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The difference between rough nobby opal and seam opal from Lightning Ridge

There are two types of rough opal found in Lightning Ridge; nobby opal and seam opal. What are they? And how can you spot them?

Rough Nobby Opal

Rough nobby opals are found mostly in the Cooceran opal fields and the outskirts of the town area itself. They are round in shape or sometimes be cone-like on a flat base which is referred to as a “witches hat.”

There are a few theories on how nobby opal is formed, one being that there are clay balls in the earth that are washed away by silica-rich water. The silica-rich water runs through and settles in the rounded crevice, slowly building up the opal.

Rough Seam Opal

Rough seam opal is called so because it is flat and is formed by silica-rich water running through seams and cracks in the earth. It can be thin or thick, depending on the size of the fissure, and can color but not always.

If you’re looking for rough opal, or just want to see some examples, shop our rough opal selection.