My turn for a 'wierd' one...

crocoite · Post by **crocoite** » Fri Oct 06, 2006 5:38 am

Not that you would guess, but this is a photo of a form of opal known as hyalite. Found in a cavity in basalt (volcanic rock) from Bundoora, Victoria, Australia.

beetleman · Post by **beetleman** » Fri Oct 06, 2006 8:29 am

It says it is Fluoresent under UV...did you try that. I love minerals that do that

. I would assume this formed after the basalt? Nice little find Steve

crocoite · Post by **crocoite** » Sat Oct 07, 2006 1:44 am

Thanks Doug

No, this one doesn't flouresce, at least under a longwave UV light (I don't have a shortwave lamp). Yes it did form after the lava had cooled. It formed with crystals of other minerals in a gas or liquid filled cavity in the basalt.