Let’s have a chat about Pea Nobby’s and different types of rough opal.
There are two types of rough opal — Seam Opal and Nobby Opal.
Seam Opal is plate form and Grawin is exclusively Seam Country.
The Theory is — Seam opals are created by fissures, cracks, and movements underground that create a cavity for the opal to form.
The sediments of silica spheres fill up the cavity and usually form into a thin plate — on the rare occasion they can be quite thick.
Nobby Opal is nodule form and can be found in all fields in Lightning Ridge except the Grawin area.
Nobby Opals are clusters of organic matter covered by the earth, the fossil decomposes and becomes a cavity.
From there, the silica spheres soak through the ground and fill the cavities — voila, you have the beginnings of an opal!
(Well actually, this all took place over 110 million years ago in the Cretaceous period, so in fact, a very long and drawn out voila).
Justin’s favorite type of rough is Pea Nobby’s.
The ultimate is clean skin Pea Nobby’s, which is inclusion free with straight color bars running through them.
Pea Nobby’s are rounded compared to other nobby’s which come in all shapes and sizes.
Miners will look carefully through the tail out for small pea nobby’s as they could be worth up to $10,000 with a red color bar running through them.
Pea Nobby Tips
Buying — when looking at a parcel to purchase, the best way to inspect them is with a gem flashlight.
The gem flashlight will allow you to see how clean the color bar is.
Cutting — Pea Nobby’s will usually cut nice medium to high domes with a pleasing oval or round shape.
(Note: working on large parcels of Pea Nobby’s your fingers will touch the wheel quite often and wear down your skin).
The average carat size cut from a Pea Nobby is 0.5ct to 3cts.