Tag Archive | corundum

Call it what you will

We’re all used to the majority of gems being called by their name:
Diamond is diamond;

Opal is opal;

Turquoise is turquoise;

Even in it’s many different colours Topaz is still Topaz.

Emerald is emerald…well actually it’s Beryl…as is Morganite, Aquamarine, Heliodore and Goshenite!  What distinguishes each of these is the colour that the gem comes in (green, pink, pale blue, yellow and colourless respectively).

Ruby, well that’s actually a form of Corundum, called Ruby only when it is red, when it is pinky orange it is called Padparadscha.  All other colours of Corundum are called sapphires so you can find all kinds of sapphires, such as the green one below.

 

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Green sapphire

 

Tourmaline comes in a variety of colours and several of these have particular names too.  When it is red/pink it is Rubellite, green is Verdelite, blue is the fabulous Indicolite and colourless is Achroite.

Tanzanite is a form of zoisite, Morganite is a Beryl and they were both named by Tiffany and Co.

Amazonite is a type of Feldspar, as is Labradorite.  Incidentally Feldspar is the most prolific mineral in the Earth’s continental crust and can be found on Mars!  This is a good example of two types of mineral which are chemically related but clearly very different.

Quartz (the second most abundant mineral behind Feldspar) has another wide variation in colour, and many names or nicknames to go with it.  From the yellow citrine, to stunning purple amethyst (and of course the incredible ametrine is therefore part of this family).

Another variation is green quartz, sometimes referred to as green amethyst although if we were going to be strict about it that’s not it’s real name!  So we are going to go with the official Prasiolite, and here’s an example:

 

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However the quartz pseudonyms don’t stop there, even more strangely Chalcedony (see ring below), Agate, Onyx, Jasper, Tigers Eye, Aventurine and Carnelian are all types of quartz that you might not guess from the name!

 

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Blue Chalcedony

 

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Smokey Quartz

 

Of course the feminine pink of rose quartz to the stunning brown hues of smokey quartz (ring above) and the fascinating Rutilated Quartz are also, more obviously part of the family.

Another slight confusion may arise when considering the names of gems in that often the gem quality variation of a type of mineral has a different name to the non-gem form, Csarite/Diaspore, Peridot/Olivine and Iolite/Cordierite by way of example.

 

Call them what you will, they’re all beautiful to us!

The colour of love?

As it’s July we thought we should do a quick shout out for July’s birthstone today (particularly as one of us is a July baby!)

Ruby spray

Ruby is a gem quality variety of corundum, and is essentially a red variety of sapphire.  Fine rubies are actually rare as they are formed when a soft limestone rock was put under extreme heat and pressure within the Earth’s crust, but more than that the limestone then had to come into contact with just the right elements, including chromium, which makes them relatively rare.

Due to the way they are formed all natural rubies have imperfections which include colour differences or markings, and silk, although this silk is an imperfection it is important to enable natural rubies to be distinguished from synthetic rubies.

Rubies reach 9 on the Mohs scale, which

The majority of us will identify a ruby simply because it’s red, but there’s actually more to this gem’s colour than simply one word.  As they are part of the sapphire family different countries take a different approach to colour identification, for example in the United States a minimum colour saturation must be met before a “ruby” becomes a ruby rather than a pink sapphire.  The ICA takes a more liberal approach, but it’s something you should certainly turn your mind to the issue of colour.

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 True or false?

Synthetic rubies are relatively common and were first created in 1937, by 1910 the annual production of synthetic rubies had reached 1000kg.  The fewer imperfections in a ruby the more likely it is to be treated with suspicion and identified as synthetic.  In addition to its use in gemstone jewellery synthetic ruby has use in industry as they can be used to make lasers or other production where it’s hard nature is useful.

What is interesting is that in addition to having to detect synthetic rubies, a number of imitation rubies are often found in the form of glass, or the genuine gemstones such as garnet and spinel.  The confusion between ruby and other gems has been a long standing issue, sometimes not helped by the use of some trade names such as rubellite, but one of the most famous examples of this confusion can even be found in the Crown Jewels!  A stunningly large spinel can be found on the Imperial State Crown, known as the Black Prince’s Ruby.

Myth & Legend

Back in time, as with many precious stones, people used to believe that ruby had powers to preserve the health of the wearer.  Particularly ruby was seen to help the wearer by changing colour when danger was close at hand, protect from poison and plague and even make the wearer invulnerable to steel weapons.  Ruby is absolutely surrounded by acres of legend, particularly stemming from the reverence it was given in South East Asia. and it’s definitely worth a read as some of the stories are interesting.  Star rubies were even more highly prized, it was believed that the star was formed by three benign spirits which had been imprisoned in the stone for a misdemeanour, the spirits represent faith, hope and destiny and it is thought that this type of stone can bring good fortune to the wearer.

Treatments

Due to their nature and the naturally occurring imperfections the overwhelming majority of rubies are treated before coming to the jewellery market.  The most common treatment is heating, but other treatments include colour alteration, fracture filling or dissolving silk defects within the ruby.  Heating can improve both the colour and silk within the ruby.  Fracture filling does what it says on the tin, essentially using lead glass (or similar translucent) to fill the cracks within the ruby, which improves the translucency.

Unlike with some gems the treatment can be observed through a 10x loupe, and the majority of treatments are acceptable due to the nature of natural ruby.

Ruby pendant

If you do manage to find a natural, high quality, untreated ruby then snap it up as they are extremely rare!  However you should be warned that you will need deep pockets (far beyond our own means sadly) to keep hold of it!