Could it be a jawbone?

[Vopros]

This is opal from Australia

[Coco]

Hi,

 

Size ?

 

Coco

[Vopros]

15 minutes ago, Coco said:

Hi,

 

Size ?

 

Coco

109.7 x 64 x 26mm

[Pliosaur]

Doesn’t seem like one, opalized fossils are extremely rare. A bigger overall picture of the entire specimen would help a lot in identification 

[debivort]

I would guess it's a geological formation cause by repeating, slanted cracks in the material.

[jpc]

The patterns there are fracture patterns and have nothing todo with jaws or teeth.  Nice opal.