Definition
Gneiss is a common and widely distributed type of rock formed by high-grade regional metamorphic processes from pre-existing formations that were originally either igneous or sedimentary rocks
Trachyandesite is an extrusive igneous rock.
History
Origin
-
Indonesia
Discoverer
Unknown
Unknown
Etymology
From the Middle High German verb gneist (to spark; so called because the rock glitters)
From French trachyandésite, trachy + andésite andesite, a lava intermediate in composition between trachyte and andesite
Class
Metamorphic Rocks
Igneous Rocks
Sub-Class
Durable Rock, Hard Rock
Durable Rock, Medium Hardness Rock
Family
Group
-
Volcanic
Other Categories
Coarse Grained Rock, Medium Grained Rock, Opaque Rock
Fine Grained Rock, Opaque Rock