Black Opal

Boulder Opal

• The Rarest, some say the most beautiful of the Opals because its black base enhances the colours.
• 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

The Base of the Opal is Called Potch

Potch is the plain coloured "common" opal that the flashes of brilliant colours are found in. It is most commonly a dull grey colour to black.

It is the base that makes the different opal types since it depends on the rock type in the area