Menilite

Menilite is a greyish-brown form of the mineraloid opal.

[1] It is also known as liver opal or leberopal (German), due to its color.

It is called menilite because it was first described from Ménilmontant (Paris), France,[1] where it occurs as concretions within bituminous Early Oligocene Menilite Shales.

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