Black Opal - Black opal is characterised by a dark body tone causing brightness of colour which is unmatched by lighter opals. Black Opals are usually mined in Lightning Ridge, New South Wales, and are the most famous, and sought-after type of opal. The term 'black opal' does not mean that the stone is completely black (a common mistake), it simply means the stone has a dark body tone in comparison to a white opal
Boulder Opal - Boulder opal forms on ironstone boulders. This type of opal is often cut with the ironstone left on the back, as the opal seam is usually quite thin. Leaving the ironstone on the back means that boulder opal can be very dark and beautiful in color. The opal forms within the cavities of the boulders in both vertical and horizontal cracks. Boulders vary in shape and size, from as small as a pea, to as big as a family car.