195ct untreated Koroit boulder opal natural sedimentary layered multicolour gem

This piece I have one of, this is koroit opal and it is large and colourful.
 
This piece shows the sedimentary development of the opal gem, the host rock/matrix shows on the underside, the way the host rock and the silica (That becomes the opal) layers. 
 
The piece has mostly greens but blues and reds, oranges and even purples!
 
This opal is 195cts or 39 grams, rather heavy for a koroit opal.
 
The piece is too large for jewellery of course but as art, just beautiful, there is a back part where one can see waves of different Earth browns running and flowing throughout the piece.
 
The parts of coloured opal are polished however where there is rough matrix maetrial it is left unpolished giving a contrast between gem material and host rock with a matte effect.
 
The buyer can have this stone tested by GIA, 1 year extended warranty. Any treatments found return stone for full refund.

Please note that photos will appear different, monitor to monitor however I do not use any photo modification, photo adjustment or special lighting.