The opal appears as a layer or vein of opal upon the host rock. The host rock is usually a brown coloration. Boulder opals are often cut in free form and irregular shapes. Australian boulder opal is very popular with designers looking to work with asymmetrical gems and they lend themselves to a very modern aesthetic.
Boulder opals are also known for their ability to mimic scenes. We call them picture stones as they often look like a landscape with movement and color. Additionally, because boulder opals are veins of color, the natural fault line is often through the color. This results in the boulder piece splitting in two and showing two faces of opal - which can often be so similar as to make a pair of gems - perfect for earrings! Boulder opal is unique to Australia.
