Definition
Origin
Discoverer
Etymology
Class
Sub-Class
Group
Other Categories
Chalk is a soft, white, powdery limestone consisting mainly of fossil shells of foraminifers
From old English cealc chalk, lime, plaster; pebble, from Greek khalix small pebble, in English transferred to the opaque, white, soft limestone
Fine Grained Rock, Opaque Rock
Rhyolite is a fine-grained igneous rock which is rich in silica
From German Rhyolit, from Greek rhuax lava stream + lithos stone
Coarse Grained Rock, Opaque Rock