Birthstone Guide: Ruby for Those Born in July

Those born in July can call the resplendent ruby their birthstone. To find out more about this historically significant and commercially successful gemstone, we asked Gem-A tutor Lily Faber FGA DGA EG to share her insights.

The ruby slippers, a ruby red apple, ruby red lips… for those interested in gems and jewellery, and even those who aren’t, rubies are synonymous with a rich red hue.

What many don’t know is that the ruby is a member of the corundum gem species, along with sapphires, the difference being colour and the elements responsible for that colour. Rubies are specifically red and coloured by chromium, while sapphires have more flexibility with their colours (including blue and any other colour aside from red). The most valued is sometimes referred to as ‘pigeon’s blood’ – a deep, rich red that is seen to be the purest iteration of the colour.

Rubies in History

It is believed in some cultures that rubies bring prosperity and protection to those who wear them. Rubies are also the stone of passion and are often associated with love. It has even been said that rubies should be rubbed onto the skin to promote and restore youth.

Due to their colour, rubies were often connected to blood and the idea of a ‘life force’, which is one of the many reasons they were worn by warriors to, allegedly, make them unstoppable in battle.

Read more: A Quick Guide to the British Crown Jewels

Historically, all red gemstones were called a ruby until the late 18th century, when gemmology developed as a science and people were able to distinguish between various species of red stones. In fact, some of the most famous rubies, including the Black Prince’s Ruby and the Timur Ruby in the British Crown Jewels are red spinel.

Where are Rubies Found?

Commercial quantities of ruby are found in numerous locations including Myanmar, Pakistan, Afghanistan, Thailand, Sri Lanka, Tanzania and Vietnam.

Read more: What are the Most Important Gemstone Producing Countries in the World?

Treated Ruby Before and After Heat Treatment Gem A Blog July BirthstoneRuby before (left) and after being heat treated.

These locations have quite distinctive inclusions that may aid identification; however these inclusions can also frequently be seen in gemstones from other localities such as Australia, Kenya, Namibia, Madagascar, India, USA, Russia, China and Nepal, and are therefore not diagnostic.

Ruby Crystals

The most common crystal habit for a ruby is a flat, tabular hexagonal shape that can either be sharp or rounded at the edges. There may be raised, triangular growth marks on the top or bottom pinacoids of the crystal, as well as some lamellar twinning lines on the sides of the crystal. These are distinctive crystals and can be readily recognised. Twinning occurs when a crystal changes its direction of growth during formation, either one or multiple times.

Ruby Inclusions

Rubies can contain a large variety of inclusions. These can be crystals, feathers (partially healed internal fractures), silk (long, thread-like rutile inclusions), evidence of the lamellar twinning in the form of twin planes, and hexagonal colour-zoning. Silk, which forms in three directions at 120 degrees, can cause an optical effect known as asterism (a bright star shape that appears in the stone), which is highly valued in natural rubies.

Asterism or Star Ruby Gem A Blog July Birthstone Ruby 
A natural 'star ruby' caused by silk inclusions.

You can often tell if a ‘star-ruby’ is a natural one as opposed to a synthetic one because the star is not always centred, the arms of the star are slightly crooked or diffuse, and the cabochon has a rounded or deep base to preserve yield, therefore raising the price of the stone.

Ruby Treatments

The most common treatment to corundum as a whole is heat treatment to enhance or remove colour. For rubies, brown and blue tones are often removed by this method. Additionally, it is important to watch out for rubies that have been fracture-filled with lead glass to improve colour and clarity. This treatment is becoming more and more prevalent, so caution is advised when buying rubies.

Read more: What Should Be in the Ideal Gemmologist's Toolkit?

The lead glass leaves tell-tale signs, however, so look for surface-reaching fractures, a difference in surface lustre between the glass and the ruby, and a blue flash within the ruby as well as bubbles, both of which are confined to the fractures inside of which the glass sits. It is not advisable to heat these rubies as the lead glass has a low melting point and will leak out of the stone.

Flashes and Cracks in a Glass Filled Ruby Ruby Treatments Gem A BlogFlashes and cracks in a glass filled ruby. 

Ruby Care and Caution

Rubies are comparatively hard at 9 on the Mohs scale of hardness, second only to diamonds with a hardness of 10. They are excellent stones to set in jewellery due to their ability to resist scratches as well as any chemical attack. It is not advisable, however, to put them in an ultrasonic or steam cleaner, especially if the stone is fractured or has been lead-glass filled.

Read more: What Makes a Gemstone Rare? 

Rubies are a historic gem, considered to be the gem of royalty. Whether you appreciate them for their colour, multitude of inclusions, or their stature within the gem community, they are a worthy addition to anyone’s jewellery box, especially if you were born in July.

Interested in finding out more about gemmology? Sign-up to one of Gem-A's Short Courses or Workshops.

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Cover image: The Patiala Ruby Choker created by Cartier in 1931 and recently sold by Christie's. This exceptional piece, once part of the Al-Thani Collection, was commissioned by Maharaja Bhupinder Singh of Patiala, one of Cartier’s most important Indian clients of the 1920s and 1930s. Image courtesy of Christie's. 

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Understanding Spinel: The Alternative August Birthstone

The varied hues of spinel have been admired for hundreds of years, but this gemstone only recently found its place on the list of ‘alternative birthstones’. Here, Lily Faber FGA DGA EG explores the alternative birthstone for the month of August and some of its synthetic counterparts.

Spinel is a relative newcomer to the ‘official’ list of birthstones and was added as an alternative to peridot for the month of August by the Jewelers of America and the American Gem Trade Association (AGTA). It is sometimes known as the great imitator of gemstones because it can look like so many different stones with its wide variety of colours, most notably ruby.

Read more: What Should be in the Ideal Gemmologist's Toolkit?

For millennia, red spinels were commonly mistaken for rubies. As gemmology became more established as a science in the 18th century it became possible to differentiate between rubies and spinels, and other similar-looking gemstones. Red spinels are considered important stones in British regalia and other royal collections. You may see them referenced as ‘balas rubies’ in some historical records.

Did you know? The Black Prince’s Ruby in the British Crown Jewels is actually a spinel? Read more here.

Spinel Dreamscape™ 5.34 ct cut by John Dyer
Gem Courtesy of John Dyer & Co. Photo Credit: Lydia Dyer

Historically, spinel (and other red gemstones) were thought to protect their wearer from harm and enhance vitality – largely because the red colour was associated with blood or ‘life force’. Other beliefs linked spinel with banishing sadness, replenishing energy and helping their wearer to overcome challenges.

Read more: Understanding Garnets in Antique Jewellery

While red is perhaps the most popular and commercially successful colour of spinel, it can also come in a large array of colours, such as blue, green, grey, purple, orange and pink. One of the more intriguing colours on the market is a very bright pinkish-red spinel that appears like a glowing bright, neon red.

It is known as ‘jedi spinel’ because it glows like a lightsabre in the Star Wars films. It was discovered in Myanmar in the early 2000s.

Spinel in Marble Matrix. Image by Pat Daly.

Spinel Crystals

Spinels form either as octahedrons with flat, polished-looking faces that have a bright vitreous lustre, or they can form as spinel twins, which look like flat triangles with notches at the corners, known as re-entrant angles. Triangular etch pits can be found on the surface of these crystals.

Read more: What Makes a Gemstone Rare?

Spinel Crystal, Triangular Growth Marks. Image by Pat Daly.

Spinel Inclusions

Spinels often look loupe clean with minimal inclusions. Some of the more common inclusions can be octahedral crystals that are a spinel-type mineral and are usually arranged in very neat rows. You can also see zircon haloes (circular stress fractures around a zircon crystal) and iron staining.

A crystal inclusion in Spinel. Image by Pat Daly.

Synthetic Spinel

Synthetic spinel can be produced in a lab in virtually any colour. If produced by the verneuil flame fusion method, there are a few tests that you can do to differentiate between it and its natural counterpart. The refractive index of synthetic spinel is typically 1.727, which is higher than a natural spinel, which usually sits around 1.718.

Read more: The Most Important Gemstone Producing Countries

Additionally, if you put the synthetic stone on the polariscope, you will most likely see a type of strain called tabby extinction, which looks like thin, shadowy stripes that move across the stone as it is turned. Finally, observe the stone and try to find any natural inclusions like the ones mentioned above.

There are many natural spinels with minimal inclusions, but use additional tests to err on the side of caution.

Tabby Extinction in Synthetic Spinel. Image by Pat Daly.

Spinel Care and Caution

Spinels have a hardness of 8 on the Mohs scale, meaning that they can resist scratching and abrasion more easily than softer gems that fall lower on the scale. As it has a very good stability with a high resistance to heat or chemical damage, spinel can be used in jewellery dips, but it is still advised that warm water and a mild soap are used to clean spinel-set jewellery. Avoid ultrasonic and steam cleaners for good practice.

With its range of colours, good clarity and bright vitreous lustre, it is time that spinel was more appreciated as a gem material in its own right. Even though it is a lesser known gemstone on the market, it is a worthy alternative to peridot as a birthstone for August.

Do you want to learn more about gemstones? Sign up to a Gem-A Short Course or Workshop.

Start your gemmology journey with the Gem-A Gemmology Foundation qualification. Contact our Education team on to find out more. 

Cover image: Feather Inclusion in Spinel. Image by Pat Daly.

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Birthstone Guide: Opal for Those Born in October

The captivating opal is the birthstone for all those born in October. Here, Gem-A tutor Lily Faber FGA DGA EG explores the history and properties of this iridescent and rainbow coloured gemstone.

Opals have been valued for millennia, even before Ancient Greek and Roman times. There are two main types of opal: precious and common. The precious variety shows the magical play-of-colour that is so highly sought-after, while the more common variety simply does not show this optical effect but can come in a variety of colours from pink to green to blue to yellow.

Read more: Understanding the Different Types of Opal

Common Opal from Ethiopia, Image Credit Pat Daly.

Another variety is known as fire opal, which is a transparent to translucent variety that is orange, red or yellow and sometimes displays play-of-colour, but often does not.

The History of Opals

Believed by the Greeks to give one the power of prophecy and foresight, opals enjoyed a long period of favour. The Romans thought that opals represented purity and hope and they were regarded in high esteem until the 18th and 19th centuries when perceptions changed.

In the Victorian era especially, opals were believed to be unlucky and a cause of misfortune. Some even went as far as to believe that opals could bring physical harm to their wearer.

Read more: How to Assess the Value of an Opal

A well-known example of this is Queen Alexandra, a successor to Queen Victoria. She inherited a spectacular tiara that Prince Albert gifted Queen Victoria containing 11 precious opals. Fearing the opals could bring her misfortune, Queen Alexandra swiftly replaced all the opals with rubies before continuing to wear the heirloom.

Opal with Striated Colour Patches. Image Credit: Pat Daly.

Where are Opals Found?

Prized precious opals were relatively rare prior to the 19th century, the best examples coming from present-day Slovakia. Today, there are many localities where opals can be found, but the best and most valuable ones were discovered in the late 19th century in Australia.

Deposits where highly desirable opals have been found include Lightning Ridge and White Cliffs in New South Wales.

Understanding Synthetic Opals

There are many natural opals on the market, but there are also manmade ‘synthetic’ opals. First created by Pierre Gilson in 1974, these opals are very close to matching the physical and chemical structure of a natural opal. Synthetic is in quotations because it is not completely identical to its natural counterpart.

Synthetic Opal - Columnar Structure. Image Credit, Gem-A, Pat Daly.

It is essential that one must be able to distinguish between these manmade opals and the naturally forming ones when going to purchase an opal. This can be done with observation using a 10x loupe.

Natural opals with play-of-colour have irregular patches of rainbow hues that flash at many different levels within the stone as it is turned. The patches of colour are irregularly shaped and can be limited depending on the inner structure of the opal.

Identifying Synthetic Opals

‘Synthetic’ Gilson opals still display play-of-colour, but it can be much brighter and more consistently shaped and displayed throughout the stone than natural opals. Additionally, these patches of colour have a polygonal outline to them, giving a ‘lizard skin’ appearance.

If cut as a cabochon, there will also be a columnar structure to the patches of colour on the side of the cabochon, which is completely unlike natural opals.

Boulder opal. Image Credit: Gem-A.

Caring for Opals

Opals contain up to 30% water, which means that they are susceptible to drying out when exposed to heat. This can cause crazing, or cracking, that is irreversible.

When storing your opals, always make sure that it is in a cooler temperature, preferably with a bit of moisture in the air (a small dish of water or cotton ball will do). Opals are also porous and can be easily damaged by acids and chemicals such as detergents, perfumes and jewellery cleaner.

Opal Crazed Opal 8215 GemA PDAn example of crazing on a white opal. Image Credit, Gem-A, Pat Daly.

Finally, opals are soft with a hardness of 6 on the Mohs scale. This makes them vulnerable to knocks, scuffs and abrasions, which means they are more suited for earring and necklace settings rather than rings in order to keep them safe while wearing.

Today, opals are enjoying resurgence in popularity, despite the misgivings that they can bring back luck to those who wear them. For those born in October, opals can and should be considered a bit of gemstone magic to be enjoyed for their stunning play-of-colour unmatched by any other gemstone.

Start your gemmology journey with bite-sized Short Courses and Workshops.

Would you like to learn more about the science of gemmology? Discover our gemmology courses here

Cover image: Precious Opal Matrix. Image Credit: Pat Daly. 

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Birthstone Guide: Citrine for Those Born in November

As we enter the dark winter months, November’s birthstone citrine offers rays of warm yellow-orange sunshine. Here, gemmology tutor Lily Faber FGA DGA EG explores the properties and folklore around this sunny gemstone.

Citrine is a type of crystalline quartz that comes in many different hues of yellow, from pale buttercup shades to a stronger orangey or even brown-tinged yellow. Prized for its sunny appearance, citrine has long been popular in the gem and jewellery trade, especially in statement cocktail jewellery.

Citrine Myths and Folklore

For centuries, citrine has been said to hold the power of the sun. The stone is also believed by many to counteract depression and fight back against phobias. Citrine is known as a gemstone that can help its wearer remain calm in stressful situations because of its ability to attract good and positivity. Its characteristic yellow-to-orange colour is caused by a trace of iron in its structure.

Citrine Localities

Did you know? A little-known fact is that lots of citrine offered on the market is often amethyst that has been heat-treated to promote a golden colour. Natural citrine can be difficult to find, despite quartz being one of the most abundant gem minerals in the Earth’s crust.

Part of citrine GemA HMPart of a citrine crystal. Photography by Henry Mesa, Gem-A. 

This gemstone is found worldwide, but some of the most important localities of note are Brazil, India, Madagascar and Sri Lanka. In Bolivia, amethyst and citrine hues can occur together in the same crystal. These multi-colour gemstones are called ametrine.

Citrine Crystals and Inclusions

Citrine can be found as stand-alone crystals or as a geode containing multiple crystals within a rocky pocket. If sold as an individual crystal, citrine will have a hexagonally shaped prism with a pyramidal termination and slightly thicker base.

Read more: Exploring the Varieties of Quartz

There may be fractures within the crystal that cause iridescence, and the surface may feature striations that run horizontally across the prism faces (if the surfaces have not been polished).

Citrine 28.78 ctsA heated Brazilian citrine of 128.78 carats in a StarBrite cut by John Dyer & Co. Photo courtesy of Priscilla Dyer. 

Inclusions in citrine can be highly variable. However, it mostly has similar inclusions to those in amethyst, such as tiger stripes, straight colour-zoning, incipient fractures (mentioned above), crystals and two-phase inclusions consisting of a liquid and a gas, or a solid crystal and a liquid.

Citrine Care and Caution

Quartz is a 7 on the Mohs scale of hardness, endowing it with the ability to be set into any piece of jewellery, whether it is a ring, necklace or earrings. Considered hard, citrine will resist scratches and abrasions, but it is not impervious to these attacks and care should still be taken when wearing it in everyday life.

Read more: 5 Things to Consider Before Taking the Gem-A Gemmology Foundation Course 

Whether you like its appearance or the meanings behind it, citrine is a fantastic gem that can hold a high polish. This warm, bright and occasionaly overlooked gemstone that can be transformed into stunning pieces that add a touch of sunshine to any jewellery collection.

Read more: What Career Paths Can Trained Gemmologists Take? 

Start your gemmology journey by exploring our Short Courses and Workshops.

Discover more about the history of Gem-A and what makes our world-renowned gemmology education so special, here

Cover image: A rough citrine cyrstal specimen in the Gem-A Gemstone & Mineral Collection, photographed by Henry Mesa. 

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