Ruby Stone – Characteristics, Colours and Cutting

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The name ruby comes from the Latin “rubeus or “ruber” meaning red and is one of the most precious and rare stones in the world.

Ruby is one of the traditional cardinal stones for making jewellery, along with amethyst, sapphire, emerald and diamond.

The gemstone rubeus – red from Latin, signifies the courage to exist in the world and also the fact that it carries an accessory of great refinement, a symbol present in the look of great leaders and consumers of articles in exclusive versions.

Ruby Stone
Ruby Stone

Ruby is the name of the frank red variety of a mineral, corundum, which itself can have all the other colours under the name sapphire, except red which is reserved exclusively for ruby.

All samples of cornidon do not have the required qualities of transparency and colour to be considered gems.

For a long time it was referred to as “carbuncle”, confused with red spinel and pyrope garnet. It wasn’t until the 1800s that it was linked, along with sapphire, to the corundum group.

Blood red colour with a hint of blue, with notable shades, one of which is called “pigeon’s blood” and is the most prized.

Names such as Siam ruby or Burmese ruby only distinguish the colour, not the intrinsic quality.

It often contains inclusions (minerals, liquids…), which do not affect the quality of the gem, but rather guarantee its authenticity compared to synthetic stones.

If they are rutile, the ruby acquires a silky appearance when it is cut into cabochons; these tiny rutile needles cause asterism or cat’s eye depending on the cutting orientation.

The presence of chromium modifies the colour which, if broken down into bands or slopes, gives the iron a brownish hue which is not appreciated.

To speak of rubies is to speak of Burma, from where the most beautiful rubies in the world were mined and are still produced, and for which Indian princes and Marajas were enamoured.

Rubies are mined in Africa, Asia and Australia. They are most common in Myanmar, Sri Lanka and Thailand, but are also found in Montana and South Carolina in the United States.

In Brazil, ruby stones can be found in states such as Santa Catarina and Bahia, but the incidence is low and the gemological value is nowhere near that of gems originating in Asian soils.

Pedra Rubi - Caracteristicas, Cores e Lapidação

Sometimes they occur together with spinels in the same geological formations, causing confusion between the two species: however, good specimens of red spinels have a value close to ruby.

Ruby gems are valued according to various characteristics including size, colour, clarity and cut.

On the other hand, artificial rubies may not contain any imperfections.

Some manufactured rubies have substances added to them so that they can be identified as artificial, but most require gemological tests to determine their origin;

The largest star ruby in the world is the Rajaratna, which weighs 495g.

Main Gems and Precious Stones
Main Gems and Precious Stones

Ruby names used on the market

  • Burmese or Oriental – generally considered the best colour, which has traditionally been denoted by the term pigeon’s blood (red to slightly violet red in medium-dark hue and vivid saturation)
  • beef-blood – slightly darker than the pigeon-blood colour
  • French or cherry colour – slightly lighter than the pigeon-blood colour
  • Thai, Siamese or Siamese colour, also called muddy ruby – (dark red to brownish red or purplish red)
  • from Ceylon or Sri Lanka – (light in colour) often brighter than Burmese or Thai gems
  • African (Umba River) – typically orange-red 

Characteristics of the ruby stone

The ruby (aluminium oxide) has mineral characteristics that make it one of the 5 most valuable gems in the world, depending on its origin, cut and tone;

All natural rubies contain imperfections, ranging from conchoidal to irregular with a glassy lustre.

1. Hardness

Corundums (ruby and safira) are the hardest stones after diamond, with a hardness of 9 mohs.

2. Colour

Knowing the colour of the ruby stone that will make up a piece of jewellery is fundamental to identifying its value, as well as its origin and the natural characteristics that formed it, in the case of those of mineral origin.

The main colour of the ruby is red, due to the chromium, and the most sought-after shade is pigeon blood red.

So if you want to recognise the value of a ruby stone, know that the shade of red of the gem should not be too light or dark, as in these cases the gemstone loses its characteristic shine.

Therefore, when buying pendants with ruby stones, for example, make sure they are shiny, coloured and, above all, certified.

3. Transparency

From transparent to opaque.

4. Lapidation

The mineral Corundum gives rise to micro-crystals with a hexagonal (trigonal) shape and a glassy appearance, found in basalts, gravels and marbles. The cabochon type of cut is often used, but it is also found in mixed and oval faceted cuts.

5. Possible treatments

Heating followed by controlled cooling, heating and slow cooling, diffusion (heat treatment above 1900ºC in the presence of titanium oxide or another colouring agent), heat treatment; dyeing with oil, filling cavities and fractures with glass.

6. Possible confusions 

Synthetic ruby, red garnets, chrysoberyl, natural or synthetic spinel, doublet of sapphire with synthetic ruby, doublet of natural ruby and doublet of garnet and glass.

7. Natural vs synthetic ruby

Many people have doubts about the types of rubies, because know that yes, there are natural stones originating from Corundum, but there are also uniquely beautiful pieces in synthetic rubies, alternatives that also appeal to jewellery fans.

While natural gems undergo careful extraction processes, synthetic rubies are developed to achieve a shine and colour that meet the aesthetic characteristics of these products.

See Identifying a precious stone or gem is a difficult task.

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