Black Opal

Boulder Opal

• The rarest (and some say the most beautiful) of the Opals
• Strong brilliant colours on black or dark background
• Found mainly in Lightning Ridge in NSW, Australia.
• Priced by brilliance, colour and pattern
• Black or dark based Opal ablaze with a multitude of colours.
• Red on black potch* being the most valuable, closely followed by orange, yellow, green, blue, indigo and violet.
• Hydrated, hardened Silica gel containing up to 5-10% water
• First deposits found by boundary riders 1902 in Lightning Ridge, NSW

• Found only in Western Queensland
• Forms on ironstone boulders
• The main varieties are Matrix and Vein, with many varieties in between such as pancake, Yowah nut and splits
• Valued by brilliance of colour and the amount of actual precious opal present on the ironstone
• Cut mainly as free shapes and to the contours of the opal vein
• Like black opal the most valued colour is red followed by orange, yellow, green, blue, indigo and violet

White Opal

Crystal Opal

• Most common and well known of the opals
• Milky appearance with play of colour
• Found mainly in Coober Pedy, Mintabie, Andamooka in South Australia, and White Cliffs in NSW.
• Priced by predominant spectral colour
• Cut into free shapes but also calibrated due to the quantities available
• Hydrated Silica
• 5.5 - 6.5 mohs hardness (Diamonds are 10)

• Transparent opal with strong play of colour
• Found on all the opal fields in Australia
• Often has different layers of colours below the surface of the stone
• Hardened Silica gel containing 5 - 10% water
• Cut into free shapes but also calibrated

Potch

RD Opal Centre in Coffs Harbour, NSW.
   Opal Miners and Wholesalers.