Learning Library

Opal Gemstone

Opals are  beautiful  gems,  with  the  finest  Family  Opal specimens  containing  every  colour  of  the  rainbow. The name means ‘precious stone’, and is thought to have come from the Latin “Opalus” and the Greek “Opallios”.

Their unique internal colours are one of the most fascinating visual effects created by nature and is  Optical Properties  Displays opalescence correctly referred to as “play of colour”.  Opals  are doubly attractive as they often also have a beautiful iridescence (known as ‘opalescence’).

Opals  were  created  from  hydrated  silicon dioxide,  and  were  formed  when  water-based solutions  containing  silica,  deposited  a  gel- like  substance  in  gaps  and  crevices  in  rocks. Because of this they often form around areas where  there  are  hot  springs  or  geysers.  This process is fairly common and often the resulting  stone  is  a  lacklustre  ‘common  Opal’  which  is  ‘amorphous’,  meaning  that  the  atoms  are  arranged randomly within the stone and there is  no crystal structure. Common Opals also come  in a variety of different base colours, however  these often have little or no play of colour and  are therefore considered to have very little value.

Gem-quality Opals do, however, have a crystal  structure. They are loved for their kaleidoscope  of colours and internal flashes of almost neon coloured lights. There are several varieties of gem-quality Opals and the names used for them  by the gemstone industry can be quite confusing  to many people. When you hear White Opal,  Grey Opal or Black Opal, the name is referring  to the background colour of the Opal. See it as a  canvas for a painting on which beautiful colours  are  to  be  thrown  in  a  random  inspiration  of  modern art.

Boulder Opal consists of fine layers of natural Opal which have formed naturally on ironstone rock. Much like Ammolite, it is removed from its host rock while it is being cut, and then placed back onto it. This means that for most Boulder Opal the finished gem is actually a doublet or triplet opal. Boulder Opal from Queensland is declared by many experts to have the most brightness and best appearance of the Australian Opals

Opals  have  been  considered  both  good  luck  and bad luck throughout history. They were as  precious  as  Diamonds  to  the  ancient  Greeks  and used in jewellery by the Romans, whereas  in Russia the stone was considered by the Tsars  to symbolise the evil eye. When Europeans first  went to the New World they found the Aztecs of South America mining the gem, and due to  its rareness and beauty they took many back to  Europe to be presented to the royal courts.

Even  Opals  set  in  jewellery  still  contain  an  element of water and this can vary between 3%  and 20%. Because of this, Opals are considered  to  be  a  fairly  soft  precious  stone,  measuring  between 5.5 and 6.5 of the Mohs scale.

Common Opals can be found all over the world,  whereas gem-quality Opals are mostly mined in  Australia; in fact, some reports claim that 97%  of  the  world’s  gem-quality  Opals  are  sourced  from  here.  Other  areas  are  Mexico,  South  Africa, Brazil, Honduras, United States, Czech  Republic, Guatemala and Romania.

Not  all  Opals  are  opaque  and  there  are  other  body colours available too. Take a look at Fire  Opal which, due to its incredible popularity, we  have given its own section in this book. 

Recently  I  managed  to  find  a  small  parcel  of  Yellow  Opal  from  Tanzania.  These  gems  are  totally  stunning.  Whilst  they  don’t  have  the  transparency of the finest Fire Opals, they do  have a body colour which is a beautiful pastel  yellow. I have so far only discovered a small  amount  of  this  gemstone  (less  than  100ct),  but  I  have  just  dispatched  one  of  my  buyers  to Tanzania to try and find more. Keep a look  out  on  both  the  The Genuine Gemstone Company  website  and for more information.

One of the best discoveries recently has been  Pink Opals from Peru. Gem hunters the world  over are always looking for naturally coloured  pink gemstones, as it is one of the most desirable  of colours and provides a real feminine touch to  jewellery. The Pink Opal which I have recently  sourced  from  South  America  is  stunning.  We  have  had  the  pieces  cabochon  cut  in  our  Jaipur cutting house and not only is the colour  incredibly attractive, it has a wonderful surface  lustre too. 

In May of 2009, I secured a parcel of gemstones  from a trader who lives in Mali in North Africa.  He normally supplies us with Garnet, but had unearthed an opaque green gem and wondered if  we were interested.  At first we thought it might  be  Jade,  but  as  this  was  so  uncharacteristic  for the region we sent the samples off to the  laboratory  to  have  it  checked  out.  When  the  results  came  back,  we  were  amazed  that  it  turned out to be a green Opal! Therefore we  decided to call it Mali Opal after its origin. So  far we have only secured a small amount of the  gem and have had it faceted into both Ovals and  Cabochons. Keep your eyes on GemCollector. com and The Genuine Gemstone Company to see if we are able  to find more!


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A stunning Opal ring displaying opalescence