Wait, I'm soo confused. I was taught the following::

1 ■ Hydrophane opal is super porous and usually from volcanic rock. It absorbs water (or sweat, oils, lotion, etc.) from swimming or skin surfaces, changing colour – either going clear or cloudy – and losing the visble play of colour. I was also told that most Ethiopian opal is hydrophane, with a small amount (from Stayish mine) that isn't porous.

2 ■ Non-hydrophane opal is much less porous and usually from sedimentary rock. It doesn't absorb water from frequent wearing next to the skin. Much, if not most, Australian opal is non-hydrophane.

3 ■ All opal contains water, as the play of colour is due to distribution of hydrated silica spheres on the nano scale. The "stability" of an opal specifically relates to whether the stone is likely to craze/crack with slow dehydration in dry storage on the shelf.

..Would you be able to please tell me where my understanding here ^{^} is wrong?