Definition
Ijolite is an intrusive igneous rock which is composed mainly of nepheline and an alkali pyroxene, usually aegirine-augite
Arkose is a sedimentary rock, specifically a type of sandstone containing at least 25% feldspar
History
Origin
Finland, Europe
France
Discoverer
Unknown
Alexandre Brongniart
Etymology
From the first syllable of the Finnish words Ii-vaara, Iijoki, &c. commonly used geographical names in Finland, and the Gr. Xiflos, a stone
From Auvergne region of France used by a French geologist Alexandre Brongniart in 1826 who applied this term to some feldspathic sandstones
Class
Igneous Rocks
Sedimentary Rocks
Sub-Class
Durable Rock, Medium Hardness Rock
Durable Rock, Hard Rock
Family
Group
Plutonic
-
Other Categories
Coarse Grained Rock, Opaque Rock
Coarse Grained Rock, Opaque Rock