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Play of Colour

This is  a  term  that  is  used  to  describe  the  wonderful “play of colours” seen inside Precious  Opals. The visual effect is similar to viewing a child’s rotating kaleidoscope. It is truly one of the most striking visual effects seen in minerals and  the  very  finest  examples  sell  at  prices  in  excess of equivalent sized Diamonds. If the Opal  does not display “play of colour”, it is known as  a Common Opal and has little value. 

So  what  causes  an  Opal’s  “play  of  colour”?  Firstly, its structure is one of silica, water and air.  The silica is made up of small, round spherical  pieces, far bigger than those of atoms found in  a crystal; this is best understood by imagining  apples stacked in an orderly pattern on a fruit  vendor’s cart. The play of colour is seen if the  spheres are between 0.2 and 0.5 microns in size,  similar to the iridescence seen on the back of a  CD, which is caused by similar size differences  in the grooves of the track. As light falls on to the  spheres, different wavelengths are refracted at  different angles from different portions of each  sphere, producing an array of beautiful colours.

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Beautiful play of colour in this Opal pendant