Definition
Origin
Discoverer
Etymology
Class
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Other Categories
Very fine grained fault rock which is composed of glassy matrix that often contains inclusions of wall-rock fragments.
From pseudo- + tachylite, a glassy rock generated by frictional heat within faults.
Fine Grained Rock, Opaque Rock
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