Definition
Chalk is a soft, white, powdery limestone consisting mainly of fossil shells of foraminifers
Trachyte is a grey fine-grained volcanic rock which mainly consists of alkali feldspar
History
Origin
-
-
Discoverer
Unknown
Alexandre Brongniart and René Just Haüy
Etymology
From old English cealc chalk, lime, plaster; pebble, from Greek khalix small pebble, in English transferred to the opaque, white, soft limestone
From Greek trakhus rough’ or trakhutēs roughness
Class
Sedimentary Rocks
Igneous Rocks
Sub-Class
Durable Rock, Soft Rock
Durable Rock, Medium Hardness Rock
Family
Group
-
Volcanic
Other Categories
Fine Grained Rock, Opaque Rock
Fine Grained Rock, Opaque Rock