are common.
*Australia*	Strong zoning, feldspar, zircon crystals with associated haloes.
*Colombia*	Crystals of rutile are common.

Natural vs. Synthetic

Unbeknown to many, more than 90% of sapphires available on the market today have been heat treated. Whilst synthetic stones display an almost identical chemical composition to natural corundum, uncut synthetic specimens can often exhibit a variety of different crystal habits.

One of the key ways of identifying between synthetic and natural sapphires is by their characteristic inclusions.

The most common type of synthetic corundum is Verneuil flame-fusion. Verneuil sapphire commonly displays curved colour zones which occur when the boule forms as a rounded bottle-like form.

These curved growth zones can be detected through both a loupe and a microscope depending on the size of the stone and the visible depth of colour saturation. Elongated gas bubbles as well as induced 'fire marks' may also be seen, caused during the polishing process. These ‘fire marks’ are typical of corundum polished without sufficient care and are an indication that the stone is synthetic.

Left: Angular zoning in natural corundum. Right: Synthetic Verneuil flame-fusion sapphire corundum (curved zoning). Images ©Gem-A Pat Daly.

Additionally, whilst many blue sapphires show a spectrum of between 1, 2 or 3 bands, Verneuil blue and yellow sapphires do not show a spectrum whatsoever.

In summary, the primary difference between natural stones and those that are synthetic is their origin. Both stones share the same molecular composition with identical physical properties, hardness level and visual appearances.

What makes a natural gemstone rarer is that it created from the earth and then mined whereas its synthetic counterpart is lab-grown within a controlled environment. In terms of value, natural sapphires demand a higher price as they are more difficult to source and mine.

Flawless synthetic gemstones are easily made and can be produced at any time which therefore reduces their rarity and retail value. Whilst inclusions and flaws can be artificially created in lab-grown stones, it is natural gemstones with very few visible inclusions that are considered the most desirable.

Birthstone lore of sapphire

Historically the striking blue gemstone has been thought to symbolise honesty, trust, purity and loyalty.

Left: Natural sapphire corundum showing negative crystals + feather inclusions. Right: Synthetic sapphire corundum (Chatham) with flux feather inclusions. Images ©Gem-A Pat Daly.

The ancient belief that sapphire is an amulet of power and trust to those born in September still stands strong today. Such an idea would also explain why, in Ancient Rome and Greece, celestial blue sapphires were worn by the wealthy as a symbol of protection from the evil intentions of their enemies. The mystical lore behind gemstones is not a universal belief for many but what is indisputable is the fact that sapphire has long been a gem favoured by the rich and powerful.

Sapphire in engagement rings

Today sapphire has become the second most popular choice of gemstone after diamond for bridal jewellery and fine jewellery collections.

The most famous piece of sapphire jewellery to date remains to be the sapphire engagement ring, first seen in 1981 when Prince Charles proposed to Lady Diana. This beautifully decadent ring, now worn by the Duchess of Cambridge, features an 18ct oval blue sapphire with a halo of diamonds.

Top Left: Corundum sapphire with iridescent feather inclusion. Top Right: Pleochroism in corundum sapphire. Bottom: Feather inclusions in corundum sapphire. Images ©Gem-A Pat Daly.

BIRTHSTONE GUIDE: TOURMALINE FOR THOSE BORN IN OCTOBER

Gem-A gemmology and diamond tutor, Julia Griffith FGA DGA EG, looks at tourmaline, the enchanting rainbow-coloured birthstone for October. Tourmaline is the rainbow jewel of the gem world. No other gem is available in such an impressive array of colours. Paired with good durability and high lustre, this gemstone has become a favourite of many.One of the earliest reports of tourmaline in California was in 1892. In the late 1800s, tourmaline became known as an American gem through the efforts of Tiffany gemologist George F. Kunz. He wrote about the tourmaline deposits of Maine and California, and praised the stones they produced.

In spite of its American roots, tourmaline’s biggest market at the time was in China. Much of the pink and red tourmaline from San Diego County in California was shipped to China because the Chinese Dowager Empress Tz'u Hsi was especially fond of the color. There, craftsmen carved the tourmaline into snuff bottles and other pieces to be set in jewelry. San Diego County's famed tourmaline mines include the Tourmaline Queen, Tourmaline King, Stewart, Pala Chief, and Himalaya.

The miners became so dependent on Chinese trade that when the Chinese government collapsed in 1912, the US tourmaline trade also collapsed. The Himalaya mine stopped producing large volumes of gemstones. Other mines in San Diego County, like the Stewart Lithia mine at Pala, still produce sporadic supplies of gem-quality tourmaline.

The hues, tones and saturations of tourmaline seem limitless, ranging from soft shades to vibrant explosions of colour. The desirability of the colour has a huge impact on price. The more vivid, rarer colours reach higher values, such as the coveted electric-blue copper bearing Paraiba tourmaline. Many tourmalines have commercial names such as rubellite for pink to red tourmaline. It is also common to describe them simply with the pre-fix of their colour i.e., 'pink tourmaline'.

Tourmaline is also known for its colour-zoned or "parti-coloured" specimens, where different zones of colour can be seen in the cross-section or down the length of the crystal. These can be cut to display the different colour patterns either as slices, creative carvings, facetted or cabochon gemstones, or left as whole crystal specimens. The most popular colour-duo is watermelon tourmaline which display pink on the inside and a rim of green on the outside.

Tourmaline is a complex boro-silicate of aluminium, magnesium and iron and the vast selection of colours are due to trace impurities and colour centres. The availability of these impurities may vary during growth, which allows for the development of different layers of colour. Its chemical makeup is so complicated that it cannot be synthesized, and is therefore always of natural origin.

The crystals are easy to identify with the tell-tale rounded 3-sided, or 6-sided, cross sections. They are often long and prismatic with heavy striations down the length of the crystal and are topped with either a pyramid or a flat pinacoid.

First discoveries have been attributed to both Brazil and Italy in the 1500's. The name of tourmaline was derived from the Sinhalese phrase tura mali, which was used by the miners and traders to refer to "unknown stones of mixed colours". The advancement of mineralogy allowed the recognition of tourmaline as its own gem species in the 1800's.

Tourmaline has a hardness of 7 - 7.5 and good toughness, making it suitable for use in jewellery. Inclusions are fairly common in tourmaline and many contain mirror-like fractures within them, which can be quite attractive, but may compromise the durability if knocked. Inclusion free stones are available and will fetch a premium price. Parallel needle-like cavities are also common in tourmaline, which in vast numbers can create chatoyancy, or the "catseye", effect.

Since their discovery, tourmalines have been used as talismans for protection against toxins and radiation as well as many other healing properties which are associated with particular colours of tourmaline. They are said to emit far-infrared rays that penetrate the body and stimulate and soothe the tissue within. This association is likely linked to the ability of tourmalines to become charged when heated, which is known as pyroelectricity.This property causes tourmalines to readily attract dust, and so a regular flick with a duster is recommended if they are displayed under hot lighting - arguably, a small inconvenience for such a stunner of a gem.

BIRTHSTONE GUIDE: TOPAZ FOR THOSE BORN IN NOVEMBER

Gem-A gemmology tutor, Lily Faber FGA EG, takes a look at topaz, the beautiful and warming birthstone of November, guaranteed to brighten up this chilly month of winter.

The name topaz most likely originated from the Sanskrit word 'tapas', meaning 'fire'. This gemstone is thought to promote creativity, increase sensitivity to taste to enhance your dining experiences, boost mental clarity and to uncover lies and illusions. The ancient Greeks believed that topaz could render the wearer invisible - though I have yet to see proof of this effect! Topaz is the state stone for Texas and Utah in the United States of America, and is the talisman for the astrological sign Sagittarius.

Blue topaz with incipient cleavage seen under table. Photo courtesy of Lily Faber.

Colours and Localities

Most often associated with the colours yellow, orange, blue or pink, topaz can also be colourless, green and brown. One of the most valued colours is known as 'Imperial Topaz', which is pinkish-orange to red-orange. Another highly valued colour is 'sherry topaz', which is brownish-yellow to orange or yellow-brown.

Figure 1. The Imperial Flame, a magnificent natural-color Brazilian topaz, was cut from a 615 ct crystal recovered some 20 years ago. The finished 89.53 × 20.56 × 19.15 mm sculpture weighs 332.24 ct. Photo courtesy of Sonja Kreis Unique Jewelry.

Striated topaz crystal with iridescence due to internal fractures. Photo courtesy of Lily Faber.

Topaz can be found in Brazil, Russia, Pakistan, Mexico, the USA, Madagascar and Sri Lanka. In the 19th century, the main source for pink topaz was in the Ural Mountains in Russia. The imperial family, including the tsars, reserved exclusive rights to own and wear the colour, this imparting the name 'Imperial topaz'. It is less common than other naturally occurring colours of topaz, and is thought to resemble the colours of the setting sun.

Historically, all yellow stones were called topaz, which has since been corrected, for the most part. In some shops, misnomers can still be seen today. Names such as 'quartz topaz', 'Scotch topaz' or 'Spanish topaz' are a few names used for citrine quartz that are misleading, so don't fall for it!

It should be noted that almost all pink topaz on the market today is mined in Brazil and heat-treated to bring out the pink colour. Natural blue topaz is typically pale, and stronger colours like 'London blue' or 'Swiss blue' are achieved by irradiating and heating a colourless topaz to promote and stabilize the blue colour. One colour that was not created by nature is known as 'mystic' topaz. It is a colourless topaz that has been coated with a thin metallic layer to produce extreme iridescence.

Properties and Inclusions for topaz

Topaz is a relatively hard material, with a level of 8 on the Mohs scale of hardness. While it can take a high polish and show a bright vitreous lustre, its perfect and easy cleavage lets it down. Cleavage is a directional breakage that occurs along a crystal plane in only crystalline materials. Topaz has what is called 'basal' cleavage, which is 90 degrees to the direction of crystal growth, or the c-axis. This breakage leaves a flat base (basal pinacoid) with the tell-tale terrace-like markings that look like tiny, wavy rivers running across the flat surface of the crystal. Any forceful knock or pressure can split the stone in two along this direction, and great care is taken when fashioning these stones.

If wearing topaz set in a ring, it would be advisable to either wear it in a rub-over setting to protect as much of the stone as possible. Otherwise, simply wear it in a necklace, earrings or, if you are feeling very fancy, a tiara.

Rhombic cross-section of topaz crystal. Photo courtesy of Lily Faber.

Topaz crystals are typically transparent with multiple straight, parallel striations running down the length of the crystal and a pyramidal termination at the top. They have a rhombus-shaped cross-section which looks like an elongated kite-shape. Inclusions can consist of healed internal fractures (feathers), long tube-like cavities and two-phase inclusions or a cavity with two immiscible liquids. Iridescence can be seen in both rough crystals and cut stones where there are internal fractures, or where cleavage is just starting to extend into the stone from the surface (also known as incipient cleavage). Also seen are variously coloured mineral inclusions.

Topaz cabochon with cleavage and fracture detail. Photo courtesy of Lily Faber.

Whether appreciating topaz in rough crystal or faceted form, it is a lustrous gem of many beautiful colours that warrants attention.

Iridescence within incipient cleavage. Photo courtesy of Lily Faber.

BIRTHSTONE GUIDE: TURQUOISE FOR THOSE BORN IN DECEMBER

The beautiful and enchanting gemstone turquoise is one of three birthstones for December, enriched with cultural significance and ancient medieval lore. Join us as we explore the blue hues of this gemstone in our final birthstone round-up of 2017. One of the first gemstones to be mined and used in jewellery, turquoise is one of three birthstones for the month of December. Admired since ancient times, this gemstone is known for its beautifully unique colour, ranging from powdery blue to an unrivalled 'robin's egg' blue. Its colour and historic significance have resulted in turquoise becoming a favourite of many.

Overview

Gem turquoise is a polycrystalline copper material typically occurring in thin seams or small nodules. Turquoise is found in dry, barren, arid regions where copper, leached from rocks by rainwater, reacts with aluminium and phosphorus. The result of this reaction is a porous, semi-translucent to opaque compound of hydrous copper aluminium phosphate with some evidence of iron. Copper produces the blue hues whilst chrome and iron add tonal variations of green.

Quite often, small patches or veins of brown or black host rock, known as matrix can be seen in the stone. The presence of these 'spider-web' patterns can often lower the value of the stone. However, some buyers actively seek stones with a presence of its matrix as they can be more unusual and attractive. In terms of market-value, turquoise stones completely free from traces of matrix command a higher value, whilst those with evident spider-web patterns classified as desirable fetch second-place value in the trade.

Turquoise simulant; paste. Photo courtesy of Pat Daly.

Localities

The earliest evidence we have of this gemstone dates back to 3000 BCE, under the reign of King Tut, within the oldest turquoise mines located in the Sinai Peninsula of Egypt. Extraordinary pieces with elaborate displays of turquoise were found on the gold jewellery of many Egyptians, with the most extravagant display found set on the iconic burial mask of King Tut himself.

Ancient Persians believed that turquoise guaranteed protection and adorned many of their palace domes with the sky blue gemstone which they considered to represent heaven. Additionally, ancient Persians often engraved Arabic script into turquoise which would then be used to intricately decorate their daggers and horses' bridles. The highly prized 'robin's egg' blue - also known as 'Persian turquoise' - was venerated by the people of Persia (now known as Iran) as well as Siberia, Tibet, Turkey and Afghanistan. It was the Turkish traders who later introduced this 'Persian blue' stone to Europe in the 13th century through the Silk Road.

Map of localities where turquoise is found throughout the world.

Properties

The texture of turquoise is a direct result of its composition and structure. As an aggregate, polished turquoise with a smooth waxy lustre has a tightly-packed crystal structure, low porosity and a fine texture. Turquoise gems displaying a dull lustre when polished have a coarser texture and increased porosity due to a less-dense internal crystal structure. This range in texture and porosity not only directly affects the overall appearance and lustre of this gemstone but also influences its durability.

Typically, turquoise is a fairly soft stone which made it a popular choice for talisman carving across ancient history. Throughout America, many carvers fashioned turquoise into amulets of Native American significance such as birds and animals.