menilite
{{Short description|Form of opal}}
Menilite is a greyish-brown form of the mineraloid opal.[http://www.mindat.org/min-9796.html Menilite on Mindat.org] 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, where it occurs as concretions within bituminous Early Oligocene Menilite Shales.