Opal Blog – Australian Opal Hunter

Calibrated – Opal cut to standard size, for example 7mm x 5mm oval.

Carat – Measure of weight used for gemstones (5 carats to a gram).

Color Bar – Layer of color in opal differing from color layers above or below.

Color Separation Line – Often confused with cracks by the inexperienced – this fine line may occur where different color formations meet.

Concrete – Very porous and soft matrix opal from Andamooka.

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Light – Refers to the body or base colors.

Mackerel Sky – See Ribbon

Matrix - (1) Porous opal from Andamooka often dyed dark to simulate black opal. 

(2) Ironstone containing veins of precious opal which have formed in rivulets.   Exclusive to Queensland.
(3) Miners at Lightning Ridge use this term to describe a porous white impurity in black opal.

Painted Lady – Exclusive to Andamooka – a thin layer of opal on hard sandstone, usually sold as specimens.